Many police departments prohibit their officers from employing the kind of neck restraints a man used in fatally subduing Jordan Neely in the New York City subway.When a subway rider in New York used a chokehold that ended up killing a 30-year-old homeless man, Jordan Neely, he was employing a technique that many neurologists warn is so dangerous that it should not be allowed in law enforcement.Chokeholds or strangleholds are known also as neck compressions, which involve applying pressure to both sides of the neck. They are allowed in some martial arts competitions, and certain U.S. military personnel in ground-combat units may learn to apply chokeholds, and associated safe releases, in training.But in the past few years, police departments have increasingly banned the use of chokeholds, following events such as the deaths of Eric Garner and George Floyd.There are few data on how often police have used the holds, or what the consequences were. Among the few studies is one reporting that officers in Spokane, Wash., used neck restraints 230 times in the eight years before May 2021, when Washington State banned them.While there were no fatalities recorded in the use of the holds by that department, neurologists say the dangers of neck compression are indisputable.Dr. Altaf Saadi, a neurologist at Massachusetts General Hospital, explained that chokeholds and strangleholds could kill or cause brain injuries in two ways. They can compress the trachea, preventing the person from getting air into the lungs. And they can compress the carotid arteries, which are on either side of the neck, adjacent to the trachea. Seventy percent of the blood going to the brain passes through the carotids, Dr. Saadi said. If that blood flow is cut off in a chokehold or a stranglehold, some people can become unconscious in three to four seconds. If the flow continues to be restricted, a person can die within three to four minutes.

Donanemab is not a cure and comes with significant side effects, but patients had longer periods of independent living while on the drug.The drug manufacturer Eli Lilly announced on Wednesday that a clinical trial of an experimental Alzheimer’s drug showed it can slow progress of the feared disease and allow patients to have more time when they can still live independently, performing tasks like cooking meals, going to the store and driving a car.Lilly announced its results, from a trial involving 1,736 patients, in a news release, as required by the Securities and Exchange Commission. A peer-reviewed paper will follow.The drug, donanemab, is not a cure, but along with two other drugs recently approved by the Food and Drug Administration, it may be a turning point in the long and frustrating quest to find an Alzheimer’s treatment. “These all point in the same direction,” said Dr. Ronald Petersen, the director of the Alzheimer’s Disease Research Center at the Mayo Clinic. He added that the donanemab results were “modest” but “meaningful.” Dr. Petersen has done paid consulting work for pharmaceutical companies, including Lilly. He was not involved in the design or execution of any of the recent trials.Dr. Samuel Gandy, a professor of Alzheimer’s disease research at Mount Sinai, was more subdued.“Families and researchers are stuck with what we know now, which is that two drugs have a statistically meaningful but only modest clinical benefit,” he said, echoing Dr. Petersen’s assessment. He has consulted and received research support from pharmaceutical companies but was not involved in the Lilly trial.Dr. Petersen said that patients and their families must be counseled about a dire side effect of donanemab — a risk of brain swelling that can result in death. Three patients in the Lilly trial died.A similar percentage of deaths from the same side effect followed in the clinical trial of Leqembi, an F.D.A.-approved Alzheimer’s drug from the company Eisai. A third drug, Aduhelm, was also approved by the F.D.A., but is rarely used because of concerns about its effectiveness and its high price. Brain swelling was reported in its clinical trial and deaths were reported in patients taking Aduhelm after it was approved.The results come after decades of failed attempts, despair, discouragement and billions of dollars spent. Most big pharmaceutical companies simply gave up on Alzheimer’s drugs.After those failures, some researchers decided that a leading hypothesis about the disease — that it is driven by hard, Brillo-like plaques in the brain made of amyloid protein — was incorrect. But the successes of the new drugs, which attack amyloid, bolster the hypothesis.Taking the drugs is not like taking an antibiotic and seeing a fever go away. To measure the new drug’s effectiveness, the Lilly researchers instead looked at how likely patients were to progress through the categories of Alzheimer’s disease, going from mild cognitive impairment to mild dementia, or from mild to moderate dementia. These are significant changes that have a profound effect on patients and their families.The company reported that two to three out of 10 patients taking donanemab progressed over the next 18 months as compared to the expected three to four patients who did while taking a placebo.They also studied how likely it was that a patient’s disease would remain absolutely stable over a period of time.“One of the common things we always hear from patients who have Alzheimer’s but are very early in the disease is, ‘If I could just stay at this level I could get by,’” said Dr. Daniel Skovronsky, chief medical and scientific officer at Eli Lilly and Company.With the new drug, 47 percent of patients stayed stable over the subsequent year compared with 29 percent who took the placebo.In the Lilly trial, 24 percent of patients had the side effect of brain swelling and bleeding, and 6 percent had symptoms like dizziness, headache or fainting. That is twice the rate observed with Leqembi, the Eisai drug.But, Dr. Skovronsky said, it is difficult to compare data across trials because the studies had different patient populations — the Leqembi patients had less severe Alzheimer’s — and different designs. The M.R.I. scans were done on different schedules, and the way the scans are read can vary.Deaths from brain swelling and bleeding are rare, but still these drugs “are not for everyone,” Dr. Petersen said.“They do not make you better but they slow the disease,” he said.Dr. Petersen added that what is really needed is a drug that stops the disease before symptoms arise.With that goal in mind, Eisai and Lilly are testing their drugs in new studies of people who have large amounts of amyloid in their brains but no symptoms yet of Alzheimer’s.Advocacy groups applauded the data in the Lilly trial.George Vradenburg, chairman and co-founder of UsAgainstAlzheimer’s called the donanemab results “exciting news.” Lilly, along with other companies, gives the group general funding but not for any specific project.In a news release, he said, “Talk to anyone with early-stage Alzheimer’s and they will tell you that living independently and having a higher quality of life for a longer period of time are among the most important things to them.”

On the evening of Jan. 15, 2021, in a remote Arizona desert town, Christine Benton saved a life.She and her husband, Brian Benton, were traveling the country in a recreational vehicle and had parked near other R.V.ers at a winery in Willcox. As the couple were eating dinner, someone started shouting from an R.V. behind them. A woman had collapsed and was in cardiac arrest. She had no pulse. Frantic, her husband called 911 while two other people started cardiopulmonary resuscitation.“She looked like she was gone,” said Ms. Benton, a retired paramedic firefighter.But Ms. Benton had made a consequential decision before she and her husband started out: She had bought a personal automated external defibrillator, or A.E.D., which can shock a person’s heart back to life if it suddenly stops beating. Her plan was to to keep it with her, just in case. It was expensive, it was highly unlikely she would ever use it and her husband was hesitant. But she was adamant.“If I were ever in a situation where I could save a life and I didn’t have an A.E.D., I could never live with myself,” she told her husband at the time.As a firefighter, Ms. Benton had been trained to use a defibrillator. She knew that if someone’s heart stopped, a rescuer should start CPR immediately, pushing hard and rhythmically on the chest, while another rescuer went to get an A.E.D. As soon as that second rescuer returned, the A.E.D. should be used.And Ms. Benton knew that A.E.D.s were easy to use, even for someone with no training. The device speaks to rescuers and tells them how to proceed.But even though all states have laws requiring that A.E.D.s be available in public places, Ms. Benton worried that if someone had a cardiac arrest in a place where the nearest A.E.D. was miles away, the person might die — minutes count when reviving someone in cardiac arrest. For every one-minute delay in resuscitation, the likelihood of survival falls by up to 10 percent.For Ms. Benton, the decision to buy an A.E.D. made perfect sense. I also ordered one for myself after reporting on the football player Damar Hamlin’s on-field cardiac arrest. When it arrives I am going to tell my neighborhood’s Google group that I have it.Christine Benton, a retired paramedic firefighter, had been trained to use a defibrillator, but also knew that A.E.D.s are easy to use, even for people with no training.Ash Ponders for The New York TimesBut emergency medicine specialists are divided on whether it makes sense for anyone to buy one.They know that A.E.D.s in public places like airports, where thousands of people pass by every day, can make a difference and they urge people to use them if they see someone who needs help. In the U.S., 85 to 90 percent of people who have sudden cardiac arrests do not survive and many cannot be revived, often because resuscitation attempts start too late.But the situation is different in the home.For one, there is the expense — the devices often cost more than $1,000, making them far less affordable to the average person than home medical devices like a blood pressure monitor or a pulse oximeter. While there are efforts to develop cheaper A.E.D.s, they are still underway, according to Monica Sales, a spokeswoman for the American Heart Association.The price is not the only thing that gives some specialists pause. The odds are so stacked against a dramatic save that it has proved impossible to show that personal A.E.D.’s make a difference.An estimated 1,000 people a day in the U.S. have sudden cardiac arrests, in which the heart stops beating and the person is technically dead. But that represents a minuscule portion of the American population.Even people at high risk of a sudden cardiac arrest were not helped by home A.E.D.s, a large study showed. It involved 7,001 people who had previously had heart attacks and who were randomly assigned to receive an A.E.D. or to be in a control group.Despite the huge number of study participants, very few had cardiac arrests and, even when they did, the arrests often did not occur at home or were not witnessed. In the end, just eight people in each group were resuscitated at home. The authors concluded that even if the study’s size were doubled, there would be too few events to detect an effect of home A.E.D.s.But think of an A.E.D. like a fire extinguisher, said Dr. Benjamin Abella, an emergency medicine specialist at the University of Pennsylvania. You might never use it, but having one might one day save a life.“I think it’s a terrific idea” to own one, Dr. Abella said. He recently ordered an A.E.D. for himself.For the same reason, the American Heart Association supports anyone who wants to get an A.E.D., said Dr. Comilla Sasson, a vice president at the American Heart Association and an emergency medicine physician at the University of Colorado Denver.“If we could just reduce the stigma around, ‘Hey, I can’t do this because I’m not a medical professional,’” she said. “And you don’t need to have CPR certification to use an A.E.D.”But Dr. Sumeet S. Chugh, director of the Center for Cardiac Arrest Prevention at Cedars Sinai in Los Angeles, has his doubts.“I don’t think we have the data to support widespread prophylactic purchases of A.E.D.s even if you can afford it,” he said. And, he added, many who go into cardiac arrest do not have a shockable condition. One example is asystole, a flat line on the heart monitor indicating there is no electrical activity in the heart. An A.E.D. cannot revive people with unshockable rhythms. Other patients are not discovered in time for their heart to be shocked back to life.Karen Schluter, whose life was saved in 2021 after Ms. Benton shocked her heart back into action after she had a cardiac arrest. Without the A.E.D., Ms. Schluter would have died.Andy Manis for The New York TimesThat was the situation that Mary Newman found herself in. Ms. Newman, co-founder of the Sudden Cardiac Arrest Foundation, which promotes awareness of cardiac arrest and has a support group for survivors, has an A.E.D. But when her mother collapsed in the bathroom during a family vacation, no one realized she was missing. By the time the family found her, it was too late to save her.Yet there are rare examples of people who did save a life with a personal A.E.D.One involved Esley Thorton, Jr. of Bismarck, N.D.At about 8 a.m. on Nov. 25, 2019, Mr. Thornton sank into his favorite chair, inexplicably tired.A few minutes later his wife, Melinda, heard an odd noise and came running into the room. “His body was contorted,” she said. “He was gasping for air.”Then he stopped breathing. His heart had stopped.Ms. Thornton screamed for her son Rhannon, who called 911 and grabbed an A.E.D. that another son, who works for the A.E.D. maker Stryker, had given his parents as a gift two years earlier.Rhannon put the device’s pads on his father’s chest. It said, “No pulse, administer shock,” Ms. Thornton recalled.He pressed a button.“Shock administered,” the device said.“We heard him take a deep breath,” Ms. Thornton said. Her husband’s heart was beating again.An ambulance came eight minutes after the 911 call — long enough that without Rhannon’s help, Mr. Thornton might have died or had serious brain damage.One of the paramedics was astonished, telling the family that he had been a paramedic for 22 years but had never before seen a personal A.E.D. used in a patient’s home.In Ms. Benton’s case, the woman whose heart had stopped began breathing again less than 20 seconds after Ms. Benton shocked her heart with the A.E.D.Without the A.E.D., the woman, Karen Schluter, would have died — CPR alone would not have been sufficient in that remote location where it took about half an hour for an ambulance to arrive.Yet no one would have predicted that Ms. Schluter was at risk. She was 52 and athletic — an avid bicyclist.Now Ms. Benton and Ms. Schluter are good friends. Ms. Schluter has purchased an A.E.D. and so have others whose R.V.s were parked there that evening.When the Bentons returned to their R.V. after their A.E.D. saved Ms. Schluter’s life, Mr. Benton looked at his wife and said, “I am sure glad you didn’t listen to me about buying that A.E.D.”

It was March 1827 and Ludwig van Beethoven was dying. As he lay in bed, wracked with abdominal pain and jaundiced, grieving friends and acquaintances came to visit. And some asked a favor: Could they clip a lock of his hair for remembrance?The parade of mourners continued after Beethoven’s death at age 56, even after doctors performed a gruesome craniotomy, looking at the folds in Beethoven’s brain and removing his ear bones in a vain attempt to understand why the revered composer lost his hearing.Within three days of Beethoven’s death, not a single strand of hair was left on his head.Ever since, a cottage industry has aimed to understand Beethoven’s illnesses and the cause of his death.Now, an analysis of strands of his hair has upended long held beliefs about his health. The report provides an explanation for his debilitating ailments and even his death, while also raising new questions about his genealogical origins and hinting at a dark family secret.The paper, by an international group of researchers, was published Wednesday in the journal Current Biology.It offers additional surprises: A famous lock of hair — the subject of a book and a documentary — was not Beethoven’s. It was from an Ashkenazi Jewish woman.The study also found that Beethoven did not have lead poisoning, as had been widely believed. Nor was he a Black man, as some had proposed.And a Flemish family in Belgium — who share the last name van Beethoven and had proudly claimed to be related — have no genetic ties to him.Researchers not associated with the study found it convincing.It was “a very serious and well-executed study, “ said Andaine Seguin-Orlando, an expert in ancient DNA at the University Paul Sabatier, Toulouse, in France.The detective work to solve the mysteries of Beethoven’s illness began on Dec. 1, 1994, when a lock of hair said to be Beethoven’s was auctioned by Sotheby’s. Four members of the American Beethoven Society, a private group that collects and preserves material related to the composer, purchased it for $7,300. They proudly displayed it at the Ira F. Brilliant Center for Beethoven Studies at San Jose State University in California.But was it really Beethoven’s hair?The Hiller lock, which the study found did not come from Beethoven but a woman, with its inscription by its former owner, Paul Hiller.William Meredith/Ira F. Brilliant Center for Beethoven Studies, San Jose State UniversityThe story was that it was clipped by Ferdinand Hiller, a 15-year-old composer and ardent acolyte who visited Beethoven four times before he died.On the day Beethoven died, Hiller clipped a lock of his hair. He gave it to his son decades later as a birthday gift. It was kept in a locket.The locket with its strands of hair was the subject of a best-selling book, “Beethoven’s Hair,” by Russell Martin, published in 2000, and made into a documentary film in 2005.An analysis of the hair at Argonne National Laboratory in Illinois found lead levels as high as 100 times normal.In 2007, authors of a paper in The Beethoven Journal, a scholarly journal published by San Jose State, speculated that the composer might have been inadvertently poisoned by medicine, wine, or eating and drinking utensils.That was where matters stood until 2014 when Tristan Begg, then a masters student studying archaeology at the University of Tübingen in Germany, realized that science had advanced enough for DNA analysis using locks of Beethoven’s hair.“It seemed worth a shot,” said Mr. Begg, now a Ph.D. student at Cambridge University.William Meredith, a Beethoven scholar, began searching for other locks of Beethoven’s hair, buying them with financial support from the American Beethoven Society, at private sales and auctions. He borrowed two more from a university and a museum. He ended up with eight locks, including the hairs from Ferdinand Hiller.First, the researchers tested the Hiller lock. Because it turned out to be from a woman, it was not — could not be — Beethoven’s. The analysis also showed that the woman had genes found in Ashkenazi Jewish populations.Dr. Meredith speculates that the authentic hair from Beethoven was destroyed and replaced with strands from Sophie Lion, the wife of Ferdinand Hiller’s son Paul. She was Jewish.Lab work on the Moscheles lock at the University of Tübingen in Germany.Susanna SabinAs for the other seven locks, two were inauthentic, four had identical DNA and one could not be tested. The four locks with identical DNA were of different provenances and two had impeccable chains of custody, which gave the researchers confidence that they were hair from Beethoven.Ed Green, an expert in ancient DNA at the University of California, Santa Cruz, who was not involved with the study, agreed.“The fact that they have so many independent locks of hair, with different histories, that all match one another is compelling evidence that this is bona fide DNA from Beethoven,” he said.When the group had the DNA sequence from Beethoven’s hair, they tried to answer longstanding questions about his health. For instance, why might he have died from cirrhosis of the liver?He drank, but not to excess, said Theodore Albrecht, a professor emeritus of musicology at Kent State University in Ohio. Based on his study of texts left by the composer, he described what is known of Beethoven’s imbibing habits in an email.“In none of these activities did Beethoven exceed the line of consumption that would make him an ‘alcoholic,’ as we would commonly define it today,” he wrote.Beethoven’s hair provided a clue: He had DNA variants that made him genetically predisposed to liver disease. In addition, his hair contained traces of hepatitis B DNA, indicating an infection with this virus, which can destroy a person’s liver.But how did Beethoven get infected? Hepatitis B is spread through sex and shared needles, and during childbirth.Beethoven did not use intravenous drugs, Dr. Meredith said. He never married, although he was romantically interested in several women. He also wrote a letter — although he never sent it — to his “immortal Beloved,” whose identity has been the subject of much scholarly intrigue. Details of his sex life remain unknown.The Stumpff lock, from which Beethoven’s whole genome was sequenced, with an inscription by its former owner Patrick Stirling.Kevin BrownArthur Kocher, a geneticist at the Max Planck Institute for Evolutionary Anthropology in Germany and one of the new study’s co-authors, offered another possible explanation for his infection: The composer could have been infected with hepatitis B during childbirth. The virus is commonly spread this way, he said, and infected babies can end up with a chronic infection that lasts a lifetime. In about a quarter of people, the infection will eventually lead to cirrhosis of the liver or liver cancer.“It could ultimately lead someone to die of liver failure,” he said.The study also revealed that Beethoven was not genetically related to others in his family line. His Y chromosome DNA differed from that of a group of five people with the same last name — van Beethoven — living in Belgium today and who, according to archival records, share a 16th-century ancestor with the composer. That indicates there must have been an out-of-wedlock affair in Beethoven’s direct paternal line. But where?Maarten Larmuseau, a co-author of the new study who is a professor of genetic genealogy at the University of Leuven in Belgium, suspects that Ludwig van Beethoven’s father was born to the composer’s grandmother with a man other than his grandfather. There are no baptismal records for Beethoven’s father, and his grandmother was known to have been an alcoholic. Beethoven’s grandfather and father had a difficult relationship. These factors, Dr. Lamarseau said, are possible signs of an extramarital child.Beethoven had his own difficulties with his father, Dr. Meredith said. And while his grandfather, a noted court musician in his day, died when Beethoven was very young, he honored him and kept his portrait with him until the day he died.Dr. Meredith added that when rumors circulated that Beethoven was actually the illegitimate son of Friedrich Wilhelm II or even Frederick the Great, Beethoven never refuted them.The researchers had hoped their study of Beethoven’s hair might explain some of the composer’s agonizing health problems. But it did not provide definitive answers.The composer suffered from terrible digestive problems, with abdominal pain and prolonged bouts of diarrhea. The DNA analysis did not point to a cause, although it pretty much ruled out two proposed reasons: celiac disease and ulcerative colitis. And it made a third hypothesis — irritable bowel syndrome — unlikely.Hepatitis B could have been the culprit, Dr. Kocher said, although it is impossible to know for sure.The DNA analysis also offered no explanation for Beethoven’s hearing loss, which started in his mid-20s and resulted in deafness in the last decade of his life.An 1827 lithograph of Beethoven on his deathbed by Josef Danhauser, after his own drawing.Josef Danhauser, via Beethoven-Haus BonnThe researchers took pains to discuss their results in advance with those directly affected by their research.On the evening of March 15, Dr. Larmuseau met with the five people in Belgium whose last name is van Beethoven and who provided DNA for the study.He started right out with the bad news: They are not genetically related to Ludwig van Beethoven.They were shocked.“They didn’t know how to react,” Dr. Larmuseau said. “Every day they are remembered by their special surname. Every day they say their name and people say, ‘Are you related to Ludwig van Beethoven?’”That relationship, Dr. Larmuseau said, “is part of their identity.”And now it is gone.The study’s findings that the Hiller lock was from a Jewish woman stunned Mr. Martin, author of “Beethoven’s Hair.”“Wow, who would have imagined it,” he said. Now, he added, he wants to find descendants of Sophie Lion, the wife of Paul Hiller, to see if the hair was hers. And he’d like to find out if she had lead poisoning.For Dr. Merrill, the project has been an amazing adventure.“The whole complex story is astonishing to me.” he said. “And I’ve been part of it since 1994. One finding just leads to another unexpected finding.”

The U.S. agency wants to ensure that doctors inform women that some breast anomalies require more examination.In a long-awaited ruling, the Food and Drug Administration recommended on Thursday that all mammogram centers must tell women if they have dense breasts that could put them at increased risk for breast cancer.The density of breast tissue — whether it contains mostly fatty or glandular tissues — varies from woman to woman and has nothing to do with the size or shape or feel of a woman’s breasts. The only way for a woman to know if she has dense breasts and, if so, how dense they are is by having a mammogram; she cannot tell by looking at or feeling her breasts.Dense breast tissue may obscure cancer risks because it may be more difficult to spot small tumors with a mammogram.Breast imagers divide density into four levels, designated A, B, C and D, ranging from almost entirely fatty breasts to extremely dense breasts. Only the 10 percent of women in level D, with extremely dense breasts, are at increased risk. Those in level C are at average risk for cancer, based on density alone.The updated regulations require that patients simply be told that their breasts are dense or not dense; levels A and B would be “not dense,” while C and D are “dense.”New Developments in Cancer ResearchCard 1 of 5Progress in the field.

Bempedoic acid lowers cholesterol, and a study found a modest effect on cardiac illness. But whether patients are any more willing to take it remains to be seen, experts said.Millions of Americans who are at high risk for heart attacks and whose LDL cholesterol levels are disturbingly high have been told over and over again by their doctors to take a statin. These cheap generic drugs have been shown repeatedly to slash cholesterol levels and prevent heart attacks, strokes and deaths. But many people cannot or will not take the drugs, often reporting that statins make their muscles ache.Now, a study with 14,000 patients of a drug that lowers LDL levels and was designed to avoid muscle aches was found to modestly reduce the risk of heart attacks, strokes and other complications from heart disease.It was published Saturday in The New England Journal of Medicine and presented at the annual meeting of the American College of Cardiology. The medication joins several statin alternatives that have been shown to reduce cardiac illnesses, and some experts say they doubt the drug is any more likely to be embraced by patients who are wary of statins and, often, other LDL-lowering drugs.The drug, bempedoic acid, is not new; the Food and Drug Administration approved it three years ago because it lowers LDL levels.But “it was not used a lot,” said Dr. John Alexander, a cardiologist at Duke, who was not associated with the study and wrote an accompanying editorial in the journal. The reason, he said, is that while earlier research showed that the drug lowered LDL cholesterol, no studies showed that it actually reduced a patient’s chances of a heart attack or a stroke or death from heart disease. And, because there were no outcome data, insurers generally have not covered its cost of about $140 a month.“In cardiology and cardiovascular disease prevention, we expect outcome data,” Dr. Alexander said.But the new study showed that bempedoic acid modestly decreased the combined risk of cardiovascular complications — heart attacks, strokes, blocked arteries that needed to be reopened with stents or bypass surgery, or cardiovascular death — although it did not decrease the overall mortality rate.The trial was directed by Dr. Steven Nissen of the Cleveland Clinic and was paid for by the drug’s maker, Esperion Therapeutics, which sells it under the brand name Nexletol. It involved people who were at high risk for a heart attack or stroke who were randomly assigned to take bempedoic acid or a placebo. Their average LDL level was high: 139 milligrams per deciliter. Cardiologists generally say such patients should get their LDL below 70.The participants had to sign a statement saying: “I can’t tolerate these medications (called statins) even though I know they would reduce my risk of a heart attack or stroke or death. My doctor has explained and I am aware that many patients who are unable to tolerate a single statin medication may also be able to tolerate a different statin or dose.”Bempedoic acid reduced LDL levels by about 20 percent, not enough to get patients to the goal level. At the end of the study, the average LDL level in those taking the drug was 107, compared with 136 in the patients taking a placebo. In contrast, statins can reduce LDL levels by as much as 50 percent.After just a bit more than a year and a half, 819, or 11.7 percent, of patients in the bempedoic acid group had one of the heart-related complications.In the placebo group, 927 patients, or 13.3 percent, had such an event.Participants did not have muscle aches or an increased risk of diabetes, the most common complaints with statins. With bempedoic acid, a small percentage in the trial experienced an increased risk of gout, an inflammation of joints that is treatable and increased risk of gallstones.Now the question is, how important is this drug going to be?Bempedoic acid is the sixth cholesterol-lowering drug, in addition to statins, that has been demonstrated to reduce heart attacks and strokes, noted Dr. Michael Davidson, director of the lipid clinic at the University of Chicago Pritzker School of Medicine who founded a company, New Amsterdam Pharma, that is developing a LDL lowering drug. The others are bile acid resins, niacin, ezetimibe, PCSK9 inhibitors and CETPi. They have varying effects on LDL and range from cheap to expensive. With this array of drugs, Dr. Davidson said he hoped doctors could start focusing on getting high-risk patients’ LDL levels as low as possible, whatever it takes.Dr. Harlan Krumholz, a Yale cardiologist, said that given bempedoic acid’s modest effects and the fact that other drugs also lower LDL, it “is unlikely to be a game changer.”Dr. Benjamin Ansell, a lipid expert at U.C.L.A., said that the drug was “better than nothing” but that “it isn’t enough” for people who have high LDL levels and are at high risk.Lipid experts say that many who say they cannot tolerate statins actually can. Some mistakenly attribute muscle aches from other causes to the drug. For others, a different dose of a statin or a different statin is tolerable.But primary care doctors may not have the time or inclination to go through all this with patients, especially because they have to tread delicately with patients who are adamant that they cannot or will not take the drugs.“When you come in guns ablazing and say, ‘Take this medicine,’ it turns a lot of patients off,” Dr. Ansell said. “There’s a fear the patient will not come back.”

Some doctors say that however reasonable guidelines may seem, their cumulative burden causes “constant frustration” to medical practice.The intent is admirable: Give doctors guidelines so they can be sure to cover what needs to be discussed with patients and help select options. Let’s talk about your diet and any problems you might have sleeping. Are you getting enough exercise? If not, here is some advice. You are due for colon cancer screening. Do you prefer a colonoscopy or a fecal test? Here are the pros and cons of each.But there is a problem. There are just not enough hours in a workday to discuss and act on all the guidelines.Suppose an American doctor wanted a gold star when seeing patients and followed all of the guidelines for preventive, chronic and acute disease care issued by well-known medical groups. That could require nearly 27 hours per day, a team of doctors wrote in a study last year for the Journal of General Internal Medicine.No one could actually do that, so imagine a doctor shrugged off the chronic and acute care, as well as administrative work, and merely followed the preventive care checklist recommended by the U.S. Preventive Services Task Force, an independent panel of health experts. That would be 8.6 of the doctor’s hours each day, according to a study in the American Journal of Public Health.As anyone who has been sped through a 15-minute annual wellness visit knows, doctors cannot be so exacting. That the guidelines are so thorough yet so often glossed over prompts questions about their usefulness. At the same time, doctors’ pay often depends on checking off guideline boxes.“Is this an issue? Absolutely,” said Dr. Michael Pignone, a former member of the Preventive Services Task Force and chairman of the department of internal medicine at the University of Texas at Austin’s Dell Medical School.“Suffice it to say that what has been incentivized isn’t always what delivers the most health or benefit,” Dr. Pignone said.Guidelines have become “a constant frustration,” said Dr. Minna Johansson, a general practitioner in Uddevalla, Sweden, who also directs the Global Center for Sustainable Healthcare at the University of Gothenburg. She worked with doctors in other countries on an analysis of the issue that was published last month in BMJ. “A lot of guidelines may seem reasonable when considered in isolation,” Dr. Johansson said. “But the cumulative burden of all guideline recommendations combined is absurd.”Dr. Johansson was inspired to study the issue working in a small town on Sweden’s west coast.“I have a yearly visit with my patients,” she said. Spending that precious time discussing a lifestyle prescription that, however well meaning, is unlikely to change a patient’s habits, is of dubious value, she said. And, she added, it “crowds out more important discussions.”“Maybe the patient smokes or has suicidal thoughts,” she said.And, she added, many guidelines, like those for extensive discussions about improving exercise habits or diet, have not been shown to result in important health benefits.Dr. Johansson worked with Dr. Gordon Guyatt of McMaster University in Hamilton, Ontario, and Dr. Victor Montori of the Mayo Clinic in Rochester, Minn. They argue that this problem affects medical systems throughout North America and Western Europe.In Norway, for example, guidelines for assessing and treating high blood pressure apply to the nearly three-quarters of adults with pressures above the goal of 120/80. If the guidelines were strictly adhered to, patients would need so many regular follow-up visits that accommodating them would require more general practitioners than are currently working in Norway.And implementing all the British guidelines for improving patients’ lifestyles could require more doctors and nurses than are practicing in the entirety of Britain.The researchers say that guideline makers should consider what the study calls “the time needed to treat” — how much time it takes to implement a guideline.For example, they say, the British guideline on assessing a patient’s physical activity would take 15 percent of a doctor’s visit to implement, but there is no evidence it would improve long-term health. That, they say, might suggest the guideline should be jettisoned.Dr. Carol Mangione, chair of the U.S. Preventive Services Task Force, said the task force considered the time guidelines take. And nowhere is it suggested that doctors try to tick off each guideline recommendation in a single visit.“Clinicians do not — and would never be expected to — implement all of the suggested screenings, counseling services, and preventive medications in a single patient visit,” Dr. Mangione wrote in an email. “When caring for patients, clinicians use both their judgment and the information obtained during conversations with each patient to prioritize which preventive services should be offered during each visit.”Even that is not easy, said Dr. Daniel Jonas, director of the division of general internal medicine at Ohio State University.Guidelines can serve a purpose, Dr. Jonas said. “I think they’re incredibly helpful,” he added. But, he said, “deciding what to prioritize in a busy primary care practice is a big challenge.”Dr. Montori added another complication.“To assume that patients and clinicians can sort and prioritize recommendations over multiple visits,” he said, “wishes away the fundamental problem that many patients cannot get primary care, see the same clinician or have unhurried consultations.”Dr. Pignone said that some of the burden should be shared with other professionals, like nutritionists, who can talk to patients about healthy diets. But, he said, that is only a partial solution. He’d like to see current recommendations prioritized by their impact on health and on their cost effectiveness. As examples, he said, childhood immunizations would rank high but existing guidelines to give tetanus boosters to adults who already had tetanus shots would rank lower.Dr. Guyatt said guidelines should be held to the same standard as new drugs. Before they are implemented, there should be evidence that they are helpful.“Somebody might say, ‘Oh, a new drug has side effects but what harm is there in this guideline?’” he said. “But yes, there is real harm. There is a trade-off between doing things that are actually useful and spending time on things that are useless.”

Growing research has shown that intensive interventions are needed, scientists say. Here is why their advice is changing.The American Academy of Pediatrics recently issued new guidelines for treating the more than 14 million children and adolescents with obesity in the United States. The recommendations came as a surprise to many parents, and to some experts, as they encourage vigorous behavioral interventions even for very young children, as well as drug treatment or surgery for adolescents.The guidelines spring from a scientific understanding of obesity that has been evolving for decades. Obesity is a risk factor for a number of disorders, including Type 2 diabetes, high blood pressure, joint and back pain, and several cancers. Treating the problem as early as possible may help prevent a lot of misery.Here are answers to some questions about pediatric obesity research and why experts are now advising aggressive treatment.What do the new guidelines say about the causes of obesity?The A.A.P. recommendations stress that obesity is not just a consequence of poor eating habits and a lack of exercise. Obesity is a chronic disease with many intertwined causes, including genetics.Researchers now know that obesity is one of the most strongly inherited traits. Studies conducted decades ago showed that identical twins reared apart usually grow up to have similar body shapes and weights. Adopted children tend to have the same shapes and weights as their biological parents.A genetic predisposition sets the stage for some children to gain weight in an environment in which food — often poor-quality food — is everywhere. And weight gain can become a vicious cycle.Children and adolescents with obesity often experience teasing and bullying, which, the A.A.P. committee wrote, contribute to “binge eating, social isolation, avoidance of health care services and decreased physical activity, further complicating the health trajectory.”How do scientists define overweight and obesity?They are defined by body mass index, a measure of weight and height. (It is an imperfect measure; many muscular athletes, for example, have high B.M.I.s but are in excellent shape.)Overweight means a B.M.I. at or above the 85th percentile but below the 95th percentile for children and teenagers of the same age and sex. Obesity is a B.M.I. at or above the 95th percentile for children and teenagers of the same age and sex. (The Centers for Disease Control and Prevention offers B.M.I. growth charts here.)When did pediatric obesity become such a problem?For scientists, the alarms went off in the 1980s and 1990s. Before then, experts took comfort in data from the 1960s indicating that just 5 percent of children and adolescents had obesity. It just did not seem like a pressing issue.But national data in the 1980s showed that the rate had doubled. By 2000, it had tripled, and by 2018, quadrupled. As the epidemic began, expert opinions about why it was happening circulated widely, often citing favorite villains like Big Food, too little exercise or a lack of fresh fruits and vegetables. But rigorous evidence was scarce and solutions evasive.Didn’t anyone try to do intervention studies?Yes, but results were disappointing. In the 1990s, for example, the National Institutes of Health sponsored two large, rigorous studies. The researchers asked whether weight gain in children could be prevented by intervening in schools by expanding physical education, offering more nutritious cafeteria meals, teaching students about proper eating habits and the need to exercise, and involving parents.One study, an eight-year, $20 million project sponsored by the National Heart, Lung and Blood Institute, followed 1,704 third graders in 41 elementary schools in the Southwest. Students there were mostly Native Americans, a group at high risk for obesity.The schools were divided into two groups. Some schools got intensive intervention, while others were left alone. Researchers determined, beginning in fifth grade, whether the children in the intervention schools were weighing less than those in the other schools.Sadly, they were not, although the students were deeply familiar with the importance of activity and proper nutrition. The children who got intensive treatment also ate less fat, going from 34 percent to 27 percent in the total diet.“It was not enough to change body weight,” said Benjamin Caballero of the Johns Hopkins Bloomberg School of Public Health, the study’s principal investigator.Dr. Fatima Cody Stanford, an obesity medicine specialist at Harvard, recalled her own experiences in the 1980s. Children with obesity were sent to a “healthy lifestyle” clinic where they were told to eat healthier food and to exercise more. Often, it did not help.She recalled a 15-year-old boy who weighed more than 300 pounds. “Maybe he should switch to skim milk, maybe increase his vegetables,” she told his parents. “Oh, he’s working out for half an hour every day? Let’s increase it to an hour.”That, she said, is how she was taught, and looking back “it breaks my heart.” Dr. Stanford now believes that the advice set up obese children for failure. (She has consulted for companies investigating weight loss drugs.)In a departure from past advice, the American Academy of Pediatrics recommends that children 12 and older with obesity should be offered treatment with approved drugs like Wegovy.Novo Nordisk, via Associated PressWhat do the guidelines say should be done now?It’s not that lifestyle interventions cannot work for some. The A.A.P. says that children and adolescents with overweight and obesity should be offered “intensive behavioral and lifestyle treatment,” which is the most effective intervention short of medications and surgery.The most effective programs involve at least 26 hours of in-person treatment over three to 12 months and include the family. The treatment focuses on nutrition, physical activity and behavior change. The expected result? A decline of one to three points in B.M.I.But intensive programs are not always available, and insurers often do not pay for them. The A.A.P. advises that doctors instead should “provide the most intensive program possible,” referring families to additional programs to help with food insecurity and to community recreation programs.The underlying message is one of urgency. In a significant departure from past advice, for example, the A.A.P. recommends that children 12 and older with obesity should be offered treatment with any of the few approved drugs, including newer ones like Wegovy (a brand name for semaglutide) that elicit significant weight loss by suppressing the appetite.Those 13 and older with severe obesity should be offered bariatric surgery, the academy says. These are drastic (and expensive) interventions for doctors and parents to contemplate, but the authors of the recommendations note that obesity rarely ends without a concerted effort.Are researchers focusing too much on weight loss?Although it generally raises the risks of other health problems, many people with obesity remain healthy. Weight loss is not the only route to good health, and one of the perpetual risks of intensive medical intervention is that a child with obesity may come to feel stigmatized.The conundrum here is that researchers say these children usually are already feeling stigmatized. They are frequently socially isolated, anxious and depressed, and far too often they are made to feel that they are failures who lack the willpower to control their weight. Doing nothing may deepen their isolation, not lessen it.Will the new recommendations make a difference?If they are “fully implemented and supported,” the guidelines may lower obesity rates in children, said Dr. Stephen Cook, an obesity specialist at the University of Rochester. But there are no guarantees.Insurers and the Food and Drug Administration treat obesity differently from other chronic diseases. People with obesity may need drug treatment for a lifetime, for example. But insurers have insisted on paying only for short-term treatments, like six months’ or a year’s worth of medications — if they pay at all.“If there continues to be no payment for treatment services, health systems will not put resources to delivering this care,” Dr. Cook said. “There will be none to minimal training in medical and professional schools for the next generation of health care providers to address this issue.”It takes years for doctors to start using new guidelines, noted Dr. Louis Aronne, an obesity medicine specialist at Weill Cornell Medicine in New York. “The ones for adult obesity have never really been adhered to,” he noted. Adults with obesity are already advised to get surgery or drug treatment, but just 2 percent ever do. (Dr. Aronne has consulted for companies looking into weight-loss drugs.)Researchers hope that at the very least the A.A.P. guidelines will help doctors understand that obesity is a chronic disease that afflicts children and adolescents, and that the old strategy — a kind of watchful waiting, or delayed treatment — won’t help.The new recommendations may also prod insurers, including Medicaid, to start paying for intensive lifestyle treatment and for medications that these children need.

The trauma care of the Buffalo Bills player highlighted what is done to overcome cardiac arrest, a leading cause of death in the United States.CINCINNATI — Damar Hamlin, the Buffalo Bills player whose heart stopped during a game in Cincinnati on Jan. 2, should not have survived, if statistics on cardiac arrests are any guide.Mr. Hamlin “was dead,” when he fell to the ground, said Dr. Timothy A. Pritts, chief of the section of general surgery at the University of Cincinnati Medical Center, where Mr. Hamlin was treated.But the 24-year-old safety left the hospital a week after his cardiac arrest with no apparent neurological deficits. He beat the odds after a stunning incident that traumatized his loved ones, teammates, opponents and tens of millions of Monday Night Football viewers. A visit to the hospital and the doctors, nurses and other medical staff who helped bring him back to life highlighted the mix of good preparation and good fortune that allowed Mr. Hamlin to escape a leading cause of death in the United States.Cardiac arrest, when the heart stops, is distinct from a heart attack, which occurs when blood flow in an artery feeding the heart is blocked. Outside of a hospital, more than 300,000 people a year have a cardiac arrest, also known as sudden cardiac death. The survival rate for those who have cardiac arrests outside of hospitals and, like Mr. Hamlin, have bystander cardiopulmonary resuscitation, is just 11.2 percent. For the few like Mr. Hamlin who receive immediate defibrillation, survival rises to 41 percent.Mr. Hamlin’s doctors said they were unable to discuss many of the particulars of his case, but they were able to describe the procedures they use to treat patients like him.Minutes count.“A few extra minutes or even a few extra seconds and it could have been a different outcome,” said Dr. William Knight IV, an emergency medicine and trauma specialist at the medical center.Brain damage is likely if the person in cardiac arrest goes 4 to 6 minutes without CPR, and brain death occurs after 10 minutes. Only 8 percent of cardiac arrest survivors emerge with a good neurological outcome. Most, according to Monica Sales, a spokeswoman for the American Heart Association, “have some degree of brain injury.”Damar Hamlin of the Buffalo Bills “was dead” when he fell to the ground after a hit during a game on Jan 2.Greg M. Cooper/Associated PressMr. Hamlin’s treatment began on the field at Paycor Stadium.Joshua A. Bickel/Associated PressImmediate CPR and defibrillation by medical personnel at the football game who responded rapidly is “absolutely certainly” what saved Mr. Hamlin’s life and his brain, said Dr. Benjamin Levine, professor of medicine and cardiology at the University of Texas Southwestern Medical Center and Texas Health Dallas.Dr. Levine and Dr. Jeremy Cannon, a trauma and critical care specialist at the University of Pennsylvania, emphasized the paramount importance of rapid response to cardiac arrest. Medical research to improve outcomes for cardiac arrest patients now focuses on ways to teach the public that CPR and use of a defibrillator are easy and can be learned in minutes and that many 911 operators can walk them through the procedures. The idea is to empower people to save lives.Damar Hamlin’s CollapseThe Buffalo Bills safety went into cardiac arrest during an N.F.L. game in Cincinnati on Jan. 2. He was released from the hospital on Jan. 11.Injury and Reaction: The life-threatening injury to Damar Hamlin, which was televised on “Monday Night Football,” resonated around the league and the world of sports.His Recovery: Hamlin, who returned home nine days after his collapse, appears to be on a good path for neurological recovery, though doctors said it was too early to know how far he is from returning to normal life.In His Hometown: As the news about Hamlin became more hopeful, anguish turned to “happy tears” in the tight-knit Pennsylvania borough where he grew up.Emergency Response: When Hamlin’s heart stopped, medical personnel could be heard making clear the severity of his condition and the efforts to keep him alive. Listen to the audio.CPR has changed as well. Now, it is “hands only”— no more mouth-to-mouth.“Mission critical No. 1 is blood flow to the brain,” said Dr. Charles J. Prestigiacomo, a neurosurgeon at the University of Cincinnati. The brain is the neediest organ, requiring 15 to 20 percent of the body’s blood.People are now taught to press hard on the chest 100 times a minute — singing “Staying Alive,” by The Bee Gees will give the right rhythm.But research on how to improve the odds for cardiac arrest patients has languished, according to Dr. Benjamin Abella, a resuscitation expert and emergency physician at the University of Pennsylvania. Impediments include little national data reporting, a paucity of funding and a lack of accountability for hospitals’ outcomes for said patients.Mr. Hamlin’s treatment began on the field at Paycor Stadium, where the game was being played.The National Football League and its teams contract with Level 1 trauma centers — medical centers that can provide the most comprehensive care — near every stadium where they play. The University of Cincinnati Medical Center sends seven physicians to every Bengals home game. The center also sends paramedics, respiratory therapists and an ambulance crew.The University of Cincinnati’s trauma center sends several medical personnel to every Bengals home game: concussion watchers, emergency doctors, paramedics, respiratory therapists and an ambulance crew.Maddie McGarvey for The New York TimesA trauma room at the University of Cincinnati Medical Center emergency departmentMaddie McGarvey for The New York TimesAs soon as Mr. Hamlin fell to the ground on Jan. 2, that medical team rushed to the field, communicating by radio because the stadium was so loud it was impossible to hear one another speak. The air “was vibrating” with sound, said Dr. Brett Kissela, a neurologist at the medical center who was at the game.And thus it began — an elaborate process of treating a trauma patient that requires “teams of teams,” Dr. Pritts said. In the first few hours, a severe trauma patient like Mr. Hamlin is physically touched by as many as 50 people. By the end of the first 24 hours, that number swells to 100 people.The medical center, founded in 1823, works with the U.S. Air Force to train military trauma physicians and medical teams. Its emergency department treats around 4,800 trauma patients a year.Those who were at the ready when Mr. Hamlin came in are doctors, nurses and other medical professionals who have seen the worst of the worst. Every patient who arrives in the surgical trauma intensive care unit — where Mr. Hamlin was treated — “is having the worst day of their life,” Dr. Pritts said.The staff members are deeply affected by their work with trauma patients.“When I go home, I need down time. I sit by myself for 15 minutes to decompress,” said Michele Hodge, a nurse who manages the medical center’s emergency department.Hospital employees are quick to credit Mr. Hamlin’s recovery to his youth and health. But they also attribute their intricately choreographed care and experience to having an average of five cardiac arrest patients each week.Ashleigh Schmeltzer, a CT scanner technologist, said she is reminded of the crews at the Indianapolis 500 that swarm to a car needing attention.In the emergency room, “everyone has a job and a role,” she said.“When I go home I need down time. I sit by myself for 15 minutes to decompress,” said Michele Hodge, a nurse who manages the emergency department.Maddie McGarvey for The New York TimesAshleigh Schmeltzer, a C.T. scanner technologist, said she is reminded of Indianapolis 500 crews that swarm to a car needing attention. “Everyone has a job and a role,” she said.Maddie McGarvey for The New York TimesThe first team that responds to a case like Mr. Hamlin’s includes a “doc head,” who is an airway specialist and stands at the patient’s head, and a “doc foot,” the team leader, who stands at the patient’s feet. A respiratory therapist stands at one side of the patient’s head, and a supervising airway doctor stands at the other. Two nurses and two other doctors stand on either side of the patient, while a scribe stands to the side and writes everything down. Two additional doctors stand to the side of the stretcher.Within minutes, the team wheels the patient to an adjacent room for a rapid whole body CT scan by staff members like Ms. Schmeltzer.A CT scan is so fast — taking minutes — and so accurate “it’s like eyes looking into the body,” said Dr. Mary Mahoney, professor of radiology at the medical centerA scan can’t give doctors every bit of information they want but, Dr. Mahoney said, it is invaluable to the trauma team. “It can point you in the right direction.” It can show areas that where fluid is accumulating and can show, for example, if blood is pooling in the sac around the heart.Although Mr. Hamlin’s heart was beating again by the time he reached the emergency room, he had a common complication of a cardiac arrest known as acute respiratory distress syndrome, or A.R.D.S.Because of A.R.D.S., Mr. Hamlin needed to spend most of his time lying face down. When a patient has A.R.D.S., it typically means fluid has seeped out of the blood vessels and accumulated in lung tissue. Doctors have learned that patients with A.R.D.S. are more likely to get the oxygen they need and survive if they lay face down for about 16 hours each day and on their backs for the other 8 hours. The prone position, said Dr. Amy Makley, the medical director of trauma, shifts the fluid in the lungs.“We prone patients as long as they need it,” Dr. Makley said, which meant, in Mr. Hamlin’s case, from the time he arrived in the intensive care unit until the time his doctors were able to wean him from a ventilator five days later.During that time, cooling pads were placed on Mr. Hamlin’s chest and thighs to chill his body. The doctors’ hope was that lowering body temperature to about 92.3 degrees would help to protect the brain because chemical reactions that can damage injured cells slow down as body temperature falls. But patients’ bodies try to shiver, which raises the temperature, so they must be sedated or given paralytic agents.Mr. Hamlin was already sedated to allow him to tolerate a ventilator. He was kept chilled until his ventilator was removed.A hallway of the emergency department.Maddie McGarvey for The New York TimesFor the first few days in the unit, Mr. Hamlin’s doctors worried about whether he would recover at all and, if so, to what extent.But on Jan. 4, they said in a news conference at the hospital, Mr. Hamlin had begun to improve. He was awake enough to communicate by nodding and shaking his head. To the medical staff’s delight, he even wrote, “did we win?” on a pad provided by a bedside nurse.Finally, a week after his cardiac arrest, hospital staff secreted him out of the medical center to fly back to Buffalo. Dr. Knight accompanied him to the Cincinnati airport.It still is not known why Mr. Hamlin had a cardiac arrest. A likely explanation was a rare event, commotio cordis, in which a blow to the chest — in his case, from a tackle — at exactly the right 20-millisecond interval in the heart’s cycle can make the heart stop. But Mr. Hamlin’s doctors still need to eliminate other possible causes for his injury, like a heart defect. Sometimes, they never find a cause.The staff at the medical center insists that all patients are treated the same — from the 30 percent who are uninsured to the wealthy donors to celebrities.Of course, though, Mr. Hamlin was different.“We’ve taken care of his illness before, but what do you do when you have to drive past 20 interview trucks?” asked Dr. Stewart Wright, the hospital’s chief medical officer.Flowers and cards for Mr. Hamlin arrived by the truckload, and donated meals were constantly being delivered. Fans attached posters to a chain-link fence outside, flew balloons and held candlelight vigils.There were so many callers that the medical center had to hire additional operators, but the hospital would not even confirm to callers that he was a patient.Now, the crowds and the attention are gone. The hospital is back to normal, and its staff is breathing sighs of relief for Mr. Hamlin. Back in Buffalo, he faces what could be weeks to months of recuperation.“This is the beginning of the next stage of his recovery,” Dr. Knight said.He added that he was starting his own recovery from Mr. Hamlin’s episode.“I’m exhausted,” he said.“That was the longest week in my professional career.”

Helping someone in cardiac arrest is not as daunting as it seems.Before 1958, there was no such thing as CPR. If someone’s heart stopped because of cardiac arrest, that person fell to the ground, with no pulse, no breathing. And they were simply declared dead.All of that changed when doctors at Johns Hopkins Hospital in Baltimore discovered cardiopulmonary resuscitation by accident when studying how to shock a heart. When they pressed defibrillator panels to the chest of a lab dog, they saw a blip in blood pressure. They pressed harder and discovered they could push blood through the body. And thus was born CPR.The problem is that only a tiny fraction of people who have a cardiac arrest and are not at a hospital get CPR. That, said Dr. Benjamin Abella, medical director of the Center for Resuscitation Science at the University of Pennsylvania, is “a national tragedy.” Bystander CPR can be the difference between life and death, as the case of Damar Hamlin demonstrated during a Buffalo Bills-Cincinnati Bengals football game earlier this month.CPR is not as daunting as it seems; it can be learned in minutes. At the University of Cincinnati Medical Center, where Mr. Hamlin was treated, Dr. Jason McMullan, an emergency medicine physician, has taught CPR to everyone from Cub Scouts to people in nursing homes.Here is what you need to know about what it is and how to do it.What is a cardiac arrest and how do you know if someone is having one?A cardiac arrest, also known as sudden cardiac death, occurs when the heart suddenly stops beating.The person collapses to the ground and is unconscious, appears lifeless, has no pulse and is not breathing. There can be many causes.Why do you need to do CPR? Why not just call 911?“You should call 911 but it can take several minutes or more for the ambulance to arrive,” said Dr. Sumeet Chugh, director of the Center for Cardiac Arrest Prevention at Cedars-Sinai in Los Angeles. “In the meantime, with every minute that goes by the chances for a successful revival decrease by ten percent.”How do you perform CPR?It used to be more complicated — you had to alternately press on the person’s chest and give mouth-to-mouth resuscitation. But about a decade ago, medical experts realized that mouth-to-mouth was not making things better, was difficult for the public to do and was a disincentive for people to learn CPR.“Kissing dead people is gross,” Dr. McMullan said.Research studies suggested that survival is the same with or without mouth-to-mouth. Most people whose hearts stop have enough oxygen in their blood to survive if blood can be pumped through their bodies and, especially, to their brain.Now CPR is “hands only.” Aim for the center of the chest over the breastbone, or sternum.“Join your hands together and push hard and fast on the chest 100-120 times a minute to the beat of the song “Staying Alive,” by the Bee Gees, Dr. Chugh said.There are videos showing how to do it.And, Dr. McMullan said, even if you don’t push hard enough or fast enough, “any CPR is better than no CPR.”It is possible — though unusual — to break the person’s ribs. But when that happens it is “very unlikely to have any clinical consequences,” Dr. Abella said. “Being tentative about ribs can mean worse CPR and worse survival,” he added.You need to push fast to stimulate the heart.Justin Sullivan/Getty ImagesWhy do you have to push so fast in CPR?“You want to maximize the output from the heart,” Dr. Abella said. “CPR is not very efficient in moving blood. The heart is a better pump, so to make up for that you go faster. You can’t hurt someone. They are already dead.”How long do I keep doing CPR?You should keep it up until an ambulance arrives or until another rescuer can take over for you.What about using a defibrillator?An automated external defibrillator, or A.E.D., shocks the heart and resets it. When you open the glass box that holds an A.E.D., the device should speak to you, telling you to place two pads on the person’s body according to a diagram. It analyzes the heart’s rhythm and, if a shock is appropriate, tells you to stand back, press a button and shock the heart.“For the cardiac arrests that are shockable it is almost miraculous,” Dr. Abella said. “I have seen patients in cardiac arrest who, by the time they are in the emergency room, wake up and wonder why they are there.”But defibrillators have to be applied quickly, and so it is important to have more than one rescuer — one to do CPR while the other gets the defibrillator.“If you are doing CPR you should shout and shout for help,” Dr. Abella said. “If you are alone you should run and get an A.E.D.”Finding a defibrillator is not always easy. Airports often show their locations on terminal maps.“The problem is, if you are not in an airport, what do you do?” Dr. Abella said. “For example, I am in a parking structure in the hospital. I don’t know where the nearest A.E.D. is and I am a doctor in a hospital. I have no idea.”If you spend a lot of time in a public place, it could pay off to learn the location of the nearest A.E.D.What if you forget all of this when someone collapses?Many cities have dispatch-assisted CPR. When you call 911, the operator will walk you through the steps.What if I do it wrong? Can I get sued?“If they are unresponsive and there is no breathing or pulse beat, they are going to die without CPR and it is highly unlikely that you will make the situation worse,” Dr. Cheung said. There are good Samaritan laws in all 50 states that protect bystanders, he added. And the federal Cardiac Arrest Survival Act, signed into law in 2000, provided civil immunity for users of A.E.D.s. When someone is unresponsive, consent to CPR is implied.“There has never been a successful lawsuit against someone who has provided CPR with the intent of saving an individual’s life,” Dr. Cheung said.