Quick on-the-field emergency care from well-rehearsed medical personnel is widely credited with helping save Damar Hamlin�s life. But whether his cardiac arrest could have been prevented is much less certain.

Doctors say they�re still evaluating what caused Hamlin�s heart to stop after a tackle during Monday night�s game in Cincinnati. One possibility � a fluke type of chest trauma called commotio cordis � is impossible to predict or prevent.

Existing heart conditions are the most common cause of sudden cardiac arrest in young athletes. Some of them can be detected through tests including EKGs, which measure the heart�s electrical activity, and echocardiograms, ultrasound imaging exams that show how the heart muscle and valves are working.

These tests can�t detect all heart conditions and sometimes overlook ones that can be deadly. They are routine in professional sports and used by about half of NCAA programs, said Dr. Andrew Peterson, a team physician for the University of Iowa.

The American Heart Association and American Academy of Pediatrics don�t recommend them for routine use in high school and youth sports because false-positive results would exclude too many athletes, Peterson said.

Routine physical exams should include questions about family history of heart disease and worrisome symptoms including fainting episodes, rapid heart rate and chest pain during activity, said Dr. Mariell Jessup, the heart association�s chief medical officer. Cardiac tests would be warranted to investigate those symptoms, she said.

�It�s possible for somebody to get all the way to adulthood and not have their diagnosis made,� she noted. �That particularly happens in populations that are under-resourced or don�t have the ability to see a physician on a regular basis.�

Hamlin�s health history has not been made public. The 24-year-old Buffalo Bills safety remains hospitalized, but doctors say he�s making remarkable progress, talking and breathing on his own.

Jessup said Hamlin �was extraordinarily lucky that there were people around who knew CPR� and that it was started right away.

He also benefited from the NFL�s routine emergency medical drills held at stadiums before each game.

�The meeting is an essential checkpoint to ensure officials, team medical staff and gameday medical personnel are aware of all in-game player health and safety procedures and resources,� according to online NFL player health and safety information.

Sudden cardiac arrest is among the things for which they try to prepare. It is the leading medical cause of death in young athletes, though it is rare, with an estimated 1 sudden cardiac death in 50,000 to 80,000 young athletes each year.

A rare cause of these deaths is commotio cordis, which occurs when someone receives a sharp blow to the chest in a certain spot during a specific time of the heart�s rhythm cycle. The trauma causes the heart to quiver and stop pumping blood efficiently. It used to be nearly always fatal but awareness has improved survival to about 60%, said Dr. Mark Link of UT Southwestern Medical Center in Texas.

One of the most common heart conditions involved in athlete cardiac arrests can often be detected in echocardiograms. Hypertrophic cardiomyopathy is a genetic condition that can cause part of the heart muscle to thicken, making it harder for the heart to pump blood. Affected people don�t always have symptoms and often go undiagnosed.

Former Baylor basketball player King McClure had no idea he was affected until he had a EKG and echocardiogram at the start of his freshman year in 2015.

The diagnosis was devastating: Doctors said he could die if he continued playing. One physician offered an option � an implanted defibrillator that shocks the heart to restore normal heartbeats.

The implanted device �has never activated, by the grace of God,� said McClure, now 26 and an ESPN analyst.

McClure said he saw Hamlin�s collapse and thought, �that could have been me. When you see things like that that hit so close to home, it kind of scares you,� he said. �I�m just thankful that Hamlin is OK and that he�s still here.�

Julie West, of La Porte, Indiana, became an advocate for routine heart testing in schools, more widespread use of automated external defibrillators and routine cardiac emergency drills after her 17-year-old son, Jake, died of sudden cardiac arrest during football practice in 2013.

�For Jake, no one really knew what to do right away,� she said. �The AED was in the coach�s office. The coaches stepped in and did CPR,� but it was too late.

AED awareness has increased since then, and AED procedures are emphasized at almost all level of sport, even high schools.

�It is part of our CPR renewal course,� said Eric McCauliffe, the girls varsity basketball coach at Indian Lake-Long Lake in upstate New York. �We absolutely run through it and quiz coaches on the locations of AEDs at each school as well.�

An autopsy revealed Jake had a rare hereditary heart condition that didn�t cause symptoms and wasn�t picked up during routine physical exams. His sister later had testing that revealed she has the same condition and she now wears an implanted defibrillator.

West was a teacher when Jake died and says she was trained for active shooters and fires, but not cardiac arrests.

�If they don�t have a cardiac response plan, they�re not prepared,� she said.

She formed a foundation that organizes EKG and echocardiogram screenings at Indiana schools.

West knows the tests aren�t perfect, but for her, saving one life is worth it.

(AP)