March Madness is behind us, but the threat of a young athlete's heart stopping is a year-round risk.

The shock of youthful, seemingly healthy athletes collapsing and dying from sudden cardiac arrest naturally makes athletic trainers, coaches, sports physicians and parents want to do all they can to prevent it.

Yet heart specialists and advocates are divided over just what the best prevention might be.

Some sports medicine specialists and the advocacy group Parent Heart Watch are urging that all young athletes going into the heavy training of high school or even junior high school competitive sports undergo cardiac screening as part of a pre-participation physical. They argue that testing should include an electrocardiogram and/or an echocardiogram before the athlete is cleared to play.

But an evaluation of a mandatory screening program for Israeli athletes, published last month, suggests such testing might be of limited value. Dr. Sami Viskin of Tel Aviv University examined 24 documented cases of sudden cardiac deaths among competitive athletes in Israel between 1985 and 2009. He found that 11 of the cases occurred before 1997, when mandatory testing of all competitive athletes was required by law, and 13 happened after the screening started.

Viskin's report was published in the March 15 issue of the Journal of the American College of Cardiology.

Viskin said an abnormal EKG might be seen in 10 percent of athletes being screened, requiring further costly and time-consuming testing. Based on the numbers in his review, he said, "over 30,000 athletes would have to be tested to save one life." It is estimated that 10 million to 12 million American teens and young adults take part in competitive sports.

There is also considerable disagreement about the actual toll from sudden cardiac death. The conventional estimate has been that about 1 in 300,000 young athletes is at risk. The Parent Heart Watch group says the rate may be much higher because many deaths are not widely reported and there is no national registry.

Another study, published April 4 in Circulation, a journal of the American Heart Association, looked at all NCAA athletes and found that the rate of sudden cardiac arrest among them is 1 in 44,000 a year, about seven times greater than the common estimated rate. Researchers led by Dr. Kimberly Harmon of the University of Washington examined 273 deaths from all causes among collegiate athletes.

They found that of 80 deaths from medical causes, 56 percent, or 45 deaths, were heart-related. Of 36 deaths that took place during or right after exertion, 75 percent were related to cardiac causes.

The risk for male athletes was more than three times greater than among females, and basketball had the highest risk among sports, followed by swimming. The risk of sudden cardiac death among the elite ranks of Division 1 male basketball players was one in 3,000.

Harmon, a team physician at Washington, said the findings put the screening debate in a new light. "The question is, where do you set the risk cutoff -- one in 10,000, or 40,000 or 100,000?"

Officially, a heart association task force on sports screening has not endorsed blanket testing, but instead urged a thorough physical, including a detailed personal and family medical history that may suggest a need for further tests.

Dr. Mark Russell, a pediatric cardiologist at the University of Michigan's C.S. Mott Children's Hospital, said no one screening test is able to detect the "several different heart conditions that can cause sudden death in a young athlete." EKGs may catch some defects, the echo others, while other problems may only be revealed in an exercise stress test.

Russell said some conditions, such as dilated cardiomyopathy -- an enlarged and weakened heart and the cause of death of Fennville, Mich., junior Wes Leonard, who collapsed after sinking a game-winning basket in early March -- may actually develop over time and might not be detected by a single screening done months or even years earlier.

Russell and other experts uniformly agree that, screening aside, the best ways to increase the odds of surviving cardiac arrest are to store automated external defibrillators around sports venues and to have athletic trainers on hand, along with coaches and other school personnel trained in using the devices and performing CPR.