August 8, 2011 - By Tracie White
In an effort to improve the accuracy of interpreting the electrocardiogram results of the extremely fit, researchers from the Stanford University School of Medicine have prepared a how-to guide for doctors who may be screening young athletes for heart defects.
The new recommendations, published Aug. 9 in Circulation, are based on the consensus of experts from five countries with the aim of helping to reduce the high percentage of false positives in heart screenings for athletes that lead to unnecessary follow-up tests and emotional trauma. Athletes’ electrocardiograms — which measure the electrical activity of the heart by attaching electrodes to the chest — have proven notoriously difficult to interpret. A recent Stanford study found that even highly trained pediatric cardiologists are prone to misinterpreting these results.
The reason for this, researchers say, is that athletes’ ECGs are often dramatically different from those of people with more sedentary lifestyles and don’t follow the same set of rules of interpretation. What may be interpreted as a heart attack in your average couch potato may be a perfectly normal ECG in an athlete.
“Currently there are no clear-cut guidelines for reading ECGs for athletes,” said Vic Froelicher, MD, a Stanford professor of cardiovascular medicine and one of two senior authors of the paper. He has been interpreting the ECG results of athletes going back 20 years in his work with astronauts and military pilots. “This recommendation paper we’ve put together reflects years of experience and helps to provide a consensus among experts worldwide.”
“Although physicians understand that athletes have ECGs that are different, this has never really been formalized in a detailed way,” said co-senior author Euan Ashley, MD, PhD. “So it’s hardly surprising that without good guidelines, you can get inaccurate readings.”
The recommendations are also designed to help practitioners determine what follow-up tests they need to do when they determine an ECG reading is abnormal, Ashley said.
An ongoing debate over how best to screen young athletes for heart defects that could lead to sudden death has heated up in recent years.
Some European countries require that athletes undergo heart exams via ECG before they participate in sports. The American Heart Association recommends against mandatory ECG testing, citing high costs, frequent false positives and the low rate of sudden cardiac death among young athletes — an estimated 76 per year. But these numbers are based primarily on newspaper reports and could be significantly higher, according to a recent study in Circulation by Jonathan Drezner, MD, at the University of Washington, also a co-author of this paper, whose previous study found surprisingly high rates among collegiate basketball players.
Currently, using ECGs for routine screening to uncover such diseases as hypertrophic cardiomyopathy or long QT syndrome is required for many professional athletes in the United States but not for those in college or high school.
Stanford University started voluntary ECG screening for its athletes in 2007, in part, inspired by research out of Italy that showed mandatory testing of all Italian athletes significantly reduced sudden death during competition. Experience gathered over the four years of the Italian program contributed to the new Stanford paper.
Recently, the European Society of Cardiology, an international group of experts, published recommendations for interpreting the ECGs of athletes, which were found to reduce the number of false positives.
The Stanford authors applied this new reclassification scheme to a study of Stanford collegiate athletes. Among 658 athletes tested for heart defects, 63 were found to have abnormal ECG patterns that required further testing. But when those 63 “abnormal” ECGs were evaluated using the new European criteria, only 29 (or 4 percent) remained in that abnormal category. The new criteria improved accuracy to 95 percent.
“We wanted to take the European guidelines one step further,” said Abhimanyu (Manu) Uberoi, MD, first author of the paper and a Stanford internal medicine resident. “We wanted to be able to provide more detail for physicians. When health-care providers see these readings in clinic, they have trouble interpreting them because they just don’t know how to. What is normal, what is abnormal, what needs further workup? We wanted to make it easier to make these distinctions. That was our whole goal.”
The paper provides a chart with straightforward guidelines designed to unify physician interpretations when searching for signs of possible heart defects.
“We provided more detailed criteria with explicit number cutoffs and descriptors for how an untrained evaluator could analyze the ECG tracing,” said Uberoi. “We did our best to accrue the most universally accepted definitions and pieced them together in a way that our expert panel agreed with. Within the group there was a collective experience of hundreds of years.”
Experts in cardiology from Italy, South America, Argentina, Brazil and Austria contributed to the paper and are listed as authors. Other Stanford authors include cardiovascular medicine fellows James Freeman, MD, Matthew Wheeler, MD, PhD, Frederick Dewey, MD; and Marco Perez, MD, clinical instructor in medicine.
There was no external funding for the study. Information about Stanford’s Department of Medicine, which supported the work, is available at http://medicine.stanford.edu.
Stanford Medicine integrates research, medical education and health care at its three institutions - Stanford University School of Medicine, Stanford Health Care (formerly Stanford Hospital & Clinics), and Lucile Packard Children's Hospital Stanford. For more information, please visit the Office of Communication & Public Affairs site at http://mednews.stanford.edu.