According to the latest study electrical impulses taking a few split seconds longer to traverse lower heart chambers might cause sudden cardiac death (SCD) among men.
Researchers defined SCD as death within an hour after symptoms start or change abruptly, or within 24 hours if there is no other non-cardiac cause of sudden death.
An electrocardiogram (ECG) measures electrical impulses, or waves, that travel through the heart and cause it to pump blood through its four chambers, the journal Circulation reports.
The waves have distinct patterns and are labelled on the ECG printout alphabetically from P to T. The electrical waves travelling through the lower chambers (ventricles) are shown on the ECG as the "QRS complex".
"Our results suggest that prolonged QRS duration is a potentially important predictor of sudden cardiac death. It will be clinically important to find even more specific risk markers for sudden cardiac path in the general population," said Sudhir Kurl, who led the study as research physician at the University of Eastern Finland, Kuopio, according to a Eastern Finland release.
However, they say there is not an easy, inexpensive way to screen a lot of people for risk factors that could predict SCD. "An essential part of our study is to bring the results to healthcare professionals - including those in preventive medicine-to make them aware that the simple, cheap and widely available ECG may have practical use in SCD risk stratification," Kurl said.
Researchers recruited 2,049 Finnish men, aged 42 to 60 years, between March 1984 and December 1989 and tracked them for 19 years. They evaluated their ECG records, heart risk factors, heart disease they developed during the study, whether they died, and the cause of death. They then divided the men into five groups according to their QRS durations. Among the men, 156 died from SCD.
"Our study shows that QRS duration is one of the strongest risk factors for sudden cardiac death, although left ventricular function was taken into account," Kurl said. "We believe resting ECG should be used to help assess the risk of sudden cardiac death in particular patients."
People most likely to benefit from such testing include those with known cardiovascular disease, cardiovascular risk symptoms, and those who are inactive and plan to begin exercising, researchers said.