Abnormal electrocardiograms linked to heart enlargement

When a segment of a patient’s electrocardiogram known as QRS is unusually long, the patient may also be more likely to have an enlarged left ventricle, even when there are no signs of heart failure or previous heart attack, according to a new study(PDF) in the March 1, 2005 issue of the Journal of the American College of Cardiology.

“Earlier studies demonstrated an association of QRS duration and heart chamber dimensions in patients with heart failure,” said Ramachandran S. Vasan, MD, with the Framingham Heart Study and Boston University School of Medicine in Massachusetts. “We conducted our study on a large number of individuals free of heart failure and myocardial infarction. In other words, we hypothesized that QRS duration may be a marker of cardiac chamber size even in people free of congestive heart failure,” Dr. Vasan said. . “Our data raise the possibility that increased QRS duration may be a marker of greater cardiac size.”

The researchers, including lead author Ravi Dhingra, M.D., evaluated the relationship between QRS duration to the dimensions of the left ventricle of the heart in 4,534 participants in the Framingham Heart Study who had never been diagnosed with heart failure or a heart attack. The decades-long study of people living in the town of Framingham, Mass., has produced some of the most important clues to risk factors for heart disease.

Because this study just looked at a single electrocardiogram and heart ultrasound examination for each volunteer participant, it cannot determine which of the abnormalities, the long heart beat segment or greater left ventricle size, appeared first. The study also cannot rule out a common underlying cause for both abnormalities; however, the authors pointed out several possible ways the two characteristics could be related.

The researchers called for studies that would follow individuals over time to observe the sequence of changes and to evaluate how these observations may be related to the development of heart failure. They also noted that their participants were predominantly white, so it is not known whether the same association is present in other ethnic groups.

Peter M. Okin, M.D., F.A.C.C., Professor of Medicine at Weill Medical College of Cornell University in New York, who was not connected with this study, said it was well done and confirmed earlier observations.

“The key thing is that this result should really prompt investigators to look in a serial fashion at whether increasing QRS duration is a marker of worsening left ventricular function and increasing left ventricular mass in longitudinal studies,” Dr. Okin said.

He said physicians should look more closely at patients with increased QRS duration on their electrocardiograms, even when they do not have other signs of heart failure risk.

Nora F. Goldschlager, M.D., F.A.C.C., at San Francisco General Hospital, who also was not connected with this study, said the result was not surprising.

“For the primary care provider, a message might be that when the QRS duration is wide, look for disease; do not ignore it. And consider referring the patient to a cardiologist,” Dr. Goldschlager said.