Combination of Electrocardiogram (ECG) and Heart Ultrasound Foretells Dramatically Increased Risk of Death
Mar 24, 2004
Two heart tests are better than one when it comes to predicting the risk of dying of cardiovascular disease or any cause, NewYork-Presbyterian Hospital/Weill Cornell Medical Center researchers report in the April issue of the journal Hypertension.
Those patients with an ECG finding of ST depression a possible sign of heart disease and an echocardiogram that showed an enlarged left ventricle were more likely to die during the study than those with normal test results. When the left ventricle, the heart's main pumping chamber, enlarges and thickens, it could be a sign the heart is struggling to pump efficiently.
The ECG, or electrocardiogram, is the most commonly used test to measure heart function. In this noninvasive test, electrodes are attached to the chest to measure the heart's electrical activity. An echocardiogram is an ultrasound examination of the heart that is also a common test, though it tends to be more expensive than an ECG.
Patients with both test results were more than six times as likely to die of cardiovascular disease as those without such test results. What's more, they were more than four times as likely to die of any cause during the three-year study compared with patients with a clean bill of health.
These two very simple but widely used methods for assessing cardiac performance and structure may have complementary information that could help physicians better identify people who are at risk, said Dr. Peter Okin, Professor of Medicine and Director of Clinical Affairs in the Greenberg Division of Cardiology at Weill Cornell Medical College; and Attending Physician at NewYork-Presbyterian/Weill Cornell.
The results are from the Strong Heart Study, an ongoing study of cardiovascular disease risk factors in American Indians from 13 communities in Arizona, Oklahoma, and North and South Dakota. The researchers are studying American Indians because they have so many risk factors for cardiovascular disease including smoking, high blood pressure, obesity, and diabetes.
In the study, 2,193 patients who were mostly in their 50s and 60s underwent a routine computerized ECG and a standard echocardiogram. During a three-year period, 57 people died of cardiovascular disease and 169 died of other causes.
The chance of dying of cardiovascular disease was 20.4% for those with ST depression and an enlarged left ventricle, compared with 6.5% in those with one result but not the other, and only 1.4% in patients who did not have either test result. For death due to any cause, it was 35.7% for both results, 12% for one result, and 5.5% when both tests were negative.
We know that the echocardiogram is a very good measure to look at the structure and function of the heart, and the electrocardiogram has long been used to gain information about the heart from its electrical activity, but the tests clearly reflect different aspects of the heart's function, said Dr. Okin.
Some of the study participants had high blood pressure or diabetes, and a few had heart disease, but others did not, Dr. Okin said.
We found that the combination of two things an elevated left ventricle mass and minimal amounts of ST depression provide a tremendous concentration of risk in this population, he said.
The level of ST depression picked up by the digital ECG was a very minimal amount; it's not severe enough to grab the attention of most physicians looking at it, Dr. Okin said. It's not something doctors have typically been concerned about.
Doctors may be able to use the study findings to predict their patients' cardiovascular risk and then treat them appropriately, said Dr. Okin.
Any patient that comes in for assessment for cardiac disease gets an electrocardiogram,and many of those people get echocardiograms particularly those who are susceptible to having structural abnormalities or high blood pressure, he said. We would encourage physicians to take advantage of the combined information to identify patients who appear to be at highest risk and to focus their attention on the most aggressive ways to reduce risk factors in that population.
In addition to Dr. Okin, the study co-authors include NewYork-Presbyterian/Weill Cornell's Dr. Richard Devereux and Dr. Mary Roman; Elisa Lee (University of Oklahoma Health Sciences Center); James Galloway (University of Arizona); and Barbara Howard (MedStar Research Institute).
The study was funded by grants from the National Heart, Lung, and Blood Institute, the National Institutes of Health, and a grant from The Michael Wolk Heart Foundation.