Exercise capacity, as measured in terms of VO2max, is a powerful predictor of death in patients with coronary artery disease, not just patients with heart failure. That is the finding of a Mayo Clinic study presented at the American Heart Association's Scientific Sessions 2005 in Dallas.
VO2max is the maximum amount of oxygen a person can take in during exercise. In a VO2max study, a patient walks on a treadmill for about 5 to 15 minutes and breathes through a valve; the oxygen and carbon dioxide in the expired air are measured. Results are given in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min).
"The best predictor of survival in cardiac patients is their capacity for exercise," says Thomas Allison, Ph.D., the lead author of the study, who is from Mayo Clinic in Rochester, Minn. "When we considered all of the measurable clinical variables -- such as whether they had bypass surgery or whether they have diabetes or high blood pressure -- the patient's capacity for exercise as measured by VO2max stood clear as the best predictor for 10-year survival."
In this study, the significance of low VO2max levels was examined in patients with coronary artery disease -- the top cause of death in the United States and often a precursor to a heart attack and heart failure.
A group of 282 patients, 17 percent of them women, underwent cardiopulmonary treadmill testing at the end of cardiac rehabilitation and were followed for an average of 9.8 years. The average age was 61 at the time of the test.