The participants, all in their early to mid-40s, underwent exercise stress testing. The more cigarettes smoked daily, the worse was the heart rate response to exercise. Too few coronary events occurred in the mostly premenopausal women for comparison. Exercise-related deaths and cardiac events were not reported in the study. The study redefines the role of exercise testing as a marker for cardiac disease risk in smokers, according to Michael S. Lauer, MD, a cardiologist who headed the study and codirects the coronary care unit at the Cleveland Clinic in Ohio.
Smokers often undergo exercise stress tests because they are more likely to have heart disease.
If they fail to reach their target heart rate, the results are classified as inconclusive. Such labeling greatly understates the risk, says Lauer. Smokers who have a blunted cardiac response to exercise are at high risk for having a major coronary event or even dying and should be considered for further cardiac investigation and referral to a cardiologist, he says. The study has significant implications for physicians who treat active people who smoke, says Andrew Pipe, MD, a family physician and director of the smoking cessation clinic at the University of Ottawa Heart Institute. The reason smoking blunts cardiac response to exercise is unclear, according to the researchers, though smoking has been associated with coronary vasoconstriction, abnormal coronary endothelial function, increased ischemic burden, increased peripheral vascular resistance, and subclinical pulmonary disease.