People who can exercise sufficiently on a treadmill during cardiac stress testing have a lower mortality risk regardless of their overall level of heart disease, a Mount Sinai-led team of researchers has found.
The results of their study, reported February 19 in Mayo Clinic Proceedings, underscore the potential life-saving benefits of physical fitness, a finding which researchers encouraged physicians to share with their patients.
"Our data show that assessing a person's ability to exercise during cardiac stress testing and their exercise capacity provides a stronger distinction between high- and low-risk patients than any other clinical risk factors evaluated at the time of cardiac stress testing," says Alan Rozanski, MD, Professor of Medicine (Cardiology) at the Icahn School of Medicine at Mount Sinai and lead author of the study. "Our results highlight the importance of evaluating patients' exercise ability during testing and promoting physical activity or corrections to exercise limitations among those with limited exercise ability."
The study offers the most comprehensive evaluation to date of how known risk factors such as hypertension, diabetes, smoking, and cardiac-related comorbidities such as peripheral vascular disease synergistically affect the mortality risk of patients undergoing cardiac stress testing. The team analyzed and followed for nearly seven years 15,562 patients who were given SPECT myocardial perfusion imaging, a test that assesses blood flow to the heart during both stress and rest to identify areas with reduced flow. Patients were divided into those who could perform treadmill exercise and those who could not, with the latter undergoing medication-induced coronary artery dilation as an alternative for detecting blockages.
Researchers found that among those who performed treadmill exercise, the mortality rate was less than one percent a year, regardless of the patient's burden of coronary artery disease (CAD) risk factors and comorbidities. By contrast, the annual rate of mortality was markedly higher among pharmacologically tested participants, and increased synergistically with a higher burden of CAD risk factors and comorbidities.
"While these findings do not definitively establish causality due to the observational nature of our data, the magnitude of the results strongly suggest a highly protective role for physical fitness," notes Dr. Rozanski, who is widely recognized for his novel research integrating the fields of preventive cardiology with health physiology and behavioral medicine.
The results also demonstrated the need for cardiac stress test reports to provide comprehensive evidence about a patient's ability to exercise at the time of testing. When an inability exists, according to the study, it should encourage physicians to thoroughly evaluate the underlying reasons, as they can yield valuable insights into the overall risk of adverse events and prompt appropriate interventions for patients.
"This information should prompt doctors to have more meaningful conversations with patients about the importance of staying active," emphasizes Dr. Rozanski. "Newer guidelines show that even small amounts of physical activity can improve health, and that short bursts of activity throughout the day can add up to significant cardio benefits. That's an important message for physicians to convey to patients."
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