The prognostic value of cardiorespiratory fitness and exercise stress testing

Exercise stress test is the most widely used non-invasive test in evaluation of patients with cardiovascular diseases. Albeit mainly used in the evaluation of chest pain, it is routinely used in many conditions including valvular heart diseases, cardiomyopathies and cardiac rehabilitation. Since its inception in mid last century, it continues to evolve as a robust prognostic test despite limited diagnostic accuracy. The prognostic value of exercise stress extends beyond the diagnostic parameters of ischemia. Measures of fitness such as functional capacity is a strong and independent predictor of future cardiac events. Each 1 MET increment is associated with 13% reduction in mortality and 14% reduction in non-fatal myocardial infarction. Likewise, heart rate and blood pressure response to exercise as well as heart rate recovery after exercise demonstrate independent prognostic value for cardiac mortality. Diagnostic parameters of ischemia such as ST-segment depression and angina have been incorporated in Duke Treadmill Score, which is shown to be of prognostic value in many patient population suspected of having coronary artery disease. Patients with normal Duke score has better 5-year survival than those with a score of -11 (93% vs. 67%). In addition, the combination of exercise stress test and myocardial perfusion imaging provide further prognostic value particularly in patients with normal perfusion. The evidence supporting the use of functional testing is overwhelming and its role is emphasized in the professional societies current clinical practice guidelines. Its prognostic versatility, affordability, wide availability and easy use make it an attractive diagnostic and prognostic tool especially with the era of rising cost of health care expenditure.