Exercise electrocardiogram testing and prognosis. Novel markers and predictive instruments.

Abstract

Ample evidence now exists supporting the use of the exercise test primarily for prognostic, as opposed to diagnostic, purposes. Although limitations must be recognized, the Duke exercise treadmill score, the chronotropic response to exercise, and heart rate recovery appear to function as powerful and independent predictors of risk. With the possible exception of exercise-induced ischemia, as manifested by the ST-segment and angina components of the Duke exercise treadmill score, exercise predictors of risk are not clearly modifiable. Nonetheless, they are clinically quite useful since they may well identify patients who are or are not likely to gain benefit from further testing and aggressive therapies. How so? The "plain old" exercise treadmill test makes it possible to easily, safely, and inexpensively identify a large group of patients who are at low risk for death or major cardiac events. For this reason alone, the predictive instruments described in this article should be routinely incorporated into clinical practice. It makes no sense to perform expensive and potentially risky diagnostic tests, prescribe polypharmacy, or institute invasive therapeutic procedures in patients who are already at low risk. As an example, Weiner and colleagues found that coronary bypass grafting only benefited CASS registry patients who had a high-risk exercise test result. Future research will be needed to further refine risk stratification with the exercise test, and determine how best to use adjunctive imaging studies and to reduce risk among patients with prognostically important findings.