Non-invasive risk stratification: prognostic implications of exercise testing.

The interpretation of exercise ECGs is frequently limited to an assessment of the ST segment for evaluation of ischemia. However, exercise testing represents a simple test of the complex interactions of the autonomous nervous system and provides a multitude of information with independent prognostic information. This overview summarizes available studies on the significance of chronotropic incompetence, exercise capacity, heart rate recovery after exercise, and the incidence of ventricular premature activity during or after exercise. These parameters express subclinical pathophysiological changes which cannot be identified by other means, e. g., coronary angiography or echocardiography. A reduced maximal heart rate under exercise may indicate a "blunted" sympathetic reaction as a protective myocardial reaction to an increase in left ventricular wall stretch in preclinical forms of heart failure. A reduced exercise capacity, measured in metabolic equivalents, METs, is one of the strongest predictors of cardiac and all cause mortality. A reduced heart rate recovery after exercise indicates an increased sympathetic tone or lack physiological increase in vagal tone; increased ventricular ectopy potentially identifies preclinical cardiomyopathy. This summary of study results aims at providing a new view on exercise testing that should lead to an improved understanding of relevant information included in the exercise ECG.