Chronotropic response to exercise predicts angiographic severity in patients with suspected or stable coronary artery disease

Inappropriate chronotropic response to exercise has been observed to correlate with poor prognosis in patients with coronary disease, but the mechanism for this association is not well defined. We attempted to examine the association between chronotropic response to exercise and angiographic severity of coronary disease in patients with suspected or stable coronary artery disease. The chronotropic response, expressed as peak heart rate, chronotropic index (ratio of heart rate reserve and metabolic reserve utilized), or percent maximal heart rate achieved, was correlated with angiographic findings obtained within 180 days of the test. Significant coronary disease was defined as ≥1 stenosis of ≥50% in a major epicardial artery or its main branches; severe coronary disease was defined as ≥50% stenosis in all 3 epicardial arteries, or in the left main coronary trunk, or 2-vessel disease with ≥70% proximal left anterior descending artery stenosis. We observed that peak heart rate and percent maximal heart rate achieved were independent negative predictors of both significant and severe coronary disease by logistic regression. The chronotropic index predicted severe coronary disease only. All 3 parameters of chronotropic response exhibited a significant gradient of abnormality across the spectrum of coronary disease (p < 0.01 for all), expressed by the number of vessels involved and correlated with left anterior descending artery involvement (p < 0.05 for all). We conclude that chronotropic response to exercise predicts the presence and angiographic severity of coronary disease. This association is likely related to the proportion of left ventricular myocardium rendered ischemic during stress.