Chronotropic incompetence and a higher frequency of myocardial ischemia in exercise echocardiography.

Background: Exercise echocardiography (EE) is an established method to diagnose coronary artery disease (CAD). Chronotropic incompetence (CI) during the EE may be a marker of myocardial ischemia. The purpose of this investigation was to evaluate the additive value of CI during EE in CAD diagnosis.
Methods: Between 2000 and 2006, 4042 patients (1900 men with a mean age of 56 +/- 11 years) were evaluated by EE. Based on the heart rate (HR) reached during the exercise test, the subjects were divided into two groups: G1 group - 490 patients who failed to achieve 85% of the maximal age-predicted HR, and G2 group - 3552 patients who were able to achieve 85% of the maximal age-predicted HR. Clinical characteristics, left ventricular wall motion abnormalities - wall motion score index (WMSI) - and coronary angiography (CA) were the parameters compared between the two groups.
Results: The left ventricular wall motion abnormalities were more frequent in G1 group than in G2 group (54% versus 26%; P < 0.00001). WMSI was higher in G1 group than in G2 group, both at rest (1.06 +/- 0.17 versus 1.02 +/- 0.09; P < 0.0001) and after exercise (1.12 +/- 0.23 versus 1.04 +/- 0.21; P < 0.0001). In G1 group, 82% of the patients with positive EE for myocardial ischemia presented obstructive coronary, compared to 71% (P = 0.03) in G2 group.
Conclusion: CI is associated with a higher frequency of myocardial ischemia during EE, reinforcing the concept that CI is a marker of the severity of myocardial ischemia.