The functional significance of chronotropic incompetence during dobutaminestress test

Objective-To investigate the functional significance of chronotropic incomp etence during dobutamine stress echocardiography. Patients and methods-The significance of chronotropic incompetence was eval uated during dobutamine stress echocardiography in 512 patients without bet a blocker treatment who underwent dobutamine stress echocardiography (up to 40 mu g/kg/min) and completed the protocol or reached the target heart rat e. Mean (SD) age was 60 (12) years (313 men, 199 women). Chronotropic incom petence was defined as failure to achieve 85% of the maximum exercise heart rate predicted for age and sex (220 - age in men; 200 - age in women) at m aximum dobutamine dose. Results-Chronotropic incompetence occurred in 196 patients (38%). Affected patients were significantly younger, more likely to be men (both p << 0.001 ) and smokers (p < 0.05), had a higher prevalence of previous myocardial in farction (p < 0.005) and resting wall motion abnormalities (p < 0.05), and had a lower resting heart rate (p << 0.001) and systolic blood pressure (p << 0.001) than patients without chronotropic incompetence, but there was no difference in the overall prevalence of ischaemia and significant coronary artery disease. By multivariate analysis, independent predictors of chrono tropic incompetence were a lower resting heart rate (p << 0.001), younger a ge (p << 0.001), and male sex (p << 0.001). Conclusions-The relations among sex, age, and chronotropic incompetence sho w the need to titrate the dobutamine dose using specific data based on age and sex related heart rate responses to dobutamine rather than to an exerci se stress test. Obtaining specific heart rate criteria is necessary to dete rmine whether chronotropic incompetence represents a real failure to achiev e a normal response or is the result of applying an inappropriate gold stan dard.