Comparison of exercise electrocardiography and dobutamine echocardiography

It is uncertain whether dobutamine echocardiography is a better test than exercise electrocardiography for the detection of coronary disease in patients who can exercise. We compared the hemodynamics, sensitivity, and specificity of these tests in 24 patients, 16 with coronary disease and 8 controls. The tests were performed within six weeks of one another and were interpreted without knowledge of other clinical data. The exercise electrocardiogram was considered abnormal if the patient developed one mm of ST-segment depression, while the dobutamine test (up to 40 micrograms/kg/min) was considered abnormal if the patient developed ST-segment depression or a left ventricular wall motion abnormality. Exercise testing resulted in a higher heart rate (145 +/- 29 vs. 110 +/- 24, p less than 0.001) and blood pressure (176 +/- 31 vs. 148 +/- 24, p less than 0.001). Dobutamine testing was 25% more sensitive than exercise testing (94 vs. 69%, 95% confidence interval for difference is 0 to 50%, p = 0.09), while exercise testing was 38% more specific (88 vs. 50%, 95% confidence interval for difference is -3 to 79%, p = 0.14). We conclude that exercise results in a higher heart rate and blood pressure than dobutamine infusion. Differences in sensitivity and specificity are inconclusive, but indicate that the sensitivity of exercise testing is, at best, equivalent to dobutamine testing, while any increase in specificity with dobutamine testing, compared with exercise testing, would not be clinically significant.