Incidence and correlates of complex ventricular arrhythmias during dobutamine stress echocardiography after acute myocardial infarction.

Although previous studies have confirmed the safety of dobutamine stress echocardiography, complex ventricular arrhythmias have been reported. Our aim was (1) to identify the markers of increased arrhythmic risk during dobutamine stress echocardiography and (2) to assess whether the occurrence of major ventricular arrhythmias during the test may represent a clinically useful marker of electrical instability. Three hundred and seventy-seven consecutive survivors from acute myocardial infarction, off cardioactive therapy, underwent dobutamine stress echocardiography 11.4 days after the acute event. Holter monitoring with assessment of heart rate variability and echocardiographic determination of left ventricular ejection fraction. In addition, exercise stress testing, signal averaged ECG and coronary angiography were carried out, respectively, in 357, 150 and 273 patients. Ten subjects showed complex ventricular arrhythmias (eight non-sustained and one sustained ventricular tachycardia and one ventricular fibrillation) during dobutamine stress echocardiography (group A), whilst 366 did not (group B). Complex ventricular arrhythmias were detected by Holter monitoring in 8/10 patients in group A and 45/367 patients in group B (odds ratio 28.6, 95% CI 5.4-92.2) and by exercise testing in 4/10 patients in group A and 33/347 patients in group B (odds ratio 6.3, 95% CI 1.4-27.2). Ejection fraction < 40% was present in 3/10 patients in group A and 50/367 in group B (odds ratio 2.7, 95% CI 0.3-12.2), whilst multivessel disease was present, respectively, in 8/10 and 176/263 patients (odds ratio 1.9, 95% CI 0.3-25.5). Reduced heart rate variability and the presence of late potentials on signal averaged ECG were found in, respectively, 40/367 and 13/140 patients in group B, but none were found in group A. A total of 61 events (35 CABG, 15 PTCA, four cardiac deaths and seven non-fatal reinfarctions) occurred during the follow-up (11.4 months, range 6 to 20): four in group A and 57 in group B. No documented major arrhythmic event was reported. We conclude that (1) complex arrhythmias during dobutamine stress may occur in patients early after acute myocardial infarction; (2) the preexisting evidence of frequent, as well as repetitive, arrhythmias represents a potential marker of increased risk in this connection and, finally, (3) dobutamine-induced arrhythmias seem to represent an uncommon, even though potentially dangerous, event but not a useful new "window' on electrical instability of post-MI patients.