INCIDENCE AND CORRELATES OF COMPLEX VENTRICULAR ARRHYTHMIAS DURING DOBUTAMINE STRESS ECHOCARDIOGRAPHY AFTER ACUTE MYOCARDIAL-INFARCTION

Although previous studies have confirmed the safety of dobutamine stre ss echocardiography, complex ventricular arrhythmias have been reporte d. Our aim was (1) to identify the markers of increased arrhythymic ri sk during dobutamine stress echocardiography and (2) to assess whether the occurrence of major ventricular arrhythmias during the test may r epresent a clinically useful marker of electrical instability. Three h undred and seventy-seven consecutive survivors from acute myocardial i nfarction, off cardioactive therapy, underwent dobutamine stress echoc ardiography 11.4 days after the acute event, Holter monitoring with as sessment of heart rare variability and echocardiographic determination of left ventricular ejection fraction. In addition, exercise stress t esting, signal averaged ECG and coronary angiography were carried out, respectively, in 357, 150 and 273 patients. Ten subjects showed compl ex ventricular arrhythmias (eight non-sustained and one sustained vent ricular tachycardia and one ventricular fibrillation) during dobutamin e stress echocardiography (group A), whilst 366 did not (group B). Com plex ventricular arrhythmias were detected by Holter monitoring in 8/1 0 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). Ejec tion 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 disea se 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 presenc e of late potentials on signal averaged ECG were found in, respectivel y, 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 se ven non-fatal reinfarctions) occurred during the follow-up (11.4 month s, range 6 to 20): four in group A and 57 in group B. No documented ma jor arrhythmic event was reported. We conclude that (1) complex arrhyt hmias during dobutamine stress may occur in patients early after acute myocardial infarction, (2) the preexisting evidence of frequent, as w ell as repetitive, arrhythmias repesents a potential marker of increas ed risk in this connection and finally, (3) dobutamine-included arrhyt hmias seem to represent an uncommon, even though potentially dangerous , event but not a useful new 'window' on electrical instability of pos t-MI patients.