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Background: Risk stratification after uncomplicated myocardial infarction is major clinical problem. In particular, the prognostic value of residual inducible ischaemia is still controversial. We compared the relative prognostic value of exercise ECG and dobutamine stress echocardiography performed in the early post-infarction period., Methods: Four hundred and six patients (53 female) aged 57 +/- 9 years, undergoing maximal exercise ECG and dobutamine stress echocardiography within 10 days of an uncomplicated myocardial infarction off therapy, were prospectively followed-up for 8.8 months. Age, sex, diabetes, smoking habit, hypertension, dyslipidaemia, infarct location, thrombolysis and resting wall motion score index were taken into account among clinical variables. Prognostic correlations were made vs spontaneous events (cardiac death, non-fatal reinfarction and unstable angina requiring hospitalization) whilst patients undergoing revascularization (by means of percutaneous transluminal coronary angioplasty or coronary artery bypass surgery) at the time of the procedure were censored., Results: One hundred and twenty-seven events occurred during the follow-up: 41 (10%) were spontaneous (five deaths, 12 reinfarctions and 24 unstable angina) and 86 procedural (27 angioplasty and 59 bypass surgery). Spontaneous events were not predicted by any clinical, exercise ECG or dobutamine stress echocardiography variable, but the negative predictive value of both tests was excellent (91% and 90% respectively). With a multivariate Cox analysis, male gender, positive low-workload (< 100 W) exercise ECG (P < 0.0001), positive low-dose dobutamine stress echocardiography (P < 0.0001) and rest-stress wall motion score index variation (P < 0.001) were found to predict cumulative cardiac events with an independent and additive value. Dobutamine stress echocardiography was significantly more sensitive (P < 0.05) and less specific (P < 0.01) in predicting the outcome of patients with anterior infarction, whilst exercise ECG was significantly more sensitive (P < 0.05) in patients with non-Q wave infarction., Conclusions: (1) Spontaneous events are poorly predicted by provocative tests in low-risk patients after uncomplicated myocardial infarction. (2) However, both exercise ECG and dobutamine stress echocardiography can predict a favourable outcome with a very high negative predictive value. (3) Dobutamine stress echocardiography should be considered a secondary option in cases where the exercise ECG is equivocal or when the location of ischaemia is a relevant issue. (4) The possibility that the two tests have a differential utility depending on the infarct location and type (Q wave vs non-Q wave) may be clinically relevant and deserves further evaluation.

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.