Prognostic value of residual ischaemia assessed by exercise electrocardiography and dobutamine stress echocardiography in low-risk patients following acute myocardial infarction.

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.