Prognostic interaction between viability and residual myocardial ischemia by dobutamine stress echocardiography in patients with acute myocardial infarction and mildly impaired left ventricular function

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Abstract

Dobutamine stress echocardiography (DSE) accurately detects viable myocardium and residual ischemia in patients with acute myocardial infarction (AMI). The prognostic interaction of viability and ischemia has not been completely clarified in these patients. This study assesses the long-term effect of viability, ischemia, or their combination on survival in patients with AMI and mildly impaired left ventricular (LV) function. Four hundred eleven patients (age 57 ± 9 years) underwent predischarge DSE (up to 40 μg/kg/min plus atropine if needed) after uncomplicated AMI and were prospectively followed for 23 months (range 1 to 78). According to DSE findings, patients were divided into 4 groups: viability only, ischemia only, combination of viability and ischemia, and scar. Adverse outcome occurred in 64 patients: 34 patients had hard events (9 cardiac deaths, 25 nonfatal AMI) and 30 patients had unstable angina requiring hospitalization. The combination of viability and ischemia, diabetes mellitus, and non–Q-wave AMI were significant predictors of all events at univariate and multivariate analysis. The same variables were also univariate predictors of hard events, but multivariate analysis indicated only the combination of viability and ischemia and diabetes as independent predictors. The event-free survival of patients with combined viability and ischemia was significantly lower (hazard ratio 3 [95% confidence interval 1.8 to 11]) compared with patients with ischemia only. Thus, viability and ischemia show a significant adverse prognostic interaction in patients with AMI and preserved LV function.

Section snippets

Study population

The initial study population consisted of 545 consecutive patients admitted to a coronary care unit because of first AMI documented by typical chest pain lasting >30 minutes, elevated creatine kinase and MB fraction, and electrocardiographic changes. Exclusion criteria were: (1) complicated infarction (overt heart failure, complex arrhythmia, and early recurrence of myocardial ischemia, n = 54), (2) prior infarction (n = 18), (3) ejection fraction <40% (n = 52), and (4) technically inadequate

Results

Clinical and echocardiographic characteristics of the study population are listed in Table 1. Two major adverse reactions were observed: 1 ventricular fibrillation that occurred 10 minutes after halting dobutamine infusion, which was effectively reverted by electrical defibrillation, and 1 sustained ventricular tachycardia at peak infusion. Premature termination of the test because of intolerable side effects was necessary in 2 patients.

Discussion

Because the beneficial effect of functional recovery on survival is expected to be critically correlated with the extent of LV dysfunction, the clinical relevance of myocardial viability has been mostly evaluated in patients with impaired LV function.2, 3, 6 However, this study demonstrates an unfavorable prognostic impact of the combination of myocardial ischemia and viability in patients with AMI and mildly impaired LV function. Of note, myocardial ischemia was prognostically significant only

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