Dobutamine magnetic resonance imaging predicts contractile recovery of chronically dysfunctional myocardium after successful revascularization

Objectives. This study sought to evaluate whether myocardial viability, as assessed by magnetic resonance imaging (MRI), reliably predicts postrevascularization left ventricular (LV) recovery. Background. Compared with positron emission tomographic findings, MRI has proved to be a reliable technique for the identification of residual myocardial viability. However, the predictive accuracy of MRI-assessed preserved end-diastolic wall thickness (DWT) and dobutamine-induced systolic wail thickening (SWT) for LV functional recovery has not yet been evaluated. Methods. Rest and low dose dobutamine MRI was performed in 43 patients with a chronic infarct (greater than or equal to 4 months since ischemic event) and LV dysfunction who had undergone revascularization of the infarct-related vessel. On the basis of segmental evaluation of corresponding short-axis tomograms, infarct regions were graded viable by MRI if 1) DWT was greater than or equal to 5.5 mm, and 2) dobutamine-induced SWT was greater than or equal to 2 mm in greater than or equal to 50% of dysfunctional segments related to the infarct region. Functional recovery was defined as SWT greater than or equal to 2 mm in greater than or equal to 50% of infarct-related segments at rest 4 to 6 months after successful revascularization. Results. Recovery of regional SWT could be observed in 27 (63%) of 43 patients, Comparison MRI grading before and after revascularization indicated that dobutamine induced SWT was a better predictor of LV functional recovery (sensitivity 89%, specificity, 94%) than was preserved DWT (sensitivity 92%, specificity 56%). Segments that remained akinetic after revascularization had significantly lower DWT (6.0 +/- 3.1 mm [n = 219] vs. 9.8 +/- 2.6 mm [n = 188], p < 0.001) than those with improved SWT. Left ventricular ejection fraction increased significantly in patients with dobutamine induced SWT than in those with no contractile reserve (14 +/- 9% vs. 3 +/- 9%, p < 0.0002), and the magnitude of this increase was correlated with the number of dobutamine-responsive segments per infarct region (r = 0.68, p < 0.0001). Conclusions. Quantitative assessment of dobutamine induced SWT in chronic infarcts by MRI is a highly accurate predictor of LV functional recovery, and the presence of significantly reduced DWT reliably indicates irreversible myocardial damage. Therefore, dobutamine stress testing for the assessment of myocardial viability can be restricted to patients with preserved DWT. (C)1998 by the American College of Cardiology.