Prognostic Value of Myocardial Infarct Size and Contractile Reserve Using Magnetic Resonance Imaging

Abstract

Our aim was to assess the predictive value of myocardial infarct size assessed with late gadolinium-enhanced (LGE) magnetic resonance imaging (MRI) in medically treated patients with chronic myocardial infarction relative to contractile reserve on low-dose dobutamine magnetic resonance (DSMR) for long-term event-free survival. Information on the relative merits of scar tissue and contractile reserve to predict long-term prognosis in patients with chronic myocardial infarction is lacking. A total of 177 patients with known coronary artery disease and scar tissue on LGE MRI were enrolled. Left ventricular (LV) functional parameters at rest and during low-dose DSMR were assessed, and the wall motion score index was calculated. Eleven patients (6.2%) suffered an event during follow-up (average 20.3 months). Infarct size was a stronger predictor of events than LV ejection fraction and LV volumes at rest and during low-dose DSMR. Myocardial infarct size was used to separate patients at high risk (spatial extent > or =6 segments, n = 98) from those at low risk (spatial extent <6 segments, n = 79) for mortality. In the subgroup of patients at high risk, transmurality of infarct was not a predictor of events. However, the presence of contractile reserve (n = 63) was associated with a significantly higher number of events (12.7%) compared with no change in wall motion score index (6.7%; n = 15; p = 0.008). Myocardial infarct size on LGE MRI is a stronger predictor of clinical outcome than contractile reserve in medically treated patients with myocardial infarction. In patients with large myocardial scar, the presence of contractile reserve is more important for the prediction of events than scar tissue.