Myocardial scar and insulin resistance predict cardiovascular events in severe ischaemic myocardial dysfunction: a perfusion-metabolism positron emission tomography study

Background Clinical outcome can be predicted by metabolism-perfusion positron emission tomography (PET) in patients with severe ischaemic left ventricular dysfunction. This study determined whether the amount of viable or non-viable myocardium detected with a PET scan or clinical-functional parameters might predict cardiovascular events. Methods All patients had previous myocardial infarction (> 6 months previously) and left ventricular ejection fraction (LVEF) < 40%. Metabolism-perfusion PET, echocardiogram and coronary angiography were provided. All subjects underwent short euglycaemic-hyperinsulinaemic clamp before the metabolism study. The dysfunctioning segment was defined as hibernating myocardium when metabolism was normal-moderately reduced with impaired perfusion (mismatch flow-metabolism). Cardiac death, hospital admission for myocardial infarction or heart failure were considered cardiovascular events. Results Ninety-three patients (71 males, aged 64.2 years) were studied. The LVEF was 30.2 +/- 7.7%; 48 (51.6%) suffered an anterior myocardial infarction. Fifty-three (54.1%) subjects were treated with coronary revascularization; all had optimal medical therapy. Cardiovascular events occurred in 20/93 patients at 1-year follow-up (event group). Age (P=0.7), diabetes mellitus (P=0.6) and rate of coronary revascularization (P=0.3) were not different in the two groups. Patients who experienced cardiovascular events had larger non-viable myocardium (5.8 +/- 2.7 vs. 4.1 +/- 2.6, P = 0.01), lower metabolic rate glucose (1.3 +/- 0.6 vs. 1.7 +/- 0.7 ml . kg(-1).min(-1), P = 0.04) but similar hibernating myocardium (1.6 +/- 1.6 vs. 1.7 +/- 2, P= 0.8) and baseline LVEF (28.1 +/- 4.8 vs. 30.7 +/- 8.3%, P= 0.08). Having more then five non-viable segments and a metabolic rate for glucose of < 0.9 mg - kg(-1).min(-1) predicted a worse prognosis (P=0.04, log rank, 3.89; and P=0.004, log rank, 8.1, respectively). Conclusion Non-viable myocardium revealed with PET predicts mid-term clinical prognosis. Insulin resistance seems to influence the outcome.