Quantitative Relation Between Myocardial Viability and Improvement in Heart Failure Symptoms After Revascularization in Patients With Ischemic Cardiomyopathy

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Abstract
Background Studies of patients with coronary artery disease and left ventricular dysfunction have shown that preoperative quantification of myocardial viability may be clinically useful to identify those patients who will benefit most from revascularization both functionally and prognostically. However, the relation between preoperative extent of viability and change in heart failure symptoms has not been documented carefully. We assessed the relation between the magnitude of improvement in heart failure symptoms after coronary artery bypass surgery (CABG) and the extent of myocardial viability as assessed by use of quantitative analysis of preoperative positron emission tomography (PET) images. Methods and Results We studied 36 patients with ischemic cardiomyopathy (mean left ventricular ejection fraction, 28±6%) undergoing CABG. Preoperative extent and severity of perfusion abnormalities and myocardial viability (flow-metabolism mismatch) were assessed by use of quantitative analysis of PET images with 13N ammonia and fluorine-18-deoxyglucose. Each patient’s functional status was determined before and after CABG by use of a Specific Activity Scale. Mean perfusion defect size and severity were 63±13% and 33±12%, respectively. Total extent of a PET mismatch correlated linearly and significantly with percent improvement in functional status after CABG (r=.87, P<.0001). A blood flow–metabolism mismatch ≥18% was associated with a sensitivity of 76% and a specificity of 78% for predicting a change in functional status after revascularization. Patients with large mismatches (≥18%) achieved a significantly higher functional status compared with those with minimal or no PET mismatch (P=.009). This resulted in an improvement of 107% in patients with large mismatches compared with only 34% in patients with minimal or no PET mismatch. Conclusions In patients with ischemic cardiomyopathy, the magnitude of improvement in heart failure symptoms after CABG is related to the preoperative extent and magnitude of myocardial viability as assessed by use of PET imaging. Patients with large perfusion-metabolism mismatches exhibit the greatest clinical benefit after CABG.