Ischemically compromised myocardium displays different time-courses of functional recovery: correlation with morphological alterations?

Objective: It has been demonstrated that positron emission tomography (PET) predicts the functional recovery of viable but ischemically compromised my ocardium. Reversible contractile dysfunction after revascularization has be en reported for 'hibernating myocardium' and stunned myocardium, however, t here are little data concerning the time-course and the extent of improveme nt of the two different pathophysiological conditions. Methods: Twenty-nine patients with advanced coronary artery disease and severely reduced left v entricular function (EF 18-35%) who were referred for isolated coronary art ery bypass grafting underwent preoperative PET viability assessment and wer e functionally assessed by two-dimensional echocardiography preoperatively at 11 days, 14 weeks, and more than 12 months after surgical revascularizat ion. Intraoperative biopsies were; taken from dysfunctional areas defined b y PET as segments of normal perfusion and normal metabolism (stunned myocar dium) and from areas with a 'mismatch' between perfusion and metabolism (hi bernating myocardium). The. degree of morphological alterations was evaluat ed by electron microscopy. Results: In 70% of the 240 dysfunctional segment s, 'stunned myocardium' was present whereas 'hibernating myocardium' could be detected in only 24% (P < 0.01). Hibernating myocardium was associated w ith more severe preoperative wall motion abnormalities and incomplete posto perative recovery. After 1 year, 31 % of 'stunned' segments vs. only 18% of 'hibernating' segments showed complete functional restoration (P < 0.05). This incomplete, improvement was associated with more severe morphological alterations including depletion of sarcomeres, accumulation of glycogen, lo ss of sarcoplasmatic reticulum, and cellular sequestration. Conclusions: Th ese data indicate that in patients with severe ischemic, left ventricular d ysfunction 'stunned myocardium' is more prevalent than 'hibernation'. Funct ional normalization is more frequent in 'stunned' segments, whereas areas o f 'hibernation' showed more severe tissue injury and protracted recovery. D ifferent degrees of myocardial injury coexist in most patients, which deter mined the time-course and the extent of improvement after revascularization . <(c)> 2001 Elsevier Science B.V. All rights reserved.