Time course of functional recovery after coronary artery bypass graft surgery in patients with chronic left ventricular ischemic dysfunction

Chronic left ventricular (LV) ischemic dysfunction, a condition often refer red to as myocardial hibernation, is associated in humans with ultrastructu ral alterations of the myocytes, including the loss of myofilaments and the accumulation of glycogen. Given the severity of these structural changes, contractile function is unlikely to resume immediately upon revascularizati on. Therefore, the aim of the present study was to assess the time course o f functional improvement after successful revascularization as well as its potential structural correlates. We studied 32 patients with coronary disea se and chronic LV ischemic dysfunction who underwent bypass surgery. Dynami c positron emission tomagraphy with N-13 ammonia and F-18 deoxyglucose to a ssess myocardial perfusion and glucose metabolism was performed in 29 patie nts. In all patients, a transmural biopsy was harvested from the center of the dysfunctional area, to quantify the increase in extracellular matrix an d the presence of structurally altered cardiomyocytes. LV function was seri ally measured by digitized 2-dimensional echocardiography before and at 10 days, 2 months, and 6 months after revascularization. The time course of re covery of regional function was estimated from the monaexponential decrease in dysfunctional wall motion score. At follow-up, 19 patients had improved LV function, whereas 13 patients showed persistent dysfunction. Before rev ascularization, reversibly dysfunctional segments had higher myocardial blo od flow (82 +/- 29 vs 53 +/- 21 ml . (min . 100 g)(-1), p = 0.044), higher glucose uptake (40 +/- 16 vs 21 +/- 9 mu mol (min . 100 g)(-1), p = 0.001), and less increase in extracellular matrix (25 +/- 15% vs 46 +/- 17%, p = 0 .0008) than segments with persistent dysfunction. The extent to which funct ion recovered was positively correlated with myocardial blood flow and nega tively correlated with the increase in the extracellular matrix, In patient s with reversible dysfunction, the return of segmental function was progres sive and followed a monoexponential time course with a median time constant of 23 days (range 6 to 78). The rate of recovery correlated best with the proportion of altered cardiomyocytes in the biopsy. The present study thus indicates that the recovery of regional and global LV function after succes sful revascularization is progressive and follows a monoexponential time co urse that is influenced by the extent of the structural changes affecting c ardiomyocytes. (C) 2000 by Excerpta Medica, Inc.