Myocardial vacuolization, a marker of ischemic injury, in surveillance cardiac biopsies posttransplant: Correlations with morphologic vascular disease and endothelial dysfunction.
Allograft vasculopathy (AV) causes intimal thickening with progressive luminal obstruction, endothelial dysfunction, and abnormal vasomotion. Subendocardial vacuolization indicating ongoing ischemia was observed at autopsy in transplanted hearts with severe AV. Whether myocyte vacuolization can be observed with lesser degrees of AV in cardia transplant patients has not been reported. Thirty-nine cardiac transplant patients without flow-limiting disease in large epicardial arteries underwent invasive assessment of AV. Eight to 10 segments of the left anterior descending artery were analyzed by intracoronary ultrasound, and an average intimal index was calculated. Endothelial response to acetylcholine was assessed with serial quantitative angiography. Endomyocardial biopsies taken 5 to 7 days prior to the invasive studies were histopathologically reviewed for the presence of small intramyocardial arteries and myocyte vacuolization. Myocyte vacuolization was evident in biopsies from 20 patients (51%). Intramyocardial arteries were observed in 30 cases (76%); 14 had abnormal arteries. All patients had some degree of intimal thickening by intracoronary ultrasound, and 7 (17 %) had severely abnormal average intimal index (>0.2). Endothelial dysfunction was present in 23 patients (58%). Vacuolization failed to show an association with abnormal small artery histology or large epicardial artery ultrasound disease. However, a significant association between vacuolization and endothelial dysfunction was observed (p = 0.05). Myocyte vacuolization, possibly indicating ischemic injury, is common in biopsies from cardiac transplant patients and is associated with abnormal acetylcholine response in large epicardial arteries. We speculate that myocyte vacuolization may be caused at least in part by impaired coronary flow associated with endothelial dysfunction.