Heart transplantation-associated perioperative ischemic myocardial injury - Morphological features and clinical significance

Background The frequency and clinical significance of perioperative ischemic myocardial injury (PIMI) after heart transplantation and the diagnostic features distinguishing PIMI from rejection are not well defined. Methods and Results We evaluated PIMI in the first four weekly endomyocardial biopsies and/or autopsy myocardium from 140 consecutive orthotopic heart transplantation recipients (1984 to 1991) by grading the severity of coagulative myocyte necrosis (CMN) as absent, 0; mild-focal, 1; moderate-multifocal, 2; or severe-confluent, 3, and determining the evolution of morphological features of its healing. CMN (often with contraction bands) was noted in 124 patients (89%); 24 patients (17%) had grade 3 CMN, of which 4 died within 30 days of transplantation. Nevertheless, at 1 year after surgery, survival was similar in patients with and without severe injury. Increased cold ischemic time but neither donor age nor intensity of inotropic support correlated with more severe early ischemic injury, PIMI inflammation was characterized by a predominantly polymorphonuclear/histiocytic infiltrate that contained lymphocytes and plasma cells, expanding the interstitium but not encroaching upon and separable from adjacent viable myocytes. Histological features of PIMI developed and resolved more slowly than those of typical myocardial infarct necrosis in nonimmunosuppressed patients; at 4 weeks, CMN persisted in 20% of patients and residual healing in nearly half. Diagnostic rejection was observed concurrently with PIMI in 54 of 533 biopsies (10%). Conclusions Diagnosed by conventional histological criteria, PIMI is prevalent early after heart transplantation and has a protracted healing phase that can mimic or coexist with rejection. Extensive PIMI has deleterious impact on short-term survival, but the long-term impact of PIMI remains to be established.