Fibrofatty changes in failed pediatric cardiac allografts

The pathogenesis of right ventricular fibrofatty changes can be broadly divided into genetic or acquired. The genetic cause is termed arrhythmogenic right ventricular dysplasia, an inherited cardiomyopathy characterized by fibrofatty replacement of the right ventricular myocardium, and represents an underdiagnosed cardiac entity leading to syncope, recurrent ventricular tachycardias, heart failure, and sudden death. Our study demonstrates that fibrofatty changes can also be seen in pediatric cardiac allografts. Conversely, fat replacement without fibrosis may be seen secondary to infectious myocarditis, chronic inflammation, and ischemia and as part of the aging process. We examined 29 failed cardiac allografts to identify the etiology of graft failure. In this study, 4 patients (13%) had severe right ventricular fibrofatty changes, and when compared with control patients, those with fibrofatty changes had a shorter interval from transplant to graft failure, 2.75 years vs 5.45 years (P  =  0.029). Neither body mass index nor other physiologic parameters found on electrocardiography, echocardiography, or cardiac catherization were different between groups. Furthermore, arrhythmias indicative of arrhythmogenic right ventricular dysplasia were not observed in the study group. This study suggests the fibrofatty infiltration in cardiac allografts is a clinically different entity from arrhythmogenic right ventricular dysplasia and has an unknown etiology. Our study findings suggest that identifying fibrofatty infiltrates in cardiac transplant patients during routine right ventricular biopsy can be a predictive factor for shortened life of the pediatric cardiac allograft.