Microvascular coronary arterial vasculopathy - predictive value of endomyocardial biopsy

Graft arteriosclerosis (GA) is characterized as a diffuse, usually concentr ic, proliferative lesion of uncertain pathogenesis that occurs in the coron ary arteries of cardiac allografts involving both the microvasculature and epicardial vessels, and represents the major limitation to long-term recipi ent survival. The whole length of the vessel is affected, including small d istal intramyocardial branches, which precludes optimal treatment with rout ine revascularization procedures. The prevalence of GA at 5 years after tra nsplantation is high. Early diagnosis of GA is limited by the lack of clini cal symptoms for ischemia in the denervated allogaft, by the insensitivity of coronary angiography, which frequently underestimates the extent and sev erity of the disease, and by the exclusive or predominant involvement of sm all intramyocardial vessels in some cases. The introduction of intracoronar y ultrasound imaging supports earlier pathological data indicating that cor onary angiography underestimates the severity of the disease. The use of in tracoronary ultrasound has improved the early diagnosis of large vessel dis ease, but it lacks accessibility to distal lesions; thus, the extent of int ramyocardial small artery disease remains relatively unexplored. Although i t has been proposed that EMB could provide useful information on the diagno sis and development of allograft vasculopathy, less attention has been focu sed on the small intramyocardial vessels, as they appear in the endomyocard ial biopsy (EMB), nor on the significance of the myocardial pathology resul ting from the perfusion defects caused by GA. The aim of this paper is to briefly review some of the pathogenic mechanism s responsible for the development of GA, and the pathological findings obse rved in the microvasculature of the myocardium with special attention to th e lesions that can be noticed in EMBs.