Morphological changes in small vessels on endomyocardial biopsy.

Small vessel disease has been described in various cardiac conditions including diabetes mellitus, amyloidosis, and connective tissue disease. Less well understood is the incidence and morphological features of small vessel disease in patients with myocardial disease of unknown etiology. This study examines the incidence, clinical presentation, and pathological changes of small vessel disease in patients with normal epicardial coronary arteries undergoing endomyocardial biopsy. Biopsy specimens in 110 consecutive patients were analyzed by light and electron microscopy. Small vessel abnormalities were present in 16 patients (14.6 percent) of whom five patients had associated hypertension and 11 patients had idiopathic small vessel disease. There were six males and 10 females with a mean age of 53 (26 to 76) years. Clinical presentations were arrhythmias, heart failure, or chest pain. The left ventricular ejection fraction was reduced (less than 50 percent) in 12 of these 16 patients. The morphological features of small vessel disease included marked thickening of the arterial wall owing to subendothelial deposits of heterogeneous electron dense materials consisting of microfibrils, collagen and elastic fibers, cellular debris, and other amorphous substances. Subendothelial deposits comprised a mean 60 percent (40 to 76 percent) of the arterial wall thickness.