Heart Valve Lesions following Papillary Muscle Damage

Abstract

THE genesis of rheumatic valvular disease in man has been difficult to establish owing to the scarcity of human material in the early stages and the absence of any comparable condition in experimental animals. On the evidence at present available it has been stated that the calcific lesions found in human rheumatic valvular disease are unlikely to be the direct result of the rheumatic process in the valve cusps¹. In recent experiments we have been studying the effects of papillary muscle damage and inactivation on the function of the mitral valve and the left ventricle of the dog². In these experiments either the anterior or the posterior papillary muscle was injected with 0.5–1.0 ml. ethanol and the animal allowed to recover. A surprising finding was that when the animals were killed three months later, four out of twelve dogs in addition to papillary muscle damage also had fibrotic, calcific or chondrific lesions of the mitral valve cusps (Fig. 1). In all four animals the valvular lesion was in the segment of the aortic cusp of the mitral valve which was attached to the damaged papillary muscle and there was no continuity of the valvular lesions with either the papillary muscle lesion through the chordae tendinae or the atriotomy scar in the three animals in which this had been carried out. In ten dogs used as controls in which the ethanol injection was made into the lateral wall of the left ventricle between the papillary muscles, no valvular lesions were found. Histological examination of the lesions showed a fibrous plaque on the atrial surface of the valve cusp with replacement by calcification and chondrification (Fig. 2). There was no evidence of an infective lesion.