Necropsy data from a series of 8 patients diagnosed during life as having chronic sinoatrial disorder (sick sinus syndrome) are presented. The morphology of the cardiac conducting system was studied by serial section, and the coronary vasculature was examined in detail in 5 of the 8 patients by the injection of a radiopaque medium, and in all 8 by routine histological methods. The sinoatrial nodes were found to be abnormal in 7 of the 8 patients. In 4 the node was atrophic, in 3 there was a pronounced increase in the amount offibrous tissue present in the node, and in only one case did the node appear normal on light microscopy. In 1 of the 3 patients withfibrosed nodes amyloid tissue wasfound in the node itself, and heavy deposition was noted in the atrial musculature surrounding the node. The sinoatrial-node artery was patent in all cases and major narrow-ing of the larger coronary arteries was found in only 1 case. Histological abnormalities were found in the atrioventricular conducting tissue in all but 1 case, changes being seen either in the atrioventricular node or in the His-Purkinje system. It is concluded that the aetiology of sinoatrial disease is multifactorial, but that at least in the cases studied coronary arteriosclerosis was not responsible.

Since the description by Short (1954) ofa syndrome of alternating bradycardia and tachycardia, there has been a growing volume of published reports on what has become known as sinoatrial disorder (Lloyd-Mostyn et al., 1973). There have been papers from several countries describing its various clinical features, and modes of presentation, under such synonvms as sick sinus or lazy sinus syndrome (Bouvrain et al., 1967; Ferrer, 1968; Shaw and Eraut, 1969). Furthermore, the treatment of the condition using both electrical and pharmacological methods and its mortalityand morbidity have been described (Eraut and Shaw, 1971; Aroesty et al., 1974), and a complete monograph on the subject has recently been published (Ferrer, 1974). There have been, however, very few reports of necropsy studies; indeed, a review of the published material produced only 11 cases of sinoatrial disorder of a chronic nature, in which some specialised examination of the conduction system had been undertaken at necropsy (Rossi, 1969; Patton et al., 1970; Rasmussen, 1971; Rosen et al., 1971; Rubinstein et al., 1972; Kaplan et al., 1973; Kulbertus et al., 1973; Warembourg et al., 1974; Sauerwein et al., 1976). Of these, the morphology of the sinoatrial node, atrial musculature, and the other parts of the specialised conducting system of