Aetiology of chronic heart block. A clinico-pathological correlation in 65 cases.

The cause of chronic heart block is often obscure on clinical grounds alone. Consequently there is considerable difficulty in deciding the prognosis of a patient with complete heart block even with successful artificial pacing. Coronary artery disease has been generally accepted in the past as the predominant cause of heart block, and Penton, Miller, and Levine (1956) estimated an incidence of 43 per *cent, Wright et al. (1956) one of 69 per cent, and Friedberg, Donoso, and Stein (1964) one of 48 per cent. These estimates were based on clinical and electrocardiographic evidence. Other studies suggested that areas of fibrosis involving the conducting system, either alone or in association with scattered areas offibrosis in the myocardium, were responsible for heart block (Lenegre and Moreau, 1963; Lev, 1964; Zoob and Smith, 1963). In one of our earlier patients, the only cardiac abnormality was fibrotic lesions confined to the conducting tissue, a surprising finding as severe coronary disease had been suspected, and this made us realize the importance of developing techniques for long-term artificial pacing (Portal et al., 1962). With the continuing improvement of these techniques, the prognosis of a patient will become more dependent on the cause of the heart block. In an effort to improve the clinical diagnosis of the underlying cause of heart block, a retrospective survey was carried out in 65 consecutive patients with chronic heart block who had come to necropsy during the past 3 years.