A series of 260 patients who underwent pneumonectomy for cancer of the lung was analysed for post-operative arrhythmias. Of these patients 28% developed such arrhythmias, usually in the form of atrial fibrillation, on the first to third post-operative day, rapidly yielding to fast-acting digitalis preparations. Possible aetiological factors were investigated, but no single cause was demonstrable. The indication for pre-operative digitalization, if any, is discussed.Arrhythmias are fairly common following thoracic surgery. Numerous analyses on patients with diseases of the lung have shown that the incidence increases with the extent of the procedure, from 5% after lobectomy to about 30% after pneumonectomy (Cohen and Pastor, 1957;Mowry and Reynolds, 1964). Aetiological theories are many and not always equally well founded. Among the more plausible and well substantiated ones there are:(1) advancing age (Cohen and Pastor, 1957;Currens, White, and Churchill, 1943;Massie and Valle, 1947;Mowry and Reynolds, 1964);(2) extent of operation (Mowry and Reynolds, 1964); (3) co-existing heart disease (Burman, 1965;Cohen and Pastor, 1957;Dodd, Sims, and Bone, 1962;Mowry and Reynolds, 1964).Moreover, a number of more hypothetical factors have been advanced, e.g., (4) reduction in the pulmonary vascular bed (Cerney, 1957); (5) and in the Department of Thoracic Surgery, Bispebjerg Hospital, Copenhagen. The patients did not have a follow-up in the ordinary sense of the word, as it was only the period up to a few months after the operation which was of interest in connexion with post-operative arrhythmias.The patients totalled 260 (one record is missing, so that the patient was excluded from the analysis)-24 women and 236 men. The age distribution is apparent from Table I. In 135 cases the pneumonectomy was right-sided.in 125 cases left-sided. The tumour originated in the upper or middle lobe in 158 cases and in the lower lobe in 102. In several cases its origin was difficult to decide because of invasion into the adjacent areas. so that these figures have to be considered with reserve. The histology did not differ from that found in other series, showing squamous-cell carcinoma in the majority. Forty-four patients died as a result of the operation, or within the first post-operative day; the causes of death were pulmonary emboli, 17; uncontrollable haemorrhage, 9; pulmonary oedema, 5; aspiration into the lung, 2; cerebral embolus, 1; cerebral metastases, 1; invasion of the superior vena cava, 1; perforation into the oesophagus, 1; while in 7 cases the cause was unknown. 568 on 9 May 2018 by guest. Protected by copyright.