Conduction Disturbances in Patent Ductus Arteriosus

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Abstract
A study of conduction disturbances in 200 patients with patent ductus arteriosus was carried out. The atrioventricular (AV) conduction was found generally disturbed as compared with normal cases. A significant delay in AV conduction was demonstrated by the high incidence (10.5 per cent) of first-degree AV block, by the elevated percentage of high values of the P-R index and by a high mean P-R index in the whole series (0.85 versus 0.75 in normal subjects). After surgery a significant improvement in AV conduction was noted. First-degree AV block disappeared in 79 per cent of the cases, and in some instances the block decreased in intensity. In cases without diagnosis of AV block the improvement, as manifested by the diminution of the P-R index, was observed in 62 per cent of the cases. The improvement in AV conduction was greater in those groups with higher preoperative P-R index. The impression was that a large number of cases with high values of the P-R index, although still below the upper limit of normal (1.00), actually have first-degree AV block, undiagnosed by the usual criteria. The mean P-R index after surgery for the whole group was 0.79. It was suggested that the AV conduction disturbances in patent ductus arteriosus are related, in some way, to the hemodynamic conditions of this entity and particularly to the left-to-right shunt between aorta and pulmonary artery. Six cases (3 per cent) of incomplete right bundle-branch block and five (2.5 per cent) of incomplete left bundle-branch block were found. These disturbances did not change after surgery.