[The short PR syndrome: sino-atrial block with preservation of sino-nodal conduction].

From among the theories which have been advanced to explain the finding on ECG of a shorter than normal PR interval, in addition to the short circuit theory we should mention the explanation given by Condorelli before the first publication on the "short PR-normal QRS" syndrome appeared. While studying the mechanism of conduction of a stimulus in the atrial myocardium, he showed that a short PR may result from a conduction defect in the sino-atrial pathways, while sino-nodal conduction remains normal. In this report there is an example which supports the validity of Condorelli's hypothesis. It involves a female patient with mitral valve disease beginning to affect the tricuspid. Her rheumatic disease had just relapsed, and after this there was a long period of attacks of tachycardia with arrhythmia during the course of which the surface electrocardiogram showed a short PR and normal QRS. Electrophysiological investigations allowed us to interpret these findings in the light of Condorelli's hypothesis (sino-atrial block with normal sino-nodal conduction). This study suggests that it is useful to separate off those cases with a short PR and normal QRS to a clinical entity of their own, as this syndrome may have a different pathogenesis. Therefore, if there is no electrocardiographic evidence of an accessory pathway, far from indicating accelerated conduction, the short PR may be due to an isolated defect of conduction in the atrial myocardium, as Condorelli suggested. It is also correct that this author should be given credit for describing the first cases. To him also should go credit for first describing the short PR.