Paradoxical shortening of the second PR interval during 3:2 atrioventricular nodal block

A patient with 3:2 second-degree AV block after acute inferior wall myocardial infarction showed consistent PR interval shortening on the second conducted beat in each periodicity. Intracardiac electrophysiologic evaluation revealed that the site of block was nodal. A typical Wenckebach pattern with prolongation of the AH interval was noted. The shorter PR resulted from a paradoxical shortening of the HV interval in the second beat, most likely due to supernormal conduction in the setting of concomitant trifascicular disease.