Case of the Month 05/00

In some patients with atrial fibrillation the occurrence of wide PVC-like beats is not always ventricular ectopy. Because the right bundle branch repolarizes slightly slower than the left, supraventricular impulses can come down through the AV node and bundle of his and then down the left bundle branch only. In effect giving the appearance of a one beat RBBB. The hallmarks of Ashman's beats are that they are only found in Af, are proceeded by a long-short RR interval and they are conducted in RBBB morphology. You should check for RBBB morphology in lead MCL1 or V1. These beats are harmless and require no treatment. The patient was admitted and his Atrial Fib was treated with IV Cardizem and a normal sinus returned.