Dual AV nodal pathways--vagal influences on AV nodal conduction

This 52-year-old male presented with syncope and demonstrated two distinct PR intervals on the electrocardiogram. Electrophysiologic studies showed dual AV nodal pathways. Right-sided carotid sinus massage induced prolonged periods of sinus arrest with no change in AH interval. Left-sided carotid sinus massage produced long AH intervals (slow pathway conduction) with some slowing of sinus rate. Whenever sinus rhythm with slow pathway conduction was observed (long AH) a 20-30 mmHg drop systolic pressure was seen. Following implantation of an AV sequential pacemaker, the patient has been asymptomatic.