Ventriculoatrial conduction in patients with implantable cardioverter defibrillators: implications for tachycardia discrimination by dual chamber sensing.

Incorporation of atrial electrograms in the tachycardia detection algorithm may improve tachyarrhythmia discrimination by ICDs but retrograde ventriculoatrial (VA) conduction over the AV node during ventricular tachyarrhythmia may be problematic. The present study analyzed VA conduction characteristics in 66 ICD patients who had evaluation of the VA conduction system by electrophysiological studies before implant. VA conduction was demonstrated in patients during ventricular decremental stimulation. Forty patients had inducible sustained monomorphic VT. The minimum cycle length maintaining 1:1 VA conduction during ventricular stimulation was longer than the cycle of VT in every patient (496 +/- 100 msec vs 320 +/- 81 msec; P < 0.01). Occasional VA conduction during VT was observed in five patients and one patient had 2:1 VA conduction during induced VT. No patient had 1:1 VA conduction during VT. We conclude that brisk VA conduction is uncommon and 1:1 VA conduction during VT is rare ICD recipients. VA conduction is unlikely to complicate the incorporation of atrial electrograms into tachyarrhythmia detection algorithms.