Atrial undersensing in VDD pacing: should we blame calcium-channel blockers?

Abstract

Single-lead VDD pacing is an attractive alternative to DDD pacing in patients with high-degree AV block and normal sinus node function. It provides physiological AV synchronous stimulation with a single lead. Owing to easier implantation, VDD systems have shorten the operation time by up to 40% and reduce the intraoperative fluoroscopy time by up to 55%. Additionally, they showed a trend towards a reduction in perioperative complications compared with DDD systems, and also showed a reduction in cost. 1 Therefore, why are single-lead VDD systems used infrequently in patients with isolated high-degree AV block? First, concerns exist about testing for sinus node dysfunction and development of sinus bradycardia during long-term follow-up. Sinus bradycardia during VDD pacing may result in VVI stimulation or necessitate the implantation of an atrial lead. However, in properly selected patients, sinus node function remains stable in the vast majority of patients. 2 Secondly, scepticism exists about the reliability of atrial sensing, using a floating atrial dipole within the right atrium. When I (B.N.) personally had the first contact with single-lead VDD pacing at a presentation given by Seymour Furman in Munich in the year 1990, I asked him whether he really thought that this concept might work, he answered: ‘Just put it in, it works’. Many studies thereafter have shown that he was right. Reliable atrial sensing can be accomplished with the floating atrial dipole, achieving AV synchrony .99%, with the prerequisite that atrial sensitivity is programmed to very sensitive values. 3‐5