Atrial rate-responsive pacing in sinus node disease

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Abstract
Patients with sinus node disease (SND) who are unable to achieve an adequate increase in heart rate during exercise are candidates for atrial rate-responsive pacing (AAI-R). We have implanted 40 AAI-R systems in SND patients with an average follow-up of 125 ± 8 (range 3–30) months. All the patients received an acitivity-sensing pulse generator (Activitrax®, Medtronic or Sensolog®, Siemens-Pacesetter) with a single atrial lead. Only patients with an intraoperative A V nodal block cycle-length above 100 beats min−1 were included. During follow-up, one patient was observed to have transient asymptomatic 2:1 A V-block during sleep. No patient developed persistent A V-block or chronic atrial fibrillation. Twelve patients with persistent chronotropic incompetence were assigned for a randomized double-blind crossover study, comparing exercise treadmill capacity in AAI-R with conventional atrial inhibited pacing (AAI). During AAI-R pacing the maximum heart rate during exercise was 120±l beats min−1 compared with 97±21 beatsmin−1 during AAI pacing (P<0.01). The average exercise time increased from 11.2 ± 2 min during AAI-pacing to 13.4 ± 3 min during AAI-R pacing (P < 0.01). AAI pacing should be considered for patients with SND and chronotropic incompetence.