Syncope in patients paced for atrioventricular block

Aims: Although syncope is the main reason for cardiac pacing in ∼40% of patients affected by atrioventricular block (AVB), very few data are available on the benefit of cardiac pacing in preventing syncopal recurrences.

Methods and results: We retrospectively evaluated 229 consecutive patients (124 males, age 80 ± 10 years) who had received a permanent pacemaker from January 2009 to December 2013 for AVB and syncope (94 patients, 41%) or AVB without syncope (135 patients, 59%). In patients with AVB and syncope, a third-degree or Mobitz II second-degree AVB had been documented in 73 and was only suspected in another 21, all of whom had bundle branch block. Follow-up was available in 223 patients. At 5 years, the actuarial syncope recurrence rate was 1% (95% CI, 0-3) in patients with documented AVB plus syncope and 3% (95% CI, 1-5) in those without syncope, whereas it was 14% (95% CI, 0-28) in patients with undocumented AVB plus syncope (P = 0.001). The actuarial combined recurrence rate of syncope and/or pre-syncope was 2% (95% CI, 0-4) in patients without syncope, 8% (95% CI, 0-17) in patients with documented AVB plus syncope, and 19% (95% CI, 1-37) in patients with undocumented AVB plus syncope, P = 0.002. All syncopes occurred in patients without overt structural heart disease (SHD), the corresponding actuarial estimate being 4% (95% CI, 0-6) at 1 year and 6% (95% CI, 4-8) at 5 years (P = 0.002 vs. patients with SHD).

Conclusions: Cardiac pacing is highly effective in preventing syncopal recurrences when AVB is documented. Syncope may recur in a non-negligible minority of paced patients when AVB is suspected but not documented and in patients without SHD.