Syncope in patients paced for atrioventricular block

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.

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).

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.