Long-Term Follow-Up of Second-Degree Heart Block in Children.

Little is known about the outcomes of children with second-degree heart block. We aimed to determine whether children with structurally normal hearts and Mobitz 1, 2:1 block or Mobitz 2 are at increased risk for progressing to complete heart block (CHB) or requiring a pacemaker (PM) at long-term follow-up. We searched our institutional electrophysiology database for children with potentially concerning second-degree block on ambulatory rhythm monitoring between 2009 and 2021, defined as frequent episodes of Mobitz 1 or 2:1 block, episodes of Mobitz 1 or 2:1 block with additional evidence of conduction disease (i.e. first-degree heart block, bundle branch block), or episodes of Mobitz 2. Ambulatory rhythm monitor, ECG, and demographic data were reviewed. The primary composite outcome was CHB on follow-up rhythm monitor or PM placement. 20 patients were in the final analysis. Six (30%) patients either developed CHB but do not have a PM (4 = 20%) or have a PM (2 = 10%). Median follow-up was 5.8 years (IQR 4.4-7.0). Patients with CHB or PM were more likely to have second-degree block at maximum sinus rate (67% vs. 0%, p = 0.003), a below normal average heart rate (67% vs. 14%, p = 0.04), and 2:1 block on initial ECG (50% vs. 0%, p = 0.02). In this study of children with potentially concerning second-degree block, 30% of patients progressed to CHB or required a PM. Second-degree block at maximum sinus rate, a low average heart, and 2:1 block on initial ECG were associated with increased risk of disease progression.