Abstract 12149: Adverse Effects of First-Degree AV-Block in Patients With Sinus Node Dysfunction: Data From the Mode Selection Trial
Objective: Patients with a pacing indication and a first-degree AV-block (1st AVB) pose a clinical challenge. Atrial pacing exaggerates the AV-delay, while unnecessary right ventricular pacing has been shown to be detrimental. The prognostic impact of 1st AVB in patients with sinus node dysfunction (SND) and the impact of pacing in this setting is not known.
Methods: In the Mode Selection Trial (MOST), 2010 patients with SND were randomized to either dual-chamber (DDDR) or ventricular (VVIR) pacing and followed for a median of 33 months. The lower rate was programmed to be ≥60 bpm. In the DDDR group, the AV delay was recommended to be between 120 and 200 ms. We report on clinical outcomes in patients with 1st AVB (PR-interval >200 ms) compared with patients who had a normal PR-interval at baseline.
Results: Patients with 1st AVB (n=378) were older (median [Q1, Q3]; 76 [70, 82] vs. 73 [66, 79] years, P≤0.0001), more often male (57 vs. 49%, P=0.0049) and had more comorbidity, such as hypertension (66 vs. 60%, P=0.034) and heart failure (HF) (24 vs. 17%, P=0.0050) than patients with normal AV-conduction (n=1159). The percentage of pacing was higher among patients with 1st AVB in the VVIR (68 [34,91] vs. 56 [20,86] %, P=0.0076) as well as in the DDDR-arm (95 [82, 99] vs. 86 [52, 98] %, P≤0.0001). In multivariable analyses, patients with 1st AVB were at greater risk of death, stroke, or HF hospitalization (HR 1.31, 95% CI 1.06-1.61, P=0.013) (Figure). A trend towards a higher incidence of atrial fibrillation was seen (HR 1.24, 95% CI 0.98-1.55, P=0.069). No significant interactions between pacing arm and prolonged vs. normal PR were found for any end-point, and hazard ratios were consistent across subgroups.
Conclusion: 1st AVB is associated with more advanced disease but is still an independent predictor of poor clinical outcome, which may be driven by a higher percentage of ventricular pacing. Neither DDDR nor VVIR pacing, as employed in MOST, eliminate the negative effects associated with 1st AVB.
- © 2013 by American Heart Association, Inc.