Adverse effects of first-degree AV-block in patients with sinus node dysfunction: data from the mode selection trial

Area of Science:

• Cardiology
• Electrophysiology
• Clinical Trials

Background:

• First-degree atrioventricular (AV)-block presents a clinical challenge in patients requiring pacing.
• The prognostic implications of first-degree AV-block and the efficacy of pacing in sinus node dysfunction remain unclear.

Purpose of the Study:

• To investigate the clinical outcomes of patients with sinus node dysfunction and first-degree AV-block compared to those with normal AV conduction.
• To evaluate the impact of dual-chamber (DDD-R) versus ventricular (VVI-R) pacing in this patient population.

Main Methods:

• Analysis of data from the Mode Selection Trial (MOST), randomizing 2,010 patients with sinus node dysfunction to DDD-R or VVI-R pacing.
• Comparison of clinical outcomes between patients with first-degree AV-block (PR interval > 200 ms) and those with normal PR intervals.

Main Results:

• Patients with first-degree AV-block were older, more frequently male, and had higher comorbidity rates (hypertension, heart failure).
• First-degree AV-block independently predicted a higher risk of death, stroke, or heart failure hospitalization (HR 1.31, P=0.013).
• A trend towards increased atrial fibrillation incidence was observed (HR 1.24, P=0.069), with no significant interaction with pacing mode.

Conclusions:

• First-degree AV-block is an independent predictor of adverse clinical outcomes in patients with sinus node dysfunction.
• Current pacing strategies (DDD-R or VVI-R) did not mitigate the negative prognostic impact of first-degree AV-block.