Related Experiment Video
Updated: Apr 30, 2026
Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice
Published on: June 29, 2022
Adverse effects of first-degree AV-block in patients with sinus node dysfunction: data from the mode selection trial
Fredrik Holmqvist1, Anne S Hellkamp, Kerry L Lee
1Clinical Cardiac Electrophysiology, Duke University Medical Center, Durham, North Carolina; Duke Clinical Research Institute, Duke University Medical Center, Durham, North Carolina.
Insights
First-degree atrioventricular (AV)-block in patients with sinus node dysfunction is linked to worse outcomes. Pacing did not negate these negative effects, highlighting the need for further research into managing this patient group.
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.
Background:
Patients with a pacing indication and first-degree atrioventricular (AV)-block pose a clinical challenge. The prognostic impact of first-degree AV-block in patients with sinus node dysfunction and the impact of pacing in this setting are not known.
Methods:
In the Mode Selection Trial (MOST), 2,010 patients with sinus node dysfunction were randomized to either dual-chamber (DDD-R) or ventricular (VVI-R) pacing and followed for a median of 33 months. We report on clinical outcomes in patients with first-degree AV-block (PR interval > 200 ms) compared with patients who had a normal PR interval at baseline.
Results:
Patients with first-degree AV-block (n = 378) were older (median [Q1, Q3]; 76 [70, 82] years 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 (24% vs 17%, P = 0.0050) than patients with normal AV-conduction (n = 1,159). In multivariable analyses, patients with first-degree AV-block were at greater risk of death, stroke, or heart failure hospitalization (hazard ratio [HR] 1.31, 95% confidence interval [CI] 1.06-1.61, P = 0.013). 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 versus normal PR were found for any endpoint, and hazard ratios were consistent across subgroups.
Conclusions:
First-degree AV-block is associated with more advanced disease but is still an independent predictor of poor clinical outcome. Neither DDD-R nor VVI-R pacing, as employed in MOST, eliminate the negative effects associated with first-degree AV-block.
Related Concept Videos
01:18Dysrhythmias IV: Characteristics of Bradyarrhythmias
01:24Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers
01:22Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers
Class 1A Antiarrhythmic Drugs: These drugs work by moderately blocking sodium channels,...
01:20Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers
Verapamil, a calcium channel blocker, inhibits calcium movement across myocardial cell membranes and vascular smooth muscle. This results in the dilation of coronary and...
01:22Heart Failure Drugs: β-Blockers
01:16ECG Interpretation of Arrhythmias I: Sinus Arrhythmias
Types of Arrhythmias
Sinus Node Arrhythmias
Sinus Bradycardia: Originating from the sinoatrial (SA) node, sinus bradycardia involves slower impulses, resulting in a heart rate of less than 60 beats per minute (bpm). Causes include sleep, vagal stimulation, beta-blockers, hypothyroidism,...