Left ventricular function in atrial fibrillation during overdrive pacing

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Pacing

Background:

• Atrial fibrillation (AF) causes irregular heart rhythms, decreasing stroke volume and cardiac output.
• Ventricular pacing after AV node ablation can improve left ventricular function.
• Overdrive pacing was hypothesized to benefit cardiac performance in AF by regularizing rhythm.

Purpose of the Study:

• To quantify the impact of ventricular pacing on stroke volume and cardiac output in patients with atrial fibrillation.
• To assess if regularizing ventricular rhythm through pacing can mitigate the hemodynamic deficits of AF.

Main Methods:

• Studied 18 patients with chronic AF and permanent pacemakers.
• Measured aortic time velocity integral (TVI) via continuous-wave Doppler as a surrogate for stroke volume.
• Compared stroke volume during AF with stroke volume during ventricular pacing at a fixed cycle length (666 ms) and minimum pacing rate.

Main Results:

• Ventricular pacing at a cycle length of 666 ms significantly increased relative stroke volume by 18%.
• No significant difference in cardiac output was found between pacing at the minimum rate and the corresponding AF cycle length.
• Stroke volume improvements were observed only at pacing rates at or above the upper limit of the normal physiologic range.

Conclusions:

• Regularizing ventricular rhythm with overdrive pacing in AF patients can enhance stroke volume.
• Cardiac output benefits from pacing in AF are contingent on pacing rates within or exceeding the normal physiologic range.
• Pacing strategies should consider rate-dependent effects on hemodynamics in AF patients.