Related Experiment Video
Updated: Jul 11, 2026

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
Published on: December 11, 2017
Slow rate during AF improves ventricular performance by reducing sensitivity to cycle length irregularity
Zoran B Popović1, Kent A Mowrey, Youhua Zhang
1Department of Cardiovascular Medicine, The Cleveland Clinic Foundation, Ohio 44195, USA.
Slowing heart rate during atrial fibrillation (AF) reduces the impact of irregular ventricular cycle lengths (VCL) on heart performance. This finding suggests that managing VCL irregularity is less critical when heart rate is controlled.
Area of Science:
- Cardiology
- Physiology
Background:
- Atrial fibrillation (AF) presents with rapid and irregular ventricular cycle lengths (VCL).
- Heart rate slowing (VCL prolongation) is known to benefit AF patients, but the effect of irregularity itself is less understood.
Purpose of the Study:
- To investigate the impact of ventricular cycle length (VCL) irregularity on left ventricular (LV) performance during atrial fibrillation (AF).
- To determine if prolonging VCL affects the sensitivity of LV performance parameters to cycle length irregularity.
Main Methods:
- Studied 10 anesthetized dogs during induced AF.
- Recorded R-R intervals, LV pressure, and aortic flow.
- Manipulated VCL using AV nodal vagal stimulation to achieve 75%, 100%, and 125% of intrinsic sinus cycle length.
- Assessed cycle length irregularity using the RR(p)/RR(pp) ratio.
- Analyzed LV performance metrics (maximum LV power, dP/dt_min, relaxation time constant) via nonlinear fitting.
Main Results:
- Prolonging VCL led to a significant decrease in the dependence of LV performance on cycle length irregularity.
- A plateau effect was observed, indicating reduced sensitivity to irregularity as VCL increased.
- LV performance parameters showed less variability with increased VCL.
Conclusions:
- Prolongation of VCL during AF significantly reduces the sensitivity of LV performance parameters to cycle length irregularity.
- These findings highlight the importance of heart rate control in mitigating the adverse effects of irregular rhythms in AF.
More Related Videos
08:10Estimating Bilateral Atrial Function by Cardiovascular Magnetic Resonance Feature Tracking in Patients with Paroxysmal Atrial Fibrillation
Published on: July 20, 2022
08:05Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice
Published on: June 29, 2022
Related Concept Videos
The Cardiac Cycle
The Process
Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and empty blood into the...
Cardiac Cycle
During the cardiac cycle, blood flow through the heart is regulated entirely by changing pressure gradients. This sequence of events begins with the heart in a state of total relaxation, known as mid-to-late diastole, during which blood passively flows from...
Disturbances in Heart Rhythm
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...
Dysrhythmias III: Characteristics of Dysrhythmias
Dysrhythmias IV: Characteristics of Bradyarrhythmias
ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias