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Association Between Frequency of Atrial and Ventricular Ectopic Beats and Biventricular Pacing Percentage and Outcomes in Patients With Cardiac Resynchronization Therapy
Study Questions:
What is the relationship of increased ectopic beats (both atrial and ventricular) to biventricular (BiV) pacing percentage and subsequent adverse outcomes?
Methods:
From the MADIT-CRT trial, 801 patients with an implanted cardiac resynchronization therapy-defibrillator (CRT-D) device, with data available on BiV pacing percentage and preimplantation 24-hour Holter recordings, were included. Using logistic regression, the authors estimated the influence of ectopic beats on percentage of BiV pacing. Reverse remodeling was measured as reductions in atrial and left ventricular end-systolic volumes (LVESVs) at 1 year. Cox models were used to assess the influence of ectopic beats on the outcomes of heart failure (HF) or death, ventricular tachyarrhythmias (VTAs), and death.
Results:
In the pre-implantation Holter recording, ectopic beats accounted for a mean 3.2% (± 5.5%) of all beats. The probability of subsequent low BiV pacing percentage (<97%) was increased threefold (odds ratio [OR], 3.37; 95% confidence interval [CI], 1.74-6.50; p < 0.001) in patients with 0.1-1.5% ectopic beats and 13-fold (OR, 13.42; 95% CI, 7.02-25.66; p < 0.001) in patients with >1.5% ectopic beats, when compared to those with <0.1% ectopic beats. Patients with ≥0.1% ectopic beats had significantly less reverse remodeling (% reduction LVESV: 31 ± 15) compared to patients with <0.1% ectopic beats (% reduction LVESV: 39 ± 14; p < 0.001). The risk of HF/death and VTA was significantly increased in those with 0.1-1.5% (hazard ratio [HR], 3.13 and HR, 1.84) and for >1.5% (HR, 2.38 and HR, 2.74, respectively).
Conclusions:
Relatively low frequencies of ectopic beats (≥0.1%) dramatically increase the probability of low BiV pacing (<97%) with reduced CRT efficacy by less reverse remodeling and higher risk of HF/death and VTA. This supports pre-implantation Holter monitoring for patients selected for CRT for optimal outcome.
Perspective:
There is a large body of evidence that maximizing BiV pacing is associated with improved outcomes. From this and other reports, it appears that the physician should not be satisfied until virtually 100% BiV pacing is accomplished. While this study did not include patients with atrial fibrillation, the findings are consistent with CRT studies involving patients with atrial fibrillation, and prior studies of premature ventricular contractions. The current study expands the concept to include atrial ectopy as well. Prospective studies will be needed to define the role of antiarrhythmic drugs versus ablation therapy in patients with ectopy and/or atrial fibrillation.
Keywords: Defibrillators, Cardiac Pacing, Artificial, Heart Failure, Stroke Volume, Electrocardiography, Ambulatory, Ventricular Premature Complexes, Logistic Models, Cardiac Resynchronization Therapy, Tachycardia
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