Right Atrial Pacing and the Risk of Postimplant Atrial Fibrillation
Background: In patients with cardiac resynchronization therapy (CRT) devices, right atrial (RA) pacing introduces a significant prolongation in interatrial conduction time, delaying left atrial mechanical systole and curtailing left ventricular filling. The resultant increase in left-sided filling pressures may facilitate atrial fibrillation (AF). We sought to determine whether the extent of RA pacing influences the incidence of AF after CRT.
Methods: Consecutive CRT patients (n = 309) followed at our institution were retrospectively studied for percentage of RA pacing and incidence of high atrial rates, as determined by regular device interrogations. Additional clinical data were collected from the medical record.
Results: The mean follow-up was 18.1 ± 13.3 months, during which 209 (67.6%) patients had at least 1 detected high atrial rate episode consistent with AF. Higher percentages of RA pacing were associated with a greater risk of postimplant AF, with its incidence increasing incrementally with quartiles of RA pacing: 44.6%, 64.3%, 79.7%, and 81.6%, respectively (P < .001). After controlling for all factors predictive of postimplant AF on univariate analysis (right atrial pacing quartile, follow-up duration, mitral regurgitation severity, and prior AF history), RA pacing quartile remained a significant predictor of post-CRT AF (hazard ratio 1.92, 95% CI 1.40-2.62, P < .001) upon multivariate analysis. In addition to predicting AF incidence, higher RA pacing quartiles were also associated with significantly greater AF burden.
Conclusions: Compared to atrial sensing, atrial pacing is associated with a 2-fold increased risk of post-CRT AF. Prospective comparison of DDD and VDD pacing modes in CRT is warranted.
Cardiac resynchronization therapy (CRT) has become an integral component of heart failure (HF) treatment in patients with marked left ventricular dysfunction, intraventricular conduction delay, and severe HF symptoms, providing symptomatic and structural improvement in two thirds of patients. Cardiac resynchronization therapy systems for patients not in permanent atrial fibrillation (AF) use 3 endocardial pacing leads: a right atrial (RA) lead usually placed in the RA appendage, a right ventricular lead, and a coronary sinus (or epicardial) left ventricular lead. Devices are typically programmed to provide atrio-biventricular pacing (ie, DDD mode) with a short atrioventricular (AV) delay to ensure that the device provides ventricular electrical capture, thus maximizing resynchronization.
Heart failure is commonly associated with AF, presumably because chronically elevated filling pressures contribute to the pathogenesis of AF. Cardiac resynchronization therapy may decrease the incidence and burden of AF, perhaps by improving cardiac hemodynamics, although most studies to date have been inadequately controlled or neglected device-based diagnostics. Acute CRT studies have demonstrated that DDD pacing may mitigate CRT's hemodynamic benefit by curtailing ventricular filling when compared with atrial-tracked, biventricular pacing (ie, VDD mode) (Figure 1). Higher left-sided filling pressures may ensue, potentially increasing the propensity of the atria to fibrillate. No study examining AF burden in CRT has reported RA pacing burden to date.
(Enlarge Image)
Figure 1.
Pathophysiologic basis for greater LV preload with VDD pacing compared to DDD pacing with CRT. Transmitral flow is depicted above the corresponding ECG tracing. Note the delayed onset of left atrial systole (ie, A wave) with DDD pacing because of the greater delay between onset of atrial electrical systole and left atrial mechanical systole. Because the AV delay must be relatively short to ensure biventricular capture, especially in the setting of intact AV nodal conduction, the A wave is attenuated in the DDD mode. IACT, Interatrial conduction time; MVC, mitral valve closure.
We hypothesized that RA pacing burden increases the incidence of post-CRT AF. A retrospective analysis of all CRT patients followed at our institution between 2000 and 2007 was performed to examine this question.
Abstract and Introduction
Abstract
Background: In patients with cardiac resynchronization therapy (CRT) devices, right atrial (RA) pacing introduces a significant prolongation in interatrial conduction time, delaying left atrial mechanical systole and curtailing left ventricular filling. The resultant increase in left-sided filling pressures may facilitate atrial fibrillation (AF). We sought to determine whether the extent of RA pacing influences the incidence of AF after CRT.
Methods: Consecutive CRT patients (n = 309) followed at our institution were retrospectively studied for percentage of RA pacing and incidence of high atrial rates, as determined by regular device interrogations. Additional clinical data were collected from the medical record.
Results: The mean follow-up was 18.1 ± 13.3 months, during which 209 (67.6%) patients had at least 1 detected high atrial rate episode consistent with AF. Higher percentages of RA pacing were associated with a greater risk of postimplant AF, with its incidence increasing incrementally with quartiles of RA pacing: 44.6%, 64.3%, 79.7%, and 81.6%, respectively (P < .001). After controlling for all factors predictive of postimplant AF on univariate analysis (right atrial pacing quartile, follow-up duration, mitral regurgitation severity, and prior AF history), RA pacing quartile remained a significant predictor of post-CRT AF (hazard ratio 1.92, 95% CI 1.40-2.62, P < .001) upon multivariate analysis. In addition to predicting AF incidence, higher RA pacing quartiles were also associated with significantly greater AF burden.
Conclusions: Compared to atrial sensing, atrial pacing is associated with a 2-fold increased risk of post-CRT AF. Prospective comparison of DDD and VDD pacing modes in CRT is warranted.
Introduction
Cardiac resynchronization therapy (CRT) has become an integral component of heart failure (HF) treatment in patients with marked left ventricular dysfunction, intraventricular conduction delay, and severe HF symptoms, providing symptomatic and structural improvement in two thirds of patients. Cardiac resynchronization therapy systems for patients not in permanent atrial fibrillation (AF) use 3 endocardial pacing leads: a right atrial (RA) lead usually placed in the RA appendage, a right ventricular lead, and a coronary sinus (or epicardial) left ventricular lead. Devices are typically programmed to provide atrio-biventricular pacing (ie, DDD mode) with a short atrioventricular (AV) delay to ensure that the device provides ventricular electrical capture, thus maximizing resynchronization.
Heart failure is commonly associated with AF, presumably because chronically elevated filling pressures contribute to the pathogenesis of AF. Cardiac resynchronization therapy may decrease the incidence and burden of AF, perhaps by improving cardiac hemodynamics, although most studies to date have been inadequately controlled or neglected device-based diagnostics. Acute CRT studies have demonstrated that DDD pacing may mitigate CRT's hemodynamic benefit by curtailing ventricular filling when compared with atrial-tracked, biventricular pacing (ie, VDD mode) (Figure 1). Higher left-sided filling pressures may ensue, potentially increasing the propensity of the atria to fibrillate. No study examining AF burden in CRT has reported RA pacing burden to date.
(Enlarge Image)
Figure 1.
Pathophysiologic basis for greater LV preload with VDD pacing compared to DDD pacing with CRT. Transmitral flow is depicted above the corresponding ECG tracing. Note the delayed onset of left atrial systole (ie, A wave) with DDD pacing because of the greater delay between onset of atrial electrical systole and left atrial mechanical systole. Because the AV delay must be relatively short to ensure biventricular capture, especially in the setting of intact AV nodal conduction, the A wave is attenuated in the DDD mode. IACT, Interatrial conduction time; MVC, mitral valve closure.
We hypothesized that RA pacing burden increases the incidence of post-CRT AF. A retrospective analysis of all CRT patients followed at our institution between 2000 and 2007 was performed to examine this question.