The effect of posture, exercise, and atrial pacing on atrioventricular conduction in systolic heart failure

Abstract

Background Optimization of atrioventricular (AV) intervals for cardiac resynchronization therapy (CRT) programming is typically performed in supine patients at rest, which may not reflect AV timing in other conditions. Objective To evaluate the effects of posture, exercise, and atrial pacing on intrinsic AV intervals in patients with CRT devices. Methods Rate‐dependent A‐V delay by exercise was a multicenter, prospective trial of patients in sinus rhythm following CRT implantation. Intracardiac electrograms were recorded to analyze atrial to right ventricular (ARV), atrial to left ventricular (ALV), and RV to LV (VV) time intervals. Heart rate was increased with incremental atrial pacing in different postures, followed by an exercise treadmill test. Results This study included 36 patients. At rest, AV intervals changed minimally with posture. With atrial pacing, AV interval immediately increased compared with sinus rhythm, with ARV slopes being 8.1 ± 7.7, 8.8 ± 13.4, and 6.8 ± 6.5 milliseconds per beat per minute (ms/bpm) and ALV slopes being 8.2 ± 7.7, 9.1 ± 12.8, and 7.0 ± 6.5 ms/bpm for supine, standing and sitting positions, respectively. As the paced heart rate increased, ARV and ALV intervals increased more gradually with similar trends. Interventricular conduction times changed less than 0.2 ms/bpm with atrial pacing. During exercise, the direction of change of intrinsic ARV intervals, as heart rate increased, was variable between patients with relatively small overall group changes (0.1 ± 1.4 and 0.2 ± 1.2 ms/bpm for ARV and ALV, respectively). Conclusion Posture and exercise have a smaller effect on AV timing compared with atrial pacing. However, individualized optimization and dynamic rate related changes may be needed to maintain optimal fusion with left ventricular (LV) stimulation.

The impact of chronotropic incompetence on atrioventricular conduction times in heart failure patients

“…As shown previously, ARV and ALV intervals increased rapidly in all subjects from atrial sense to atrial pacing as shown by a larger slope and then increased gradually as the paced heart rate increased, as shown by a smaller slope. 14 New data reported here shows that patients with CI have significantly greater prolongation of AV intervals than CC patients. These results are summarized in Table 2.…”