Abstract 821: How Much AV Delay Shortening do Patients with Biventricular Pacemaker Need During Exercise?
Background: Biventricular pacemakers (Biv PM) have programmable atrioventricular (AV) delays for varying heart rates (HR) & paced & sensed atrial rhythms, however little is known on the magnitude of AV delay shortening that is physiologic for increased HR in patients (pts) with Biv PM.
Methods: We used pulsed Doppler (PW) echocardiography to obtain optimal AV and interventricular delays by optimizing left ventricular (LV) filling and ejection at rest. Rate adaptive AV delay was then programmed and increased HR was achieved in 42 pts by a symptom limited exercise by hall walk or treadmill and in 9 pts by a-pacing to 90 bpm. PW Doppler was then repeated immediately post exercise or a-pacing. AV delay was changed until mitral E and A seperation on PW Doppler was achieved.
Results: Out of 52 pts, 75±13 yrs, 83% M, NYHA class 2.7±0.7 and LV ejection fraction 0.32±0.1, 71% achieved HR of ≥100 bpm during exercise. Data on baseline, rest optimal and stress optimal AV delays is shown in the Table⇓. Correlation b/w change in HR (ΔHR) and change in AV delay (ΔAVD) was r= 0.47, p= 0.1 for all pts; r= 0.70, p= 0.01 for 26 pts a-sensing at rest and exercise; r= 0.62, p= 0.05 for 9 pts a-pacing throughout and r= 0.35, p= 0.05 for 17 pts a-pacing at rest but a-sensing at exercise. The equation for AV delay shortening was ΔAVD=2.7*ΔHR-13 for 9 pts with a-pacing and ΔAVD=1.6*ΔHR-20 for 26 pts with a-sensing at rest and exercise. Optimal AV delay at rest was significantly higher (197±45 ms) for 9 totally a-pacing pts vs 17 pts a-pacing at rest but a-sensing at exercise(163±35) and 26 pts totally a-sensing at rest and exercise (100±27 ms).
Conclusion: Optimal rest AV delay as well as magnitude of AV delay shortening with exercise is longer than the current Biv PM algorhythms. AV delay shortening is predictable except in a-paced pts at rest but a-sensed at exercise. Our equations may be compared against conventional algorhythms for improvement in functional capacity in pts with heart failure and Biv PM.