Abstract 3029: Endothelial Function Worsens with Right Ventricular Pacing.
Purpose - Several pacemaker and ICD trials have suggested that conventional right ventricular pacing (RVP) is associated with reduced left ventricular (LV) systolic and diastolic function, increased mortality, heart failure hospitalisation, and stroke. In many cases irrespective of the presence or absence of preserved AV synchrony. The pathophysiology underlying these deleterious effects is not clearly understood. The purpose of this study was to investigate the effects of RVP on endothelial function, resting and exercise cardiac output.
Methods - 22 patients (mean age (± SD)= 68.4±8.8 years, male=19) with dual chamber pacemakers for sinus node disease were studied after chronic pacing in 3 randomly assigned pacing modes: dual chamber with long atrioventricular delay (AVD): DDD-L, (mean AVD=270.5±42.8ms), dual chamber with short AVD: DDD-S, (mean AVD=113.2±17.3ms) and ventricular pacing (VVI). Five patients (23%) had LV systolic dysfunction (LVEF<40%), eleven had LV hypertrophy and seven were normal. Cardiac output was determined by the inert gas rebreathing method and endothelial function was measured using the reactive hyperaemia - peripheral arterial tone (RH-PAT) index. A value <1.67 was considered to indicate abnormal endothelial function.
Results The mean percentage (± SD) of RVP in the 3 modes was 14.7±20.3% in DDD-L, 90.2±15.7% in DDD-S and 43.4±27.3% in VVI (p<0.001). Endothelial function was significantly decreased when patients were in modes with more RVP: 1.96±0.37 in DDD-L, 1.73±0.33 in DDD-S and 1.67±0.25 in VVI (p<0.05). Resting and exercise cardiac output was similar in all modes 4.75±1.32L/min and 7.65±3.15/min in DDD-L vs 4.27±1.08L/min and 7.05±2.61L/min in DDD-S vs 4.27±1.57L/min and 7.25±2.84L/min in VVI respectively.
Conclusion - This novel finding suggests that RVP is associated with a significant deterioration of endothelial function. This may provide the pathophysiological mechanism for the worse outcomes associated with right ventricular pacing.