89-08: Coronary resynchronisation and the differing effects of epicardial and endocardial pacing on coronary wave energetics. (10th June 2016) - Claridge, Simon
Abstract: Background: Wave intensity analysis has previously shown that the increase in global coronary flow seen with biventricular epicardial pacing is mediated by an increase in the dominant backward expansion wave (BEW). Little is known about the effect of conventional CRT on wave energies in the left epicardial arteries or the effect of endocardial stimulation on coronary physiology. Methods: Eleven patients with a biventricular pacemaker underwent an acute hemodynamic study. Coronary flow and pressure were measured with different forms of ventricular pacing (endo/epicardial) and compared with baseline. Results: Epicardial biventricular pacing increased flow in the LAD mediated by an increase in the dominant backward expansion wave (p = 0.004). Endocardial biventricular pacing resulted in an increase in flow mediated by an increase in both the forward compression wave (FCW) (p = 0.048) and BEW (p = 0.036) (see Figure. A:Sinus rhythm, B:Epi, C:Endo). There was no effect on Cx parameters with different pacing protocols. Conventional CRT resulted in homogenisation in timing of coronary flow compared with baseline (p = 0.017). Conclusions: Epicardial and endocardial pacing result in increased coronary flow in the LAD. The increase in both the FCW and BEW with endocardial pacing may be the result of a more physiological activation pattern than epicardial pacing which resulted only in an increase in the BEW. This mechanism may explain the beneficial effect of endocardial pacing over conventional CRT. This is the first time that changes in electrical activation have been shown to have mechanical effects on regional coronary flow.