Effects of Epicardial and Endocardial Cardiac Resynchronization Therapy on Coronary Flow: Insights From Wave Intensity Analysis

Abstract

BackgroundThe increase in global coronary flow seen with conventional biventricular pacing is mediated by an increase in the dominant backward expansion wave (BEW). Little is known about the determinants of flow in the left‐sided epicardial coronary arteries beyond this or the effect of endocardial pacing stimulation on coronary physiology.Methods and ResultsEleven patients with a chronically implanted biventricular pacemaker underwent an acute hemodynamic and electrophysiological study. Five of 11 patients also took part in a left ventricular endocardial pacing protocol at the same time. Conventional biventricular pacing, delivered epicardially from the coronary sinus, resulted in a 9% increase in flow (average peak velocity) in the left anterior descending artery (LAD), mediated by a 13% increase in the area under the BEW (P=0.004). Endocardial pacing resulted in a 27% increase in LAD flow, mediated by a 112% increase in the area under the forward compression wave (FCW) and a 43% increase in the area under the BEW (P=0.048 and P=0.036, respectively). There were no significant changes in circumflex parameters. Conventional biventricular pacing resulted in homogenization of timing of coronary flow compared with baseline (mean difference in time to peak in the LAD versus circumflex artery: FCW 39 ms [baseline] versus 3 ms [conventional biventricular pacing], P=0.008; BEW 47 ms [baseline] versus 8 ms [conventional biventricular pacing], P=0.004).ConclusionsEpicardial and endocardial pacing result in increased coronary flow in the left anterior descending artery and homogenization of the timing of waves that determine flow in the LAD and the circumflex artery. The increase in both the FCW and the BEW with endocardial pacing may be the result of a more physiological activation pattern than that of epicardial pacing, which resulted in an increase of only the BEW.

Major influence of a ‘smoke and mirrors’ effect caused by wave reflection on early diastolic coronary arterial wave intensity

“…While an oft-stated benefit of coronary wave intensity is that it allows clear assessment of upstream and downstream processes (Siebes et al 2009;Lu et al 2011;Kyriacou et al 2012;Rolandi et al 2012;Claridge et al 2015;Lee et al 2016;Raphael et al 2016), a key conclusion of this study is that, mechanistically, both upstream and downstream processes can have a significant effect on the magnitude of both forward and backward waves (directly and via wave reflection). However, with additional knowledge of aortic wave intensity, we have described a novel method to unmask the effect of wave reflection and recover information about upstream and downstream forces (such as distal suction) on early-diastolic coronary waves.…”

“…C and D, time-averaged R 1 during the 'sys' and 'dia' periods (C), and reflection index calculated from the local incident and reflected waves (D), obtained from all terminal 1D segments supplying the left ventricular free wall and septum. Claridge et al 2015;Narayan et al 2015). The BDW dia is currently interpreted as arising solely from a suction effect within the coronary microcirculation, as the relaxing myocardium releases the external (intramyocardial) pressure developed during systole (Davies et al 2006a;Kyriacou et al 2012;Narayan et al 2015).…”

“…; Claridge et al . ). Three main waves have been consistently identified during this early‐diastolic phase of the cardiac cycle (Fig.…”

“…incremental changes in blood pressure and velocity) arising from active forces such as myocardial contraction/relaxation or from wave reflection. Given the diastolic dominance of coronary arterial flow, there has been particular interest in the wave dynamics underlying the early-diastolic flow surge and how waves around this time are affected by various forms of heart disease and medical intervention (Davies et al 2006a(Davies et al , 2011Kyriacou et al 2012;Lockie et al 2012;De Silva et al 2013;Claridge et al 2015). Three main waves have been consistently identified during this early-diastolic phase of the cardiac cycle ( Fig.…”

A step toward clinically applicable noninvasive coronary wave intensity analysis

“…The assumption that the backward decompression wave (the sole wave showing agreement between invasive and noninvasive approaches) is the most clinically important wave for myocardial perfusion holds true in many settings (4,6,8,11,13). However, recent evidence points to substantial increases in not only the backward decompression wave but also the earlysystolic forward compression wave during improved coronary perfusion occurring with endocardial pacing in cardiac resynchronization therapy (4) or after stenting of a coronary artery stenosis (15).…”