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

BACKGROUND: The 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 RESULTS: Eleven 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). CONCLUSIONS: Epicardial 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.

Myocardial perfusion distribution and coronary arterial pressure and flow signals: clinical relevance in relation to multiscale modeling, a review.

Coronary artery disease, CAD, is associated with both narrowing of the epicardial coronary arteries and microvascular disease, thereby limiting coronary flow and myocardial perfusion. CAD accounts for almost 2 million deaths within the European Union on an annual basis. In this paper, we review the physiological and pathophysiological processes underlying clinical decision making in coronary disease as well as the models for interpretation of the underlying physiological mechanisms. Presently, clinical decision making is based on non-invasive magnetic resonance imaging, MRI, of myocardial perfusion and invasive coronary hemodynamic measurements of coronary pressure and Doppler flow velocity signals obtained during catheterization. Within the euHeart project, several innovations have been developed and applied to improve diagnosis-based understanding of the underlying biophysical processes. Specifically, MRI perfusion data interpretation has been advanced by the gradientogram, a novel graphical representation of the spatiotemporal myocardial perfusion gradient. For hemodynamic data, functional indices of coronary stenosis severity that do not depend on maximal vasodilation are proposed and the Valsalva maneuver for indicating the extravascular resistance component of the coronary circulation has been introduced. Complementary to these advances, model innovation has been directed to the porous elastic model coupled to a one-dimensional model of the epicardial arteries. The importance of model development is related to the integration of information from different modalities, which in isolation often result in conflicting treatment recommendations.