Effects of Epicardial and Endocardial Cardiac Resynchronization Therapy on Coronary Flow: Insights From Wave
Simon Claridge1, Zhong Chen1, Tom Jackson1
1King's College, London, UK (S.C., Z.C., T.J., K.D.S., J.B., M.S., J.W., E.H., M.L., K.A., R.W., S.N.).
Insights
Endocardial pacing significantly increases left anterior descending artery flow by enhancing both forward compression and backward expansion waves. This method offers a more physiological activation pattern compared to conventional epicardial pacing.
Area of Science:
- Cardiovascular Physiology
- Electrophysiology
- Medical Device Technology
Background:
- Conventional biventricular pacing increases global coronary flow via the backward expansion wave (BEW).
- Determinants of left-sided epicardial coronary artery flow and endocardial pacing effects are not well understood.
Purpose of the Study:
- To investigate the impact of endocardial pacing on coronary physiology.
- To compare endocardial pacing with conventional epicardial biventricular pacing.
Main Methods:
- Acute hemodynamic and electrophysiological study in 11 patients with biventricular pacemakers.
- Protocol included conventional epicardial pacing and left ventricular endocardial pacing.
- Analysis of coronary flow parameters, including peak velocity and wave analysis (FCW, BEW) in the LAD and circumflex arteries.
Main Results:
- Conventional biventricular pacing increased LAD flow by 9% (via BEW).
- Endocardial pacing increased LAD flow by 27% (via FCW and BEW).
- Both pacing methods homogenized coronary flow timing between LAD and circumflex arteries.
Conclusions:
- Endocardial pacing enhances LAD coronary flow more effectively than epicardial pacing.
- Endocardial pacing's greater effect may stem from a more physiological activation pattern.
- Pacing influences coronary flow dynamics and timing homogenization.
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.
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