Changes in contractility determine coronary haemodynamics in dyssynchronous left ventricular heart failure, not vice
Simon Claridge1, Natalia Briceno2, Zhong Chen1
1Department of Imaging Sciences, King's College, London, United Kingdom.
International Journal of Cardiology. Heart & Vasculature
|June 28, 2018
Summary
Biventricular pacing improves cardiac contractility, which in turn enhances coronary blood flow. Increasing coronary flow directly does not improve cardiac contractility in patients with heart failure.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Biventricular pacing acutely increases cardiac contractility and coronary flow, but the causal link is debated.
- The hypothesis posits that enhanced coronary flow is a consequence of improved cardiac contractility.
Purpose of the Study:
- To investigate the relationship between cardiac contractility and coronary blood flow.
- To determine if modulating coronary flow affects cardiac contractility.
Main Methods:
- Altered left ventricular contractility and lusitropy by adjusting pacing locations in 8 patients.
- Temporarily inhibited coronary autoregulation using intracoronary adenosine.
- Measured coronary flow velocity, coronary pressure, and left ventricular pressure during various pacing conditions, with and without induced hyperemia, and performed wave intensity analysis.
Main Results:
- Multisite pacing effectively modified left ventricular contractility and lusitropy.
- Intracoronary adenosine reduced microvascular resistance and increased left anterior descending (LAD) flow velocity but did not acutely alter contractility.
- The magnitude of the Backward Expansion Wave correlated with contractility and lusitropy.
- Perfusion efficiency increased during hyperemia and correlated with contractility and lusitropy.
Conclusions:
- Acute enhancement of coronary blood flow with adenosine does not improve contractility in patients with systolic heart failure.
- Coronary flow changes observed with biventricular pacing likely result from improved cardiac contractility due to resynchronization, not the reverse.
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