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Persistent right coronary flow reserve at low perfusion pressure.
H Murakami1, S J Kim, H F Downey
1Department of Physiology, Texas College of Osteopathic Medicine, Fort Worth 76107.
The American Journal of Physiology
|April 1, 1989
Summary
Right coronary blood flow reserve remains even at low perfusion pressures. Adenosine can restore oxygen demand despite reduced supply, indicating functional flow reserve below autoregulation.
Area of Science:
- Cardiovascular Physiology
- Coronary Circulation Research
- Myocardial Blood Flow Dynamics
Background:
- Autoregulation is crucial for maintaining myocardial blood flow.
- Understanding coronary flow reserve at low perfusion pressures is vital for clinical assessment.
Purpose of the Study:
- To investigate the persistence of right coronary (RC) flow reserve below the autoregulatory range.
- To assess the impact of reduced perfusion pressure on right ventricular (RV) myocardial oxygen consumption and flow reserve.
Main Methods:
- Controlled perfusion of the RC artery in anesthetized dogs at varying pressures.
- Measurement of RC blood flow (RCBF) and RV blood flow using radioactive microspheres.
- Assessment of RV myocardial oxygen consumption (MVo2) and lactate extraction ratio.
- Pharmacological vasodilation using intracoronary adenosine.
Main Results:
- RCBF significantly decreased with reduced RC perfusion pressure (RCPP).
- Adenosine administration increased RCBF at 40 mmHg, indicating preserved flow reserve.
- RV subendocardial flow reserve was greater than the epicardial region at reduced pressures.
- RV MVo2 decreased at 40 mmHg but normalized with adenosine, with no signs of ischemia.
Conclusions:
- Right coronary flow reserve is maintained at perfusion pressures below the apparent autoregulatory range.
- RV oxygen demand adjusts to reduced coronary supply, and flow reserve can be mobilized by vasodilation.
- Adenosine effectively restores RV MVo2 by mobilizing coronary flow reserve, even at low perfusion pressures.