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Left ventricular energetics in closed-chest dogs
1Department of Medicine, University of Texas Health Science Center, San Antonio.
The American Journal of Physiology
|October 1, 1993
Summary
Ventricular energetics in intact animals show reduced efficiency at high heart rates but maintained efficiency with dobutamine. Both interventions increased oxygen demand for excitation-contraction coupling.
Area of Science:
- Cardiovascular Physiology
- Cardiac Energetics
- Myocardial Oxygen Consumption
Background:
- Ventricular energetics studies typically use isolated hearts, limiting in vivo application.
- Understanding myocardial oxygen consumption (MVO2) in relation to pressure-volume area (PVA) is crucial for intact animal models.
Purpose of the Study:
- To characterize the MVO2-PVA relationship in intact animals.
- To investigate the impact of heart rate (HR) and dobutamine on ventricular efficiency and MVO2.
Main Methods:
- Eight closed-chest dogs were instrumented to measure MVO2, PVA, and hemodynamics.
- High-fidelity micromanometers, piezoelectric crystals, coronary flow probes, and oximetric catheters were utilized.
- The effects of increased heart rate via pacing and dobutamine administration were assessed.
Main Results:
- A linear relationship was observed between MVO2 and PVA.
- High heart rates decreased contractile efficiency (EFF) and increased end-systolic elastance (Ees).
- Dobutamine increased MVO2 and contractility (Ees) without altering EFF.
Conclusions:
- Intact animals exhibit reduced ventricular efficiency at high heart rates.
- Dobutamine stimulation maintains ventricular efficiency while increasing contractility and oxygen demand.
- Both interventions augment MVO2 per minute, indicating increased energy for excitation-contraction coupling.