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Optimization of coronary perfusion rate during cardiac surgery in man
Insights
Increasing coronary blood flow by 25% during cardiac surgery improved myocardial oxygen consumption (Vo2) in patients with aortic valve disease. Higher flows did not yield further benefits, suggesting an optimal perfusion level for these patients.
Area of Science:
- Cardiovascular Surgery
- Cardiac Physiology
- Cardiomyopathy Research
Background:
- Aortic valve disease often leads to left ventricular hypertrophy.
- Hypothermic cardiopulmonary bypass is used during cardiac surgery.
- Optimizing coronary perfusion is crucial for myocardial recovery.
Purpose of the Study:
- To investigate the impact of varied coronary perfusion on myocardial oxygen consumption (Vo2) and lactate flux.
- To determine optimal coronary flow rates during hypothermic cardiopulmonary bypass in patients with aortic valve disease and left ventricular hypertrophy.
- To assess myocardial Q10 and coronary vascular resistance at different flow levels.
Main Methods:
- Measurement of myocardial oxygen consumption (Vo2) and lactate flux in 12 patients.
- Utilized hypothermic cardiopulmonary bypass with artificial coronary perfusion.
- Coronary flow was adjusted to standard, +25%, and +50% of standard flow (defined by 110 mm. Hg line pressure).
Main Results:
- Lactate flux remained insignificant across all tested flow rates.
- Myocardial oxygen consumption (Vo2) increased significantly at +25% flow compared to standard flow.
- No further significant increase in Vo2 was observed at +50% flow.
- Optimal myocardial Q10 and coronary vascular resistance were approached at +25% flow (mean coronary flow of 203 ml/min).
Conclusions:
- A 25% increase in coronary perfusion above standard levels appears optimal for enhancing myocardial oxygen consumption in this patient group.
- Further increases in coronary flow beyond +25% did not provide additional benefits.
- Standardizing coronary perfusion requires further investigation for practical clinical application.
Abstract:
Myocardial oxygen consumption (Vo2) and lactate flux were measured in 12 patients with aortic valve disease and left ventricular hypertrophy during cardiac surgery with hypothermic cardiopulmonary bypass and artificial coronary perfusion. Coronary flow was varied from "standard" flow-defined as giving a "line pressure" of 110 mm. Hg-to 25 or 50 percent higher than standard flow. Lactate flux was not significant at any flow. Vo2 was higher at +25 percent flow that at standard flow, but no significant further increase in Vo2 occurred at +50 percent. Myocardial Q10 and coronary vascular resistance also approached optimal values at a flow of +25 percent, corresponding with a mean coronary flow of 203 ml. times min -1. The difficulties are discussed of standardizing coronary perfusion in useful practical terms.