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Extracoronary collateral myocardial blood flow during cardioplegic arrest
Insights
Extracoronary collateral blood flow (QE) varies significantly in patients undergoing cardiac surgery. This systemic blood flow can unpredictably affect cardioplegia efficacy and may compensate for coronary artery disease.
Area of Science:
- Cardiovascular Surgery
- Cardiac Anesthesia
- Myocardial Protection
Background:
- Cold cardioplegia is standard for myocardial protection during cardiac surgery.
- Understanding collateral circulation is crucial for optimizing cardioplegic arrest.
- Extracoronary blood flow (QE) represents systemic-to-coronary collateral circulation.
Purpose of the Study:
- To quantify extracoronary collateral myocardial blood flow (QE) during cold cardioplegic arrest.
- To investigate the relationship between QE and myocardial temperature.
- To determine how QE varies with different cardiac conditions and coronary artery disease severity.
Main Methods:
- Studied 54 patients during cold cardioplegic arrest.
- Measured coronary venous return with aorta/pulmonary artery clamped and vena cavae occluded.
- Infused cold cardioplegia solution and monitored myocardial septal temperature.
- Quantified QE using hematocrit of right atrial effluent.
Main Results:
- QE ranged from 0 to 1470 ml-100 min-1 (mean 241.1 ml-100 min-1).
- QE was lowest in mitral valve stenosis and higher in aortic valve disease.
- Very high QE (>800 ml-100 min-1) observed only in severe three-vessel coronary artery disease.
- No significant correlation found between QE and myocardial rewarming rate.
Conclusions:
- Extracoronary collateral blood flow is highly variable and can unpredictably influence cardioplegia.
- QE may partially compensate for severe coronary artery disease.
- Understanding QE is essential for personalized myocardial protection strategies.
Abstract:
Extracoronary blood flow to the myocardium was studied in 54 patients during cold cardioplegic arrest. Coronary venous return was measured with the aorta and the pulmonary artery cross-clamped, both venae cavae occlusively snared, and the heart completely drained. Cold St. Thomas' cardioplegic solution was infused into either the aortic root or the coronary ostia. Myocardial septal temperature was continuously monitored. The amount of blood in the right atrial effluent was determined by means of the hematocrit and was considered to be the extracoronary collateral myocardial blood flow (QE), originating from the systemic circulation. QE ranged from 0 to 1470 ml-100 min-1 (x = 241.1 ml-100min-1). The myocardial spontaneous rewarming rate was not significantly correlated to QE. QE was lowest in pure mitral valve stenosis (x = 39.9 ml-100 min-1) and higher in aortic valve disease (x = 165.5 ml-100 min-1). Very high QE values (greater than 800 ml-100 min-1) were only observed in patients with severe three vessel coronary artery disease. Patients with angina at rest appear to have lower QE values than patients with equally severe coronary artery disease suffering from angina under excise only. It is concluded that extracoronary collateral blood flow may unpredictably influence the efficacy of clinical cardioplegia and may to some extent compensate for severe coronary artery disease.