Extracoronary Collateral Myocardial Blood Flow during Cardioplegic Arrest

Summary

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 · 100 min^-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 (> 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 exercise 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.

Key words

Extracoronary myocardial blood flow - Myocardial ischemia - Cardioplegic arrest - Coronary artery disease - Coronary obstruction score