Extracoronary Collateral Myocardial Blood Flow during Cardioplegic Arrest

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.

The influence of non-coronary collateral blood supply on the electively arrested heart during ischemia and reperfusion

“…It is generally undesired because it washes out cardioplegic solutions from the myocardium [6], raises the myocardial temperature [3,7,8], and presents as one of the principal causes of the inhomogenous reaction of the myocardium on ischemia [5]. Our results present non-coronary collateral circulation in a new light.…”

“…The influence of non-coronary collateral blood circulation on the electively arrested ischemic myocardium "protected" with a chemical cardioplegic solution has been a subject of much controversy [4,5,8]. The principal argument against it is its warming-up effect onthe myocardium.…”

“…These non-coronary collaterals pierce the aortic and pulmonary trunks, which they serve as vasa vasorum, before they traverse the pericardial reflections at the base of the heart and anastomose with the atrial branches of the coronary arteries [2,4,6,9,10]. The presence and extent of these extracardial connections can be demonstrated by the ligation of the pulmonary artery and subsequent cardiopulmonopexy [2,10], coronary angiogram [8], or by injecting a cadmium-containing resin Biodur E 201 rot (which sets with the application of the hardener Biodur E 21) viscous enough to prevent capillary-venous passage, into the coronary main stems. Using this after technique, the coronary arteries are filled first, followed by the retrograde demonstration of the noncoronary collateral channels.…”

“…Thus, it reduces the protective action of myocardial cooling. Assuming a warming-up of the myocardium ata rate of 0.34°-0.5°C/rain [3,7,8], a rise ofl0°C would have been reached within 20-25 min. This temperature rise would have caused a doubling of the myocardial metabolic requirements in accordance with van t'HolTs law.…”

Cardiopulmonary Bypass

“…Collateral blood fl ow threatens myocardial protection by washing out the cardioplegia solution, rewarming the heart, returning electromechanical activity, and distending the myocardium [110], which all increase myocardial oxygen demand. Decompressing the myocardium alone lowers oxygen demand by 30%-40% [111,112].…”