Hemodynamic study of counterpulsation with special reference to its effects on coronary blood flow and mean aortic pressure

Abstract

A considerable amount of research has been reported on the effect of counterpulsation, a method of assisted circulation. It seems well established that counterpulsation reduces the left ventricular work load, but controversy continued as to whether coronary blood flow is increased by counterpulsation. The present study was designed to investigate the hemodynamic effects of counterpulsation on an intact dog, especially its effects on coronary blood flow and aortic mean pressure. Materials and Methods Counterpulsation (CP) was performed using a Standard Isochronous Myocardial Augmentation System (SIMAS) with a rigid polyethylene cannula inserted from the abdominal aorta into the middle portion of the thoracic descending aorta. Thirty-one experiments were made using 17 healthy adult mongrel dogs weighing 11-20 kg. They were anesthetized with intravenous pentobarbital sodium (25-40 mg/kg) followed by the administration of a mixture of ether and oxygen through an intratracheal tube. Respiration was controlled by a manual method. The heart was exposed by a bilateral anterior thoracotomy. Aortic pressure was monitored with a strain gauge pressure transducer connected to a catheter inserted into the aortic arch via the axillary artery. Left and right ventricular pressure were monitored each with a strain gauge transducer connected to a short catheter punctured into the ventricle. Coronary sinus blood flow was measured directly through a catheter inserted and secured in the coronary sinus via the right atrial appendage. Myocardial oxygen consumption was measured by gasmetry with an IL Meter Model 113 and hemoglobinometry with a hemoglobinometer. To evaluate the cardiovascular response, the following parameters were adopted : aortic mean pressure (AMP), aortic systolic mean pressure (ASMP), aortic diastolic mean pressure (ADMP), left ventricular systolic mean pressure (LVSMP), right ventricular systolic mean pressure (RVSMP), coronary sinus blood flow (CSF), myocardial oxygen consumption (qO2), and TTI. Each parameter is measured before and during CP. According to the procedure and result, experiments were divided into the following groups : I (a+b) : 24 experiments in which CP was performed under normovolemic condition, I (a) : 15 experiments in which CSF was reduced in group I (a+b), I(b) : 9 experiments in which CSF was increased in group I(a+b), II : 7 experiments in which aortic mean pressure was slightly elevated by means of transfusion during CP.