Left ventricular filling during coronary artery bypass grafting

Abstract: Left ventricular (LV) filling, determination of preload, right ventricular end-diastolicvolumes, volume contributions during early (E) and atrial (A) phases of LV filling andmitral valve opening areas were studied in 75 patients scheduled for elective coronaryartery bypass grafting (CABG).The purposes of the study were: (1) To evaluate changes in LV filling judged as peakvelocity E/A ratios deterrnined by Doppler transesophageal echocardiography duringand in the early phase after CABG. (2) Validation of clinical determination of LVdimension before and after cardiopulmonary bypass (CPB) by comparing twomeasures of preload: (i) inspection of the line of contact between the heart (margoacutus) and the diaphragmatic pericardium and (ii) the end-diastolic LV cross-sectionalarea determined by two-dimensional transesophageal echocardiography. (3) Todetermine the right ventricular end-diastolic volume by fast response thermodilutionusing the relation of the acute margin of the heart to the diaphragm as an endpointwhen transfusing the patients during weaning from CPB. (4) To validate the volumecontribution during early and atrial phases of left ventricular filling assessed byDoppler transesophageal echocardiography by comparing it with nuclear cardio-angiography during CABG. (5) To measure the mean and maximum cross-sectionalarea of the mitral valve by two-dimensional transesophageal echocardiography duringthe early and atrial phases of left ventricular filling.Results: (1) There was an altered diastolic filling pattern in the immediate phase afterCABG, with a gradual recovery of the peak velocity E/A ratio from 0.46+0.06 to0.87+0.08 during the first 6 hours in the intensive care unit. (2) A clinical measure,inspection of the line of contact between the heart and the diaphragm provided reliableinformation on LV preload during weaning from CPB. There was a strong correlation,r 0.88, between left ventricular end-diastolic area before and after CPB. (3) Theclinical measure of preload was determined more by the left ventricle than the rightand there was a weak correlation, r=0.54, between right ventricular end-diastolicvolume before and after CPB. (4) There was a good agreement between Dopplerechocardiographic and nuclear angiocardiographic methods regarding volumecontributions during the E, r=0.98, and A, r=0.88, phases of left ventricular filling. (5)The mean opening area of the mitral valve, determined by echocardiography, duringthe E and A phases was the same and recordings of the mitral velocity time integraltherefore reflect volumetric flow. Myocardial ischemia during aortic occlusion,increased heart rate, and decreased VTI E/A ratio, did not alter the area.Key words: Heart: surgery, coronary artery revascularization, ventricle, mitral valve Cardiopulmonary bypass Cardiac output Thermodilution Echocardiography: transesophageal, two-dimensional, Doppler Radionuclide ventriculographySten Samuelsson: Left ventricular filling during coronary artery bypass grafting; Stockholm 1995 ISBN 91-628-1799-X