Continuous epicardial echocardiographic assessment of postoperative left ventricular function

History of intraoperative ultrasound

Intraoperative ultrasound (IOUS) using A-mode or non-real-time B-mode imaging started in the 1960s; however, it was not widely accepted mainly because of difficulty in image interpretation. In the late 1970s, IOUS became one of the topics in the surgical communities upon the introduction of high-frequency real-time B-mode ultrasound. Special probes for operative use were developed. In the 1980s, all over the world the use of IOUS spread to a variety of surgical fields, such as hepatobiliary pancreatic surgery, neurosurgery, and cardiovascular surgery. IOUS changed hepatic surgery dramatically because IOUS was the only modality that was capable of delineating and examining the interior of the liver during surgery. After 1990, color Doppler imaging and laparoscopic ultrasound were incorporated into IOUS. Currently, IOUS is considered an indispensable operative procedure for intraoperative decision-making and guidance of surgical procedures. For better surgical practice, education of surgeons in the use of ultrasound is the most important issue.

Effect of coronary bypass surgery and valve replacement on left ventricular function: assessment by intraoperative two-dimensional echocardiography

Intraoperative two-dimensional echocardiography (2DE) was performed in 15 patients during coronary artery bypass grafting (CABG) and in 14 patients during aortic (AVR) or mitral valve replacement (MVR) before and immediately after cardiopulmonary bypass by means of a 3.5 MHz transducer. Left ventricular ejection fraction (LVEF), end-diastolic (LVEDV) and end-systolic (LVESV) volumes were measured by a light pen system and biplane Simpson's rule from short-axis and apical two-chamber views. In seven patients with CABG and new abnormal Q waves or greater than 5% MB to total CPK ratio postoperatively, the mean LVEF decreased significantly (from 52 +/- 10 to 43 +/- 12%, p = 0.005). Patients undergoing MVR for mitral regurgitation showed, a significant decrease in LVEF (from 63 +/- 10 to 42 +/- 23%, p less than 0.025) and LVEDV (from 166 +/- 34 to 147 +/- 44 ml, p less than 0.05). Mean LVEF also decreased after AVR for aortic regurgitation (from 46 +/- 16 to 26 +/- 15%, p less than 0.05). Six patients with valve replacement and postoperative hypotension had the greatest decrease in intraoperative LVEF (from 50 +/- 12 to 24 +/- 10%, p less than 0.005). It is concluded that: Intraoperative 2DE can be used to assess immediate changes in left ventricular function after CABG or valve replacement. LVEF decreases significantly immediately after AVR for aortic regurgitation and MVR for mitral regurgitation. Intraoperative 2DE may identify those patients who can benefit from inotropic support in the immediate postoperative period after valve replacement.

Application of transesophageal echocardiography to continuous intraoperative monitoring of left ventricular performance

Transesophageal M mode echocardiography was used for continuous monitoring of left ventricular dimensions in 21 patients (11 with valvular and 10 with coronary heart disease) undergoing open heart surgery. Echocardiograms were recorded in six stages of the procedure and simultaneous measurements of cardiac output (with dye dilution) and atrial pressures were made. Measurements of left ventricular diameters with the transesophageal technique correlated excellently with the corresponding measurements obtained with the standard parasternal method. In patients with volume overload, surgical correction was accompanied by a decrease in diastolic dimension, velocity of circumferential fiber shortening, mid wall stress and end-diastolic stiffness, and an increase in cardiac output. Pericardial and chest wall closures generally caused a significant decrease in cardiac output, and correlated with a decrease in diastolic diameter and an increase in the stiffness constant of the left ventricle. Thus, the decrease in cardiac output may have been due to decreased distensibility of the ventricular cavity secondary to mechanical restriction by the pericardium and chest wall. Pericardial opening caused a significant delay in septal motion that was reversed by closing the pericardium. This study confirms the validity of transesophageal echocardiography and its usefulness in monitoring changes in ventricular function during cardiac surgery.