Comparison of Four Different Techniques for Estimation of Left Ventricular Volumes Using Intraoperative Real Time Three Dimensional Transesophageal Echocardiography--A Prospective Observational Study

Abstract

The primary objective of the present study was to compare cardiac output derived with four methods of QLab (Philips, Amsterdam, Netherlands) software using real-time three-dimensional (3D) transesophageal echocardiography, with cardiac output obtained with the 3D left ventricular outflow tract (LVOT) cardiac output method. The secondary objective was to assess left ventricular (LV) volumes, LV ejection fraction, and cardiac output derived with four different methods of real time 3D transesophageal echocardiography processed in QLab software and to determine whether these parameters differed among these four methods. A prospective observational study. A tertiary referral center and a university level teaching hospital. The study comprised 50 patients scheduled for elective coronary artery bypass surgery without any concomitant valvular lesions. Three-dimensional full-volume datasets were obtained in optimum conditions. The 3D datasets were analyzed using four different methods in QLab, version 9. In method A, LV volumes were derived without endocardial border adjustment. In method B, LV volumes were obtained after endocardial border adjustment in the long-axis view alone. In method C, the iSlice tool (Philips) was used to adjust the endocardial borders in 16 short-axis slices. In method D, endocardial borders were adjusted after dataset processing to obtain LV volumes. The cardiac output derived with the 3D echocardiography LVOT method was 3.93 ± 1.44 L/min, with method A was 3.26 ± 1.42 L/min, with method B was 3.51 ± 1.2 L/min, with method C was 4.01 ± 1.40 L/min, and with method D was 4.18 ± 1.58 L/min. There was a significant positive correlation between the cardiac output derived using the 3D LVOT method and method C (r = 0.71). Readjusting the endocardial border contours resulted in higher LV volumes than the volumes estimated using semiautomated border algorithms. The iSlice method produced the highest and the most accurate LV volumes, although it required the longest time to analyze and derive results. The ejection fraction obtained with all four methods of QLab demonstrated no statistical differences and had a strong correlation with the two-dimensional echocardiography-derived left ventricular ejection fraction.