Measurement of cardiac output by real-time 3-D echocardiography in patients undergoing assessment for cardiac transplantation

Abstract

Heart transplant assessment includes cardiac output calculation by right heart catheterisation. Real-time 3D echocardiography (RT-3DE), unlike 2D echocardiography, can measure stroke volume without inaccurate geometrical assumptions. The purpose of this study was to assess the feasibility and accuracy of non-invasive RT-3DE cardiac output calculation. Forty consecutive patients referred for transplant assessment underwent transthoracic RT-3DE. Full volume 3DE data sets were acquired from apical views with the iE33 ultrasound system (Philips Ultrasound, Bothell, USA). Four patients were excluded due to poor image quality. The remaining 36 patients had end-diastolic (LVEDV) and end-systolic (LVESV) left ventricular volumes manually traced, using endocardial detection software. Cardiac output was subsequently calculated: [(LVEDV - LVESV) x heart rate]. Thermodilution derived cardiac outputs, under the same haemodynamic conditions, were used as reference for comparison. There was close correlation between RT-3DE and catheter derived cardiac outputs (r = 0.91, y = 0.86x + 0.45, SEE 0.39 L/min, mean difference from reference -0.06 L/min, SD 0.40 L/min). RT-3DE data analysis took 3 min per case. This study shows RT-3DE is an accurate method for calculating cardiac output. In patients requiring serial evaluation of cardiac function, this non-invasive test may be preferable to invasive right heart catheterisation.