Precision of measurements of right and left ventricular volume by cine computed tomography.

Abstract

Precise determination of left and right ventricular stroke volumes is limited with conventional imaging techniques. We determined whether right and left ventricular stroke volumes could be precisely measured with cine computed tomography (CT). Cine CT enables simultaneous imaging of the right and left ventricles at an 8 mm slice thickness with a maximal scanning rate of 17 frames/sec (50 msec acquisition intervals). In eight dogs, true right ventricular and left ventricular stroke volumes were determined by dividing thermodilution cardiac output by heart rate and/or with the use of an aortic electromagnetic flow probe implanted over a long term. After at least 5 sec of suspended respiration, cine CT images were acquired during central venous injection of a nonionic contrast agent. Multiple perturbations in stroke volume were induced in each dog by the administration of dobutamine, sodium pentobarbital, or sodium nitroprusside or by coronary artery occlusion. Right and left ventricular stroke volumes were obtained by Simpson's reconstruction of end-diastolic and end-systolic short-axis tomograms from apex to base. The cine CT left ventricular stroke volume (range 11 to 45 ml) correlated highly with the true left ventricular stroke volume (r = .99, slope = 1.01, y intercept = -0.2 ml, SEE = 1.5 ml, n = 25). The cine CT right ventricular stroke volume (range 11 to 34 ml) also correlated highly with the true right ventricular stroke volume (r = .98, slope = 0.9, y intercept = 2.2 ml, SEE = 1.7 ml, n = 15). In 12 studies, the mean difference between nearly simultaneous right and left ventricular stroke volumes by cine CT was 1.1 ml (range 0.1 to 3.2 ml). Calculation of right and left ventricular stroke volumes from data from cine CT were highly reproducible. Intraobserver variability in measurements of right ventricular stroke volume (r = 1.0, slope = 0.99, y intercept = 0.19 ml) and left ventricular stroke volume (r = 1.0, slope = 1.02, y intercept = -0.21 ml) was minimal. Interobserver variability in measurements of right ventricular stroke volume (r = .98, slope = 0.90, y intercept = 1.66 ml) and left ventricular stroke volume (r = .99, slope = 0.97, y intercept = -0.02 ml) was likewise minimal. Thus, precise and highly reproducible measurements of right and left ventricular stroke volumes can be obtained with cine CT.