Comparison of Continuous Left Ventricular Volumes by Transthoracic Two-Dimensional Digital Echo Quantification with Simultaneous Conductance Catheter Measurements in Patients with Cardiac Diseases

Abstract

Automated border detection enables real-time tracking of left ventricular (LV) volume by 2-dimensional transthoracic echocardiography. This technique has not been previously compared with simultaneously measured continuous LV volumes at rest or during transients in humans. We performed 18 studies in 16 patients (age 50 ± 15 years, range 22 to 70; ejection fraction 63 ± 20%, range 15% to 85%) in which continuous LV volumes acquired by digital echo quantification (DEQ) were compared with simultaneous conductance catheter volume obtained by cardiac catheterization. Both volume signals were calibrated by thermodilution-derived cardiac output and ventriculogram-derived ejection fraction. Volume traces acquired at rest were averaged to generate a comparison cycle. The averaged volume waveforms acquired by DEQ and by conductance catheter were similar during all phases of the cardiac cycle and significantly correlated (conductance catheter = slope·DEQ + intercept, slope = 0.94 ± 0.09, intercept = 5 ± 8 ml, r2 = 0.86 ± 0.12, all p <0.0001). Steady-state hemodynamic parameters calculated using either averaged volume signal were significantly correlated. Transient obstruction of the inferior vena cava yielded a 45 ± 13% decrease in end-diastolic volume. Successful recordings of DEQ volume during preload reduction were obtained in only 50% of studies. End-diastolic volumes from the 2 methods were significantly correlated (mean slope 0.88 ± 0.31, mean intercept 14 ± 37 ml, average r2 = 0.89 ± 0.11, all p <0.01), as were end-systolic volumes: mean slope 0.80 ± 0.43, intercept = −20 ± 26 ml, r2 = 0.67 ± 0.18, all p <0.05). We conclude that automated border detection technique by DEQ is reliable for noninvasive, transthoracic, continuous tracking of LV volumes at steady state, but has limitations in use during preload reduction maneuvers in humans.