Real-time Three-dimensional Echocardiography for Determining Right Ventricular Stroke Volume in an Animal Model of Chronic Right Ventricular Volume Overload

TLDR

Two‑dimensional echocardiography lacks a reliable noninvasive method to assess right‑ventricular volume and function. The study aimed to evaluate a novel real‑time three‑dimensional echocardiographic system for measuring right‑ventricular stroke volume. In six sheep with surgically induced right‑ventricular volume overload, 14 steady‑state hemodynamic conditions were examined using electromagnetic flow probes and a Duke‑developed phased‑array volumetric 3D imaging system, and RV stroke volumes were calculated from parallel‑slice 3D data by subtracting end‑systolic from end‑diastolic cavity volumes. Multiple regression revealed a strong correlation (r = 0.80) and small bias (−2.7 ± 6.4 mL/beat) between EM‑derived and real‑time 3D RV stroke volumes, indicating that the 3D system accurately estimates reference stroke volumes and holds promise for clinical use.

Abstract

Background —The lack of a suitable noninvasive method for assessing right ventricular (RV) volume and function has been a major deficiency of two-dimensional (2D) echocardiography. The aim of our animal study was to test a new real-time three-dimensional (3D) echo imaging system for evaluating RV stroke volumes. Methods and Results —Three to 6 months before hemodynamic and 3D ultrasonic study, the pulmonary valve was excised from 6 sheep (31 to 59 kg) to induce RV volume overload. At the subsequent session, a total of 14 different steady-state hemodynamic conditions were studied. Electromagnetic (EM) flow probes were used for obtaining aortic and pulmonic flows. A unique phased-array volumetric 3D imaging system developed at the Duke University Center for Emerging Cardiovascular Technology was used for ultrasonic imaging. Real-time volumetric images of the RV were digitally stored, and RV stroke volumes were determined by use of parallel slices of the 3D RV data set and subtraction of end-systolic cavity volumes from end-diastolic cavity volumes. Multiple regression analyses showed a good correlation and agreement between the EM-obtained RV stroke volumes (range, 16 to 42 mL/beat) and those obtained by the new real-time 3D method ( r =0.80; mean difference, −2.7±6.4 mL/beat). Conclusions —The real-time 3D system provided good estimation of strictly quantified reference RV stroke volumes, suggesting an important application of this new 3D method.