A New Technique for Assessing Right Ventricular Ejection Fraction Using Rapid Multiple-gated Equilibrium Cardiac Blood Pool Scintigraphy: Description, Validation and Findings in Chronic Coronary Artery Disease

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Abstract

SUMMARY

A reproducible, noninvasive technique for determining right ventricular ejection fraction (RVEF) was developed using multiple-gated equilibrium blood pool scintigraphy, which allows serial rapid measurements without reinjection of radioactivity. Studies were obtained using in vitro labeled technetium- 99m red blood cells, gamma camera and computer. In 20 patients, RVEF determined by multiple-gated equilibrium imaging in the left anterior oblique view was compared with RVEF measured by first-pass scintigraphy. For both types of imaging, multiple regions of interest (ROIs) were used for RVEF. The accuracy of RVEF using equilibrium scintigraphy was also evaluated using a single ROI. In 20 additional patients, rapid (2-minute) equilibrium scintigraphy for RVEF was compared with standard (6-minute) imaging. Excellent correlation (r = 0.94) for RVEF was found between multiple-gated equilibrium scintigraphy and the first-pass technique when multiple ROIs were used. Inter- and intraobserver variations for the equilibrium method were small (r = 0.91 and r = 0.98, respectively). RVEF with the 2-minute equilibrium technique correlated well with the 6-minute method (r = 0.98). In contrast to the high correlation when multiple ROIs were used, analysis of equilibrium scintigraphy by single ROI severely underestimated first-pass RVEF and showed poor correlation (r = 0.60).

In 15 normal subjects and 21 patients with significant coronary artery disease and different degrees of right coronary artery stenosis, simultaneous left ventricular ejection fraction (LVEF) and RVEF were measured. RVEF was less than LVEF in normal subjects (0.48 ± 0.05 vs 0.63 ± 0.08, mean ± SD). In patients with coronary artery disease, RVEF was not significantly different from that in the normal group, regardless of the degree of stenosis of the right coronary artery. We conclude that 1) multiple-gated equilibrium scintigraphy is a very accurate and reproducible new technique for determining RVEF; 2) the technique may be performed rapidly, and is therefore well suited to serial assessment of right ventricular function during exercise; 3) multiple ROIs are necessary for accurate measurement with this technique; and 4) RVEF is normally less than LVEF and is not significantly affected at rest by right coronary artery disease.

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