Noninvasive quantitation of right-ventricular volume overload in adults by gated equilibrium radionuclide angiography

R-wave-synchronized equilibrium radionuclide angiography (RNA) is a noninvasive method whose time-activity curves provide count information that is proportional to ventricular volume. We have performed resting gated RNA in nine consecutive adult patients undergoing cardiac catheterization for evaluation of left-to-right shunting. Pulmonary/systemic flow ratios (Qp/Qs) calculated from RNA correlated well with Qp/Qs defined by oximetry (r = 0.87, y = 0.85x + 0.11, sy·x = 0.46). In five patients imaged before, and within 1 mo after, successful surgical repair, RNA Qp/Qs declined from a mean (±s.d.) of 2.9 ± 1.0 to 1.1 ± 0.2. Right/left ventricular end-diastolic volume ratios declined from 3.1 ± 1.3 to 1.7 ± 0.2. Although left-ventricular ejection fraction did not change, right-ventricular ejection fraction declined in these patients. Imaging in nine patients with right-ventricular dysfunction, but without shunt or regurgitation, yielded a mean Qp/Qs of 0.94 ± 0.27. We conclude that Qp/Qs, right-ventricular ejection fraction, and relative ventricular enlargement may be accurately quantitated and followed serially after therapeutic intervention using gated RNA.