Radionuclide regurgitant index: value and limitations.

The radionuclide regurgitant index, defined as left ventricular/right ventricular stroke counts obtained from gated equilibrium studies, has been reported to predict the presence and severity of left-sided valve regurgitation. This study evaluated the radionuclide regurgitant index in 100 patients in whom left-sided valve regurgitation was angiographically graded (0 to 4+) with regard to most severe mitral or aortic regurgitation. Regurgitation was graded 0 in 44 of the 100 patients, 1+ in 22, 2+ in 8, 3+ in 6 and 4+ in 20. The radionuclide regurgitant index was 0.9 to 1.5 in 51 patients, 1.6 to 2.4 in 23 and 2.5 to 12.0 in 26. The mean radionuclide regurgitant index was 1.34 in the group with no regurgitation and 1.60 in those with 1+, 2.01 in those with 2+, 2.80 in those with 3+ and 3.85 in those with 4+ regurgitation. There was a significant difference (p less than 0.05) in the radionuclide regurgitant index between patients with no regurgitation and each group with regurgitation and between groups with regurgitation separated by two or more grades of angiographic regurgitation. Twelve patients had a discordant radionuclide regurgitant index; their index either predicted clinically significant or severe regurgitation when they had no or trivial regurgitation, or predicted no or trivial regurgitation when they had clinically significant regurgitation. Eight of 10 patients with a left ventricular ejection fraction of less than 0.30 had a discordant index (p less than 0.0005). All three patients with mitral valve prolapse associated with frequent ventricular extrasystoles had a discordant index (p less than 0.0005).