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Radionuclide regurgitant index: value and limitations
Insights
The radionuclide regurgitant index can predict left-sided valve regurgitation severity. However, it showed discordance in patients with low ejection fraction or mitral valve prolapse.
Area of Science:
- Cardiology
- Nuclear Medicine
- Medical Imaging
Background:
- The radionuclide regurgitant index (LV/RV stroke counts from gated equilibrium studies) is a non-invasive method to assess left-sided valve regurgitation.
- Previous studies suggest its utility in predicting the presence and severity of mitral or aortic regurgitation.
Purpose of the Study:
- To evaluate the accuracy of the radionuclide regurgitant index in grading left-sided valve regurgitation.
- To identify patient subgroups where the radionuclide regurgitant index may be discordant with angiographic findings.
Main Methods:
- 100 patients with left-sided valve regurgitation underwent angiographic grading (0-4+).
- Radionuclide regurgitant index was calculated using gated equilibrium studies.
- Comparison between radionuclide regurgitant index values and angiographic grades of regurgitation.
Main Results:
- A significant correlation was found between the radionuclide regurgitant index and angiographic regurgitation severity (p < 0.05).
- Mean radionuclide regurgitant index increased with higher regurgitation grades.
- Twelve patients (12%) showed discordant results, with higher rates in those with low ejection fraction (<0.30) or mitral valve prolapse with ventricular extrasystoles.
Conclusions:
- The radionuclide regurgitant index is a valuable tool for assessing left-sided valve regurgitation severity.
- Caution is advised in interpreting the radionuclide regurgitant index in patients with significantly reduced left ventricular ejection fraction or specific arrhythmias like mitral valve prolapse with frequent ventricular extrasystoles, as discordance is more likely.
Abstract:
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).