Validation of Yeo's index in assessing severity of rheumatic mitral stenosis in mixed valve lesions

Introduction: Yeo's Index, product of the mitral leaflet separation index and dimensionless index, is a novel measure of the severity of rheumatic mitral stenosis (MS). We assess Yeo's index in patients with rheumatic MS with or without mixed valve disease. Methods: In a retrospective cohort study, Yeo's index was measured in 237 cases of rheumatic MS - 124 in a transthoracic echocardiography validation cohort using mitral valve area (MVA) by pressure half-time and planimetry as comparator and 113 in a transesophageal echocardiography (TEE) validation cohort using TEE three-dimensional MVA as comparator. Patients were considered to have mixed valve disease if they had MS and concomitant mitral regurgitation or aortic valve disease. Results: There were 113 patients with isolated MS and 124 patients with mixed valve disease. Overall, Yeo's index <= 0.26 cm showed 93.0 % sensitivity and 87.5 % specificity for identifying severe MS (MVA <= 1.5 cm2). In isolated MS, Yeo's index <= 0.26 cm showed sensitivity of 94.6 % and specificity of 90.0 % for identifying severe MS, while in mixed valve disease sensitivity was 90.6 % and specificity 86.7 %. Overall, Yeo's index <= 0.15 cm showed 83.6 % sensitivity and 94.3 % specificity for very severe MS (MVA <= 1.0 cm2). In isolated MS, the threshold of <= 0.15 cm showed sensitivity of 84.4 % and specificity of 92.6 % for very severe MS, while in mixed valve disease sensitivity was 81.3 % and specificity 95.3 %. The presence of atrial fibrillation did not influence the performance of Yeo's index. Conclusion: Yeo's Index accurately differentiates severity of rheumatic MS with or without mixed valve disease.