Abstract Body (Do not enter title and authors here): Introduction: Yeo’s index, the product of the mitral leaflet separation index and dimensionless index of mitral valve, was recently described to accurately identify severe rheumatic mitral stenosis (MS). We aimed to study the association between Yeo’s index and clinical outcomes in patients with rheumatic MS.

Methods: We studied 297 patients with rheumatic MS. Clinical and echocardiographic data were obtained from the electronic medical record and Yeo’s index was measured in all cases. The outcome studied was a composite of all cause death, heart failure (HF) hospitalisation, mitral valve intervention and stroke or transient ischaemic attack. We also performed subgroup analysis of patients without pre-existing atrial fibrillation (AF) to assess for association with new onset AF.

Results: After a median follow up of 6.3 years, 145 patients (48.8%) developed the composite outcome. Yeo’s index (p<0.001), mitral valve area (MVA) by pressure half-time (PHT) (p=0.028) and planimetry (p<0.001), age (p=0.016), history of diabetes mellitus (p=0.029), previous HF (p=0.021), left ventricular ejection fraction (p=0.022), and pulmonary artery systolic pressure (p=0.007) were univariately associated with the composite outcome. Yeo’s index remained independently associated (p<0.001, HR 0.094, 95% CI 0.260-0.340) with the composite outcome in multivariate analysis. In subgroup analysis of patients without pre-existing AF, Yeo’s index was independently associated (p=0.024, HR 0.354, 95% CI 0.143-0.874) with new onset AF. MVA by PHT and planimetry were not associated with new onset AF.

Conclusion: Yeo’s index was independently associated with clinical outcomes in patients with rheumatic MS.