Degenerative Mitral Regurgitation Outcomes in Asian Compared With European-American Institutions.

Background: Clinical outcome and interventional thresholds for degenerative mitral regurgitation (DMR) were developed in studies of patients at European and American institutions (EAIs), but little is known about patients at Asian institutions (AsIs).

Objectives: This study sought to contrast DMR presentation/management/outcomes of AsI patients vs EAI patients.

Methods: Patients with DMR due to flail leaflet from Hong Kong and Singapore (AsI cohort, n = 737) were compared with EAI patients (n = 682) enrolled in the MIDA (Mitral regurgitation International Database) registry with similar eligibility criteria.

Results: AsI patients presented similar DMR lesion/consequences vs EAI patients, but they were younger, with fewer symptoms (74% vs 44% Class I), more sinus rhythm (83% vs 69%), and lower EuroSCORE II (European System for Cardiac Operative Risk Evaluation II) (0.9 ± 0.5 vs 1.4 ± 1.5; all  < 0.0001). Imaging showed smaller absolute left atrial/ventricular dimensions in AsI patients, belying cardiac dilatation with larger body surface area-indexed diameters (all  < 0.01). Surgical/interventional mitral repair was similarly predominant (90% vs 91%;  = 0.47), and early repair was similarly beneficial (for AsI patients, adjusted HR: 0.28; 95% CI: 0.16-0.49; for EAI patients, HR: 0.32; 95% CI: 0.20-0.49; both  < 0.0001). However, AsI patients underwent fewer interventions (55% ± 2% vs 77% ± 2% at 1 year;  < 0.0001) and incurred excess mortality (adjusted HR: 1.60 [95% CI: 1.13-2.27] vs EAI patients;  = 0.008) at long-term postdiagnosis. Propensity score matching (434 patient pairs), which balanced all clinical characteristics, confirmed that there was undertreatment and excess mortality in the long term in AsI patients with DMR ( < 0.0001).

Conclusions: Imaging may underestimate volume overload in AsI patients due to smaller cardiac cavities related to smaller body size compared with EAI patients with similar mitral lesions and DMR severity. AsI patients enjoy similar mitral repair predominance and early intervention benefits but undergo fewer mitral interventions than EAI patients and incur subsequent excess mortality, suggesting the need to account for imaging and cultural specificity to improve DMR outcomes worldwide.