Long-Term Incidence and Risk Factors of Subaortic Pannus Overgrowth After Bileaflet Mechanical Aortic Valve Replacement

OBJECTIVES: Subaortic pannus overgrowth is a recognized complication following aortic valve replacement (AVR) with mechanical prostheses, potentially requiring reoperation. Since data on its incidence and risk factors remain scarce, this study aimed to determine the incidence and risk factors for subaortic pannus overgrowth after AVR with bileaflet mechanical valves. METHODS: We retrospectively analysed 1145 patients who underwent AVR with bileaflet mechanical valves between 1995 and 2010 at a cardiac referral centre. Subaortic pannus overgrowth was defined by imaging evidence causing clinical stenosis and confirmed intraoperatively. Cumulative incidence was estimated using competing risks analysis, and risk factors were identified using Fine and Gray models. RESULTS: During a mean follow-up of 16.5 years, 47 patients (4.1%) developed subaortic pannus overgrowth requiring reoperation (mean interval 13.6 years). The 10- and 20-year cumulative incidence was 1.1% and 5.0%, respectively. Multivariable analysis identified female sex (hazard ratio [HR]: 2.18), smaller prosthetic valve size (21 mm vs ≥23 mm, HR: 8.62, and ≤19 mm vs ≥23 mm, HR: 12.02), and concomitant mitral valve replacement (HR: 2.63) as independent risk factors. Older age at AVR was protective (HR: 0.69 per 10-year increase). Recurrence occurred in 1 patient after isolated pannus resection. CONCLUSIONS: Subaortic pannus overgrowth is a late complication after bileaflet mechanical AVR, with a gradually increasing incidence. Female sex, smaller prosthesis size, younger age, and concomitant mitral valve replacement are significant risk factors. Complete pannus removal and valve replacement should be considered during reoperation. Further research into the underlying mechanisms is warranted for prevention strategies.