Incidence and Risk Factors of Pannus after Mechanical Aortic Valve Replacement

BACKGROUND: This study was conducted to evaluate the occurrence rate and risk factors of subaortic pannus (SAP) after bileaflet mechanical aortic valve (AV) replacement. METHODS: Between 1990 and 2014, 862 patients underwent primary AV replacement with bileaflet mechanical prosthesis. SAP was defined as (1) gradual increase in mean pressure gradient through mechanical AV without any evidence of motion limitation of the leaflets on echocardiography and (2) AV mean pressure gradient >40 mm Hg or AV peak velocity >4 m/s on echocardiography, and (3) any visible subaortic tissue ingrowth beneath the mechanical AV on echocardiography or computed tomography. Clinical and echocardiographic follow-up durations were 13.8 ± 8.0 and 10.7 ± 7.9 years, respectively. RESULTS: Mean age was 51.1 ± 12.1 years and concomitant surgeries were performed in 503 patients (58.4%). Overall survival at 10 and 20 years was 84.2 and 67.1%, respectively. SAP occurred in 33 patients, and in only 2 patients during the first 10 years after surgery. The cumulative incidence of SAP formation at 10, 20, and 25 years were 0.3, 5.0, and 9.9%, respectively. The Fine and Gray model demonstrated that small prosthetic valve size (hazard ratio [HR] [95% confidence interval, CI] = 0.738 [0.575-0.946]), young age (HR [95% CI] = 0.944 [0.909-0.981]), and concomitant mitral valve replacement (MVR) (HR [95% CI] = 3.863 [1.358-10.988]) were significant risk factors for the SAP formation. CONCLUSIONS: SAP occurred gradually over time with 10- and 20-year cumulative incidence of 0.3 and 5.0%, respectively. Young age, small prosthetic valve size, and concomitant MVR were risk factors for SAP formation. Therefore, we recommend efforts to select large prostheses for young patients requiring concomitant MVR.