Impact of Prosthesis-Patient Mismatch After Mitral Valve Replacement: A Multicentre Analysis of Early Outcomes and Mid-Term Survival
Does prosthesis-patient mismatch (PPM) after mitral valve replacement impact clinical outcome?
From 2001 to 2009, 1,006 mechanical and bioprosthetic mitral valves were implanted across 10 institutions in Australia. Effective orifice areas (EOAs) were obtained from a literature review of in vivo echocardiographic data. Absent, moderate, and severe PPM were defined as indexed EOA (EOA/body surface area) of >1.20 cm2/m2, >0.90 to ≤1.20 cm2/m2, and ≤0.9 cm2/m2, respectively. Early outcomes and 7-year survival were compared between groups.
PPM was absent in 34%, moderate in 53%, and severe in 13% of patients. Patients with PPM were more likely to be male (42% vs. 52% vs. 62%, p < 0.0001) and obese (14% vs. 20% vs. 56%, p < 0.0001). Postoperatively, there were similar 30-day mortalities (5% vs. 5% vs. 6%, p = 0.83) and early all-cause mortality/morbidity (24% vs. 27% vs. 29%, p = 0.40). Seven-year survival was similar between groups (72 ± 4.1% vs. 76 ± 3.2% vs. 69 ± 10.3%, p = 0.76). PPM did not predict adverse events after logistic and Cox regressions with and without propensity score adjustment. Subgroup analyses of those with isolated mitral valve surgery, patients with preoperative congestive heart failure, and nonobese patients failed to show an association between PPM and mid-term mortality.
The authors concluded that overall, PPM was not associated with poorer early outcomes or mid-term survival. Oversizing valves may be technically hazardous, and does not yield superior outcomes. Easier implantation by appropriate sizing appears to be justified.
PPM (in which a valve orifice is inadequate for a patient despite normal prosthesis function) traditionally has been of greatest concern after aortic valve replacement; the larger mitral orifice was thought to be more forgiving and PPM less of a clinical issue. At least one earlier publication suggested that mitral PPM is an independent predictor of mortality after mitral valve replacement (Magne J, et al., Circulation 2007;115:1417-25). Those findings were not reproduced in this study. Methodologically, the use of published reference standards for prosthesis EOA is problematic, owing to substantial variation between patients. In light of challenges in reliably obtaining valve area and long-term follow-up in large groups of patients after valve replacement, along with confounding comorbid conditions, the topic of whether PPM (mitral or aortic) definitively is an independent risk for excess mortality after valve replacement likely will remain a topic of contention.
Keywords: Heart Valve Prosthesis, Follow-Up Studies, Australia, Heart Failure, Mitral Valve, Echocardiography
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