The Impact of Age in Prosthesis-patient Mismatch on Long-term Survival after Aortic Valve Replacement: in-vitro versus in-vivo Values
Alexander Manché *
Department of Cardiothoracic Surgery, Mater Dei Hospital, Malta
Aaron A. Casha
Department of Cardiothoracic Surgery, Mater Dei Hospital, Malta and Faculty of Medicine, University of Malta, Malta
Liberato Camilleri
Department of Statistics and Operations Research, Faculty of Science, University of Malta, Malta
*Author to whom correspondence should be addressed.
Abstract
Aim: We studied the effect of age on survival in the setting of prosthesis-patient mismatch (PPM).
Study Design: Retrospective single surgeon practice.
Place and Duration of Study: Cardiothoracic department, Mater Dei Hospital Malta, between January 1995 and December 2014.
Methodology: 572 consecutive patients undergoing aortic valve replacement (AVR) were divided into four age groups and followed up for a maximum of 20 years (mean 8.2). Date of death was derived from the National Statistics Office. PPM was classified according to defined criteria, and calculated according to manufacturers’ tables (in-vitro) and from in-vivo values published by independent researchers. The impact of age and PPM on long-term survival was studied using the Cox proportional hazard model.
Results: Mean in-vitro derived indexed effective orifice area (EOAi) was significantly higher than in-vivo EOAi (1.04±0.22 vs 0.93±0.16, p=0.000) and incidence of PPM was lower using in-vitro criteria (moderate 18.0% vs 24.1%, p=0.01, severe 1.9% vs 4.7%, p=0.008). For patients with mismatch the odds of dying (in-vitro vs in-vivo) was increased by 9.2% vs 38.1%, with moderate PPM 7.6% vs 30.9%, and with severe PPM 85.7% vs 69.7%. The odds of dying increased with age (by 7-8% for every year) and PPM severity. Age was a significant predictor of survival but PPM was not. For every 0.1unit increase in EOAi the risk of dying decreased by 8.0% (in-vitro) and 8.7% (in-vivo).
Conclusion: Age is a significant predictor of survival times, with the odds of dying increasing by about 7% for every additional year. Long-term survival hazard was increased by PPM but the effect was not significant. When EOAi is analysed as a continuous variable it significantly effects survival.
Keywords: Aortic valve replacement, long-term survival, age, prosthesis-patient mismatch, in-vitro, in-vivo