Long-term survival following aortic valve replacement : the influence of age, prosthesis-patient mismatch and indexed effective orifice area

Abstract

Background: Prosthesis-patient mismatch (PPM) has been linked to reduced long-term survival after aortic valve replacement. We studied the influence of age, PPM and indexed effective orifice area (iEOA) in this setting. Methods Patients (n=586) subjected to aortic valve replacement were followed up for a mean of 7.8 (maximum 20) years. The study population was divided into four equivalent groups by age. Mortality data was extracted from the National Statistics database. Data pertaining to patient body surface area and valve effective orifice area was collected prospectively and mismatch (moderate or severe) was defined according to established values. The Cox proportional hazard model was used to study the effect of age, mismatch and iEOA on survival. The Log Rank test was used to compare survival curves by age groups and date of surgery. Results The incidence of moderate PPM was 24.6%, and of severe PPM 3.9%. Mismatch increased the hazard of death by 31.2% for moderate PPM and 70.3% for severe PPM but did not reach statistical significance. Mean age of patients with mismatch (n=167) was 2.52 years less than in those without (63.35±10.61 versus 65.87±11.69, p=0.016). Age significantly affected survival, increasing the risk of death by 7.3% for every incremental year. Mean iEOA was 0.94±0.15cm2/m2; for every 0.1unit increase in iEOA the risk of death decreased by 8.8%. Conclusions Long-term survival was significantly affected by age at operation. Although mismatch increased hazard of death the effect did not reach statistical significance. A larger iEOA had a significant beneficial effect on survival.