Background
Small prosthesis size has been associated with worse postoperative outcomes in aortic valve replacement (AVR). We hypothesized that the use of small AVR prostheses does not independently increase operative mortality following AVR, but rather mortality may be related to co-morbidities.
Methods
From 2003–2008, 4,621 patients underwent primary AVR operations at 13 different statewide centers. Patients were stratified by prosthesis size into small AVR (≤21 mm, n=1,810) and standard AVR (≥23 mm, n=2,811) groups. The effect of prosthesis size on outcomes was evaluated by univariate and multivariable regression analyses.
Results
Operative mortality among primary AVR operations was 3.7%. Among isolated operations, small AVRs included more females (79.9% vs. 21.0%, p<0.001), older patients (68.9±12.3 years vs. 63.8±13.9 years, p<0.001,) and higher STS predicted risk of mortality (3.1 [3.0] vs. 2.2 [2.0], p<0.001) compared to standard AVRs. Small AVRs incurred more major complications (19.5% vs. 15.7%, p=0.01), higher mortality (3.9% vs. 2.3%, p=0.03), longer postoperative length of stay (6.0 [3.0] vs. 5.0 [3.0] days, p<0.001) and higher total costs ($29,738 [18,196] vs. 26,679 [14,890], p<0.001) compared to standard AVR. However, using multivariate regression, small AVR prosthesis size and female gender were not independent predictors of mortality while advanced age, bypass time, and aortic annular enlargement were important predictors of operative mortality.
Conclusions
Small aortic valve prosthesis size does not independently increase operative mortality following primary aortic valve replacement. Elevated morbidity and mortality among patients undergoing small AVR is related to the confounding effects of preoperative and operative risk factors. Annular enlargement may not always improve mortality.