Observed change in peak oxygen consumption after aortic valve replacement and its predictors

Abstract

Objective

To assess the change in peak oxygen consumption (pVO ₂) and determine its outcome predictors after aortic valve replacement (AVR) for aortic stenosis (AS).

Methods

Patients with AS and preserved left ventricular ejection fraction who were referred for single AVR had cardiopulmonary exercise testing prior to and 9 months post-AVR. Predictors of outcome for pVO ₂ were determined by multivariate linear and logistic regression analyses. A significant change in pVO ₂ was defined as a relative change that was more than twice the coefficient of repeatability by test–retest (>10%).

Results

The pre-AVR characteristics of the 37 study patients included the following: median age (range) 72 (46–83) years, aortic valve area index (AVAI) 0.41 (SD 0.11) cm ²/m ², mean gradient (MG) 49.1 (SD 15.3) mm Hg and New York Heart Association (NYHA)≥II 27 (73%). Pre-AVR and post-AVR mean pVO ₂ was 18.5 and 18.4 mL/kg/m ² (87% of the predicted), respectively, but the change from pre-AVR was heterogeneous. The relative change in pVO ₂ was positively associated with the preoperative MG (β=0.50, p=0.001) and negatively associated with brain natriuretic peptide > upper level of normal according to age and gender (β=−0.40, p=0.009). A relative increase in pVO ₂ exceeding 10% was found in 9 (24%), predicted by lower pre-AVR AVAI (OR 0.18; 95% CI 0.04 to 0.82, p=0.027) and lower peak O ₂ pulse (OR 0.94; 95% CI 0.88 to 0.99, p=0.045). Decreases in pVO ₂ exceeding 10% were found in 11 (30%) and predicted by lower MG (OR 0.93; 95% CI 0.86 to 0.99, p=0.033).

Conclusions

Change in pVO ₂ was heterogeneous. Predictors of favourable and unfavourable outcomes for pVO ₂ were identified.