Objectives  Age may modify the impact of prosthesis–patient mismatch (PPM) on outcomes after aortic valve replacement (AVR), as physical functioning decreases with age, and comorbidities become more prevalent. We hypothesised that the consequences of PPM in patients 70 years old or older may be less important than in younger patients.

Methods  In total, 707 aortic stenosis patients were followed for a maximum of 17.5 years after AVR. PPM was defined as an in vivo indexed effective orifice area ≤0.85 cm²/m², and severe PPM as ≤0.65 cm²/m².

Results  In patients less than 70 years of age with normal LV function, the presence of PPM did not significantly alter survival. However, in patients under 70 with LV dysfunction, PPM was associated with decreased survival (HR 2.2; p=0.046). In patients aged 70 years of age or older, PPM had no effect on survival, regardless of LV function. Similarly, PPM was predictive of postoperative congestive heart failure (CHF) in patients under 70 with LV dysfunction (HR 3.6; p=0.046) but not in older patients. Similar results were observed for the composite endpoint of death or CHF. Postoperative LV mass regression was impaired by increased age (p=0.019), and by PPM in patients aged 70 years of age or older with LV dysfunction (by 28.8 g/m²; p=0.026).

Conclusions The impact of PPM on outcomes after AVR depends on age at operation. PPM in patients under age 70 years with LV dysfunction is associated with decreased survival and lower freedom from CHF. In patients 70 years of age or older, PPM does not impact mortality or symptoms, but impairs LV mass regression beyond that explained by age alone.