Bicuspid versus tricuspid aortic stenosis: differences in etiology and clinical outcomes

Background Bicuspid aortic valve (BAV) predisposes to earlier aortic stenosis due to structural abnormalities. Although outcomes in BAV are often attributed to younger age, emerging evidence suggests prognostic differences beyond age alone. The mechanisms underlying differences between BAV and tricuspid aortic valve (TAV) remain unclear. As treatment options expand and life expectancy increases, clarifying these differences is important for optimal management. Purpose To determine whether BAV and TAV differ in clinical outcomes beyond age and whether such differences reflect distinct disease pathogenesis. Methods We retrospectively analysed 1349 consecutive patients undergoing isolated surgical or transcatheter aortic valve replacement for aortic stenosis at two cardiovascular centres. Patients aged 60–89 years were included; those without preoperative cardiac computed tomography were excluded. The final cohort comprised 988 patients (108 BAV, 880 TAV). Primary endpoints were all-cause mortality and major adverse cardiac and cerebrovascular events (MACCE: death, heart failure, cerebrovascular events, reoperation, and endocarditis). Median follow-up was 37.1 months (22.9–51.9). Baseline characteristics were compared unadjusted. Postoperative variables were analysed using analysis of covariance, and clinical outcomes using Cox proportional hazards models adjusted for age, sex, body surface area, aortic stenosis severity, and procedures. Results BAV patients were younger (74.8±8.2 vs 81.9±5.4 years) and more often in male (55.6% vs 33.9%). Hypertension, peripheral artery disease, diabetes, and chronic kidney disease were less prevalent in BAV. Echocardiography showed smaller left atrial diameter and less moderate-or-greater mitral and tricuspid regurgitation. Arterial characteristics differed between groups: pulse wave velocity was lower in BAV (1337 [1165–1535] vs 1588 [1401–1837] cm/s). Computed tomography demonstrated higher aortic valve calcification volume in BAV [766(498 – 1302) vs. 448(270 – 703) mm3), whereas mitral annular calcification (0(0 – 0) vs. 34(0 – 296) mm3) was lower compared with TAV. And then in BAV, systemic aortic calcification volumes (977(258 – 2497) vs. 3469(1725 – 6288) mm3) were lower compared with TAV. At 1 year, echocardiographic differences were no longer significant after adjustment. Unadjusted analyses showed lower all-cause mortality (HR 0.45, 95% CI 0.28–0.75) and MACCE (HR 0.36, 95% CI 0.24–0.56) in BAV. After adjustment, mortality differences were attenuated (HR 0.74, 95% CI 0.44–1.25), while MACCE remained significantly lower (HR 0.50, 95% CI 0.31–0.81). Conclusion After comprehensive adjustment, BAV remained associated with an approximately 50% lower risk of MACCE. Patients with bicuspid aortic valve demonstrated a greater propensity for intrinsic valvular calcification, yet tended to have less advanced systemic atherosclerosis than those with tricuspid aortic valve.