Epidemiological studies of bioprosthetic aortic valves

Abstract

Background: The use of bioprosthetic valves is common and offers a prosthetic option that does not require anti-coagulant therapy, but with shorter valve longevity compared to mechanical prostheses. Valve model selection might influence the long-term performance of the prosthesis. The research questions in the four studies were 1) Does blood type A-like antigens on porcine valves lead to decreased long-term performance of the valve in blood type B/0 patients, 2) Is there a difference in long-term performance between bovine and porcine valves, 3) Does some aortic valve models perform better or worse compared to other aortic valve models, 4) Does prosthesis-patient mismatch (PPM) impact long-term survival, valve reintervention and heart failure hospitalization.

Methods and results: Study I. Patients who received a porcine valve between 1995 and 2012 were identified from the Swedish cardiac surgery register and categorized according to blood type B/0 (1693, 49.5%) and A/AB (1724, 50.5%). The groups had similar baseline characteristics. The cumulative incidence of valve reintervention at 15 years was 3.4% (95% CI: 2.5 to 4.4%) and 3.6% (95% CI: 2.6 to 4.6%) in the B/0 and A/AB groups, respectively. After multivariable adjustment, there was no difference in valve reintervention (HR 0.95, 95% CI: 0.62 to 1.45), heart failure hospitalization (HR 0.92, 95% CI: 0.77 to 1.08) and all-cause mortality (HR 0.95, 95% CI: 0.87 to 1.05) rates in patients with blood type B/0 compared to patients with blood type A/AB. Study II. Patients who received a porcine (4194, 33%) or bovine (8647, 67%) aortic valve between 1995 and 2012 were identified from the Swedish cardiac surgery register. Inverse probability of treatment weighting was used to adjust for inter-group differences. Porcine valves were associated with improved survival (HR 0.90, 95% CI: 0.85 to 0.96) and an increased risk for valve reintervention (HR 1.48, 95% CI: 1.11 to 1.98). There was no difference in heart failure hospitalization between porcine and bovine valves. Study III. All patients who underwent primary surgical bioprosthetic aortic valve replacement in Sweden 2003 to 2018 were identified from the Swedish cardiac surgery register. Patients were categorized according to valve model; Perimount, Mosaic/Hancock, Biocor/Epic, Mitroflow/Crown, Soprano and Trifecta. Regression standardization was used to account for differences in baseline characteristics. Perimount had the lowest, and Mitroflow/Crown had the highest cumulative incidence of reintervention (3.6%, 95% CI: 3.1 to 4.2% and 12%, 95% CI: 9.8 to 15%), all-cause mortality (44%, 95% CI: 43 to 45% and 54%, 95% CI: 52 to 57%) and heart failure hospitalization (13%, 95% CI: 12 to 14% and 20%, 95% CI: 18 to 23%) at ten years, respectively. Study IV. All patients who underwent primary surgical bioprosthetic aortic valve replacement in Sweden 2003 to 2018 were identified from the Swedish cardiac surgery register. Patients were categorized according to no (7377, 45%), moderate (8502, 52%) and severe (544, 3%) PPM, estimated by valve model, valve size and the patient’s body surface area. The survival difference at ten years was 4.6% (95% CI: 0.7 to 8.5%) and 1.7% (95% CI: 0.1 to 3.3%) between no versus severe and moderate PPM, respectively. Severe PPM was also associated with a significant increase in heart failure hospitalization, with a ten-year difference of 6.0% (95% CI: 2.2 to 9.7%) compared to no PPM. There was no difference in valve reintervention between different grades of PPM.

Conclusions: 1) It is safe to use porcine valves irrespective of blood type, 2) Porcine valves increases the risk for subsequent valve interventions, 3) The widespread use of the Perimount valve is supported by excellent long-term clinical performance, and an increased clinical vigilance is warranted in patients with a Mitroflow/Crown or Soprano valve, 4) Steps should be taken to avoid severe PPM, but the clinical effect of moderate PPM might be negligible.