Mechanical versus Tissue Aortic Prosthesis in Sexagenarians: Comparison of Hemodynamic and Clinical Outcomes

Mechanical versus Bioprosthetic Aortic Valve Replacement in Patients Aged 50 to 70 Years

Background

This study compared the outcomes of surgical aortic valve replacement (AVR) in patients aged 50 to 70 years based on the type of prosthetic valve used.

Methods

We compared patients who underwent mechanical AVR to those who underwent bioprosthetic AVR at our institution between January 2000 and March 2019. Competing risk analysis and the inverse probability of treatment weighting (IPTW) method based on propensity score were employed for comparisons.

Results

A total of 1,580 patients (984 patients with mechanical AVR; 596 patients with bioprosthetic AVR) were enrolled. There was no significant difference in early mortality between the mechanical AVR and bioprosthetic AVR groups (0.9% vs. 1.7%, p=0.177). After IPTW adjustment, the risk of all-cause mortality was significantly higher in the bioprosthetic AVR group than in the mechanical AVR group (hazard ratio [HR], 1.39; 95% confidence interval [CI], 1.07-1.80; p=0.014). Competing risk analysis revealed lower risks of stroke (sub-distributional hazard ratio [sHR], 0.44; 95% CI, 0.28-0.67; p<0.001) and anticoagulation- related bleeding (sHR, 0.35; 95% CI, 0.23-0.53; p<0.001) in the bioprosthetic AVR group. Conversely, the risk of aortic valve (AV) reintervention was higher in the bioprosthetic AVR group (sHR, 6.14; 95% CI, 3.17-11.93; p<0.001).

Conclusion

Among patients aged 50 to 70 years who underwent surgical AVR, those receiving mechanical valves showed better survival than those with bioprosthetic valves. The mechanical AVR group exhibited a higher risk of stroke and anticoagulation-related bleeding, while the bioprosthetic AVR group showed a higher risk of AV reintervention.

Savings associated with surgical aortic valve replacement with a RESILIA tissue valve based on seven-year COMMENCE trial results

BACKGROUND

Bioprostheses with RESILIA tissue demonstrate a reduction in calcification and improve health outcomes in pre-clinical and clinical studies. Prior economic analyses which relied on 5 years of evidence from the COMMENCE trial demonstrate financial savings for RESILIA tissue valves relative to mechanical valves after surgical aortic valve replacement (SAVR). Given the recent release of 7-year COMMENCE data, this economic evaluation updates the estimate for long-run savings of bioprosthetic valves with RESILIA.

METHODS

Simulation models estimated disease progression across two hypothetical SAVR cohorts (tissue vs. mechanical) of 10,000 patients each in the US. The primary comparison calculated the SAVR-related expenditures associated with each valve type ($US, 2023). Health outcome probabilities were based on the COMMENCE trial though year 7 and projected for an additional 8 years based on prior studies of tissue and mechanical SAVR. Costs for key outcomes (mortality, reoperation, bleeding, thromboembolism, endocarditis) and anticoagulant monitoring were sourced from the literature. Incidence rates of health outcomes associated with mechanical valves relied on relative risks of tissue valve versus mechanical valve patients.

RESULTS

Seven-year savings are $13,415 (95% CI = $10,472-$17,321) per patient when comparing RESILIA versus mechanical SAVR. Projected 15-year savings were $23,001 ($US, 2023; 95% CI = $17,802-$30,421). Most of the 15-year savings are primarily attributed to lower anti-coagulation monitoring costs ($21,073 in ACM savings over 15 years), but lower bleeding cost (savings: $2,294) and thromboembolism-related expenditures (savings: $852) also contribute. Reoperation and endocarditis expenditures were slightly larger in the RESILIA cohort. If reoperation relative risk reverts from 1.1 to 2.2 (the level in legacy tissue valves) after year 7, savings are $18,064. RESILIA SAVR also reduce costs relative to legacy tissue valves.

CONCLUSION

Patients receiving RESILIA tissue valves are projected to have lower SAVR-related health expenditures relative to mechanical and legacy tissue valves.

Long-run savings associated with surgical aortic valve replacement using a RESILIA tissue bioprosthetic valve versus a mechanical valve

BACKGROUND

Prior economic analyses demonstrate that legacy tissue valves are associated with substantial financial savings over the long run after a surgical aortic valve replacement (SAVR). Bioprostheses with RESILIA tissue reduce calcification, the primary cause of structural valve deterioration (SVD), and have demonstrated promising pre-clinical and 5-year clinical results. This economic evaluation quantifies the expected long-run savings of bioprosthetic valves with RESILIA tissue relative to mechanical valves given 5-year clinical results and expected performance through year 15.

METHODS

Simulation models estimated disease progression across two hypothetical SAVR cohorts (tissue vs. mechanical) of 10,000 patients in the US over 15 years. One comparison evaluated RESILIA tissue valves relative to mechanical valves. The other compared legacy SAVR tissue and mechanical valves. Health outcome probabilities and costs were based on literature and expert opinion. Incidence rates of health outcomes associated with mechanical valve were calculated using relative risks of expected outcomes in tissue valve versus mechanical valve patients. The comparisons also accounted for anti-coagulation monitoring in both cohorts. Savings estimates are based on US healthcare costs and do not yet account for the premium associated use of RESILIA relative to a standard tissue valve.

RESULTS

Relative to mechanical SAVR, the median net discounted savings for a patient receiving SAVR with a RESILIA tissue valve is $20,744 ($US, 2020; 95% CI = $15,835-$26,655) over a 15-year horizon. While 30-day and 1-year savings were not significant, expected savings after 5 years are $9,110 (95% CI = $6,634-$11,969). Net savings for RESILIA SAVR valves were approximately 30-50% larger than savings anticipated using legacy tissue SAVR valves.

CONCLUSION

RESILIA tissue valves are associated with lower health expenditures relative to mechanical valves.

Reimbursement Savings Associated With Tissue Versus Mechanical Surgical Aortic Valve Replacement in Thailand

OBJECTIVES

Surgical aortic valve replacement (SAVR) is an indicated treatment for severe aortic stenosis. Although mechanical valves are typically more durable, tissue SAVR valves do not require lifetime anticoagulation monitoring and may have lower rates of expensive sequelae. This economic evaluation estimates payer costs to the 3 largest Thai health insurance mechanisms for tissue versus mechanical SAVR.

METHODS

A deterministic and Monte Carlo simulation model based on literature and expert opinion estimated total payer costs for tissue and mechanical valves over a 25-year duration for 3 separate age cohorts (45, 55, and 65 years). Reimbursements levels for hospitalization services were from the Thai Diagnosis Related Groups. Separate models are generated for the 3 main Thai health insurance mechanisms.

RESULTS

The discounted expected 25-year reduction in payer savings associated with tissue SAVR are $2540, $2529, and $2311 per surgery for patients aged 45, 55, and 65 years, respectively, for the largest Thai insurer. Expected cost reductions associated with tissue SAVR are larger for each of the other schemes and generally decrease with patient age. Most savings accrue within 10 years of surgery. Reoperation costs are larger with tissue valves, but reductions in complications and anticoagulation monitoring more than offset these expenditures. Results are robust to multiple sensitivity and scenario analyses.

CONCLUSIONS

Coverage and reimbursement of tissue valves can financially benefit Thai insurers and reduce expenditures in the Thai health system compared with mechanical valves. As tissue valve technology evolves and reoperation rates decline, the financial benefit associated with tissue valves will increase.

A computational study of the hemodynamics of bioprosthetic aortic valves with reduced leaflet motion

We employ a reduced degree-of-freedom aortic valve model to investigate the flow physics associated with early-stage reduced leaflet motion in bioprosthetic aortic valves. The model is coupled with a sharp-interface immersed boundary based incompressible flow solver to efficiently simulate the fluid-structure interaction. A total of 19 cases of flow through aortic valves with varying degrees of reduced leaflet motion (RLM) are considered. The characteristics of the aortic jet and the consequent aorta wall loading patterns are analyzed. Our results show that asymmetric RLM tilts the aortic jet and leads to large reverse and recirculating flow regions downstream from leaflets with restricted mobility. The changes in flow patterns increase wall pressure and shear stress fluctuations, and result in asymmetric oscillating shear on the aorta wall. These findings have implications for auscultation based diagnosis of this condition as well as the health of the aorta.

Long-term Healthcare Expenditures Over Time for Tissue and Mechanical Aortic Valve Replacement

BACKGROUND

Guidelines currently indicate the use of surgical aortic valve replacement (SAVR) to treat severe cases of aortic stenosis, particularly for low- to medium-risk patients. Although several studies have compared health outcomes of tissue and mechanical SAVR, this economic simulation model estimates the difference in long-term healthcare costs associated with tissue relative to mechanical SAVR.

METHODS

The deterministic and Monte Carlo simulation models used literature-based epidemiologic and cost inputs to calculate annual expenditures related to SAVR for up to 25 years after initial surgery. A series of 3 cohort studies across different age groups provided the health outcome probabilities for tissue valve patients. Outcome probabilities for mechanical valve patients were based on relative risks reported in comparative meta-analyses or large cohort studies.

RESULTS

Relative to mechanical SAVR the expected net discounted savings for a patient receiving tissue SAVR at ages 45, 55, and 65 years were $12,266, $15,462, and $16,008, respectively (based on 2018 US dollars) over a 25-year horizon (95% confidence intervals exceed $0). For a 45-year-old tissue SAVR patient, the estimated per-patient cost difference (relative to mechanical SAVR) of reoperation over 25 years ($16,201) were offset by expected savings on anticoagulation monitoring ($26,257) over the same period. In a sensitivity analysis in which mortality risk was assumed equal, significant long-term savings associated with tissue SAVR still accrued in each of the 3 age cohorts.

CONCLUSIONS

Payers, providers, and the healthcare system may financially benefit from the use of tissue valves because significant savings were associated with the use of tissue valves relative to mechanical valves for SAVR.