Today, valve repair is the preferred surgical intervention for mitral valve disease. However, a significant number of patients present with irreparable valvular disease upon arrival in the operating room, leading many to undergo mitral valve replacement with either mechanical or biological prostheses. The choice of prosthesis for each patient is often unclear, presenting surgeons with the challenge of balancing risks, such as prosthetic deterioration and reoperation, against the need for lifelong anticoagulation, thus requiring a tailored approach for each patient. 

Current European and American guidelines recommend mechanical prostheses for patients under 65 years and biological prostheses for those over 70 years in the mitral position. Nonetheless, additional factors must be considered when making a final decision, which may allow for the use of either prosthesis type in patients, particularly those aged 65 to 70 years. Important factors include not only the patient’s life expectancy but also lifestyle aspects, profession, comorbidities that increase the risk of hemorrhagic and thromboembolic complications, adherence to treatment, risk of reoperation, and patient preference. The difference in readmission rates between patients with mechanical or biological prostheses is also crucial for patients, surgeons, and the National Health System. 

The present study aims to compare patient outcomes and readmission rates after mitral valve replacement with mechanical vs biological prostheses. This is a retrospective multicenter study across 28 U.S. states, using the Nationwide Readmissions Database (NRD). All isolated mitral valve replacements in patients aged 18 and older between January 1, 2016, and December 31, 2018, were included, totaling 31474 procedures. Patients were divided into two groups based on prosthesis type. To minimize bias, propensity score matching was conducted to balance confounding factors between groups. 

The authors concluded that patients with mechanical prostheses had a higher overall readmission rate at 30 and 90 days. The most common reasons for readmission were heart failure, arrhythmias, infection, and bleeding or coagulopathy. Heart failure decompensation was more frequent among those with biological prostheses, whereas bleeding or coagulopathy was more common in patients with mechanical prostheses. There were no differences in infection or arrhythmias between the two groups. 

COMMENTARY:

There is a growing preference for using bioprostheses over mechanical prostheses in the aortic and mitral positions. In the cohort studied in this article, bioprostheses were used three times more frequently than mechanical prostheses. Currently, more elderly patients with increased comorbidities and greater overall frailty are undergoing intervention. This population is precisely the group at increased risk for complications related to chronic anticoagulation with vitamin K antagonists, which is necessary for patients with mechanical prostheses. 

Given these considerations, we pose the question: is it worth justifying the use of mechanical prostheses over biological ones due to the risk of degeneration and subsequent reoperation? Decision-making should consider new available options. For instance, recently developed biological prostheses specifically for the mitral position, such as those with the innovative Resilia® tissue technology by Edwards Lifesciences® (Edwards Mitris Resilia® prosthesis), potentially offer greater durability than conventional options. Furthermore, transcatheter valve implantation (TAVI) procedures in the mitral position, achievable through various approaches (transseptal or transapical), have demonstrated favorable outcomes in experienced centers. 

In conclusion, selecting the appropriate prosthesis type for a patient requires an individualized decision that takes into account factors such as age, comorbidities, treatment adherence, INR monitoring capability, profession, and patient preference. The reviewed article suggests that, in the intermediate age group (55-65 years) with a moderate comorbidity burden, where mechanical prostheses are typically used, biological prostheses offer a similar safety profile and outcomes with fewer readmissions over a one-year follow-up period. However, given that this is a retrospective study based on a national database, important factors such as race, preoperative risk, and pre- or postoperative medications were not analyzed, which are critical for robust statistical analysis and clinical extrapolation. 

Equally important, it is essential to remember that reducing readmissions among our patients depends on early identification and close follow-up, especially to mitigate hemorrhagic or thromboembolic complications associated with mechanical mitral prostheses. 

REFERENCE:

Sylvester CB, Ryan CT, Frankel WC, Asokan S, Zea-Vera R, Zhang Q, Wall MJ Jr, Coselli JS, Rosengart TK, Chatterjee S, Ghanta RK. Readmission After Bioprosthetic vs Mechanical Mitral Valve Replacement in the United States. Ann Thorac Surg. 2024 Jan;117(1):113-118. doi: 10.1016/j.athoracsur.2022.05.064.