When someone needs a new mitral valve, they have an important decision to make: whether to opt for a mechanical valve made of metal or a bioprosthetic valve made from tissue from a cow or pig. Although both types of valve work remarkably well, each has advantages and disadvantages that must be weighed against the patient’s individual needs. Clinical investigators at The Texas Heart Institute and Baylor College of Medicine recently explored patient outcomes and hospital readmission rates after mitral valve replacement surgery as a way to unravel the differences between the two valve types.

Mechanical valves require long-term anticoagulation, whereas bioprosthetic valves can degenerate over time and must be replaced. As a result, younger patients (who are more likely to outlive the life cycle of a bioprosthetic valve) usually opt for a mechanical valve, whereas older patients (who are likely to have more health problems) tend to choose bioprosthetic valves.

Patients for the study came from a large sample of deidentified records from hospitals in 28 states. From that database, the investigators identified 31,474 adults who underwent mitral valve replacement surgery during the 3-year study period. Bioprosthetic valves were almost three times more common than mechanical valves. Patients with bioprosthetic valves were older, had more health problems, and were more likely to die while hospitalized after their operation.

To compare similar patients and determine if valve type influenced outcomes, a statistical technique filtered the initial sample into a smaller group of 15,549 patients (7,773 bioprosthetic replacement valves versus 7,776 mechanical replacement valves) matched for age, sex, health problems, and whether their surgery was optional or an emergency.

After matching, the bioprosthetic valve group had a similar in-hospital death rate and comparable hospital costs but were hospitalized for fewer days, compared with the mechanical valve group. Readmission to the hospital within 30 days, 90 days, and 1 year was more common in the mechanical valve group than in the bioprosthesis group; readmission for bleeding or impaired blood clotting was more frequent in that group, whereas readmission for heart failure was more frequent in the bioprosthesis group.

The higher 1-year readmission rate for patients with mechanical valves might be lowered by using better anticoagulation strategies and at-home monitoring, which could reduce the likelihood of bleeding events, impaired blood clotting, and stroke. Although the risk for such adverse outcomes in the bioprosthetic valve group was only half that in the mechanical valve group, this advantage must be weighed against the likelihood that a bioprosthetic valve will need to be replaced in the long term.

Notes Ravi K. Ghanta, MD, senior author of the study, “Valve choice is a critical decision for both patients and surgeons. By comparing similar patients, we confirmed that bioprosthetic and mechanical valves have similar operative outcomes, but that mechanical valve patients are more frequently readmitted to the hospital—primarily due to anticoagulation and bleeding issues. Optimal medical therapy for patients with mechanical valves is absolutely essential to lower their risk for rehospitalization.”

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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 2022. doi: 10.1016/j.athoracsur.2022.05.064. Online ahead of print.

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News Story By Jeanie F. Woodruff, BS, ELS

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