Minimally Invasive Mitral Valve Replacement in the Gray Zone: Bioprosthetic vs. Mechanical Valves in Patients Aged 50–69 Years

<b>Background</b>: Mitral valve replacement presents considerable challenges in the field of cardiothoracic surgery, particularly in patients aged 50 to 69, where the decision between bioprosthetic and mechanical valves is critical. Nevertheless, the optimal selection of prosthetic valves for candidates within this age-related gray zone remains inadequately defined, necessitating a thorough evaluation of long-term outcomes and associated risks. <b>Objective</b>: This study aims to assess mid-term outcomes of MIMVR in patients aged 50 to 69, comparing reoperation rates, prosthesis-related morbidity, and overall survival between bioprosthetic and mechanical valves. While many prior studies on valve choice in patients aged 50 to 69 years are derived from sternotomy cohorts, the novelty of our work lies in the exclusive focus on patients undergoing minimally invasive techniques. <b>Methods</b>: A retrospective analysis was conducted in accordance with the <i>Strengthening the Reporting of Observational Studies in Epidemiology</i> (STROBE) guidelines, including 172 patients aged 50-69 years who underwent minimally invasive mitral valve replacement via right minithoracotomy at a high-volume center in Germany between 2011 and 2023. Of the 172 patients, 95 underwent MIMVR using biological prostheses, while 77 received mechanical prostheses. Comprehensive data on demographics, surgical procedures, and postoperative complications, as well as long-term outcomes, were analyzed. <b>Results</b>: With a mean follow-up of 7.1 years, early outcomes revealed no significant differences in 30-day mortality (7.4% for bioprosthetic vs. 2.6% for mechanical; <i>p</i> = 0.06). There was no significant differences in all-cause mortality at 1 year (8.4% vs. 3.9%; <i>p</i> = 0.22), 3-year (9.5% vs. 7.8%; <i>p</i> = 0.69), and 5-year (13.7% vs. 10.4%; <i>p</i> = 0.19), or at the longest follow-up (13.7% vs. 10.4%; <i>p</i> = 0.51). Kaplan-Meier analysis showed no significant difference in long-term survival between the groups (<i>p</i> = 0.5427). Postoperative arrhythmia occurred significantly more frequently in the biologic group compared to the mechanical group (18.9% vs. 6.5%; <i>p</i> = 0.01). <b>Conclusions</b>: For patients aged 50-69 undergoing MIMVR using a bioprosthetic or mechanical valve, the mid-term survival and incidence of reoperation and re-hospitalization were comparable up to 7 years. This provides evidence supporting the safe application of the MICS approach with either valve type in this gray-zone age group.