Patients with symptomatic mitral valve disease who are not candidates for surgical mitral valve repair can be effectively treated through replacement with either a biological (bMVR) or mechanical prosthesis (mMVR). 

This study retrospectively analyzes patients who underwent mitral valve replacement (MVR) at the Department of Cardiovascular Surgery at the German Heart Center in Munich, Germany, between 2001 and 2020. Propensity score matching was used to compare survival and reoperation incidence between patients receiving a biological versus a mechanical prosthesis in the mitral position. A total of 2,027 patients were included, with 1,658 in the bMVR group and 369 in the mMVR group. The mean age at surgery was 65.9 ± 12.9 years. The median follow-up duration was 6.83 years (interquartile range 1.11–10.61 years). Concomitant procedures were performed in 1,467 cases (72.4%). 

The authors concluded that both groups demonstrated comparable survival. Indeed, survival following bMVR and mMVR remained similar throughout the follow-up period, reaching up to 20 years. However, patients with mMVR exhibited a significantly lower incidence of reoperation (20-year: 15% vs. 59%, p < .001). 

COMMENTARY: 

The choice between a biological or mechanical prosthesis can present a considerable clinical challenge. Anticoagulation or reoperation? That is the question. 

The current European clinical guidelines recommend mMVR for patients aged 65 years or younger, while American guidelines set this threshold at 70 years. However, the progressive aging of the population increasingly leads to prosthetic degeneration at ages when reoperation involves a high risk of morbidity and mortality. On the other hand, the durability of mechanical prostheses necessitates lifelong anticoagulation, carrying associated bleeding risks. It is also crucial to consider the subgroup of younger female patients with reproductive aspirations, where a biological prosthesis is preferred. This study provides data that can be useful for decision-making in this frequent clinical dilemma encountered by cardiac surgeons. 

The authors conclude that patients who received mechanical mitral valve replacement had significantly fewer reoperations, while survival was comparable between the mechanical and biological prosthesis groups. 

Within the analyzed cohort, the age groups of 46–55 and 56–65 years showed no survival differences between prosthesis types. These results contrast with recent literature, which suggests higher survival with mMVR for patients aged 50–69. Notably, survival was also higher in the mMVR group prior to propensity score matching. Although propensity score matching is a valuable statistical tool for comparing techniques that often involve dissimilar patient profiles, such as mMVR and bMVR, it is crucial not to overlook the inherent biases associated with its use. 

Although this study’s selection of variables is comprehensive, an analysis of mortality in patients requiring reoperation during follow-up is absent. Additionally, specifying the indications for reintervention, particularly in the mMVR group, would be insightful. These data could be especially useful for personalizing clinical treatment. 

Information on anticoagulation-related complications during follow-up in the mMVR group would also be pertinent, given their impact on both quality of life and survival. The current trend is to implant biological prostheses in increasingly younger patients, grounded in numerous studies showing a higher bleeding risk after mMVR and increased durability of contemporary biological prostheses. 

Finally, the potential of transcatheter therapies in mitral valve reoperation should not be overlooked, as this could represent a paradigm shift similar to the TAVI valve-in-prosthesis approach in aortic valve disease over the last decade. However, for mitral valve pathology, the risk of left ventricular outflow tract obstruction remains a significant challenge to further advancing structural interventions in this area. More research and experience in percutaneous mitral valve treatment are needed to potentially offer a viable alternative to surgical reoperation. 

In conclusion, this study provides valuable information for decision-making in the surgical treatment of mitral valve disease. These findings can guide cardiac surgeons in individualizing treatment, taking into account not only the comparable survival between both types of prostheses and the reduced reoperation risk with mMVR but also the quality of life considerations associated with long-term anticoagulation. 

REFERENCE: 

Feirer N, Buchner A, Weber M, Lang M, Dzilic E, Amabile A, et al. Mechanical versus biological mitral valve replacement: Insights from propensity score matching on survival and reoperation rates. J Thorac Cardiovasc Surg. 2024 Jul 26:S0022-5223(24)00652-4. doi: 10.1016/j.jtcvs.2024.07.038.