Survival after mitral valve surgery in the context of infective endocarditis (IE) is poorer compared to aortic valve cases. For extensive infections in aortic valve endocarditis, the aortic root may be replaced. For the mitral valve, aggressive debridement of abscesses is necessary, with the main limiting factor being the integrity of the atrioventricular groove. This approach reinforces and seals the area but consequently limits antimicrobial penetration, increasing the risk of reinfection and compromising patient survival. Clinical guidelines recommend mitral valve repair, as repair outcomes are generally better than replacement. However, studies advocating repair often include heterogeneous populations, mixing patients with active and cured endocarditis. 

The Cleveland Clinic study investigates the clinical, pathological, bacteriological, and surgical characteristics of patients with isolated mitral endocarditis, analyzing short- and long-term outcomes of reinfection, reoperation, and mortality in patients undergoing repair versus replacement. A retrospective review from 2002 to 2020 identified 2,303 endocarditis surgeries, including 447 cases of isolated mitral valve endocarditis (429 patients). Primary endpoints included surgical complications, defined by the STS database: reinfection, reoperation for infectious or non-infectious mitral valve causes, mitral insufficiency during follow-up, and mortality. 

Of the 447 isolated mitral endocarditis cases, 236 involved the native valve (NV) and 121 a mitral prosthesis (MP). Patients were categorized into three groups: untreated NV (n=282; 63%), repaired NV (RV, n=44; 9.8%), and MP (n=121; 27%). Staphylococcus aureus was the predominant infectious agent in all groups. Of the 326 NV patients with IE, 88 (27%) underwent standard repair, 43 (13%) extended repair, and 195 (60%) valve replacement. Patients receiving standard repair were younger with fewer comorbidities. Hospital mortality was 3.8%; none in the standard repair group, 3 patients in the extended repair, 8 patients in the previous mitral valve replacement (PM) group, and 6 in those requiring mitral valve replacement. With a median follow-up of 4.4 years, survival at 1, 5, and 10 years for any repair was 91%, 75%, and 62%, while for replacement, it was 86%, 62%, and 44%. Renal failure emerged as the primary mortality risk factor. Risk-adjusted results and survival were similar across all groups. 

The authors concluded that surgical solutions should be tailored to each patient based on clinical status and risk factors. The apparent superiority of repair in the IE context relates more to patient characteristics than to surgical technique. Renal failure is the most significant mortality risk factor, and in cases of extensive destruction, replacement is preferable to complex repairs. 

COMMENTARY: 

Historically, the Cleveland Clinic has pioneered advancements in medicine. This article is no exception, presenting the largest report on the microbiological, pathological, and surgical outcomes of isolated mitral endocarditis. The core message is simple: endocarditis affects a diverse and highly heterogeneous population. Surgeons must choose the most appropriate technique based on the patient, perioperative conditions, and intraoperative findings. The more localized the infection, the more feasible valve repair becomes. The study also highlighted that extended repairs offered no benefits over mitral valve replacement in terms of reoperation, reinfection, or survival. This reinforces the general approach in endocarditis surgery: perform the procedure efficiently and safely. If complex valve reconstruction, tissue deficits, or challenging repair are anticipated, it indicates advanced infection and suggests prosthesis implantation. 

In addition to reporting impressive mortality figures (3.8% overall hospital mortality over 20 years, 0% in the standard repair group), the article discusses cardiorenal and cardiohepatic syndromes in the endocarditis context. Preoperative renal dysfunction was the most significant mortality risk factor, and hyperbilirubinemia emerged as a risk factor for infection recurrence. A “J”-shaped non-linear relationship between plasma conjugated bilirubin levels and adverse in-hospital outcomes likely reflects bilirubin’s anti-inflammatory and antioxidant properties. These findings are essential for risk stratification and potential therapeutic interventions. 

Finally, it is essential to note the study’s limitations. Although the most extensive report on isolated mitral endocarditis, it remains a single-center, observational, retrospective study. The Cleveland Clinic is a national reference center that also treats international patients, so their patient cohort may not represent typical daily practice. Therefore, antimicrobial therapies varied in coverage and duration. Additionally, the surgeons involved had extensive mitral repair experience, with an annual case rate of 25 mitral repairs—a milestone few surgeons achieve, let alone maintain. 

In conclusion, today’s article talks about the importance of offering targeted and personalized surgery. Both repair and replacement have their place in these surgeries, the important thing is to choose which one will benefit our patient the most. Remembering the old surgical aphorism: “patients should be offered the surgery they need, not the one we would like to perform.” 

REFERENCE: 

Moore RA, Witten JC, Lowry AM, Shrestha NK, Blackstone EH, Unai S, Pettersson GB, Wierup P; Endocarditis Study Group. Isolated mitral valve endocarditis: Patient, disease, and surgical factors that influence outcomes. J Thorac Cardiovasc Surg. 2024 Jan;167(1):127-140.e15. doi: 10.1016/j.jtcvs.2022.01.058. Epub 2022 Apr 5. PMID: 35927083; PMCID: PMC9532471.