This raises the possibility that preventive strategies should vary based on the type of mitral surgery, but more research is needed.
Infective endocarditis (IE) over the long term is much more common in patients who have undergone mitral valve (MV) replacement surgery than in those treated with MV repair or who have a moderate risk of IE for other reasons, a Danish study shows.
The 10-year cumulative incidence of IE was 6.1% after replacement, 1.6% after repair, and 1.7% in the moderate-risk group, researchers led by Amna Alhakak, MD (Copenhagen University Hospital – Rigshospitalet, Denmark), report in a paper published online recently the European Heart Journal.
Overall, the findings suggest that MV replacement carries a high risk of IE and MV repair a moderate risk of IE, but further studies around antibiotic prophylaxis and prevention efforts will be needed, say researchers.
“Our study may lay the framework for hypothesis-generating research in both future prospective studies and randomized clinical trials to determine whether antibiotic prophylaxis and preventive strategies in general should differ between those who underwent mitral valve replacement or repair,” Alhakak said.
Commenting for TCTMD, Gilbert Tang, MD (Icahn School of Medicine at Mount Sinai, New York, NY), said the progressive increase in IE risk over the long term is to be expected.
“All prosthetic valves, whether tissue or mechanical, have foreign materials and they are the nidus of infection, especially when antibiotic prophylaxis was not taken prior to invasive procedures,” he explained via email.
The study “also tells us that when possible, mitral valve repair would be preferable to replacement, since preserving native human tissue would protect the patient against prosthetic materials that would risk infection,” he added. “In addition, the body heals over prosthetic mitral annuloplasty bands and rings, but in bioprosthetic [replacement] valves, the animal tissue and commissural posts are still exposed to the bloodstream and potential infection.”
Insights Into Long-term Risks
The 2023 endocarditis guidelines from the European Society of Cardiology recommend antibiotic prophylaxis prior to dental procedures for patients with a high risk of IE, including those with surgically implanted prosthetic valves and those who have undergone surgical cardiac valve repair. However, the guidelines don’t explicitly discuss whether patients undergoing MV surgery have a moderate or high risk of IE or whether risks differ between replacement and repair in this setting.
In addition, Alhakak said, prior studies exploring the risk of IE after MV surgery have primarily focused on short-term outcomes or recurrent endocarditis.
To provide some insights into longer-term risks of first-time IE, the researchers examined Danish national registry data on patients who underwent surgical MV replacement (n = 1,220), those who underwent surgical MV repair (n = 3,239), or those deemed to have a moderate risk of IE related to other conditions (n = 209,517) between 2000 to 2020. The latter group encompassed patients with cardiac implantable electronic devices, congenital heart valve anomalies, hypertrophic cardiomyopathy, rheumatic heart diseases, and nonrheumatic degenerative valve diseases affecting the mitral and aortic valves.
In the replacement group, roughly half of patients were treated with a bioprosthetic valve and half with a mechanical valve. For most repair patients (91.8%), surgery involved an annuloplasty ring.
By 1 year of follow-up, the incidence of IE was already higher in the replacement group (2.1%) than in either the repair (0.46%) or moderate-risk (0.36%) groups. Risk progressively increased, particularly after replacement, through follow-up lasting up to 10 years (median 3.8 years).
After accounting for potential confounders, IE risk was significantly higher in patients who underwent MV replacement than in the moderate-risk patients (adjusted HR 3.52; 95% CI 2.73-4.52), with no significant difference between the repair and moderate-risk groups (adjusted HR 0.76; 95% CI 0.56-1.04). All three groups, however, had significantly greater IE risks compared with the general population.
Within the replacement group, the 10-year cumulative incidence was higher in those treated with a bioprosthetic versus mechanical valve (7.6% vs 5.1%), but, the researchers say, “this difference should be interpreted with caution, as it may be confounded by indication since a bioprosthetic valve is usually chosen for older patients with reduced life expectancy and more comorbidities compared with those receiving a mechanical valve.”
Looking at all-cause mortality, risks were lower in both the MV replacement (HR 0.80; 95% CI 0.73-0.89) and repair (HR 0.61; 95% CI 0.57-0.66) groups compared with patients who had moderate risk. “The moderate-risk group represents a broad and heterogeneous group of patients with more serious comorbidities, which may contribute to the higher observed mortality rate in this group,” the authors suggest. “In contrast, patients who underwent MV surgery had lower overall mortality rates despite higher rates of IE, which may reflect a healthier population with more favorable prognostic characteristics due to their suitability for surgery.”
In an accompanying editorial, Daniele Giacoppo, MD, PhD (University of Catania, Italy), welcomes the new findings.
“After multiple studies on native and prosthetic aortic valve IE, the analysis of Danish registries represents an outstanding opportunity to define the contemporary risk of IE after MV repair and MV replacement,” he said, adding that the study provides “insights for implementing preventive strategies and surveillance programs for patients who have undergone prosthetic MV replacement” as well as new research on how strategies might be tailored to surgery type.
Implications for Surgical Decision-Making
Because of the observational study design, these findings should not be used to guide treatment decisions, Alhakak said, noting that the choice of replacement or repair takes into account a variety of factors like valve pathology, patient anatomy, comorbidity burden, life expectancy, and surgical feasibility and expertise.
Additional research is needed, too, to explore the best preventive measures and surveillance strategies in patients undergoing MV replacement and repair, “which could include more structured follow-up, improved patient education in recognizing infection signs and symptoms, and targeted antibiotic prophylaxis, especially prior to dental procedures, in those with prosthetic valves, Alhakak said.
Regarding choice of surgery, Tang noted that “as surgeons, we always advocate for repair over replacement, not just because of survival benefit but also because it’s always better to preserve your own valve, since any prosthetic valve will have a limited lifespan and the foreign materials will subject the patient to IE risk, as shown in this paper.”
He stressed the importance of going to an experienced mitral center for treatment, pointing out that a replacement would be better than a suboptimal repair, which will likely result in an eventual replacement anyway. Seeing a skilled physician also is critical if patients are opting for a less invasive mitral transcatheter edge-to-edge repair (M-TEER), because findings from the CUTTING-EDGE registry showed that when patients have a failed M-TEER, the vast majority (more than 95%) end up with a surgical replacement.
“My recommendation is to go to an experienced mitral center with expertise in surgical MV repair to get a repair when possible, rather than an MV replacement or a bad transcatheter repair which requires an MV replacement afterwards,” Tang said.