Best Timing of Surgery for Active Mitral Endocarditis Remains Controversial

Reed Miller

February 01, 2010

February 1, 2010 (Fort Lauderdale, Florida) — New retrospective data suggest surgery to treat mitral regurgitation in the presence of infective endocarditis is safe. However, in the absence of large controlled studies, experts remain skeptical that so-called "early" surgery in these patients will improve their outcomes [1].

At the recent Society for Thoracic Surgeons (STS) 2010 Annual Meeting, Dr Matthew Romano (University of Michigan, Ann Arbor) presented results from 126 patients with active endocarditis who underwent mitral-valve-repair surgery prior to the completion of six weeks of antibiotic therapy. "The traditionally held belief has [supported] a prolonged course of intravenous antibiotics for six to eight weeks, to sterilize the field to minimize prosthetic material infection, with early surgery reserved only for ongoing sepsis, antibiotic failure, and worsening congestive heart failure," Romano said. "Recently, there's been a shift in paradigm toward earlier surgery for mitral-valve endocarditis, which may improve early and late mortality and may increase the repair rate."

All the patients in the trial were hospitalized and undergoing antibiotic therapy to treat the endocarditis infection at the time of the surgery. The average time from admission to surgery in this group was six days, ranging from two to 33 days. The average preoperative left ventricular ejection fraction was 54%, the average NYHA heart-failure class was 3.4, and 6% of the patients were in cardiogenic shock.

Mitral-valve-repair surgery was completed in 56% of the patients, which compares favorably to the 15% rate shown in the STS national database for patients with early and/or active endocarditis. The overall perioperative mortality rate was 8.9%. The operative mortality for patients undergoing mitral repair alone was 4.8% and when concomitant with aortic-valve repair was 4.6%.

In patients in whom the surgeon decided repair was impossible and therefore replaced the entire mitral valve, the mortality rate was 14% when only the mitral valve was treated and 17% in patients undergoing concomitant aortic repair. The patient subset with the highest mortality comprised patients undergoing reoperation for endocarditis of a previously implanted prosthetic valve.

Romano also noted that, although 40% of patients had preoperative head CT abnormalities, there was only one stroke in the study. "The data show that, despite the fact that there are positive findings on CT scan or MRI imaging, the conversion rate to a hemorrhaging stroke or a neurologic event rate postoperatively was relatively low; going to the operating room earlier may decrease the risk of systemic embolization and also favor repair and minimize valve destruction."

How Early Is Too Early?

When the audience was given an opportunity to comment on the study at the STS meeting, Dr James Gammie (University of Maryland, Baltimore) said the study results mirror his center's experience with mitral-endocarditis patients. "The global mortality rate for patients admitted to the hospital with left-sided endocarditis remains very high, at about 30%, so an appropriately timed and executed operation offers us the single best opportunity to decrease that mortality rate.

"Patients can indeed undergo early surgery, and operating on them early affords prevention of further embolic events and probably increases the likelihood of achieving a mitral repair," Gammie said.

However, several experts who spoke to heartwire about the study said that it is not enough to show that surgery after only a few days of antibiotics should be the preferred strategy for mitral endocarditis.

Dr David Bach (University of Michigan, Ann Arbor) told heartwire "Conventional wisdom and current standard of care state that infective endocarditis is a medically treated disease; surgery is reserved for failure of medical therapy and for the sequelae of endocarditis. In the absence of a randomized trial showing superior outcomes associated with early surgery, a change in conventional practice does not seem appropriate.

"The main positive messages [from this study] might be that mitral-valve surgery is feasible if it is indicated within the six weeks during which antibiotics are still being given for endocarditis and that earlier surgery might increase the feasibility of repair [as opposed to valve replacement]," he said. However, "more data would be needed before concluding that early surgery is preferred over conventional therapy for endocarditis."

Dr Robert Siegel (Cedars-Sinai Heart Institute, Los Angeles, CA) suggested that perhaps the surgeries in the study should not be considered "early" at all. Patients in the study had an average NYHA heart-failure class of between 3 and 4, which is already an indication for surgery in patients with mitral endocarditis. "If all the patients were class 4, then that's not 'early' operation," he said. "That's [recommended under] the current guidelines, so there's nothing new there." He also pointed out that patients with persistent infection and embolization are also already indicated for surgery under current guidelines, but that it is not clear how many patients in the study already met either of those criteria.

Dr Maurice Sarano (Mayo Clinic, Rochester, MN) told heartwire that because mitral endocarditis is such a heterogeneous condition, it is difficult to apply the overall results of the study to any one subgroup of patients. The study included patients with or without concomitant aortic disease and patients with endocarditis in a native valve or a prosthetic valve, and there was no indication as to how many of the patients were still considered infectious based on positive blood cultures, Sarano said.

"You can't have a uniform study in endocarditis unless you do a collaborative study that allows you to have very large numbers, and then you can select specific subgroups," he said. To conduct a large multicenter trial of valve repair in endocarditis patients will require better collaboration between infectious-disease researchers focused on endocarditis and researchers studying valve surgery, he said.