by Will Boggs, MD

Last Updated: 2008-01-02 13:24:33 -0400 (Reuters Health)

NEW YORK (Reuters Health) – The risk of embolic stroke in infective endocarditis falls significantly after a week of antibiotic therapy, according to a report in the December issue of the American Heart Journal.

"Whenever perceived embolic risk is a factor in a decision about valvular surgery in a patient with endocarditis, the duration of antimicrobial therapy at the time of consultation needs to be brought into the clinical thinking," Dr. Stuart A. Dickerman told Reuters Health. "After a week of appropriate antibiotic therapy, the risk of embolism falls sharply enough (in most cases) to remove embolic risk from the decision-making equation."

Dr. Dickerman from New York University School of Medicine, New York, and colleagues in the ICE Prospective Cohort Study used a registry of patients with infective endocarditis to investigate the temporal occurrence of stroke and to define the relationship between the initiation of antibiotic therapy and the risk of subsequent stroke.

Fifteen percent of the patients with infective endocarditis had a stroke, the authors report; in half, the stroke occurred before the initiation of antibiotics while in half it occurred after the initiation of antibiotics.

The daily rate of stroke fell significantly with the initiation of antibiotics, the report indicates, declining from 4.82 per 1000 patient-days during the first week of therapy to only 1.71 per 1000 patient-days in the second week of antibiotic therapy and continuing to decline with ongoing therapy.

Infection with Staphylococcus aureus, the presence of vegetation on the mitral valve, and the presence of myocardial abscess increased the risk for stroke, whereas infection with the viridans group of streptococci decreased the risk of stroke.

Patients with native valve infective endocarditis had similar stroke rates to patients with prosthetic valve endocarditis, the investigators say, and the incidence of stroke was lower in patients who underwent valvular surgery (10.0%) than in patients who did not undergo surgery (15.2%).

Nevertheless, the researchers note, "If there are no other clear indications for valvular surgery, this study suggests that the risk of stroke may fall quickly enough to preclude such risk as a justification for valvular intervention."

"There may be subsets of patients, of course, such as those with prior embolic events, or those with large, mobile vegetations, for whom the risk of embolization will be sufficiently high enough in and of itself to warrant surgical intervention after this duration of therapy," the authors add.

"The original ICE case report form did not include entries for echocardiographic details such as vegetation size and mobility," Dr. Dickerman said. "We have formed an echo substudy group, which is going ‘back to the videotape’ to enter such information into the ICE database. Once this is done, I plan to look at how vegetation size and mobility interacts with the variable of duration of antimicrobial therapy with regards to the incidence of stroke."

Am Heart J 2007;154:1086-1094