Systemic Embolization in Infective Endocarditis
Abstract & Commentary
Synopsis: The risk of systemic embolization in left-sided IE after initiating antibiotic therapy is increased with increased vegetation size.
Source: Vilacosta I, et al. J Am Coll Cardiol. 2002; 39:1489-1495.
Systemic embolization is a serious complication of infective endocarditis (IE). Effective strategies to prevent embolization remain unclear. Thus, Vilacosta and colleagues studied 217 episodes of left-sided IE in 211 patients at 5 centers in Spain and Argentina. Unlike older studies, all patients had transesophageal echocardiography (TEE). Definite endocarditis by the Duke criteria was present in 91%; 9% were probable. By TEE, 85% had vegetations. Prosthetic valves were infected in 72 episodes. There were 34 embolic events in 28 episodes of IE (13% of episodes) after antibiotic therapy was begun. The majority of embolic events were cerebral (52%) and two thirds occurred during the first 2 weeks after therapy was started. There were 57 embolic events in 43 episodes before treatment was begun (20% of episodes). Therefore, antibiotic treatment seemed to reduce the incidence of emboli.
The relative risk of embolization after treatment was begun was related to: prior embolization (before treatment), 1.7 (P = .05); vegetation size, 3.8 (P = .07); vegetation size with staphylococcus injection, 23.7 (P = .04); increasing vegetation size on therapy, 2.6 (P = .02); vegetation size with mitral valve infection, 23.5 (P = .03). The risk of embolization with vegetation < 10 mm was 6.5%; 16.7% with 10-20 mm; and 20.8% with > 20 mm. Surgery was performed in 115 (53%) of patients for standard indications (not vegetation size), including the 6 patients with 2 embolic episodes. Vilacosta et al concluded that the risk of systemic embolization in left sided IE after initiating antibiotic therapy is increased if emboli occurred before therapy was begun; with increased vegetation size, especially with staphylococcus infection and mitral valve involvement; and with increasing vegetation size on therapy.
Comment by Michael H. Crawford, MD
Previous studies of embolic risk in patients with IE have had significant deficiencies. Many included emboli that occurred prior to echocardiography, which would tend to increase the numbers of those with small or no vegetations and would diminish the effect of antibiotic treatment on embolic events. Also, most prior studies were small and did not use TEE in all. Thus, it is not surprising that the importance of vegetation size and antibiotic treatment has been controversial. This study clearly shows that vegetation size is an important predictor of embolic events, especially in those with staphylococcal infection and mitral valve involvement. Vegetation mobility was not predictive, but probably because most mobile vegetations were large. Of interest is that a change in vegetation size either larger or smaller was predictive of emboli—the latter is probably explained by vegetation fragmentation. Also, antibiotic therapy was associated with a reduction in emboli.
There are several clinical implications of this study. The sooner the diagnosis is made and antibiotic therapy is started the better. This means that TEE should be done early if there is clinical suspicion of IE. Despite the beneficial effects of antibiotic therapy, most emboli occurred in the first 2 weeks after therapy was initiated. Thus, patients with vegetations > 10 mm in size, especially with staphylococcal infection and mitral valve involvement, should be considered for surgery. Also, patients whose vegetation size increases should be considered for surgery. This conclusion presumes that a second TEE is done, which was the case in 122 of their episodes (56%). Vilacosta et al do not state why the second echo was done, although it was done at a mean of 14 days after starting therapy. Perhaps evidence of persistent injection, deteriorating hemodynamics, and changes in heart murmurs or emboli occasioned the second echo. At this time a routine second echo cannot be supported, but one should probably have a low threshold for a repeat study given these results.
Finally, the effect of surgery is difficult to ascertain from this study. More than half the patients had surgery, usually for heart failure, persistent infection, or severe valve dysfunction. Also, all 6 patients with 2 embolic episodes had surgery. Vegetation size was not a criterion for surgery, nor was the mere presence of a prosthetic valve (one third of their patients). Surely they are rethinking vegetation size as a criterion for surgery.
Dr. Crawford is Professor of Medicine, Mayo Medical School; Consultant in Cardiovascular Diseases, and Director of Research, Mayo Clinic, Scottsdale, AZ.
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