Response to Letter Regarding Article, “Endocarditis Secondary to Microsporidia: Giant Vegetation in a Pacemaker User”
We appreciate Dr Henrikson’s interest in our study1 and the opportunity to clarify several issues. Dr Henrikson had a very precise observation concerning the electrocardiogram, and we agree with the comments made. Indeed, it was a normofunctioning dual-chamber pacemaker, and the electrocardiogram was taken just before open heart surgery, with the pacemaker programmed to asynchronous ventricular pacing mode considering atrial lead manipulation.
Moreover, in our article, we report a novel agent for implantable pacemaker infection in a patient with persistent bacteremia despite the fact that blood cultures were all negative, as highlighted by Dr Henrikson. Most cases of pacemaker lead infections are due to pathogens from the skin flora, with positive blood culture ranging in the literature from 80% to 100% of the cases. Making a parallel with heart valves in the human, there are many causes of culture-negative endocarditis. The causative agents of culture-negative endocarditis in the heart are fastidious bacteria (Bartonella quintana, Coxiella burnetii, or brucella species), fungi, and the usual organisms (mainly streptococci) found in patients who have received antibiotic treatment before blood samples are obtained for culture.2 Thus, we present here another possible etiology in this context, now related to pacemaker infections. While these fastidious bacteria yield negative hemocultures requiring different diagnostic approaches such as serology, in the case of microsporidium, electron microscopy is fundamental and should be complemented by polymerase chain reaction.1
Dr Henrikson also pointed out that no signs of endocarditis were present even though a large vegetation was disclosed. Pacemaker endocarditis may be limited to the pacemaker lead or involve the cardiac valves, generally the tricuspid, which can be demonstrated by the echocardiogram or intraoperatively. In our case there was no vegetation in this valve by both methods, but the mass entailed in valve insufficiency, present in 25% of the cases in one series.3 We cannot rule out that microscopic endocarditis was present because no biopsy specimens were taken from the valve. Nonetheless, the good clinical outcome after a long-term follow-up period makes this possibility unlikely.
Filho MM, Ribeiro HB, Paula LJ, Nishioka SA, Tamaki WT, Costa R, Siqueira SF, Kawakami JT, Higuchi ML. Endocarditis secondary to Microsporidia: giant vegetation in a pacemaker user. Circulation. 2009; 119: e386–e388.
Brouqui P, Raoult D. New insight into the diagnosis of fastidious bacterial endocarditis. FEMS Immunol Med Microbiol. 2006; 47: 1–13.