Absence of Borrelia burgdorferi in the myocardium of subjects with normal left ventricular systolic function: a study using PCR and electron microscopy.

Background: Several studies have demonstrated the presence of the Borrelia burgdorferi (Bb) genome in the myocardium of patients with dilated cardiomyopathy (DCM). To further support a causal relationship between the presence of Bb in the heart muscle and the development of DCM, demonstration of the absence of Bb in the myocardium of subjects with normal left ventricular (LV) systolic function is needed.
Aim: To determine the prevalence of Bb by polymerase chain reaction (PCR) and electron microscopy (EM) in individuals with normal LV systolic function and no history suggestive of myocarditis.
Methods: We investigated 50 patients (67 ± 9 years, 15 women) with normal LV ejection fraction (EF) ≥ 50% undergoing cardiac surgery. During surgery, four samples from the right atrial appendage were obtained and subsequently examined by PCR and EM for the presence of Bb, and by immunohistochemistry to detect inflammatory cells. Serological testing of antibodies against Bb was also performed.
Results: Neither PCR nor EM detected Bb in any of the subjects. Immunohistological examination revealed myocardial inflammation in 2 individuals (4%). Serological analysis by enzyme-linked immunosorbent assay demonstrated IgM antibodies against Bb in 4% and IgG antibodies in 12% of the study cohort; Western blot revealed IgM as well as IgG positivity in 14% of patients.
Conclusions: The absence of Bb in the myocardium of individuals who undergo cardiac surgery and have normal LV systolic function supports the idea of Bb pathogenicity in the development of DCM.