Lyme disease: an active agent in dilated cardiomyopathy?

Manifestations of Lyme carditis

The first data of Lyme carditis, a relatively rare manifestation of Lyme disease, were published in eighties of the last century. Clinical manifestations include syncope, light-headedness, fainting, shortness of breath, palpitations, and/or chest pain. Atrioventricular (AV) electrical block of varying severity presents the most common conduction disorder in Lyme carditis. Although is usually mild, AV block can fluctuates rapidly and progress from a prolonged P-R interval to a His-Purkinje block within minutes to hours and days. Rarely, Lyme disease may be the cause of endocarditis, while some studies and reports, based on serological and/or molecular investigations, have suggested possible influence of Borrelia burgdorferi on degenerative cardiac valvular disease. Myocarditis, pericarditis, pancarditis, dilated cardiomyopathy, and heart failure have also been described as possible manifestations of Lyme carditis. The clinical course of Lyme carditis is generally mild, short term, and in most cases, completely reversible after adequate antibiotic treatment.

Atteinte cardiaque dans la maladie de Lyme

Cardiac manifestations of Lyme Borreliosis are relatively infrequent, occurring within weeks after the infectious tick bite (median of 21 days), and resulting at this stage from a direct borrelial infection of the myocardium, as indicated by reports of spirochete isolation from pericardium and myocardium. They may persist or appear in the late, tertiary phase of the illness, being then more likely due to infection-triggered autoimmunity. Lyme carditis typically presents with a fluctuating degree of atrioventricular block that spontaneously resolves in several days. Rarely, myocarditis may occur with or without pericardial involvement, in patients presenting with chest pain, ST depression or T wave inversion, mimicking an acute myocardial infarction, and various arrhythmias are reported, as well as pericardial effusion or heart failure. A complete recovery is usually observed, spontaneous or after antibiotherapy. Severe myocarditis or Pericarditis leading to death is exceptional. The diagnosis of Lyme carditis is based on the same association of clinical and laboratory features as in Lyme disease without cardiac involvement. But the occurrence of conduction disturbances in healthy young people suggests screening for other criteria of Lyme disease. The management of Lyme carditis does not differ from the treatment of Lyme disease without carditis and is mainly based upon the use of doxycycline or ceftriaxone.

Evidence of Borrelia autoimmunity-induced component of Lyme carditis and arthritis

We investigated the possibility that manifestations of Lyme disease in certain hosts, such as arthritis and carditis, may be autoimmunity mediated due to molecular mimicry between the bacterium Borrelia burgdorferi and self-components. We first compared amino acid sequences of Streptococcus pyogenes M protein, a known inducer of antibodies that are cross-reactive with myosin, and B. burgdorferi and found significant homologies with OspA protein. We found that S. pyogenes M5-specific antibodies and sera from B. burgdorferi-infected mice reacted with both myosin and B. burgdorferi proteins by Western blots and enzyme-linked immunosorbent assay. To investigate the relationship between self-reactivity and the response to B. burgdorferi, NZB mice, models of autoimmunity, were infected. NZB mice infected with B. burgdorferi developed higher degrees of joint swelling and higher anti-B. burgdorferi immunoglobulin M cross-reactive responses than other strains with identical major histocompatibility complex (DBA/2 and BALB/c). These studies reveal immunological cross-reactivity and suggest that B. burgdorferi may share common epitopes which mimic self-proteins. These implications could be important for certain autoimmunity-susceptible individuals or animals who become infected with B. burgdorferi.