[Lyme borreliosis--a possible cause of atrioventricular block].

Eight cases of Lyme borreliosis of clinical certainty with carditis are reported. In six patients, AV-blocks were predominant, two patients had a myopericarditis. Six acute cases were seropositive, but one case remained seronegative. The titer was border-line in that patient, who was studied 4 years after the acute disease. A Lyme carditis should be considered in each case, in which AV-blocks appear acutely.