Case of the quarter: Lyme carditis: a reversible cause of complete atrioventricular block

A 54-year-old American woman presented with an episode of syncope. This  had  occurred  against  a  background  of  several  days  of  dizziness  and palpitations. Her medical history included Bell’s palsy, which had been diagnosed three  weeks  earlier.  On  examination,  she  had  a  resting  bradycardia  of  31  beats per minute and her electrocardiogram demonstrated third-degree atrioventricular (AV)  block.  She  was  referred  to  cardiology  for  consideration  of  permanent pacemaker implantation. Given her facial nerve palsy and AV block, a diagnosis of Lyme borreliosis was suspected. Within 48 hours of initiation of ceftriaxone, she reverted to sinus rhythm, albeit with a marked first-degree AV block. Subsequent serology confirmed the diagnosis. Reversible causes of complete AV block should always be considered and appropriate therapy may avoid the need for permanent pacemaker insertion.