Lyme Carditis Causing Complete Heart Block After Travel to Mexico

Lyme carditis can cause life-threatening heart block—even without a rash or known tick bite.

A previously healthy woman presented with sudden-onset dyspnea and chest pain. Four days earlier, she experienced a syncopal episode. Electrocardiogram (EKG) revealed a third-degree atrioventricular (AV) heart block.

The patient, a resident of Nuevo León, Mexico, reported recent travel to a region considered endemic for Lyme disease.

Jiménez-Castillo and colleagues reported seroprevalence rates of 3.9% in Nuevo León, 6% in Coahuila, and 14% in Tamaulipas, supporting regional exposure risk to Borrelia burgdorferi.

Lyme Disease Suspected Without Rash or Tick Bite

The patient did not recall a tick bite and denied having an erythema migrans rash.

Lyme disease was suspected based on the absence of another cause for her cardiac findings and her recent travel history.

For more on early signs, see Lyme disease without rash.

Diagnosis and Treatment

The patient was treated empirically with a 21-day course of intravenous ceftriaxone and required temporary cardiac pacing.

Serologic testing confirmed the diagnosis. IgM antibodies to Borrelia burgdorferi were positive and later confirmed by immunoblot.

Despite treatment, the patient continued to require pacing and ultimately underwent permanent pacemaker placement.

Clinical Implications

Lyme carditis should be considered in young patients presenting with high-degree AV block without an obvious cause.

This case also highlights that Lyme disease can occur outside traditionally recognized endemic regions.

Learn more about Lyme carditis and its cardiac manifestations.

Clinical Takeaway

Lyme carditis can cause complete heart block—even without rash or known tick exposure.

Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention