The ECG (Figure 2) demonstrates atrioventricular dissociation. Close examination of the ECG reveals two independent rhythms: a junctional tachycardia at 130 beats/min and a sinus tachycardia at 100 beats/min. The rhythm strip (Figure 1) demonstrates an interval of nonconducted P waves indicative of heart block. Taken together, the data suggest extensive conduction system disease.
In light of the findings on this ECG and of the high incidence of Lyme disease in Connecticut, further history was solicited from the patient. When asked specifically about outdoor activities, he reported that he had been on a hiking trip 1 month before this visit to the ED, and he remembered being bitten by a tick. He also stated that a rash appeared on his legs several days later, but that he thought little of it and applied some over-the-counter cream in an effort to make it go away.
Lyme disease is an infectious, tick-borne process endemic to Wisconsin, Minnesota, and the northeastern United States. It was first recognized in 1975 after chronic infections by the spirochete Borrelia burgdorferi were discovered in three Connecticut communities, where an epidemic of oligoarticular arthritis was noted. The organism is transferred by the Ixodes (dammini) scapularis deer tick. The incidence is approximately 6-8 cases per 100,000 people in the United States, according to estimates by the Centers for Disease Control and Prevention; 93% of cases occur in the above-mentioned endemic areas. Approximately 20,000 new cases are reported every year.
Patients presenting with symptoms of Lyme disease may or may not remember removing a tick from their body; the ticks often go unnoticed because they are about the size of a pencil tip. With increased awareness and treatment in the first stage of Lyme disease, extracutaneous manifestations have decreased.
Although Lyme disease presents with erythema chronicum migrans (ECM) in 70% of cases, extracutaneous disease is well known (eg, heart block by itself occurs in < 1% of cases). The disease may involve the skin, central nervous system (CNS), heart, joints, and eyes. Lyme disease results in few deaths; they are typically limited to patients who are also infected with babesiosis and ehrlichiosis (also known as human granulocytic anaplasmosis).
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