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A previously healthy 31-year-old man without a history of cardiac disease presented to the emergency department with a 5-day history of a sore throat, neck stiffness, progressive dyspnea, transient confusion, fever, palpitations, and a generalized rash. His medical history was unremarkable. He reported no recent local or foreign travel, sick contacts, vaccinations, new medications, or exposure to human immunodeficiency virus or hepatitis. He had not been on any recent camping trips and had had no tick or rodent exposure. Of note, he lived in northwestern Wisconsin.
Physical examination revealed a heart rate of 113 beats/min, a blood pressure of 104/55 mm Hg, and a temperature of 36.7°C. His oxygen saturation was 100% on room air.
Cardiopulmonary examination revealed inspiratory wheezes in both lung bases and 1/6 systolic murmur consistent with tricuspid regurgitation. Abdominal examination revealed hepatomegaly; the abdomen was otherwise nontender and soft with positive bowel sounds. Skin examination revealed extensive tattooing covering the entire body (done in the distant past), with multiple, diffuse, raised, well-circumscribed, nonblanching, nonpurpuric, nontender, nonpruritic erythematous plaques approximately 5 to 10 cm in diameter involving his back, neck, trunk, and all extremities but sparing his palms and soles. The patient stated that he had never had such lesions before.
Initial laboratory studies yielded the following results (reference ranges provided parenthetically): hemoglobin, 13.0 g/dL (13.5-17.5 g/dL); leukocytes, 10.2 × 109/L (3.5-10.5 × 109/L); sedimentation rate, 34 mm/1 h (0-22 mm/1 h); C-reactive protein, 34.7 mg/L (<8.0 mg/L); alkaline phosphatase, 294 U/L (45-115 U/L); aspartate aminotransferase, 165 U/L (8-48 U/L); alanine aminotransferase, 277 U/L (7-55 U/L); γ-glutamyltransferase, 216 U/L (9-31 U/L), troponin, <0.01 ng/mL times 2 (<0.01 ng/mL), and creatine kinase–MB, 2.4 ng/mL (≤6.2 ng/mL). Blood cultures were obtained.
Electrocardiography showed the following: sinus tachycardia (atrial rate, 108 beats/min), absent PR depression, a ventricular rate of 118 beats/min, third-degree or complete heart block with atrioventricular dissociation and capture beats, low anterior forces, and nonspecific ST- and T-wave abnormalities.
Lyme disease is an arthropod-borne disease known to affect primarily the skin, heart, and nervous system. It is caused by the spirochete Borrelia burgdorferi, introduced to the host by the bite of ticks of the Ixodes species. Lyme disease is endemic in the areas in which Ixodes ticks and the vector-competent animal hosts are found. From 2003 through 2005, approximately 93% of cases in the United States were reported from 10 states: Massachusetts, Connecticut, Rhode Island, New York, New Jersey, Pennsylvania, Delaware, Maryland, Minnesota, and Wisconsin.9 B burgdorferi organisms are present in the midgut of the unfed nymphal ticks. On attachment of the ticks to the host, the bacteria multiply quickly, with a doubling time close to 4 hours, and reach a maximum number after 72 hours of attachment.10 During the initial 15-hour period, the spirochetes appear restricted to the tick gut, but after 48 hours they disseminate to the salivary glands, supporting previous data showing a low risk of infection before 36 hours of tick attachment.10,11
Clinical features of Lyme disease vary during the course of the infection and are divided into stages: early localized disease, early disseminated disease, and late disease.
Early localized disease usually occurs between a few days to one month after the tick bite and is manifested by the presence of skin lesions (EM), which occur in 50% to 70% of patients. During the first few days, EM lesions may be uniformly red; as they expand, however, some central clearing often develops, and they may have a more complex target or bull's eye appearance. In an observational cohort study of 118 cases of EM in which B burgdorferi infection was confirmed by culture or polymerase chain reaction, the EM lesion was homogeneous in 59%, had central erythema in 32%, and had central clearing in 9%.12 Constitutional symptoms that may occur include fatigue, malaise, lethargy, headache, stiff neck, myalgia, arthralgias, and lymphadenopathy. Early disseminated disease, which occurs between a few days to 10 months after the tick bite, may be characterized by carditis, which may present as conduction defects, cardiomyopathy, or myopericarditis. It may also present with neurologic disease manifesting as lymphocytic meningitis, encephalitis, cranial and peripheral neuropathy, myelitis, or even liver disease (eg, liver function abnormalities, hepatitis). Late disease can appear months to years after the tick bite, presenting as arthralgia, chronic monoarthritis, or neurologic disease manifesting as encephalopathy, peripheral neuropathy, or ataxia.1
Lyme carditis is a rare manifestation of the disease.13 It is estimated that only 4% to 10% of patients with untreated Lyme disease develop Lyme carditis.14 Cardiovascular manifestations of Lyme disease often occur within 21 days of exposure. The most frequent cardiac symptom is AV block (first-, second-, and/or third-degree or even an alternating variant of them). Patients with high-degree AV block are often symptomatic with palpitations, dyspnea, chest pain, and dizziness, whereas patients with first-degree block are generally asymptomatic. Other cardiac manifestations include myopericarditis, bundle branch block, and chronic heart failure.15 It has been suggested that the mechanism by which Lyme disease affects the conduction system is the result of the direct dissemination of spirochetes into cardiac tissues, the inflammatory response associated with the infection, or a combination of both.13 The overall prognosis of patients with Lyme carditis is very good; however, delayed recovery and late manifestations (eg, dilated cardiomyopathy) have been described.15
Patients with minor cardiac disease (first-degree AV block with a PR interval <300 ms) could be treated with oral doxycycline, tetracycline, or amoxicillin. Administration of doxycycline is preferred because of the higher efficacy in other tick-borne diseases (babesiosis, ehrlichiosis, and anaplasmosis) that could be cotransmitted with Lyme disease. Patients with more severe conduction system disturbances (first-degree AV block with a PR interval >300 ms, second- or third-degree AV block) should be observed in a telemetry unit and given intravenous ceftriaxone or high-dose intravenous penicillin G according to Infectious Diseases Society of America guidelines. Transcutaneous pacing is required in up to one-third of cases with Lyme carditis. Insertion of a temporary pacemaker may be required if warranted by the specific case. Implantation of a permanent pacemaker is not usually required.13
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Correct answers: 1. e, 2. d, 3. c, 4. b, 5. a