Abstract
Introduction
It is rare to see heart block as the first-and-only presentation of Lyme disease, the reported incidence being just 1% in untreated patients.
Case presentation
We report a patient who presented with syncope secondary to a fluctuating heart block. He had no previous manifestations of Lyme disease. Lyme carditis was suspected after the other usual etiologies of heart block were ruled out. Later, serologies came positive and patient’s heart block resolved on ceftriaxone therapy.
Conclusion
In at-risk individuals, clinicians should rule out this readily-treatable cause of heart block before proceeding with permanent pacemaker implantation due to enormous clinical and cost implications involved. Missing the diagnosis also exposes the patient to the risk of developing the late complications of Lyme disease. Diagnosis of isolated Lyme carditis is a challenge because the clinician does not have the diagnostic-clues that can usually be gleaned from the more common stigmata of Lyme disease.
Introduction
In 2006, 19,931 cases of Lyme disease were reported to the Centers for Disease Control and Prevention, Atlanta. 1 Worldwide, the annual incidence of Lyme disease continues to soar with approximately 65,500 cases reported annually in Europe. 2 This makes Lyme disease the most common tick-borne infection in the United States and Europe.1,2 Climate change has hastened the spread of the disease vector to hitherto non-endemic areas. 3 The causative agent of Lyme disease is the spirochete, Borrelia burgdorferi in the United States, and Borrelia afzelii and Borrelia garinii in Europe and Asia.4,5 This spirochete is transmitted through the bite of the infected Ixodes tick. 6
The early localised stage of Lyme disease presents with erythema migrans, an expansive rash with central clearing at the bite site, with or without constitutional symptoms. This usually occurs within 1 month following the tick bite. This characteristic rash occurs in approximately 80% of the cases. 7 Erythema migrans is fairly easily recognised, thanks to the low index of suspicion in endemic areas. Hence, most cases of Lyme disease get successfully treated by antibiotics at this stage which prevents further disease progression. In untreated patients, or patients where the early localised stage is missed owing to lack of specific signs or symptoms, Lyme disease can progress to the early disseminated stage, which is characterised by musculoskeletal (60% of untreated patients), neurologic (15% of untreated patients), or cardiac (5% of untreated patients) manifestations. 8 The incidence of these manifestations in patients who do receive timely and appropriate treatment for Lyme disease is not known, but is probably lower. Eventually, untreated Lyme disease may progress to the late chronic disease stage with persistent musculoskeletal, neurologic and/or cutaneous symptoms.
Cardiac involvement in Lyme disease is a relatively uncommon manifestation, being seen in approximately 5% of untreated patients. 8 Up to 20% of patients with cardiac involvement will either not recall a tick bite, or have no history of erythema migrans or other characteristic features of Lyme disease. 7 Thus, approximately 1 out of 100 untreated patients would present with cardiac involvement in the absence of any prior features of Lyme disease, making the diagnosis a challenge.
We report the case of a healthy middle aged male who presented with syncope secondary to a fluctuating heart block; this being the first and sole manifestation of his Lyme disease. The report highlights Lyme carditis as an easy-to-miss cause of heart block, yet something that is readily reversible. This, thus has significant patient-care and cost implications.
Case presentation
A 47-year-old Caucasian man with no significant past medical history except for childhood asthma, presented to the emergency room after he lost consciousness sitting at his desk. He reported feeling lightheaded before he lost consciousness. Till 2 days ago, he had been in good health when he started experiencing intermittent palpitations. He works as an insurance agent, and had attributed his symptoms to ‘stress’ at work. The syncopal episode was witnessed by his coworkers who denied seeing any convulsive activity, and said that the patient was unconscious for a few seconds. The patient came-to spontaneously and did not report any post-episodic confusion, or loss of bladder or bowel control. He also denied having any aura like symptoms before the event and did not have any focal weakness or other sensory symptoms after the episode. He was not on any medications, and denied having chest pain, diaphoresis, fever, headache, or rash.
The patient drank alcohol socially, did not smoke, and had never used illicit drugs. He had lived his entire life in the North-Eastern United States, and led an active lifestyle. He was adopted, and was unaware of his biological family history.
On physical examination, the patient looked anxious but was not in any obvious acute distress. His pulse rate fluctuated between 54 and 79 beats/minute, but was regular. Blood pressure was 104/76 mm Hg, and he was not orthostatic. He was afebrile. Cardiovascular exam revealed bradycardia, with normal S1 and S2. No murmurs, rubs, or gallops were heard. His remaining physical exam was normal.
Investigations revealed a normal blood count and electrolytes. The cardiac enzymes were normal. CT scan of the head was unremarkable. An EKG done showed sinus rhythm with first degree atrioventricular (AV) block (PR interval 216 ms).
Half-an-hour in to being worked up for his condition, the patient again complained of lightheadedness. At this time his heart rate dropped to 24 beats/minute with a blood pressure of 90/74 mm Hg. A repeat EKG showed complete AV dissociation, with an idioventricular rhythm (Figure 1). He received atropine, with no response. A transvenous pacemaker was then placed that improved the patient’s hemodynamics. Over the next day of hospitalisation, the patient kept fluctuating between first and third degree heart block. A transthoracic echocardiogram and a cardiac catheterisation were performed, both of which proved to be normal.
EKG showing heart block with complete atrioventricular dissociation, and idioventricular rhythm at 24 beats/minute.
Presence of a fluctuating heart block in an apparently healthy middle-aged male with no structural heart disease prompted the search for reversible causes of heart block. He was not on any medications that might have impaired conduction. Neither did he have features of other causes of heart block like infiltrative diseases, collagen vascular disease, or familial diseases. He did not report any previous signs or symptoms compatible with Lyme disease. However, since he was a native of an endemic area for Lyme disease, Lyme serologies were sent and patient was empirically started on intravenous ceftriaxone. Patient had a complete resolution of his heart block over the next three days. Lyme serologies later revealed a positive enzyme-linked immunosorbent (ELISA) assay for IgG and IgM antibodies against Borrelia (later corroborated by a positive confirmatory Western blot analysis). Patient was discharged home on oral doxycycline and completed a 21-day course of antibiotics. His follow up was uneventful.
Discussion and review of published literature
Clinical implications
It is rare to see carditis (manifesting as heart block) as the first and only presenting feature of Lyme disease (the incidence is about 1% in patients who are not treated for Lyme disease at the early localised stage).7,8 This has serious implications for patient care, and cost. The clinician may unnecessarily subject the patient to the implantation of a permanent pacemaker; a classical case of treating the symptoms but not the disease. A timely diagnosis also ensures that the patient receives prompt antibiotic treatment which prevents disease progression that could otherwise result in neurological and musculoskeletal complications. Misdiagnosis also greatly increases the cost of healthcare. An average pacemaker can cost upwards of $30,000 (not including the cost of the procedure and follow up).
Disease manifestations and pathophysiology
Lyme carditis occurs during the early disseminated stage of Lyme disease, weeks to months after the tick bite. In patients with Lyme carditis, the features of cardiac involvement could be palpitations (69% of patients), conduction abnormalities like heart block (19%), myocarditis (10%), and left ventricular failure (5%). 9 These may manifest clinically as lightheadedness, syncope, palpitations, shortness of breath, and/or chest pain. Alternating tachycardia and bradycardia is a common clinical sign, and patients can rapidly fluctuate between first and third degree heart block within a matter of minutes.9,10 The bradycardia usually does not respond to atropine. Thus, Lyme disease is thought to directly affect the conducting system of the heart, rather than increase the vagal tone. 11 A retrospective analysis of patients with conduction abnormalities secondary to Lyme carditis revealed that 86% had atrioventricular block, 40% had Wenckebach block, and 50% had complete heart block. 11 The highest risk of progression to complete heart block is in patients with a PR interval >300 ms. 12 Other features include valvular dysfunction and myopericarditis, both of which are exceedingly rare.9,10 Myocarditis secondary to Lyme disease is usually self-limited and clinically inapparent. 12 Chronic congestive cardiomyopathy secondary to B. burgdorferi has also been reported in a case report from Europe, but has not been shown in the United States. 13 Most patients with Lyme carditis will have coincident musculoskeletal (migratory arthralgias), neurologic (lymphocytic meningitis,encephalitis, cranial neuropathy, etc.), dermatologic (multiple erythema migrans), hepatic, and/or renal disease, which greatly aids in the diagnosis. If left untreated at this stage, Lyme disease can progress within months-to-years to the late chronic stage characterised by musculoskeletal involvement like intermittent or persistent mono/oligo-arthritis, neurologic disease, or skin disease in the form of acrodermatitis chronica atrophicans or localised scleroderma-like lesions.
Diagnosis and differentials
Common causes of acquired atrioventricular block that need to be ruled out when considering a diagnosis of Lyme carditis include ischemic heart disease and acute myocardial infarction, idiopathic progressive cardiac conduction disease, cardiomyopathies including hypertrophic obstructive cardiomyopathy, infiltrative myocardial processes (e.g. amyloidosis, sarcoidosis, hemochromatosis, lymphoma, multiple myeloma), hyperkalemia, collagen vascular disease (e.g. lupus, rheumatoid arthritis), increased vagal tone (due to pain, carotid sinus hypersensitivity, athletic training), thyroid disease, and drugs (beta blockers, calcium channel blockers, amiodarone, digitalis, adenosine, etc.). Most of these conditions will be apparent on history, or have readily observable manifestations that will help in pinpointing the diagnosis. Hence, it is apparent that the list of causes of acquired heart block in young healthy patients with no other manifestations is limited.
Diagnosis of Lyme carditis depends to a large extent on the epidemiology and the typical clinical features of Lyme disease. A history of tick bite is helpful but might go unnoticed. There is evidence that indicates that only about 25% of patients with early localised disease recall a tick bite. 14 In our patient’s case, it is conceivable that he just did not recall a history of tick bite or rash. Other clues include residence in, or travel through endemic areas, and prior history of erythema migrans. A thorough history and physical examination should be performed to ascertain the presence of other coexisting neurologic, musculoskeletal, and dermatologic complications. Rarely, as in this case, heart block might be the first and only manifestation, and hence Lyme carditis might not be easily suspected when it occurs in individuals with no prior features of Lyme disease. These patients may present with lightheadedness, syncope, or palpitations. Shortness of breath and chest pain may be reported in patients who have associated left ventricular failure and/or myocarditis, respectively. EKG and echocardiogram may provide diagnostic clues that will support or refute the diagnosis. A stress test or a cardiac catheterisation may be warranted to rule out ischemic disease.
Serologic tests to detect the presence of IgM and IgG antibodies against B. burgdorferi help support the diagnosis. Unlike patients with early localised Lyme disease (where only 20–40% patients might be seropositive), most patients with early disseminated disease (e.g. Lyme carditis, or neuroborreliosis) have IgM and IgG antibodies against B. burgdorferi. 15 Patients suspected to have early disseminated disease who are seronegative should undergo repeat serologic testing in 2 weeks since 70–80% of the patients will be seropositive by 4 weeks of infection. 16 A conditional two-tier strategy is recommended to support the serologic diagnosis of Lyme carditis. This approach recommends the use of a sensitive test, the ELISA, as the first test. If the ELISA is negative, no further testing is required although patients might be retested in 2 weeks if clinically warranted. If the ELISA is positive or equivocal, the same serum sample is subjected to a Western blot assay which is the specific confirmatory test. 17 This approach is more indicative of the disease since the ELISA alone is associated with a high rate of false-positivity; up to 5% of the normal population in Lyme disease endemic areas is seropositive by ELISA. 10 However, serologic positivity alone is by no means confirmatory of active disseminated Lyme disease since the antibody response may persist years after prior Lyme disease even after appropriate antibiotic treatment. Hence, it may in no way be causally related to the current cardiac disease. Finally, the sera of patients who have received the vaccine against Lyme disease (that was pulled from the market in 2002) might display false positive bands on Western blot testing. 18 Therefore, the clinician should use serologic testing only to complement his clinical assessment.
Treatment and prognosis
Antibiotic therapy forms the mainstay of treatment of Lyme carditis and should not be delayed awaiting the results of serologic tests. Prompt antibiotic treatment prevents the later chronic complications of Lyme disease. However, there is no evidence that antibiotic treatment shortens the duration of cardiac manifestations, or quickens the resolution of the heart block. 19 There are no head-to-head trials to identify the optimal antibiotic regimen for Lyme carditis. However, guidelines of the Infectious Diseases Society of America recommend that patients who are symptomatic (e.g. chest pain, syncope, etc.), have a first-degree heart block with a PR interval >300 ms, or have a second- or third-degree atrioventricular block, should be monitored on telemetry and treated with parenteral antibiotics like ceftriaxone, cefotaxime, or penicillin G. Typically intravenous antibiotics are continued till the heart block resolves, after which the patient can be switched to oral antibiotics such as doxycycline, amoxicillin, or cefuroxime axetil, for a total duration of 21 days.
Asymptomatic patients with first degree heart block and a PR interval <300 ms can be treated with oral therapy from the outset. 19
Conduction abnormalities secondary to Lyme carditis usually run a benign course and have a favorable prognosis. Patients with high degree heart block and/or who are symptomatic might require temporary pacemaker support. 20 However, permanent pacing is rarely, if ever required in instances of persistent heart block. 21 Heart block can persist up to 6 weeks and often resolves spontaneously, with no risk of recurrence in the future. 12
Conclusion
Complete heart block is usually an ominous finding that might require placement of a permanent pacemaker. Lyme carditis is a reversible cause of cardiac conduction abnormalities that should definitely be considered in the differential diagnosis of heart block before resorting to permanent pacemaker implantation, especially in patients from endemic areas. An erroneous diagnosis denies timely antibiotic treatment for the patient, and has enormous cost implications. A suggestive history and physical exam, coupled with positive serologic tests helps in the diagnosis. Clinicians should be cognizant of the fact that Lyme carditis could be the first and only presentation of Lyme disease. Early antibiotic treatment stops disease progression and prevents future complications.
Footnotes
Declaration of conflicting interests
None declared.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.