Case Report doi: 10.4183/aeb.2011.405 AN UNUSUAL PRESENTATION OF HYPERTHYROIDISM: ATRIOVENTRICULAR COMPLETE HEART BLOCK Z. Aritürk *,Y. Islamoglu, E. Tekbas, H. Çil, S. Soydinç, M. Yazici Dicle University - Faculty of Medicine, Cardiology Department, Diyarbakir, Turkey Abstract of the conduction system in about 50% of Complete heart block associated with patients and by ischemic heart disease in hyperthyroidism is infrequent, and the 40%; the remaining cases are due to drugs diagnosis of hyperthyroidism is usually not (e.g., betablockers, Ca channel blockers), considered in the absence of tachycardia. A increased vagal tone, or congenital heart 55-year-old woman was admitted to our diseases. Hyperthyroidism commonly emergency clinic with dizziness and causes cardiovascular disorders such as syncope attack. Her electrocardiogram sinus tachycardia, atrial fibrillation, and showed complete heart block. AV conduction defects and blocks (1). Hyperthyroidism had been diagnosed, Hyperthyroidism is even more difficult to and she had been treated with diagnose in patients with an unusual propylthiouracil as an anti-thyroid treatment presentation such as AV conduction 3 years ago, although she had not taken this defects; a review of the English literature drug during the last 2 months. Her thyroid revealed only a few cases of complete function tests showed hyperthyroidism. Anti- heart block associated with hyper- thyroid treatment was started again. Her thyroidism (2). rhythm returned from complete In this paper, we aimed to review the atrioventricular block to normal sinus rhythm approaches of AV conduction defects on the seventh day of hospitalization. associated with hyperthyroidism. Keywords: Hyperthyroidism, atrioventricular block, cardiac conduction system. CASE REPORT A 55-year-old woman was admitted INTRODUCTION to our emergency clinic with dizziness. Two hours prior to admission she had a Atrioventricular (AV) block is syncopal attack. Hyperthyroidism had caused by idiopathic fibrosis and sclerosis been diagnosed 3 years ago, and she had *Correspondence to: Aritürk Zuhal, Dicle University - Faculty of Medicine, Cardiology Department, Diyarbakir 21100, Turkey . Email: zariturk@yahoo.com Acta Endocrinologica (Buc), vol. VII, no. 3, p. 405-409, 2011 405
A. Zuhal et al. been treated with propylthiouracil (PTU). Thyroid function tests confirmed hyper- She had stopped therapy 2 months earlier thyroidism with a serum free triiodo- on her own. In her anamnesis, she did not thyronine (FT3) level of 0.594 ng/dL report hyperthyroidism-related symptoms (normal range 0.182–0.462), free thyroxin such as sweating or heat intolerance. (FT4) level of 2.02 ng/dL (0.932–1.710), Examination revealed a diffuse goiter. and thyrotropine (TSH) level of 0.005 Her blood pressure was 120/80 mm Hg, IU/mL (0.270–4.200). Of note, the but, surprisingly, her pulse rate was autoimmune thyroid antibodies were regular, at only 45 beats/min. She had negative for both thyrotropin receptors been taking olmesartan 20 mg and and microsomes. hydrochlorothiazide 25 mg for the past Although there were no previous 5 years. Examination of her electrocardiograms for comparison, cardiovascular system revealed heaving electrocardiography showed complete and displaced apex beat, and there was a heart block (Fig. 1). A transthoracic systolic murmur at the left sternal edge echocardiogram revealed degenerative radiating to the axilla. Her lungs were mitral valve and only moderate mitral clear. According to laboratory parameters, valve insufficiency, good left ventricular her levels of myoglobin, troponin I, systolic function, and left ventricular creatin kinase, and CK-MB were detected hypertrophy. Enlarged thyroid glands above normal ranges (70 ng/mL, 0.01 with multiple nodules were detected by ng/mL, 148 U/L, and 3.4 ng/ml, thyroid ultrasonography. We did not respectively). She had a cholesterol level consider a temporary transvenous of 241 mg/dL, triglyceride level of 321 pacemaker because of stable mg/dL, low-density lipoprotein (LDL) hemodynamical parameters. The patient level of 125 mg/dL, and high density was treated with PTU. Her rhythm lipoprotein (HDL) level of 52 mg/dL. returned from complete AV block to I V1 II V2 III V3 aVR V4 aVL V5 aVF V6 Figure 1. Electrocardiography showing complete heart block. 406
Atrioventricular block and hyperthyroidism I V1 II V2 III V3 aVR V4 aVL V5 aVF V6 Figure 2. Electrocardiography showing return from complete AV block to normal rhythm on the seventh day of hospitalization. normal rhythm on the seventh day of presentations. Ho et al. (4) presented a 16- hospitalization (Fig. 2). Coronary year-old girl with fever, Graves disease, angiography was not considered because and complete AV block. Although the of hyperthyroidism. Cardiac monitoring heart block in this patient could have been showed sinus rhythm without any a result of a focal myocarditis affecting evidence of bradycardia or heart block in the region around the AV node, the very the following 5 days; subsequently, the rapid response to therapy suggested a patient underwent an uncomplicated metabolic etiology rather than myocardial subtotal thyroidectomy. necrosis (5). In the present case, the patient was 55 years old and receiving anti-hypertension treatment with normal lipid parameters. Considering the risk DISCUSSION factors for cause AV block, acute ischemia, electrolyte imbalance and Over the last four decades, a review medication was not available. of the literature has revealed only a few The clinical, electrophysiological, cases of complete heart block associated and biochemical abnormalities with hyperthyroidism (3), with a female- associated with thyrotoxicosis may be to-male ratio of up to 2:1 and age range completely reversible, restoring the between 16 and 68 years (average of 43 euthyroid state (5). Especially, rapid years) (2,4). The diagnosis of improvement of AV block with anti- hyperthyroidism is usually not considered thyroid medication give rise to thought in the absence of tachycardia and atypical 407
A. Zuhal et al. block may be due to hyperthyroidism. mortality, thyrotoxicosis can lead to Topaloglu et al. (2) reported an sudden death by cardiac arrhythmia and electrophysiology study (EPS) myocardial infarction (6). performed in two cases. In the first case, In conclusion, the AV nodal block they found that only AH interval may be reversible with the curing of the (between the atrial electrogram and the primary endocrine disease. Beta His deflection) was prolonged, and adrenergic blocking agents could other findings were normal. aggravate an AV conduction disturbance; In the second case, all findings therefore, thyrotoxic patients should be were normal. According to this study (2), carefully screened for electrocardio- EPS is unnecessary for patients with heart graphic evidence of conduction block associated with hyperthyroidism. disturbances before and during the We thought that repolarization administration of such drugs. The clinical, abnormalities in the electrocardiogram electrophysiological, and biochemical were due to left ventricular hypertrophy abnormalities associated with thyro- seen in echocardiography. toxicosis may be completely reversible, In the light of this information, restoring the euthyroid state. If the hyperthyroid patients must be followed up hemodynamic status is unstable, a after anti-thyroid treatment. Interstitial temporary transvenous pacemaker may be inflammation of the AV node in a considered. hyperthyroid patient with PR References prolongation on electrocardiography has been reported (7). There was no previous 1. Stern MP, Jacobs RL, Duncan GW. syncope or near syncopal attacks in our Complete heart block complicating paper, suggesting that a new AV block hyperthyroidism. JAMA 1970; 212: 2117-9. had developed due to sudden syncopal 2. Topaloglu S, Topaloglu OY, Ozdemir O, attack. Osman F et al. (8) reported a 30- Soylu M, Demir AD, Korkmaz S. year-old woman presenting subacute Hyperthyroidism and complete thyroiditis with 2:1 heart block. The exact atrioventricular block-a report of 2 cases cause of AV conduction abnormalities is with electrophysiologic assessment. unknown, but complete heart block Angiology 2005, 56(2):217-220. associated with hyperthyroidism has 3. Miller RH, Corcoran FH, Baker WP. generally been seen in patients with Second and third degree atrioventricular additional risk factors such as infectious block with Graves’ disease: a case report diseases and mitral regurgitation (9-12). and review of the literature. Pacing Clin On top, T3 may also have an effect Electrophysiol 1980, 3(6):702-711. on the myocardium and on a patient’s 4. HO, S.C., P.H. Eng, Z.P. Ding, A.C. Fok electrophysiological function, specifically, and D.H. Thyroid storm presenting as the region of the AV node (13). Miller et jaundice and complete heart block. Ann al. (3) had demonstrated that a failure to Acad Med Singapore 27:748-751, 1998. recognize heart block due to 5. Suresh Krishnamoorthy, Rajay Narain, thyrotoxicosis may result in morbidity and John Creamer. Unusual presentation of mortality. As a possible cause of thyrotoxicosis as complete heart block and 408
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