Case Report
Volume 8 Issue 7 - 2021
A Rare Case of Severely Symptomatic and Reversible 2:1 Atrioventricular Block Associated with Subclinical Hypothyroidism: Case Report
Meryem Haboub*, Imane Tlohi, Salim Arous, Mohamed El Ghali Benouna, Leila Azzouzi and Rachida Habbal
Cardiology Department, Hospital University Ibn Rochd, Casablanca, Morocco
*Corresponding Author: Meryem Haboub, Cardiology Department, Hospital University Ibn Rochd, Casablanca, Morocco.
Received: June 03, 2021; Published: June 25, 2021




Abstract

Background: It has long been recognized that hypothyroidism, leads to sinus bradycardia, low amplitude P and T waves with low voltage QRS complexes and lengthening of the corrected QT interval on the surface electrocardiogram. However, the degree by which the heart rate slows down is often modest and disturbances in atrioventricular conduction seem to be rare. It is unknown whether patients with AV block are expected to have a benign course after the initiation of appropriate thyroid hormone replacement therapy, the time course between the initial therapy and recovery of AV block is not clear and it is challenging for clinicians to manage patients with AV block in association with hypothyroidism. The question “Does the thyroid hormone replacement therapy improve both the AV conduction and hypothyroidism?” remains controversial. We are reporting a case of complete resolution of 2:1 AV block associated with subclinical hypothyroidism in an elderly woman under thyroid hormone replacement therapy.

Case Presentation: A 68 year old woman, not receiving any AV node blocking agent, presenting with recurrent lipothymia without symptoms or signs of hypothyroidism. Physical examination at admission at the Intensive Cardiology Care Unit finds a regular heart rhythm, pulse: 37 bpm with no other signs. 12-lead electrocardiogram on admission finds a regular rhythm, heart rate: 37 bpm, 2:1 AV block. A temporary transvenous pacing using a percutaneous approach of the right femoral vein guided by ultrasound was performed. Demand temporary pacemaker was set to 70/min. Transthoracic echocardiogram was normal. Coronary angiography showed normal coronary arteries, no atheroma and no stenoses. Thyroid function testings: TSH: 12 (normal range: 0.4 - 4 mUI/l), serum free T3: 0.1 (0.2 - 0.5 ng/dl), serum free T4: 0.8 (0.8 - 2.8 ng/dl). Thyroid investigations have confirmed Hashimoto thyroiditis. L-thyroxine was prescribed. We could withdraw temporary pacing at 5 days of thyroid hormone replacement therapy after checking the spontaneous underlying rhythm: regression of 2:1 AV block, regular sinus rhythm at 50 bpm. 24 Holter monitoring showed no episodes of AV block. At 8 days, the patient was discharged with a cardiology and endocrinology follow-up. At 5 months follow-up, the patient was asymptomatic, taking a 75 mcg dose of L-thyroxine daily, normal TSH, free T3 and T4 levels with a 12-lead ECG showing a regular sinus rhythm at 70 bpm and no AV block on 24 hours Holter monitoring.

Conclusion: High degree AV block can be explained by hypothyroidism and thyroid hormone replacement therapy could improve both AV block and hypothyroidism avoiding unnecessary pacemaker implantation.

Keywords: Subclinical Hypothyroidism; 2:1 Atrioventricular Block; Thyroid Hormone Replacement Therapy; Pacemaker

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Citation: Meryem Haboub., et al. “A Rare Case of Severely Symptomatic and Reversible 2:1 Atrioventricular Block Associated with Subclinical Hypothyroidism: Case Report”. EC Cardiology 8.7 (2021): 04-09.

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