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Cover page of the Journal of Health Sciences

 Table of Contents  
Year : 2021  |  Volume : 14  |  Issue : 2  |  Page : 284-286

Sick sinus syndrome and hyperthyroidism: A rare phenomenon

1 Department of Emergency Medicine, AIIMS, Jodhpur, Rajasthan, India
2 Department of Emergency Medicine, Max Hospital, Delhi, Delhi, India
3 Department of Emergency Medicine, Shantiram Medical College and Hospital, Nadhyala, Andhra Pradesh, India
4 Department of Nursing, Indian Railway Health Services, Bikaner, Rajasthan, India

Date of Submission11-Feb-2021
Date of Acceptance03-May-2021
Date of Web Publication31-May-2021

Correspondence Address:
Dr. Nitesh Kumar
Department of Emergency Medicine, AIIMS, Jodhpur, Rajasthan
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/kleuhsj.kleuhsj_23_21

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Cardiovascular complications play a very crucial part in hyperthyroidism and increased mortality and morbidity risk. Besides tachyarrhythmia, impaired systolic ventricular dysfunction and diastolic dysfunction may cause thyrotoxic cardiomyopathy in a small percentage of the patients, as another high mortality complication. Bradycardia in hyperthyroidism is a rare phenomenon which is associated with the sinus node dysfunction, atrioventricular node dysfunction, and conduction disturbance, or due to the effect of the drugs, i.e. beta-blockers. A 70-year-old female patient was brought to the emergency department with the history of feeling dizziness, lightheadedness, and bradycardia. While waiting in emergency, she had an episode of syncope, followed by regain of consciousness after 20 min. The patient was shifted for pacemaker insertion. Furthermore, hyperthyroidism and sick sinus syndrome are rare phenomena; it is highlighted mainly among patients with Graves' disease.

Keywords: Bradycardia, cardiovascular, hyperthyroidism, sick sinus syndrome

How to cite this article:
Kumar N, Verma D, Gupta K, Kiran M, Yadav P, Pareek S. Sick sinus syndrome and hyperthyroidism: A rare phenomenon. Indian J Health Sci Biomed Res 2021;14:284-6

How to cite this URL:
Kumar N, Verma D, Gupta K, Kiran M, Yadav P, Pareek S. Sick sinus syndrome and hyperthyroidism: A rare phenomenon. Indian J Health Sci Biomed Res [serial online] 2021 [cited 2021 Jun 17];14:284-6. Available from: https://www.ijournalhs.org/text.asp?2021/14/2/284/317401

  Introduction Top

Hyperthyroidism is associated with tachycardia, atrial fibrillation, sinus tachycardia and increased pre-load and after load.. Cardiovascular disorders are crucial in hyperthyroidism and increased morbidity risk and mortality. In the United States, the prevalence of hyperthyroidism is 1.3%. It occurs more commonly in female compared with male, and the incidence increases with age, iodine deficiency, and race.[1] Most patients with Graves' disease, toxic multinodular goiter, and toxic adenoma have higher mortality and morbidity as compared to the general population. Atrial fibrillation, atrial enlargement, stroke, and congestive heart failure are important cardiac complications of the disease, which are more prevalent in the older group patients.[2] First reported electrophysiological study documenting the occurrence of SSS in thyrotoxicosis was reversed by effective antithyroid treatment.[3] Bradycardia is associated with the presyncope or syncope. It can be due to the presence of sick sinus syndrome (SSS) and beta-blocker therapy. The patient may have severe bradycardia which may lead to syncope or heart failure and sudden cardiac death. Few studies suggested that attempts should be made to identify underlying thyrotoxicosis in all patients with SSS, especially in the older age group.[3]

  Case Report Top

A 70-year-old female patient was brought to the emergency department by her relatives. She had a history of the feeling dizziness and lightheadedness. She was a known case of diabetic mellitus, hyperthyroidism, hypertension, and atrial fibrillation with controlled ventricular rate. As per clinical examination, the patient was looking anxious and her airway was patent. She was breathing normally and there were no signs of respiratory distress. Vital signs highlighted that blood pressure was 140/90 mm of Hg, pulse rate was 33/min, SpO2 was 100% on room air, and random blood sugar was 230 mg/dl. Exophthalmos was present in both eyes, and other general examinations were normal. She was having minor tremor in the upper limb at resting phase attributed to hyperthyroidism. Systemic examination was unremarkable. She was taking tablet metoprolol 50 mg twice a day, tablet acitrom 2 mg once a day, tablet telmisartan 40 mg once a day, tablet methimazole 10 mg three times a day. Recent blood investigations revealed that TSH was 0.006 mIU/mL, FT3 was 15.46 ng/dL (normal value ranges from 4.0 to 8.3), and FT4 was 48.02 ng/dL. Echocardiography was normal with EF >50, no regional wall motion abnormalities, and no valvular abnormalities.

While waiting in emergency, she had an episode of syncope, followed by regain of consciousness after 20 min. Urgent electrocardiogram (ECG) was done and the findings revealed bradycardia (heart rate of 33/min) [Figure 1]. The possible causes of bradycardia were SSS and age-related degenerative changes in the heart. In view of her bradycardia with syncope, injection atropine 0.6 mg was given intravenously, followed by infusion of dopamine at 1.0 μg/kg/min – the advanced cardiac life support, but her heart rate did not respond to the atropine. The pulse rate was still less than 40/min and she started feeling panic and dizziness with sweating. Cardiology consultation was done immediately and advice incorporated. Family members of the patient were counseled regarding the need of temporary pacemaker insertion, and the patient was shifted to the cath lab for pacemaker insertion.
Figure 1: Electrocardiogram findings showing changes in heart rate

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  Discussion Top

There are exogenous or endogenous factors which may lead to hyperthyroidism.[4] The cardiac conduction system is affected among Graves' disease patients.[5] Because most of the reported cases with SSS or/and atrioventricular (AV) block have been observed among patients with Graves' disease, it has been suggested that the same autoimmune pathological process that affects the thyroid could influence the conducting system.[2],[3] Cases of high-grade AV block complicating hyperthyroidism have been reported as early as 1970; Miller et al. communicated that second and third-degree AV block are associated with Graves' disease. The AV nodal block is reversible endocrine disease with thyroid hormone replacement.[6] Thyroid hormone has the direct effect on the AV node conduction and bundle of His. A 39-year-old woman with 2-year history of graves' disease, who suddenly developed dizziness and syncope, 1 month after discontinuing her antithyroid medications. The patient manifested with a third-degree AV block necessitating temporary pacemaker insertion. Moreover, with control of hyperthyroidism, the rhythm reverted to normal and the pacemaker was eventually removed. In the present case, the patient was managed with pacemaker. In addition, it is known that beta-blocker causes the AV node blocking; all thyrotoxicosis patients should be screened by ECG for bradycardia and should be advised for regular follow-up patients. SSS/Sinoatrial node/AV node block can be corrected by treating the hyperthyroidism to euthyrodism, which may obviate need for the pacemaker. Furthermore, a 65-year-old female with TSH less than 0.1 ng/ml developed SSS associated with thyrotoxicosis which resolved upon achieving a euthyroid state, thus obviating the need for permanent pacemaker implantation.[7] The present case revealed that bradycardia was managed with pacemaker insertion. In this context, a case study communicated that a 48-year-old female with hyperthyroidism presented with the history of palpitation, diaphoresis, and weight loss had diffuse goiter; she was taking tablet methimazole 30 mg and tablet metoprolol 50 mg. After 3 days, she was presented with syncope and severe bradycardia managed with an atrial inhibited pacemaker.[5] Moreover, a 50-year-old woman was transported to a hospital complaining of marked general malaise and epigastralgia with diarrhea and vomiting. Her ECG showed sinus arrest with a duration of nearly 8 s. SSS and her symptoms were corrected after the treatment of hyperthyroidism without a pacemaker.[8] Hence, few case studies highlighted that management of SSS among hyperthyroidism patients can be done with or without pacemaker.[9],[10] In our case, it is important to underline that the patient was having SSS and managed with pacemaker.

  Conclusions Top

Hyperthyroidism and SSS are rare phenomena; it occurs mainly among patients with Graves' disease. SSS/SA/AV node block can be corrected by treating the hyperthyroidism to euthyrodism, which may obviate need for the pacemaker. Present case highlighted the presence of SSS in hyperthyroidism followed by pacemaker insertion. With control of hyperthyroidism, the rhythm reverted to normal and the pacemaker eventually may be removed.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Significance of the case report

SSS is a rare condition among hyperthyroidism patients. It is important to discuss the rare phenomenon of diseases with medical students.

Core competencies

Medical knowledge, emergency care, prompt action.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Sharma A, Stan MN. Thyrotoxicosis: Diagnosis and management. Mayo Clin Proc 2019;94:1048-64.  Back to cited text no. 1
Biondi B, Kahaly GJ. Cardiovascular involvement in patients with different causes of hyperthyroidism. Nat Rev Endocrinol 2010;6:431-43.  Back to cited text no. 2
Talwar KK, Gupta V, Kaul U, Ahuja MM, Bhatia ML. Electrophysiological studies in thyrotoxicosis with and without associated sick sinus syndrome. Clin Cardiol 1987;10:249-54.  Back to cited text no. 3
Alper AT, Hasdemir H, Akyol A, Cakmak N. Subclinical hyperthyroidism presenting with bradycardia-associated syncope. West Indian Med J 2008;57:173-4.  Back to cited text no. 4
Tudoran M, Tudoran C. Hyperthyroidism and sick sinus syndrome, a rare but challenging association: A study of three cases. Niger J Clin Pract 2017;20:1046-8.  Back to cited text no. 5
[PUBMED]  [Full text]  
Miller RH, Corcoran FH, Baker WP. Second and third degree atrioventricular block with Graves' disease: A case report and review of the literature. Pacing Clin Electrophysiol 1980;3:702-11.  Back to cited text no. 6
Lubitz RM, Acker JJ. Thyrotoxicosis induced sick sinus syndrome: Medical therapy may avoid permanent pacing. Pacing Clin Electrophysiol 1990;13:700-2.  Back to cited text no. 7
Sampana AG, Jasul GV. High grade AV block complicating hyperthyroidism: A case report. Phil J Int Med2010;48:38-40.  Back to cited text no. 8
Cueto-García L, Maisterrena J, Bolaños F, Medina JA, Arriaga J. Thyrotoxicosis associated with sick sinus syndrome: A diagnostic and therapeutic dilemma. Rev Invest Clin 1985;37:35-7.  Back to cited text no. 9
Namura M, Kanaya H, Ikeda M, Shibayama S, Ohka T. Hyperthyroidism complicated with sick sinus syndrome. Jpn Circ J 1995;59:824-8.  Back to cited text no. 10


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