What is the management of thyroid storm causing atrial fibrillation (afib)?

From the Guidelines

Management of thyroid storm causing atrial fibrillation requires immediate, aggressive treatment targeting both the thyrotoxicosis and the cardiac arrhythmia, with a focus on rate control using beta-blockers, such as propranolol or esmolol, as the primary goal initially rather than rhythm control, as recommended by the 2014 AHA/ACC/HRS guideline 1. The treatment approach should include:

• Initial therapy with propylthiouracil (PTU) 600-1000 mg loading dose followed by 200-250 mg every 4-6 hours to block new thyroid hormone synthesis and peripheral T4 to T3 conversion
• Administration of potassium iodide (SSKI) 5 drops every 6 hours or Lugol's solution 10 drops every 8 hours to block thyroid hormone release, one hour after PTU
• Beta-blockers, such as propranolol 60-80 mg orally every 4-6 hours or esmolol IV infusion (50-300 μg/kg/min), to control tachycardia and atrial fibrillation
• Glucocorticoids, such as hydrocortisone 100 mg IV every 8 hours, to reduce T4 to T3 conversion and treat potential relative adrenal insufficiency
• Supportive measures, including cooling, IV fluids, and nutritional support, to manage the patient's condition The underlying precipitant of thyroid storm must be identified and treated, and once the patient is stabilized, definitive treatment of hyperthyroidism through radioactive iodine or thyroidectomy should be considered to prevent recurrence, as thyroid storm has a high mortality rate if not promptly and appropriately managed, with a mortality rate that can be reduced with aggressive treatment, as suggested by the ACC/AHA/ESC guidelines 1. Key considerations in the management of thyroid storm causing atrial fibrillation include:
• The importance of rate control using beta-blockers as the primary goal initially rather than rhythm control
• The need for aggressive treatment with intravenous beta-blockers in cases of thyroid storm
• The potential use of nondihydropyridine calcium channel antagonists for rate control, as recommended by the 2014 AHA/ACC/HRS guideline 1
• The importance of identifying and treating the underlying precipitant of thyroid storm
• The need for definitive treatment of hyperthyroidism to prevent recurrence, as suggested by the ACC/AHA/ESC guidelines 1.

From the FDA Drug Label

Propylthiouracil inhibits the conversion of thyroxine to triiodothyronine in peripheral tissues and may therefore be an effective treatment for thyroid storm. The management of thyroid storm, including cases causing afib, may involve the use of propylthiouracil (PO), as it can inhibit the conversion of thyroxine to triiodothyronine in peripheral tissues, which is a key aspect of managing the condition 2.

• The drug can be used to treat hyperthyroidism and thyroid storm by reducing thyroid hormone production and inhibiting the conversion of thyroxine to triiodothyronine.
• However, the label does not provide specific guidance on the management of afib in the context of thyroid storm.

From the Research

Management of Thyroid Storm Causing Atrial Fibrillation

• The management of atrial fibrillation during thyroid storm includes anticoagulation for the risk of clot propagation 3.
• Physiologic changes that occur in patients with thyroid storm may lead to heparin resistance and inappropriate anticoagulation, with factors contributing to heparin resistance including antithrombin deficiency, increased heparin clearance, and increased levels of factor VIII 3.
• Anticoagulation should be considered for patients with severe thyrotoxicosis and atrial fibrillation, irrespective of the CHADS2 score, as it appears to increase the risk of thromboembolic episodes 4.
• The initial treatment for atrial fibrillation in hyperthyroid patients is to control the heart rate with routine pharmacologic therapy and to start antithyroid therapy as quickly as possible, with attempted cardioversion deferred until approximately the fourth month of maintaining a euthyroid state 5.

Treatment Options

• Propylthiouracil and methimazole are used to treat thyroid storm, with some guidelines recommending propylthiouracil over methimazole, although the difference in outcomes associated with each treatment is unclear 6.
• A comparative effectiveness study found no significant differences in mortality or adverse events in patients treated with propylthiouracil or methimazole for thyroid storm 6.
• Treatment involves bridging to a euthyroid state prior to total thyroidectomy or radioactive iodine ablation to limit surgical complications 7.

Clinical Considerations

• Thyroid storm is diagnosed as a combination of thyroid function studies showing low to undetectable thyroid stimulating hormone (TSH) with elevated free thyroxine (T4) and/or triiodothyronine (T3), positive thyroid receptor antibody (TRab), and with clinical signs and symptoms of end organ damage 7.
• Early recognition and prompt treatment of thyroid storm are essential, with a high risk of thromboembolic events and atrial fibrillation 4, 5.