Management of Hypothyroidism with Tachycardia and Bronchospasm

Clinical Context and Rate Control

In a hypothyroid patient presenting with tachycardia and bronchospasm, a nondihydropyridine calcium channel antagonist (diltiazem or verapamil) is the drug of choice for rate control, as beta-blockers are contraindicated due to the bronchospasm, according to the American Heart Association, American College of Cardiology, and Heart Rhythm Society guidelines 1.
The presence of bronchospasm creates a critical contraindication to beta-blockers, which would otherwise be first-line for tachycardia control, as stated by the American College of Cardiology 1, 6.
Hypothyroidism typically causes bradycardia, not tachycardia, making this presentation unusual and suggesting either concurrent hyperthyroidism, a rare manifestation of severe hypothyroidism with paradoxical tachyarrhythmia, or coexisting cardiac pathology, with a strength of evidence supported by the American College of Cardiology 2, 3, 4, 5.

The AHA/ACC/HRS guidelines provide a Class I recommendation that a nondihydropyridine calcium channel antagonist is recommended to control ventricular rate in patients with atrial fibrillation and chronic obstructive pulmonary disease or bronchospasm, with a high strength of evidence 1, 6.
Diltiazem or verapamil are the specific agents to use, as they slow AV nodal conduction without causing bronchospasm, according to the British Journal of Sports Medicine 1, 7.
Verapamil dosing: 5-10 mg IV over 60 seconds for acute rate control, with caution in heart failure, as recommended by the British Journal of Sports Medicine 7.

Beta-blockers are absolutely contraindicated in this patient due to bronchospasm, as stated by the American College of Cardiology and the American Heart Association 1, 6.
Adenosine can precipitate bronchospasm in asthmatic patients and should not be routinely used, according to the British Journal of Sports Medicine 7.

If the patient is actually hyperthyroid, beta-blockers are recommended as first-line for thyrotoxicosis-induced tachycardia unless contraindicated, with a strength of evidence supported by the American College of Cardiology and the American Heart Association 1, 6, 8.
When beta-blockers cannot be used due to bronchospasm, a nondihydropyridine calcium channel antagonist is recommended, according to the American College of Cardiology and the American Heart Association 1, 6, 8.

For elderly patients or those with cardiovascular disease, start levothyroxine at 25-50 mcg daily, avoiding full-dose replacement to prevent cardiac complications, as recommended by the American College of Cardiology and the American Thyroid Association, with a moderate strength of evidence 2.
Increase gradually by 12.5-25 mcg increments, and recheck TSH and free T4 after 6-8 weeks of any dose change, according to the American College of Cardiology and the American Thyroid Association 2.

If hemodynamically unstable, direct-current cardioversion is indicated, as stated by the American Heart Association and the American College of Cardiology 1, 6.
Check for thyroid storm, and rule out adrenal insufficiency before starting levothyroxine to prevent acute adrenal crisis, according to the American Family Physician and the American College of Cardiology 2, 9.