A 40-year-old woman comes to the emergency department due to a 6-hour history of palpitations. She describes "fluttering in the chest" that has never happened before. In addition, over the last few months, the patient has experienced anxiety, fatigue, and a 7-kg (15-lb) weight loss. Her medical history is unremarkable, and she takes no medications. The patient does not use tobacco, alcohol, or illicit drugs. Her blood pressure is 110/80 mm Hg, and pulse is 125/min and irregular. Examination reveals lid lag and a fine tremor in the outstretched hands. No murmurs are audible, and the lungs are clear to auscultation. ECG shows atrial fibrillation with rapid ventricular response. Which of the following is the best next step in management of this patient?

Question

A 40-year-old woman comes to the emergency department due to a 6-hour history of palpitations.  She describes "fluttering in the chest" that has never happened before.  In addition, over the last few months, the patient has experienced anxiety, fatigue, and a 7-kg (15-lb) weight loss.  Her medical history is unremarkable, and she takes no medications.  The patient does not use tobacco, alcohol, or illicit drugs.  Her blood pressure is 110/80 mm Hg, and pulse is 125/min and irregular.  Examination reveals lid lag and a fine tremor in the outstretched hands.  No murmurs are audible, and the lungs are clear to auscultation.  ECG shows atrial fibrillation with rapid ventricular response.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

11ec25c8_d350_891b_bc81_cf3db77e011d_MD0003_00 This patient has symptomatic atrial fibrillation (AF) with rapid ventricular response. She also has additional features (weight loss, lid lag, hand tremor) to suggest hyperthyroidism as the underlying cause. AF is the most common supraventricular arrhythmia in hyperthyroidism, occurring in 5%-15% of patients. Thyroid hormones cause an increase in beta-adrenergic receptor expression, which leads to an increase in sympathetic activity. Beta blockers (eg, propranolol, atenolol) are recommended as initial therapy to control heart rate and hyperadrenergic symptoms. In addition, propranolol decreases conversion of T4 to T3 in peripheral tissues. The beta blocker should be initiated as soon as hyperthyroidism is diagnosed and should be continued until the hyperthyroidism is adequately treated with thionamides, radioiodine, and/or surgery. (Choice A) Adenosine induces a transient block at the atrioventricular (AV) node and is often used in patients with supraventricular tachycardia in whom the diagnosis is unclear. Its short duration of action limits its role in management of patients with AF, in whom it can have proarrhythmic effects. (Choices B and D) Antiarrhythmic drugs (eg, amiodarone, flecainide) are occasionally used for maintenance of sinus rhythm in patients with paroxysmal AF. However, this patient's tachycardia should first be controlled with a beta blocker, and treatment of the underlying hyperthyroidism will likely eliminate the need for antiarrhythmics (which can be associated with adverse effects, including thyroid dysfunction). (Choices C and H) Digoxin and calcium channel blockers (eg, verapamil, diltiazem) are often used for rate control in patients with AF. However, unlike beta blockers, they do not ameliorate the hyperadrenergic drive in patients with hyperthyroidism and are not effective for heart rate and symptom control. (Choices E and G) Electrical or chemical cardioversion with ibutilide can restore sinus rhythm in patients with AF. However, patients with hyperthyroidism will likely fail to convert or maintain sinus rhythm unless the underlying hyperadrenergic state is corrected. Educational objective: Several systemic and cardiac manifestations of hyperthyroidism are due to an increase in sympathetic activity. Beta blockers are recommended as initial therapy for atrial fibrillation due to hyperthyroidism and should be continued until the patient becomes euthyroid with thionamides, radioiodine, and/or surgery. References: Thyroid disease and the heart. (http://www.ncbi.nlm.nih.gov/pubmed/17923583) Short-term effects of ß-adrenergic antagonists and methimazole in new-onset thyrotoxicosis caused by Graves' disease. (http://www.ncbi.nlm.nih.gov/pubmed/22975536) Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. (http://www.ncbi.nlm.nih.gov/pubmed/21510801)

A 40-Year-Old Woman Comes to the Emergency Department Due to a 6-Hour