A 76-year-old man comes to the physician due to a several-week history of fatigue and lethargy. He lives in an assisted living facility and takes naps during the day but still feels exhausted in the evening. The patient does not use tobacco or alcohol. His medical problems include hypertension, type 2 diabetes mellitus, coronary artery disease, and ischemic cardiomyopathy. He also underwent coronary artery bypass grafting 5 years ago.
The patient was hospitalized 4 months ago with dizziness, palpitations, and near-syncope and was diagnosed with monomorphic ventricular tachycardia. He underwent electrical cardioversion and was started on amiodarone and high-dose metoprolol. Laboratory workup during that time was unremarkable, and his echocardiogram showed a left ventricular ejection fraction of 25%. An automated implantable cardioverter-defibrillator (AICD) was implanted before discharge. The last device interrogation 4 weeks ago showed multiple episodes of non-sustained ventricular tachycardia but no defibrillator shocks.
His blood pressure is now 140/90 mm Hg and pulse is 62/min and regular. The patient has normal jugular venous pressure. There is no thyromegaly. Lung fields are clear to auscultation. A faint mid-systolic murmur is heard at the left sternal border. There is 1+ peripheral edema bilaterally and his skin is dry. Deep tendon reflexes are diminished bilaterally. Laboratory studies are shown below:

Which of the following is the best next step in managing this patient?

Question

A 76-year-old man comes to the physician due to a several-week history of fatigue and lethargy.  He lives in an assisted living facility and takes naps during the day but still feels exhausted in the evening.  The patient does not use tobacco or alcohol.  His medical problems include hypertension, type 2 diabetes mellitus, coronary artery disease, and ischemic cardiomyopathy.  He also underwent coronary artery bypass grafting 5 years ago.
The patient was hospitalized 4 months ago with dizziness, palpitations, and near-syncope and was diagnosed with monomorphic ventricular tachycardia.  He underwent electrical cardioversion and was started on amiodarone and high-dose metoprolol.  Laboratory workup during that time was unremarkable, and his echocardiogram showed a left ventricular ejection fraction of 25%.  An automated implantable cardioverter-defibrillator (AICD) was implanted before discharge.  The last device interrogation 4 weeks ago showed multiple episodes of non-sustained ventricular tachycardia but no defibrillator shocks.
His blood pressure is now 140/90 mm Hg and pulse is 62/min and regular.  The patient has normal jugular venous pressure.  There is no thyromegaly.  Lung fields are clear to auscultation.  A faint mid-systolic murmur is heard at the left sternal border.  There is 1+ peripheral edema bilaterally and his skin is dry.  Deep tendon reflexes are diminished bilaterally.  Laboratory studies are shown below:

Which of the following is the best next step in managing this patient?

Quizplus · Accepted Answer

11ec193a_97ae_1aeb_853d_c17cea76f4ee_MD0002_00 This patient's clinical presentation - fatigue, lethargy, dry skin, diminished reflexes, elevated TSH, and low free T₄ - is consistent with amiodarone-induced hypothyroidism. Long-term amiodarone use can cause thyroid dysfunction (hypothyroidism or hyperthyroidism) in 5%-30% of patients. The individual risk of thyroid dysfunction depends on the patient's underlying thyroid status and dietary iodine intake. Amiodarone-induced hypothyroidism is more likely than hyperthyroidism in iodine-sufficient areas and in patients with underlying autoimmune thyroid disease. In contrast, hyperthyroidism is more common in iodine-deficient areas and in patients with multinodular goiter or latent Graves' disease. ₄ This patient has severe left ventricular (LV) systolic dysfunction and recurrent episodes of nonsustained ventricular tachycardia (VT). Treatment with amiodarone to prevent recurrent VT and automated implantable cardioverter-defibrillator (AICD) shocks is indicated. In these patients, amiodarone should be continued and hypothyroidism can be easily corrected by thyroid replacement therapy with levothyroxine. (Choice A) Anti-thyroid peroxidase (anti-TPO) antibodies are present in patients with chronic autoimmune or Hashimoto's thyroiditis. These would be helpful for delineating patients with subclinical hypothyroidism (TSH <10 µU/mL), but this is not the case in this patient. (Choices C and D) Amiodarone should be discontinued and/or replaced if the patient continues to have recurrent ventricular arrhythmias. It should not be discontinued in patients who have been treated appropriately but then develop hypothyroidism. (Choice E) Thyroid ultrasound with color Doppler is a very useful tool for differentiating type I (increased vascularity) from type II (absent vascularity) amiodarone-induced thyrotoxicosis. However, it would not be helpful in the management of amiodarone-induced hypothyroidism. Educational objective: Long-term amiodarone use can cause thyroid dysfunction (hypothyroidism or hyperthyroidism). Patients with overt hypothyroidism should continue amiodarone but initiate thyroid replacement therapy. __________ References: Thyroid function abnormalities during amiodarone therapy for persistent atrial fibrillation (http://www.ncbi.nlm.nih.gov/pubmed/17904459) Amiodarone and the thyroid (http://www.ncbi.nlm.nih.gov/pubmed/15989900)

A 76-Year-Old Man Comes to the Physician Due to a Several-Week