What is the management for a patient presenting with palpitations and tachycardia due to hyperthyroidism (elevated Free Triiodothyronine (FT3) levels) in the Emergency Room (ER) setting?

Management of Palpitations and Tachycardia with Elevated FT3 in the Emergency Room

Administer intravenous beta-blockers immediately to control the ventricular rate in patients presenting with palpitations and tachycardia due to hyperthyroidism, as this is the Class I recommendation for acute rate control in thyrotoxicosis-induced arrhythmias. 1

Immediate Rate Control Strategy

First-Line: Beta-Blocker Therapy

• Intravenous beta-blockers are the primary treatment for controlling ventricular rate in hyperthyroidism-related tachyarrhythmias, particularly when aggressive rate control is needed 1
• High doses may be required, especially if thyroid storm is suspected 1
• Propranolol is specifically effective in thyrotoxicosis as it also blocks peripheral conversion of T4 to T3 2, 3
• The FDA label for metoprolol warns that beta-blockers may mask tachycardia in hyperthyroidism, but this does not contraindicate their use for rate control 4

Alternative: Calcium Channel Blockers

• If beta-blockers are contraindicated, administer diltiazem or verapamil intravenously to control ventricular rate 1
• This is a Class I recommendation when beta-blockers cannot be used 1
• These agents are particularly useful if the patient has bronchospastic disease where beta-blockers are relatively contraindicated 4

Critical Diagnostic Considerations

Rhythm Assessment

• Obtain a 12-lead ECG immediately to determine the specific arrhythmia 1
• Atrial fibrillation occurs in 10-25% of hyperthyroid patients, more commonly in elderly males 1
• While rare, ventricular tachycardia can occur with thyrotoxicosis even without structural heart disease 2

Hemodynamic Status

• If the patient is hemodynamically unstable with rapid ventricular response, proceed directly to electrical cardioversion 1
• Hemodynamic instability includes hypotension, altered mental status, chest pain, or acute heart failure 1

Important Contraindications and Pitfalls

Avoid These Medications

• Do NOT use digoxin as monotherapy for acute rate control in thyrotoxicosis—beta-blockers are more effective 1
• Antiarrhythmic drugs and electrical cardioversion are generally unsuccessful while the thyrotoxic state persists 1
• If atrial fibrillation with pre-excitation (WPW pattern) is present, avoid AV nodal blocking agents entirely and use procainamide instead 1

Abrupt Beta-Blocker Withdrawal Risk

• Never abruptly discontinue beta-blockers once started, as this may precipitate thyroid storm 4
• The FDA label specifically warns against abrupt withdrawal in thyrotoxicosis 4

Concurrent Antithyroid Treatment

Initiate Definitive Therapy

• Start methimazole in the ER to begin addressing the underlying hyperthyroidism 5, 2, 3, 6
• The FDA label indicates methimazole crosses placental membranes, so verify pregnancy status first 5
• Treatment is primarily directed toward restoring euthyroid state, which typically leads to spontaneous reversion to sinus rhythm 1

Monitoring Requirements

• The FDA label for methimazole requires monitoring for agranulocytosis and vasculitis 5
• Patients should be instructed to report sore throat, fever, or rash immediately 5

Thromboembolism Prevention

Anticoagulation Decision

• Initiate oral anticoagulation (INR 2.0-3.0) for atrial fibrillation associated with thyrotoxicosis to prevent thromboembolism 1
• This is a Class I recommendation even though specific evidence in hyperthyroid-induced AF is limited 1
• Continue anticoagulation until euthyroid state is restored, then reassess stroke risk using standard criteria 1

Disposition and Follow-Up

Admission Criteria

• Admit patients with persistent tachycardia despite initial rate control 1
• Admit if thyroid storm is suspected (hyperpyrexia, systemic decompensation) 6
• Admit for new-onset atrial fibrillation requiring anticoagulation initiation 1

Outpatient Management

• Patients achieving adequate rate control with beta-blockers can be discharged with close endocrinology follow-up 2, 3
• Continue beta-blocker therapy until euthyroid state is achieved 1, 2
• Arrange thyroid function testing within 1-2 weeks 5