SAT-320 - Thyroid Storm in an Otherwise Healthy Young Woman Complicated by Reversible Thyrotoxic Cardiomyopathy

Case Presentation
A 39-year-old woman with no prior medical history presented with three days of progressive shortness of breath, palpitations, cough, nausea, and diarrhea. She denied fever, infection, trauma, iodine exposure, or new medications. On presentation, vital signs were heart rate 193 bpm, blood pressure 108/60 mmHg, respiratory rate 22/min, oxygen saturation 94% on room air, and temperature 37.8°C. She was diaphoretic and tachypneic. Cardiovascular exam revealed an irregularly irregular rhythm without murmurs; pulmonary exam showed bibasilar crackles. No goiter, ophthalmopathy, or tremor was present.

Laboratory evaluation demonstrated TSH < 0.01 mIU/L (0.4–4.5), free T4 >7.0 ng/dL (0.8–1.7), and thyrotropin-binding inhibitory immunoglobulin 35.63 IU/L, consistent with Graves’ disease. Additional labs showed lactic acid 2.5 mmol/L, AST 81 U/L, ALT 42 U/L, and alkaline phosphatase 182 U/L. ECG revealed atrial fibrillation with rapid ventricular response. Chest radiography showed mild pulmonary congestion. Transthoracic echocardiography demonstrated left ventricular ejection fraction ~30% with global hypokinesis and no valvular disease. Burch–Wartofsky score was 55. No precipitating trigger was identified.

Management
Although ICU care is often recommended for thyroid storm, the patient was managed on a cardiac telemetry unit due to hemodynamic stability. She received IV fluids, propylthiouracil, propranolol, and glucocorticoids. Anticoagulation was initiated despite a CHA₂DS₂-VASc score of 1 due to new-onset atrial fibrillation, reduced ejection fraction, and thyrotoxic hypercoagulability. She received diuresis and guideline-directed therapy for heart failure and was transitioned to methimazole for maintenance. She spontaneously converted to sinus rhythm with recovery of systolic function.

Discussion
Thyrotoxic cardiomyopathy is a rare complication of severe thyrotoxicosis and may present with acute heart failure and atrial fibrillation, even in patients without classic thyroid findings. Left ventricular dysfunction is often reversible with early recognition, endocrine-directed therapy, and effective rate control. Nonselective beta-blockade provides adrenergic suppression and inhibits peripheral T4-to-T3 conversion but requires careful monitoring in reduced ejection fraction. This case highlights individualized decisions regarding monitoring level and anticoagulation.

Conclusion
Thyroid storm should be considered in patients presenting with new-onset atrial fibrillation and acute systolic heart failure, even without a clear precipitant. Early endocrine-directed therapy can lead to complete reversal of thyrotoxic cardiomyopathy. Select stable patients may be safely managed outside the ICU with close monitoring and clinical judgment.

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