Tachycardia in a 61-Year-Old Woman

Jeffrey Siegelman, MD; Daniel M. Lindberg, MD

Disclosures

June 24, 2015

Further testing may be indicated as part of a search for the precipitating cause of clinical decompensation, such as infection, myocardial infarction, or diabetic ketoacidosis. Electrocardiography most often reveals sinus tachycardia. Atrial fibrillation is also not uncommon, particularly in elderly patients and in the setting of underlying heart disease.

Although thyroid storm requires more rapid and aggressive therapy than thyrotoxicosis, differentiating between the two conditions can sometimes be difficult, as it was in this patient. Burch and Wartofsky[4] developed a scoring system to assist in making this distinction that takes into account thermoregulatory dysfunction, central nervous system effects, gastrointestinal dysfunction, the degree of tachycardia, the extent of congestive heart failure, the presence of atrial fibrillation, and the presence or absence of a precipitating event.

Cardiac complications from thyrotoxicosis include arrhythmias, congestive heart failure, and pulmonary hypertension. The most common arrhythmia in thyrotoxicosis is sinus tachycardia; however, atrial fibrillation occurs in 10%-20% of patients with thyrotoxicosis, most often those who are older than 60 years. Risk factors for atrial fibrillation in these patients include male sex, increasing age, coronary heart disease, heart failure, and structural heart or valvular disease.

Congestive heart failure in thyrotoxicosis is predominantly caused by either persistent tachyarrhythmias (tachycardia-induced cardiomyopathy) or uncontrolled hypertension as a consequence of thyrotoxicosis. Systolic dysfunction can occur as a consequence of the persistent cardiac arrhythmias, but it usually resolves once the hyperthyroid state is treated. Pulmonary hypertension can also occur in thyrotoxicosis, either as a result of a primary effect of thyroid hormone on pulmonary arteriolar resistance vessels, decompensated left heart failure, or increased pulmonary arterial blood flow (high-output).[1]

The differential diagnosis for thyrotoxicosis and thyroid storm may include anxiety, congestive heart failure, heat exhaustion or heatstroke, factitious disorder, neuroleptic malignant syndrome, panic disorder, septic shock, serotonin syndrome, anticholinergic or sympathomimetic toxicity, and alcohol or benzodiazepine withdrawal syndromes.[5] Because infection is a common trigger for thyroid storm, an initial misdiagnosis of sepsis is not uncommon because of similar characteristics, such as tachycardia, fever, and altered mental status.

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