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Abstract

Introduction: Abstract: Various neurotransmitters and endogenous chemicals such as serotonin and epinephrine are known to cause atrial fibrillation. We report a case of refractory atrial fibrillation with rapid ventricular response in a patient with carcinoid tumor. The atrial fibrillation in this case was secondary to elevated serotonin levels and responded to treatment with octreotide. Case: A 56 year-old woman was admitted for management of superior vena-cava (SVC) syndrome. She had a diagnosis of thyroid cancer with papillary, Hurthle cell and anaplastic histopathology after total thyroidectomy for goiter few years back. Later on, she was diagnosed with bronchial carcinoid based on an endobronchial biopsy. Her chest imaging showed a mediastinal mass and a left lower lobe endobronchial lesion with several metastatic lesions. She was treated with chemoradiation and a bronchial stent was placed. During her current hospitalization, her respiratory status deteriorated necessitating transfer to the intensive care unit and intubation. A bedside bronchoscopy confirmed the diagnosis of pneumonia. The patient was noted to have atrial fibrillation with rapid ventricular response (>160). A 2D echocardiography of the heart was performed and showed a normal left ventricle with an ejection fraction of 55%, normal right ventricle and no valvular abnormalities. The atrial fibrillation was initially attributed to sepsis and the patient was treated accordingly with appropriate resuscitation and antibiotics. However, the patient continued to have recurrent episodes of atrial fibrillation with rapid ventricular rhythm. Rate control was attempted but was unsuccessful. Treatment included beta-blockers (intravenous metoprolol), calcium channel blockers (intravenous diltiazem boluses and drip), intravenous amiodarone (bolus and drip) and intravenous digoxin over a period of several days. Because of the history of bronchial carcinoid cancer and the lack of response to conventional medications, neurotransmitter related atrial fibrillation was suspected. A random 5-HIAA to creatinine ratio was sent and was elevated at 20 ng/mg. octreotide therapy was initiated at 500 microgram subcutaneous every 8 hour. Patient responded within few hours, converting and remaining in normal sinus rhythm. Elevated epinephrine levels, seen in association with metastatic anaplastic thyroid cancer could have contributed to the atrial fibrillation and 24-hour urine collection for 5-HIAA and catecholamines would have been useful to further support the diagnosis but was not obtained. Nevertheless, the clinical response to octreotide therapy was compelling. Similar case reports of treatment of atrial fibrillation by methysergide and cyproheptadine has been described. Conclusions: We present a case of refractory atrial fibrillation due to elevated serotonin levels that responded to octreotide treatment. Atrial fibrillation has been described in association with vasoactive neurotransmitters like serotonin or epinephrine. Management options including agents such as octreotide, which inhibits the secretion of these neurotransmitters should be considered.