Acquired Long QT Syndrome Manifesting with Torsades de Pointes in a Patient with Panhypopituitarism due to Radiotherapy
A 64-year-old man was admitted to our hospital from shock caused by a UTI. The patient had a medical history of local radiation therapy on the surgical area after undergoing functional endoscopic sinus surgery for a nasal tumor (left maxillary cancer, squamous cell carcinoma) 20 years ago. The radiation therapy included the pituitary gland. He was followed up for 5 years after the surgery, but the follow-up was discontinued, as there was no possibility of recurrence. He had lived without any discomfort. He took tamsulosin for benign prostatic hypertrophy and used Spiriva® (Spiriva®, Boehringer Ingelheim GmbH, Germany) inhaler for chronic obstructive pulmonary disease.\nAt admission, the patient's blood pressure was 70/40 mm Hg, his pulse rate was 88 beats/min, his respiration rate was 26 times per minute, and his body temperature was 38.0℃. The patient was managed for septic shock with antibiotics, including ceftazidime, in the intensive care unit (ICU), and his blood pressure stabilized. On the 4th day of ICU admission, non-sustained polymorphic VT (TdP) occurred for 20 seconds. The VT disappeared spontaneously (). The patient indicated that he briefly felt drowsy, but his blood pressure after the event was 110/70 mm Hg. Laboratory tests reported the following findings: glucose 141 mg/dL (70-110 mg/dL); Na+ 144 mEq/L (135-145 mEq/L); K+ 3.8 mEq/L (3.5-5.5 mEq/L); corrected Ca2+ 8.6 mg/dL (8.4-10.2 mg/dL); and Mg2+ 1.4 mg/dL (1.9-2.5 mg/dL).\nThe patient was treated with a loading dose of Mg (2 g) and a maintenance dose of Mg (1 g/day for 8 days). After the administration of magnesium, the patient's laboratory parameters were as follows: Na+ 144 mEq/L (135-145 mEq/L); K+ 4.2 mEq/L (3.5-5.5 mEq/L); corrected Ca2+ 8.8 mg/dL (8.4-10.2 mg/dL); and Mg2+ 2.4 mg/dL (1.9-2.5 mg/dL).\nAlthough his Mg level normalized, the QTc interval prolongation and T wave inversion persisted, and TdP recurred several times. When TdP appeared, the patient's blood pressure was stable, but he became stuporous. Therefore, echocardiography, coronary angiography, and temporary ventricular overriding pacing with a ventricular rate of 90 beats per minute were performed. Echocardiography demonstrated a left ventricular ejection fraction of 54% with no regional wall motion abnormality, and no abnormal findings were observed during coronary angiography. A thyroid function test showed reduced values: T3 35 ng/dL (65-150 ng/dL); free T4 0.36 ng/dL (0.78-1.54 ng/dL); and thyroid-stimulating hormone (TSH) 0.27 µIU/mL (0.35-5.5 µIU/mL).\nLuteinizing Hormone (LH) and follicle stimulating hormone (FSH) were measured to evaluate abnormal thyroid functioning. The TSH releasing hormone stress test demonstrated no increase in TSH (0.22 µIU/mL; range 0.35-5.5 µIU/mL), LH (0.9 mIU/mL; range 1.0-5.3 mIU/mL); and FSH (72.5 mIU/mL; range 1.1-13.5 mIU/mL). After panhypopituitarism was diagnosed, brain CT and brain MRI with enhancement were performed, and a small pituitary gland was found. Before treatment, the average urine output was 4 L daily. The patient's serum and urine osmolarity were 300 mOsm/kg (275-295 mOsm/kg) and 247 mOsm/kg (300-900 mOsm/kg), respectively.\nTo correct the pituitary gland dysfunction, a steroid (prednisolone, 7.5 mg), thyroid hormone (levothyroxine, 100 µg), and desmopressin (Minirin nasal spray®, 5 µg bid) were administered. After one week of hormone treatment, the QTc prolongation and T wave inversion decreased mildly. After 4 weeks of steroid hormone, thyroid hormone, and desmopressin treatment, electrocardiography showed a normal QTc range (430 ms), and the T wave inversion disappeared ().\nTdP did not recur. After desmopressin administration, the patient's symptom of diabetes insipidus improved, and his urine output decreased to 1-2 L daily. His serum osmolarity normalized to 288 mOsm/kg (275-295 mOsm/kg), and his urine osmolarity increased to 544 mOsm/kg (300-900 mOsm/kg).