Ventricular Tachyarrhythmias in a Patient with Andersen-Tawil Syndrome
An 18-year-old girl was transferred to our emergency room for post-resuscitated status. She was initially admitted to a local hospital for paralysis and paresthesia of lower extremities, which started 2 days ago. She had experienced recurrent periodic paralysis on both lower extremities for the past 7 months, and it was aggravated after exercise. Each episode lasted for 2 or 3 days. After admission to the local hospital, sudden cardiac arrest developed. Her initial serum potassium level was 3.0 mmol/L, but it rapidly decreased to 1.8 mmol/L at the time of cardiac arrest. She was resuscitated after two minutes of cardiac compression.\nWhen she arrived at our hospital, she was semicomatous. She showed frequent episodes of tachycardia with the heart rate of 200 beats per minutes. She had a short stature as 149 cm (1.5% percentile for her age), broad forehead, small jaw, and clinodactyly on the right fifth finger (). Interestingly, her mother also had clinodactyly on both fifth fingers (). However, there was no family history of cardiac disease. The initial neurologic exam revealed grade 0 strength of both lower and upper extremities. Deep tendon reflexes were absent on biceps, triceps, brachioradialis, knee and ankle.\nHer initial electrocardiogram (ECG) showed sinus rhythm with prolonged QT interval of 657 ms and frequent premature ventricular contractions (). Her initial laboratory tests showed Na+ 147 mEq/L, K+ 2.0 mEq/L and Cl- 123 mEq/L. Blood gas analysis revealed pH 6.85, pCO2 126 mm Hg, pO2 216 mm Hg, and HCO3- 22.5 mmol/L revealing severe respiratory acidosis, and she was intubated for acute respiratory difficulty. Other lab findings were not significant, including the thyroid function test. Until the serum potassium was corrected to above 2.5 mmol/L, several episodes of wide and narrow QRS tachycardia were observed (). Interestingly, the wide QRS tachycardia was sometimes changed to narrow QRS tachycardia with the same cycle length of 360 ms. Another ECG, taken after the cardioversion, prolonged QT interval with prominent U wave and right bundle branch block pattern premature ventricalaric contractions are seen at the end of the T wave ().\nDysmorphic features, ventricular arrhythmia, and periodic paralysis made the diagnosis with ATS. During the maintaining of intravenous administration of potassium and bicarbonate, her mental status became alert and she was extubated on the hospital day 3. By hospital day 4, she recovered her motor strength to grade 5/5 on both of the upper and lower extremities, and was able to walk without assistance. After treatment with oral potassium replacement and potassium sparing diuretics, her paralysis symptoms and hypokalemia did not recur during the 2 year follow up period.