A 49-year-old man was referred to our clinic for suspected
hypoglycemic symptoms of palpitation, cold sweat, faintness and sinking feeling at movement since 43 years old. The 75 g oral
glucose tolerance test showed a decrease in plasma
glucose to 56 mg/dl at five hours, but this was not associated with clear
hypoglycemic symptoms, and normal plasma
glucose level recovered naturally after the test. At 48-hour fasting test, plasma
glucose dropped to under 50 mg/dl, but the patient didn't feel
hypoglycemia symptom and plasma
glucose recovered naturally, but the patient developed cold sweat and
hyperventilation after returning to his own room after the test. At that stage, the heart rate increased to 140 beats/min of
sinus tachycardia, as confirmed by Holter monitoring.
Postural orthostatic tachycardia syndrome (POTS) was suspected because
tachycardia occurred only in daytime after an event such as consumption of diet and urination. A head-up tilt test was ordered since
sinus tachycardia developed especially on standing. The results showed an increase in heart rate without reduction in blood pressure, confirming the diagnosis of POTS. A repeat head-up tilt test under the use of a beta-blocker showed no increase in heart rate. Though it is generally difficult to distinguish POTS from other forms of
tachyarrhythmia, such as inappropriate
sinus tachycardia and sinus node reentry
tachycardia, and from neutrally mediated reflex
syncope (NMS), POTS should be differentiated from
hypoglycemia since each condition should be treated differently.