OBJECTIVESyncope is one of the common problems in clinical pediatrics. In recent years, vasovagal reflex was identified as the most common reason for unexplained syncope. Head-up tilt test (HUT) was regarded as one of the important diagnostic criteria. But the sensitivity of baseline head-up tilt test (BHUT) is low. To improve the sensitivity of HUT, we evaluated the diagnostic value of head-up tilt testing potentiated with sublingual nitroglycerin (SNHUT) in children with unexplained syncope.

METHODSTwenty-five patients (11 male and 14 female, mean age 11.8 +/- 2.1 years, ranged from 8 to 15) with unexplained syncope and 10 healthy children in control group (5 male and 5 female, mean age 11.4 +/- 2.1 years, ranged from 9 to 15) were studied. The patients and healthy children were tilted upright to 60 degrees for 45 minutes at BHUT. If syncope did not occur, sublingual nitroglycerin (4 - 6 microg/kg, maximum dose 300 microg) was administered, and continued at same degree for 20 minutes.

RESULTSCompared with controls, there was no significant difference in sex, age, supine blood pressure and supine heart rate of syncopal group (P > 0.05). During BHUT, 12 patients (48%) and none of the controls had positive response, whereas another 8 patients and 2 controls had positive response during SNHUT. In syncopal group, total positive rate was 80%. The sensitivity, specificity, and diagnostic value of SNHUT were all 80%. During SNHUT, the mean time to positive response was 5.9 +/- 2.9 minutes (from 4 to 11 minutes), and only 1 patient had mild headache.

CONCLUSIONHead - up tilt testing potentiated with sublingual nitroglycerin (4 - 6 microg/kg, maximum dose 300 microg) as pharmacological provocation test was a useful and an objective diagnostic tool for evaluating vasovagal syncope in children.