Diagnostic yield of nitroglycerin-potentiated head-up tilt test in a pediatric population with suspected reflex syncope

Background: Syncope is a prevalent issue in pediatric patients. The nitroglycerin (NTG)-potentiated head-up tilt test (HUTT) is widely used in adults for diagnosing reflex syncope; however, few and contrasting data are available in pediatric populations. The aim of our study was to evaluate the positivity rate and types of responses to NTG-potentiated HUTT in pediatric patients with suspected reflex syncope. Methods: We conducted a retrospective multicenter analysis of 307 pediatric patients (mean age: 14.4 ± 2.8 years; 57.6% female) who underwent HUTT at two syncope units in Naples, Italy. A group of 16 healthy pediatric subjects (13 ± 3.2 years; 37.5% female) with no history of syncope was used as a control. We described the HUTT overall positivity rate and responses; moreover, the positivity rate, sensitivity, and specificity were evaluated. A multivariate analysis was performed to test the association of positive response to HUTT with a set of clinical covariates. Results: The overall HUTT positivity rate was 74.9%, ranging from 51.5% to 81.6% among pediatric patients with non-classical and classical presentation, respectively. The HUTT positivity rate among healthy control group was 18.7%; consequently the HUTT specificity was 81.3%. Younger age (OR: 0.84; p = 0.005) and female sex (OR: 2.3; p = 0.005) were independent predictors of HUTT positivity; in contrast, the non-classical presentation of syncope (OR: 0.23; p < 0.001) and situational syncope (OR: 0.2; p = 0.006) correlated negatively with HUTT positivity. Conclusions: NTG-potentiated HUTT showed a high positivity rate, good sensitivity, and specificity in pediatric patients with suspected reflex syncope. Some patients and syncope-related features independently correlated with HUTT positivity. Cardioinhibitory response was more prevalent in pediatric patients with a non-classical presentation of reflex syncope.