Age-dependent response of heart rate variability parameters to head-up tilt tests in young syncope patients and controls

This study examines the utility of heart rate variability (HRV) and repolarization parameters to predict the outcome of head-up tilt tests from early phases of the response to tilting in 44 young patients with syncope and 34 age-matched controls. Synchronized to the tilting events, we extracted minute-by-minute progression of time- and frequency domain HRV descriptors as well as mean QT interval and linear QT-RR model parameters. The Wilcoxon rank sum test revealed significant effects of age in patients. Time-courses of patients and controls exhibited a high degree of concordance in young subjects whereas after start of puberty patients exhibited more prominent and persistent responses. Controls did not change significantly. This was also confirmed by ROC analysis in three temporal regions of interest (ROI1: 0-2 min after tilt, ROI2: 2-5 min after tilt and ROI3:5-2 min before tilt back) which consistently revealed higher area under curve for older subjects with sensitivity up to 79 % and specificity up to 75% in ROI2.