gms | German Medical Science

The aim of the study was to evaluate parameters of Heart Rate Variability (HRV) during Head-Up Tilt Test (HUT) in children with a history of Neurocardiogenic Syncope (NCS) in regard to the clinical outcome of the test.

Methods: 12 Channel ECG’s (continous recordings, sampling rate 500 Hz, obtained during HUT with a preceeding 10 minute phase in a supine position) of 44 patients ( 22 male, 22 female, age 7- 20 yrs) with a history of syncope and positive HUT were compared to the recordings in 36 healthy control subjects (19 female, 17 male, age 7- 19 yrs) with a negative history of syncope and negative HUT. Time domain and frequency domain features were calculated. Three Regions of Interest (ROI) were defined: the first two minutes immediately after tilt, 3-5 minutes after tilt and 3-5 minutes before tilt- back.

Results: Synchronized to the moments of tilt and tilt-back/ syncope the time courses exhibited differences between patients and controls which were strictly related to age. Discrimination between patients and controls by means of receiver operating characteristic (ROC) – analysis revealed that deflections in younger subjects (<13 yrs) were weaker and less persistent, whereas differences in elders (>13yrs) were conclusive and more prominent immediately before later syncope. The relative change of mean RR interval provided best separation for all age groups, presenting in elders in the ROI just before syncope (sensitivity 74%, specificity 80%) in contrast to the younger ones immediately after tilt (sens. 71%, spec. 74%). The relative reduction of SDNN in older subjects 2-5 minutes after tilt showed almost the same performance (sens. 74%, spec. 80%) as in the ROI before syncope (sens. 78%, spec. 73%).

Conclusion: Changes of specific parameters of linear HRV (SDNN) strongly indicate the existence of early precursors for later neurocardiogenic syncope in children during HUT. This effect is more pronounced in older than in younger children.