Exploring QT variability dependence from heart rate in coma and brain death on pediatric patients

Patients with acute brain injury (ABI) present dysfunctions of the autonomic nervous system and consequent alterations on the cardiac parameters, particularly in brain death (BD). Therefore the study of cardiovascular variabilities can provide a complementary tool for time course predicting and prognostic. QT variability (QTV) versus heart rate variability (HRV) interactions were explored using a low order AR-ARARX model, previously validated, which allows quantifying the QTV Fraction (F%) driven by HRV. High resolution 12-lead ECG Holter recordings were taken from pediatric patients admitted to the intensive care unit with ABI. Power of HRV and QTV driven and undriven fractions were calculated considering the frequency bands: < 0.04Hz (VLF), 0.04–0.15Hz (LF), 0.15–0.4Hz (HF), > 0.4Hz (HF+) and all frequencies (TP). The median of F% in patients for which BD has been confirmed was found to be significantly lower in TP, VLF and HF bands and significantly higher in HF+ (p< 0.005). Uncoupling of QT vs RR have clinical potential in differentiating the progression of the disease within children with ABI, and can contribute for a better individual adjustment in treatment type and timing, and as early prognostic predictor of BD.