Time-frequency Analysis of the Autonomic Response to Head-up Tilt Testing in Brugada Syndrome

Abstract

Cardiac events in Brugada syndrome (BS) usually occur at rest and mainly at nighttime, commonly relating changes in autonomic modulation to arrhythmogenesis. A major challenge today is to differentiate symptomatic and asymptomatic patients in order to optimize their therapy. Since autonomic assessment can be improved by the application of standard maneuveurs, this study analyzes and compares the autonomic response to head-up tilt (HUT) testing on 20 symptomatic and 45 asymptomatic BS patients. Their standard 12-lead ECG recordings were collected during a HUT test composed of the following three phases: (1) supine rest for 10 minutes, (2) tilting with an inclination of 60• for 45 minutes and (3) supine rest for 10 minutes. Spectral non-stationary heart rate variability indicators were extracted by means of a Smoothed Pseudo Wigner Ville distribution approach that adapts frequency bands to respiratory information. Symptomatic patients showed an increased parasympathetic tone and a reduced sympathovagal balance with respect to asymptomatic patients during tilting, and particularly before the 15 th minute of the test. The results provide new insights into the autonomic function in BS, with a potential impact on the use of timereduced HUT testing for risk stratification.

Multivariate Classification of Brugada Syndrome Patients Based on the Autonomic Response During Sleep, Exercise and Head-up Tilt Testing

“…Then, based on our previously reported analyses on the autonomic function of BS patients during A) exercise [11,12], B) HUT testing [14] and C) sleep [7], several HRV markers were calculated for each patient, to build a set of candidate features to be used for classification purposes.…”

“…For the design of classifiers based on HUT testing data, the same HRV markers were extracted. In this case, the mean for the whole baseline period was subtracted from each estimated HRV time series and, in order to reduce classification computational cost, only the first 5 minutes after tilting and the time period between 11-15 minutes in upright position were included, based on a previous study [14], where the most significant autonomic differences between symptomatic and asymptomatic BS patients were found before the 15 th minute in upright position.…”

“…In previous works, we reported significant differences in the autonomic function of symptomatic and asymptomatic BS patients overnight [7] and during exercise [11][12][13] and head-up tilt (HUT) testing [14,15]. In this paper, we further explore the potential of heart rate variability (HRV) markers for BS classification, by combining features extracted from these experimental conditions.…”

Model-based analysis of the autonomic response to head-up tilt testing in Brugada syndrome

“…However, autonomic assessment can be improved by stimulating the ANS through standardized autonomic maneuvers such as exercise [14,15] or the head-up tilt (HUT) test. As a matter of fact, the cardiovascular response to upright posture has been widely evaluated by means of computational models and clinical trials [16,17,18,19]. Its main hemodynamic effect is the redistribution of blood volume to the lower part of the body, causing a decrease in both central venous return and ventricular filling pressures, as well as in stroke volume [20].…”