Multifractal Analysis of Heart Rate Variability in Subjects Affected from Dysfunction of Autonomic Nervous System in Anxiety and Depression and Treated by Transcutaneous Vagus Nerve Stimulation

Rapid Communication

Austin Cardiol. 2018; 3(1): 1016.

Multifractal Analysis of Heart Rate Variability in Subjects Affected from Dysfunction of Autonomic Nervous System in Anxiety and Depression and Treated by Transcutaneous Vagus Nerve Stimulation

Conte S¹, Wang F², Sala N³, Casciaro F1,4, Orsucci F5, Serafini G6, Kaleagasioglu F1,7, Mendolicchio L1,8, Norman R1, Conte E*1

1School of Advanced International Studies on Applied Theoretical and non Linear Methodologies of Physics, Italy

2College of Science/Agricultural Mathematical Modeling and Data Processing Center, Hunan Agricultural University, China

3University of Lugano, ISSI/Cerfim, Swizerland

4Department of Biomedical Sciences and Human Oncology, University of Bari, Italy

5Division of Psychology, University College, London

6Tor Vergata University, Italy.

7Faculty of Medicine, Near East University, North Nicosia, Turkish Republic of Northern Cyprus

8Clinic Villa Miralago, Italy

*Corresponding author: Elio Conte, School of Advanced International Studies on Applied Theoretical and non Linear Methodologies of Physics, Bari, Italy; E-mail: [email protected]

Received: February 09, 2018; Accepted: March 21, 2018; Published: March 28, 2018


A diminishing or disrupting fractal/multifractal structure of HRV is consistently reported as related to a serious ANS dysfunction that of course we study in several psychological and psychiatric disorders. We observed a net improvement in the multifractal HRV structure of such subjects during the transcutaneous Vagus Nerve Stimulation.

Keywords: Depression; Anxiety; Stress; Transcutaneous vagus nerve stimulation; Neuromodulation; Heart rate variablity; Multifractals


Heart Rate Variability (HRV) is used to quantify activity of the Autonomic Nervous System. Cardiac rhythm is modulated by the two components of (ANS), the sympathetic and parasympathetic systems. Sympathetic dominance happens during stressful conditions and psychological and psychiatric disorders, whereas the vagal modulation induces normal heart rate dynamics and the correct its intrinsic variability. Consequently, Heart Rate Variability analysis (HRV) enables the study of autonomic influence as well as the effects of a number of psychological and psychiatric disorders. From a clinical point of view, the treatment of such mentioned psychological disorders requires often the continued use of drugs quite often coupled to psychotherapy. The use of alternative clinical approach is of importance especially in the several cases in which patients evidence conditions having pharmacologically resistance. A new non-invasive neurostimulating procedure, called transcutaneous Vagus Nerve Stimulation (tVNS) has been developed. The details of the applications are reported in [1].

First the subject applies a topical cream that has been designed to induce relax by counteracting adrenaline. The proprietary formula is only available in the NuCalm system and includes structured, nutrient-sourced building blocks that rapidly create a natural relaxation response. The treatment continues by applying tVNS and noise-dampening headphones with binaural beats used to bring brain to synchronize at proper frequency bands in the interval (12Hz -4Hz). The whole treatment uses light-blocking eye masks with the obvious meaning to reduce perceptive effects enhancing alpha and related relaxing bands. Since it is intuitive that the use of a such combined procedure may produce only positive treatment effects, there is to agree on the evident benefit to use the mentioned cream as well as to add brain entrainment synchronizing in the frequency bands (4- 12 Hz), it remains the basic interest to study the tVNS device from one hand under its technical profile and when applied to subjects having the above mentioned psychological disorders. We performed our studies by using the tVNS NuCalm device on subjects affected from anxiety or depressions. The study was performed on subjects having a serious ANS dysfunction as evidenced by our HRV analysis and examining the effect on the ANS of the Nu-Calm treatment for thirty minutes. During and after the tVNS treatment, the considered subjects evidenced a net improvement in ANS as indicated by multifractal analysis of HRV.

Materials and Methods

The multifractal strucuture of the device is reported in [1]. Soon after we proceeded examining 20 subjects affected from anxiety and 20 subjects affected from depression. We examined subjects all having ages between 25 and 45. All the subjects gave their written informed consent. According to the 1996 Task Force Standards of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, we selected the subjects excluding a priori those affected from well established other pathologies as we fixed in detail in [2]. To test the subjects each potential participant was given a non-structured interview following the criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM). Participants selected for the study showed symptomatology of anxiety or depression. Those selected were divided into two groups and administered tests to evaluate the level of their anxiety and depression symptoms. The scales used to measure their scores were, respectively, the Hamilton Anxiety Scale (HAM-A) and the Hamilton Depression Scale (HAM-D). Both such tests were administered and showed medium scores, with HAM-A at 42 and HAM-D at 18. In this manner we selected a group of subjects whose scores representing a sample symptomatology both for anxiety and for depression. The obtained tachograms were recorded by finger Plethysmography (PG) and each time were compared to those obtained by ECG, accounting for Pulse Wave Transit Time (PWTT)

The t-VNS device was used applying gel electrode patches near the right and left ear lobes, and setting the current value at 0.1 mA. The PG recording of five minutes was performed without tNVS. Then the PG recording was extended for 30 minutes with the subject under stimulation. This scheme enabled us to estimate HRV before and during the tVNS.


The data were subsequently analyzed by the MF-DFA-1-D.


For a detialed discussion on frctals and multifractals see the [1]. The salient feature that relates the finality of our paper is that in recent years multifractal structure has been identified in heart rate dynamics and HRV that are actually the basic objects of the present paper [3-5].

The approach is that the pathology usually reduces or can disrupt this multifractal dynamics resulting in the alteration of its fractal properties. The MFDFA-1-D method that we have used, was first conceived by Kantelhardt et al [4].