Heart rate variability in children with idiopathic ventricular tachycardia

Idiopathic ventricular tachycardia (IVT) is a rare arrhythmia in children. A great deal of uncertainty and numerous questions still remain regarding the extent of investigation, therapy, and long-term prognosis for children with IVT. The existence of subclinical cardiac disease, as well as of autonomic dysfunction in patients with ventricular arrhythmias, has been well documented. A number of experimental and clinical studies have suggested that imbalances within the cardiac autonomic system’s activity may be crucial in the generation of ventricular tachycardia, irrespective of the presence of cardiovascular pathological substrate. Heart rate variability (HRV) analysis provides a useful method for measuring the autonomic activity. This study evaluates HRV in children with IVT. The study included 31 children with ventricular arrhythmia who were divided into two groups: (1) patients with frequent ventricular extrasystoles (VES) and (2) patients with IVT. The control group comprised 23 healthy children without pathological findings on 24-h ECG Holter. Twenty-four-hour ambulatory electrocardiography recordings were obtained, and the time-domain variables were calculated. HRV was compared to age-related normal values. It was observed that the overall heart rate variability is diminished in children with IVT. We recommend HRV analysis of any child with IVT. Quantification of the autonomic nervous system activity using time domain analyses may be a helpful diagnostic tool in the clinical assessment and initial evaluation of these children. Departments at which the work was done: Clinic of Pediatrics, Clinical Center, Nis and University Children’s Hospital, Belgrade, Serbia     

Heart rate and QT variability in children with anxiety disorders: a preliminary report

This study compared beat-to-beat heart rate and QT variability in children with anxiety disorders (n = 7) and normal controls (n = 15) by using an automated algorithm to compute QT intervals. An increase in QT variability appears to be associated with a higher risk for sudden cardiac death. A decrease in heart rate variability is also linked to significant cardiovascular events. Supine detrended QT variability, QT variability corrected for mean QT interval, and QTvi (a log ratio of QT variance normalized for mean QT over heart rate variability normalized for mean heart rate) were significantly higher in children with anxiety compared to controls (P < 0.05). The largest Lyapunov Exponent (LLE) of heart rate time series was significantly lower (P < 0.05) in children with anxiety compared to controls. These findings suggest a relative increase in sympathetic activity and a relative decrease in cardiac vagal activity in children with anxiety disorders, and are discussed in the context of the effects of tricyclics on cardiac autonomic function in children, and the rare occurrence of sudden death during tricyclic antidepressant treatment.     

Autonomic control of heart rate variability in vasovagal syncope: A study of the nighttime period in 24-hour recordings

Patients experiencing vasovagal syncope have been claimed to show reduced vagal tone over 24-hour electrocardiography recordings. Assessment of sympathovagal balance in the absence of external stimuli,ie, nighttime electrocardiography monitoring, might help to clarify if increased sympathetic activity is present in these patients. Heart rate variability was examined at nighttime in 40 patients with recurrent episodes of vasovagal syncope within the last 2 years (22 men; mean age, 37 years) and 20 comparable healthy volunteers. Time domain parameters (pNN50 [proportion of successive RR intervals difference > 50 ms in %] and rMSSD [root-mean-square successive difference of RR intervals in ms]), indexes of vagal tone, and frequency domain parameters, expressing the overall heart rate variability, vagal (high frequency [HF]) and sympathetic (low frequency [LF]) activity, and autonomic balance (LF/HF ratio) were compared between groups by Mann-Whitney test. Significant (p<0.05) reduction of heart rate variability and vagal tone (pNN50 and rMSSD) were found for patients with vasovagal syncope, together with increased sympathetic activity (increased LF/HF ratio). These findings could open new insights in the pathogenesis of vasovagal syncope because of the shift of the autonomic balance toward sympathetic activation near the syncopal episode.     

Heart rate variability in brain death

The sensitivity and specificity of heart rate variability (HRV) in the corroboration of brain death diagnosis in patients with acute traumatic intracranial lesions was evaluated in 20 patients with clinical criteria of brain death, nine patients in deep coma (Glasgow scale <7) and 18 normal controls, all age matched. The electrocardiogram was sampled at 650 Hz and several parameters of HRV were calculated, in both time and frequency domains. The HRV parameters were significantly lower in the brain death group compared with the deep coma group. Linear discriminant analysis between brain death and deep coma patients was performed on a data set made of nine randomly selected patients with clinical criteria of brain death and nine patients in deep coma. Cross-validation was performed on the remaining 11 patients with clinical criteria of brain death. All patients in the data set were correctly classified (sensitivity and specificity of 100%). All patients in the cross-validation set were correctly classified (sensitivity of 100%). Further studies are necessary to evaluate the specificity of the method in the independent set of deep coma patients and in the follow-up of comatose and vegetative patients to identify irreversibility of HRV. Nevertheless, these results suggest that HRV analysis constitutes a fully sensitive and specific method for assessing brain death in potential organ donors with acute traumatic lesions of the brain. This fast, quantitative and bedside method seems very promising for the early confirmation of brain death, which is an important factor for the success of transplantation procedures and could have a high predictive value of brain death in comatose patients with brain injuries without fully diagnostic criteria.     

Heart rate variability in patients with the first and recurrent myocardial infarction

Impairment of heart rate variability (HRV) has been reported in patients after myocardial infarction (MI). However, it is currently unknown whether the similar alterations of autonomic profile that accompany the first MI will evolve after a recurrent MI. Forty male outpatients with a previous first MI (group I) and 20 age-matched male patients with a recurrent MI (group II) were studied and measures of HRV were estimated from 24-hour electrocardiograms. In comparison with group I, group II had significantly higher values of ratio of low-to high-frequency power (6.9±5.7 vs 3.7±1.8, respectively, p<0.05), and a tendency to lower values of all other measures of HRV. We conclude our study indicates that in comparison to group I, group II demonstrated augmented sympathetic drive as assessed by the indices of HRV. The shift toward adrenergic predominance detected after recurrent MI may result from altered afferent feedback from abnormally contracting left ventricular segments to the autonomic modulation of sinus node, or accompany subclinical state of heart failure not readily accessible with hemodynamic measurements.     

Heart rate variability in childhood obesity

Obesity is characterized by hemodynamic and metabolic alterations. Autonomic control on cardiac function involvement is controversial. The aim of the study was to assess early sign of cardiac autonomic dysfunction in obesity, using time- and frequency-domain heart rate variability (HRV) analysis in a pediatric population. Methods: 32 obese children (OB) (17 M, 15 F; 13.9±1.7 y) were compared with 13 healthy lean subjects (7M, 6F; 12.9±1.6y). For each participant, the authors performed a clinical examination, laboratory testing, blood pressure (BP) measurements, and 24-hour electrocardiograph/ambulatory BP monitoring. The spectral power was quantified in total power, low-frequency (HF) power, index of sympathetic tone, high-frequency (HF) power, index of vagal tone, and LF/HF ratio. Low frequency and HF were averaged to obtain 3 measures: 24-hour, daytime, and nighttime levels. Total, long-term, and short-term time-domain HRV values were calculated. Results: The obese children had higher casual and ambulatory BP, and higher fasting glucose, insulin, and triglyceride levels. Overall HRV values were not significantly lower in OB. The obese children had significantly lower 24-hour and nighttime high-frequency normalized units, and time-domain measures of vagal activity. Low-frequency power showed an inverse but not significant pattern. The OB group had significantly greater 24-hour and nighttime LF/HF ratios. Conclusions: The authors found an increase in heart rate and in BP associated with parasympathetic heart rate control decrease in stabilized obese normotensive children.     

Heart rate variability in a case of pheochromocytoma

Indices of heart rate variability (HRV) reflect cardiac autonomic tone and may be markedly affected by pheochromocytoma. The effect of pheochromocytoma on HRV was determined by Holter monitoring before diagnosis, under pre-operative -blockade and 5 and 19 months after surgery in a 40 year-old female. Mean heart rates, although higher under -blockade, were unchanged by surgery but indices of HRV reflecting both short term (vagally mediated) and longer term (mediated by vagal, sympathetic and other influences) rhythms were diminished under -blockade and post-surgery. High frequency power (0.15–0.40 Hz), an index of vagal tone, declined from 512 ms² pre-diagnosis to 220 ms² under -blockade to just over 100 ms² post-surgery. Low frequency power (0.04–0.15 Hz), a measure reflecting both vagal and sympathetic tone, declined from 409 ms² pre-diagnosis to 186 ms² under -blockade and was just over 200 ms² post-surgery. SDNN, the standard deviation of normal-to-normal interbeat intervals over 24 hours, declined from 118 ms pre-diagnosis to just over 70 ms both under -blockade and post-surgery. The ratio of low frequency to high frequency power (LF/HF ratio) increased to 0.84 under -blockade, and doubled after surgery (0.79; before, 2.05; after). These changes in HRV may provide insights into the effects of endogenous catecholamines and intrinsic counter-regulatory autonomic mechanisms on HRV.     

Heart period and variability findings in preschool children with posttraumatic stress symptoms.

BACKGROUND: Traumatic experiences for young children might result in profound neurodevelopmental changes, compared with adults. Our aim was to examine autonomic control of heart rate in traumatized young children. METHODS: Sixty-two children who had suffered traumas and 62 nontraumatized control children, aged 20 months to 6 years, were assessed for posttraumatic stress disorder (PTSD) symptoms, interbeat interval, respiratory sinus arrhythmia (RSA), family rehearsal of the trauma, and parent-child relationship quality. RESULTS: Traumatized children with PTSD and traumatized children without PTSD both had decreased heart period in response to a trauma stimulus relative to the nontraumatized group (both p < .0167). there was no main effect for RSA change scores, however, there was a significant interaction effect between parental positive discipline with PTSD symptoms and RSA. The most sympathetic children had decreased RSA during the trauma stimulus when they had caregivers with less positive discipline during a clean-up nd family rehearsal with PTSD symptoms. CONCLUSIONS: These findings underscore that psychopathology in young children ought to be assessed in the context of psychophysiology and parent-child relationship to optimally understand the mechanisms of maladaptation during this complex developmental period.     

Heart rate variability of chronic alcoholics in withdrawal and abstinence

Measurement of heart rate variability was performed in 106 healthy volunteers and 31 alcoholics. The mean momentary arrhythmia (MMA) of normal individuals showed an exponential decrease with increasing age. Cardiac autonomic neuropathy was found in 5 of 31 alcoholics. In agreement with the concept of hyperexcitability the withdrawing alcoholics had a significant increase in heart rate and decrease in MMA compared to later measurements. The result suggests that the diagnosis of autonomic alcoholic neuropathy may be reliable only after at least a one week period of abstinence from alcohol.     

Transcranial Doppler during neurocardiogenic syncope

The purpose of the present study was to investigate changes in cerebral circulation during neurocardiogenic syncope (NCS). Twenty patients with a history of unexplained syncopes were studied over a 45 min period in a tilted position. Heart rate and arterial blood pressure were recorded non-invasively using Finapres. Cerebral blood flow velocity of both middle cerebral arteries was measured with transcranial Doppler (TCD). Ten patients (50%) developed a NCS during the tilt test, with a strong reduction in blood pressure (mean, 48/34 mmHg) and heart rate (mean, 54 beats/min). Simultaneously, diastolic blood flow velocities dropped to values close to zero. However, systolic blood flow velocities did not decrease. In consequence, the pulsatility index (PI) increased considerably from 0.93 to 2.01. The increase in PI suggests that there is a constriction of cerebral resistance vessels during NCS. Despite the drop in blood pressure and the putative increase in cerebrovascular resistance, systolic blood flow velocities remained unchanged in the TCD records. This fact can be explained by a lumen narrowing of the middle cerebral artery at the site of insonation. In conclusion, the typical changes in cerebral blood flow velocity during NCS are probably due to a strong constriction of both the proximal and the peripheral segments of cerebral arteries. It is clear that, in addition to vasodepression and cardiac inhibition, cerebral vasoconstriction is a further mechanism in the pathogenesis of a NCS.     

Heart rate variability in patients with untreated Parkinson's disease

The aim of this study was to evaluate cardiovascular responses as a marker of autonomic nervous system (ANS) disturbances in patients with untreated Parkinson's disease (PD) and to assess the relationship between them and the clinical characteristics of PD. The ANS functions were investigated in 50 patients with PD and 55 healthy subjects by measuring standard cardiovascular autonomic reflexes and heart rate variability (HRV) at rest using spectral analysis (the autoregressive model and the fast Fourier transformation), the percentage of the counts of beat-to-beat variation greater than 50 ms and the fractal dimension. Significantly attenuated HRV and deficient blood pressure reaction to tilting were found in the PD patient group. The patients with hypokinesia/rigidity as the initial symptom of PD had a more pronounced HRV deficit than those with tremor onset. Untreated PD patients suffer significant failure in cardiovascular nervous system regulation, and in patients with hypokinesia/rigidity as their initial disease manifestation the risk of this ANS dysfunction is high. However, in the early stages of PD these changes did not reach significance at individual level.     

Heart rate variability in type 2 spinocerebellar ataxia

Montes‐Brown J, Sánchez‐Cruz G, García AM, Báez ME, Velázquez‐Pérez L. Heart rate variability in type 2 spinocerebellar ataxia.
Acta Neurol Scand: 2010: 122: 329–335.
© 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard. Objectives – To explore cardiovascular autonomic regulation in Spinocerebellar ataxia type 2 (SCA2) patients, using heart rate variability (HRV) analysis and neurophysiologic autonomic reflex tests, and determine relations and causal related factors of dysautonomia in SCA2. Materials and methods – Heart rate variability indices for 5 min series of RR intervals were analyzed in 97 SCA2 patients, assessed quantitatively for somatic and autonomic nervous system complaints applying the International Cooperative Ataxia Rating Scale and Scales for Outcomes in Parkinson’s disease (SCOPA‐AUT), respectively. Autonomic testing included: resting control, standing, Valsalva maneuver and deep breathing. Results – Mean RR, long‐ and short‐term variability indices and spectral density power (LF, HF) indices were lower in the patients group, whereas LF/HF ratio and LF (nu) were higher. Highly differences between groups were observed for seven diagnostic autonomic test indices. Significant correlations were found between different clinical and demographic indices and between clinical indices and some HRV indices. Conclusions – We confirm the presence of cardiovascular autonomic dysfunction in a large group of SCA2 patients.     

Heart rate and blood pressure variability in patients with myasthenia gravis

This cross-sectional case control study included subjects aged between 18 and 65 years with diagnosis of myasthenia gravis (MG) in Osserman''s Stage I and Stage IIa and those in remission with positive and negative acetylcholine receptor antibody (AChRAb). They were evaluated for heart rate variability (HRV) and other conventional autonomic functions. Patients with co-morbidities that can affect autonomic nervous system were excluded. Repetitive nerve stimulation test (RNST), nerve conduction test, AChRAb assay, and computerized tomography (CT) of chest were done in all the patients. All patients of MG who fulfilled the inclusion criteria had a minimum drug-free period of 6 h which was followed by HRV and other conventional tests. Thirty subjects fulfilling study criteria and an equal number of age and gender-matched healthy subjects were enrolled as controls. Autonomic function tests revealed significant changes in HRV (both time and frequency domain) parameters suggestive of parasympathetic deficiency as well as shifting of sympathovagal balance towards raised sympathetic tone. With regards to conventional autonomic function tests, there was statistically significant decrease in values of heart rate-based tests as well as blood pressure-based test (isometric handgrip test) in study group compared with controls, again indicative of significant parasympathetic deficiency and minimal sympathetic deficiency. We conclude that in MG, cholinergic transmission is affected more diffusely than previously thought.     

Heart rate variability is altered following spinal cord injury

Spinal cord injury (SCI) patients are know to suffer from autonomic failure as a result of their injury. The magnitude of the dysautonomia resulting from such an injury is difficult to predict or characterize and, in varying degree, it impedes the recovery of physiological homeostasis. This study is intended to investigate the effectiveness of heart rate variability (HRV) analysis as a method of quantifying and characterizing autonomic function in patients with traumatic spinal myelopathy. HRV analysis was carried out in 13 male SCI patients (six tetraplegic, seven paraplegic) and 13 age-matched, able-bodied controls. Twenty-four hour ambulatory and sleep ECG tracings were obtained. Time domain, amplitude, and power spectral analyses were used to study HRV and autonomic function. Both tetraplegic (20±12 ms, mean ±SD) and paraplegic (22±8 ms) subjects demonstrated significant loss of low frequency 24-hour HRV compared to able-bodied controls (36±14 ms, p<0.05) and during sleep. This was interpreted as being consistent with predominantly sympathetic denervation uninfluenced by degree of physical activity. There were no significant differences between groups in parasympathetically mediated high frequency HRV. We conclude that HRV analysis is capable of distinguishing between SCI or able-bodied humans and among tetraplegic and paraplegic patients. Patterns of altered HRV may be useful in more completely characterizing or stratifying changes in physiology associated with injury level and may have diagnostic, prognostic, or therapeutic significance.     

Heart rate variability in multiple sclerosis during a stable phase

Objectives – Multiple sclerosis (MS) frequently causes disturbances of autonomic functions. Cardiovascular dysautonomia has been studied by classic autonomic tests and, recently, by heart rate variability analysis in some isolated periods. Multiple authors recommended performing heart rate variability analysis with a 24 h ECG recording to increase its sensitivity. Material and methods – We analyzed the heart rate variability in time and frequency domains in 34 MS patients and 24 age and sex-matched healthy control subjects, in order to evaluate the effects of MS on sympathetic and parasympathetic cardiovascular regulatory functions measured from 24-h electrocardiogram. Results – Low frequency power (0.01) and low frequency/high frequency power (0.01) were significantly higher in multiple sclerosis patients independently, all together or in subgroups. Very low frequency (0.01) and high frequency (0,001) power were higher in less affected multiple sclerosis patients. Variability in time domain (0.05) were lower in most affected multiple sclerosis patients. Conclusions – These results suggest that multiple sclerosis causes cardiovascular autonomic dysregulation manifesting as impaired heart rate variability. This illness seems to cause an increase in sympathetic cardiovascular tone; the parasympathetic tone is most variable and depends on clinical and paraclinical findings, but the illness progression seems to provoke a decrease in it.     

Heart rate variability in anorexia nervosa and the irritable bowel syndrome

Background Many studies have reported disturbances of heart rate variability (HRV) in patients with psychosomatic disorders such as anorexia nervosa (AN) and the irritable bowel syndrome (IBS). However, both have never been directly compared. Methods We compared HRV in AN (n = 21) and in IBS (n = 21) (all females) with 42 healthy female control subjects who were matched for age and in IBS to body mass index (BMI). Recovery periods between different cardiac load tests were compared with baseline recordings and tilt test to estimate time [mean successive difference (MSD)] and frequency domain (Goldberger dimension, frequency of HF peak location and HF power, log HF power) values and to assess general reactivity of the autonomic nervous system (ANS). Key Results Significantly longer inter‐beat intervals (IBIs) in AN patients and lower values of MSD in IBS patients were found in comparison with respective controls; both were independent from experimental conditions and are found in baseline recordings only. Both effects were independent of age and BMI. We also demonstrate a significant relationship between age, BMI and some HRV parameters. Conclusions & Inferences Opposite autonomic patterns were found in AN and IBS: stronger vagal withdrawal in IBS and weaker vagal inhibition in AN patients. Records made at rest and without any autonomic load may be representative for assessment of ANS function. Age and BMI should be taken into consideration during assessment of HRV data.     

Heart rate variability in the irritable bowel syndrome: a review of the literature

Background Patients with irritable bowel syndrome (IBS) often present with disturbances of bowel habits (diarrhea, constipation) and abdominal pain/discomfort that are modulated by the autonomic nerve system (ANS). In this narrative review, we analyzed studies that measured ANS functioning in IBS by means of heart rate variability (HRV). Methods The PUBMED was searched with the keywords ‘irritable bowel syndrome’ AND (‘heart rate variability’ OR ‘autonomic function’). We included only papers that used ‘traditional’ HRV indices and diagnosed IBS based on Manning or Rome criteria. Studies were sub‐grouped according to methodological features of HRV analysis (24‐h monitoring, short‐term laboratory records, records during sleep). Key Results Most studies reported no difference in HRV when the IBS population was compared to healthy controls. Dividing the IBS sample into subgroups – according to their predominant bowel symptoms, the severity of clinical course, the presence of depressive symptoms, or a history of abuse in the past – revealed changes in autonomic functioning. Conclusions & Inferences Patients with IBS appear to experience symptoms that may be the result of changes in ANS functioning. HRV measures in clinical routine may allow assessing these changes, but further studies performed in a standardized fashion should improve the validity of HRV measures for clinical research first.     

Near death and neurocardiogenic syncope

We report the case of an 18-year-old female who presented as an out-of-hospital ventricular fibrillation cardiac arrest. She required ICD insertion and recovered without deficit. Following recurrent syncopal episodes we diagnosed the co-existence of Neurocardiogenic syncope.