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 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 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.     

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 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 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 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.     

Attenuated 24-h heart rate variability in apparently healthy subjects,subsequently suffering sudden cardiac death

Attenuated cardiac parasympathetic activity appear to be an important risk factor contributing to sudden cardiac death in subjects with overt coronary disease but its predictive value in otherwise healthy normal subjects is not known. We have for 8 years followed 260 apparently healthy adult subjects who underwent Hotler monitoring. Twelve died, 14 developed ischaemic heart disease and four suffered sudden cardiac death. A healthy control subject was matched, along with other risk factors, for each case. In each subject 24-h heart rate variability was calculated as the deviation of all normal R—R intervals from mean R—R (SD) and the percentage of successive R—R interval differences exceeding 6% (%DIF6%)—this was used as an index of cardiac parasympathetic activity. There were no significant differences in heart rate variability between the cases developing problems and controls. In the sudden cardiac death victims, however, there was a clear trend towards lower heart rate variability. In them waketime mean SD was 73 ms versus 85 ms for cases and controls respectively (p = 0.08), and for sleeptime 61 ms versus 76 ms (p = 0.07). Compared to normal limits for heart rate variability obtained in 140 subjects that remained healthy for 8 years, figures for both SD and %DIF6% in sudden cardiac death subjects were at or below 95% confidence limits. The results indicate that altered autonomic balance may contribute to sudden cardiac death even in apparently healthy subjects. Subjects with a low 24-h heart rate variability on Holter monitoring may be predicted at an early stage of being at greater risk. This has considerable implications not only for predicting subjects at risk but for assessing physiological (such as exercise) and pharmacological interventions which may reduce such risk.     

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 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.     

Heart rate variability - a potential early marker of sub-acute post-stroke infections

Günther A, Salzmann I, Nowack S, Schwab M, Surber R, Hoyer H, Witte OW, Hoyer D. Heart rate variability – a potential early marker of sub‐acute post‐stroke infections.
Acta Neurol Scand: 2012: 126: 189–196.
© 2011 John Wiley & Sons A/S. Objective – Infection is the most relevant complication after acute ischemic stroke. Activity of the autonomic nervous system seems to control post‐stroke immunodepression. We investigated heart rate variability (HRV) indices that reflect autonomic readjustments as predictors of post‐stroke infection. Materials and methods – Forty‐three patients with acute ischemic stroke were enrolled in a prospective study. The predictability of sub‐acute infections (day 4 ± 1 after admission) was investigated in 34 patients without acute infection by means of HRV indices obtained in the acute period (48 h after admission). Results – Sub‐acute infection could be predicted in patients without clinical or paraclinical (white blood cell count and C‐reactive protein) signs of infection in the acute period at (i) day: increased HFnorm, reduced LFnorm and LF/HF; (ii) night: reduced LF and VLF (P < 0.05). Conclusions – HRV indices are candidates for early markers of developing post‐stroke infections, preceding routine blood samples. Thus, HRV‐based early diagnosis of post‐stroke infection should be investigated in more detail as it may have implications as a novel tool for timely and appropriate treatment. A corresponding continuous HRV‐based risk assessment using the ECG provided by the routine stroke monitoring system would be possible without any additional burden for patients and staff.     

Heart rate variability in children with neurocardiogenic syncope

Abstract. In order to characterize the autonomic profile of syncopal children, we have studied heart rate variability (HRV) of 73 children, ages 11–18, with neurocardiogenic syncope and a positive outcome of head-up tilt testing (HUT).HRV was calculated over a 24-hour period for the time-domain indices (SDNN, SDANNi, SDNN, rMSSD, pNN50), and over 5-minute segments from night and day for frequency-domain indices (LF, HF, LF/HF). The obtained results were compared to reference values calculated for Polish children. 55% of the children had mixed response to HUT, 41% vasodepressor and 4% cardioinhibitory. Patients with syncope had significantly lower values of rMSSD and pNN50 in comparison to healthy children. Moreover, in the frequency-domain analysis they exhibited significantly higher LF and lower HF values. The day-night rhythm of HRV and the age-related changes of HRV were, however, similar in syncopal and healthy children. In addition to this, we found a significantly lower SDNN value in children with cardioinhibitory response during HUT in comparison to children with mixed response. We concluded that 1) based on HRV analysis children with neurocardiogenic syncope had alterations in basal autonomic balance, which indicated an increased sympathetic modulation in these patients, 2) syncopal children had adequate circadian rhythm of autonomic activity, 3) the changes of HRV indices with age in these groups are not altered in comparison to healthy children, 4) syncopal children may exhibit differences in HRV indices values depending on the kind of vasovagal response observed during HUT.     

Twenty-four-hour heart rate variability to assess autonomic function in Parkinson's disease

OBJECTIVES: To evaluate the autonomic dysfunction in Parkinson's disease patients by means of a 24-h heart rate variability (HRV) method. MATERIAL AND METHODS: Thirteen patients with a diagnosis of Parkinson's disease were compared with 13 age-matched healthy persons (control group). The 13 patients had a mean age of 70.5 years, and mean disease duration of 10.9 years. The autonomic function was evaluated by HRV analysis using a continuous 24-h ECG. The parameters of SDNN (standard deviation of the normal-to-normal intervals between adjacent QRS complexes), of LF (power in low frequency) and of HF (power in high frequency) were studied during the following 3 periods: 24 h, night and day. RESULTS: The data show a statistically significant difference between groups for SDNN and LF in all the periods, while for HF parameters the difference is statistically significant only in the night period. CONCLUSION: The use of the 24-h HRV method can provide more accurate and reproducible data than other conventional cardiovascular tests.     

Facial myokymia in brain death

BACKGROUND: Brain death (BD) is the irreversible loss of all functions of the brain and brainstem. Spontaneous and reflex movements of the limbs have been described in this condition. However, facial myokymia (FM) in BD has not been previously reported. The origin of that motor phenomenon in alive patients is still uncertain, since supranuclear, nuclear and peripheral mechanisms have been proposed. OBJECTIVE: We describe the presence of FM in a patient who fulfilled the criteria for BD. A 40-year-old-man had right-sided weakness and impaired consciousness. After 14 h admission, he fulfilled the criteria for BD. A CT scan of the head showed a large putaminal hemorrhage. The EEG was isoelectric. At that time, fine spontaneous twitches of the left cheek were noticed. They consisted of repetitive and rhythmic movements in groups of 3-5 lasting for < 5 s. These movements appeared every 2-10 min during 6 h. DISCUSSION: Spinal reflexes have been described in BD. The presence of any movements other than the recognized reflexes may question this diagnosis and limit organ procurement for transplantation. The recognition of FM as an accepted movement in BD patients has practical and legal implications.     

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.