Total Heart Rate Variability Research Articles

Heart rate variability in patients with severe chronic obstructive pulmonary disease in a home care program

Chronic obstructive pulmonary disease (COPD) patients present functional and structural changes of the respiratory system that have a profound influence on cardiac autonomic dysfunction. To analyse heart rate variability in COPD patients under stable condition and during acute exacerbation episodes (AECOPD). Twenty three severe COPD male patients, 69.6 ± 7.3 years, in stable condition were followed up for two years. Home visits were carried out by a nurse every month, and home or hospital visits were arranged on demand. Every three months an ECG, oxygen saturation and spirometric recording was obtained for each patient. If the patient presented AECOPD compatible clinical data the same measurements were performed before any change of treatment. Spectral parameters of heart rate variability in time and frequency domains were obtained from ECG. The time evolution of power in low frequency (LF) and high frequency (HF) bands were obtained from the spectrogram. In addition, we calculated the LF/HF ratio and total heart rate variability power (POW). We analysed 154 patient-visit records during the follow up, pertaining to 23 patients and 8 controls; 19 of the patients had experienced at least one AECOPD. Stable COPD patients had higher HF values than control subjects. No significant differences were found in LF, LF/HF ratio or POW variables. AECOPD patients had higher LF, HF and POW than the stable COPD and control groups. AECOPD patients exhibited signs of increased autonomic activity compared with stable COPD.

Acupuncture Point Laterality: Investigation of Acute Effects of Quchi (LI11) in Patients with Hypertension Using Heart Rate Variability.

Hypertension is one of the major risk factors for cardiovascular disease worldwide. Over 70% of the patients use antihypertensive drugs, so nonpharmacological treatments in addition to the medication are important. Our goal was to investigate acupuncture treatment on the Quchi acupoint using heart rate (HR) and heart rate variability (HRV) and to find out whether there is a laterality in acute effects. Sixty hypertensive patients (36 female, 24 male; mean age ± SD 55.8 ± 9.7 years) were randomly assigned to two manual needle acupuncture groups (group A: left Quchi (LI11) acupoint, group B: right Quchi acupoint). There was a significant (P < 0.05) decrease in HR immediately after inserting and stimulating the needle at the left and the right Quchi acupuncture point. In contrast, total HRV increased immediately after inserting the needle, but this increase was significant only towards the end of the stimulation phase and after removing the needle. There were some differences between stimulation of the left and right Quchi acupoint, but they remained insignificant. This study provides evidence that there is a beneficial effect on heart rate variability in patients with hypertension and that there are some effects of laterality of the acupoint Quchi.

The influence of pemirolast on autonomic imbalance in rat cystitis model

Abstract Cyclophosphamide (CP) treatment is associated with the risk of haemorrhagic cystitis (HC). Moreover, CP-induced HC is complicated by autonomic nervous system (ANS) dysfunction. Pemirolast is thought to be a mast cell stabiliser that inhibits the release of many inflammatory mediators and sensory neuropeptides, and thus, it may be considered a potential chemoprotective HC agent. The aim of the study was to indirectly estimate the effect of pemirolast in experimental HC by measuring ANS activity with the heart rate variability (HRV) method. In CP-treated rats, we found a decreasing trend of overall autonomic activity, together with an imbalance between the main components, and a dominant very low frequency (VLF) power component. Pemirolast treatment did not improve the total HRV power value or the main non-normalized HRV components. Moreover, CP-HC animals treated with pemirolast displayed a different disproportion of normalized spectral components as compared to both control and CP-HC animals without pemirolast treatment, with the balance between normalized low frequency (nLF) and normalized high frequency (nHF) shifted towards nLF. This finding, together with a relatively high VLF tension, indicates that the pemirolast treatment resulted in high sympathetic activity that may contribute to HC exacerbation; thus, this agent seems to be ineffective in CP-induced HC.

Heart rate variability remains reduced and sympathetic tone elevated after temporal lobe epilepsy surgery

PurposeThere is evidence of autonomic dysregulation in temporal lobe epilepsy. The structures removed during temporal lobectomy are important centers of central cardiovascular control; therefore surgery may conceivably alter the cardiovascular autonomic function. The effects of temporal lobectomy on autonomic cardiac control are controversial. We investigated the effects of temporal lobectomy on heart rate variability (HRV) in the early and late postoperative periods. MethodsWe used 1-h ECG recordings to assess heart rate variability by spectral analysis in 24 consecutive patients who underwent temporal lobectomy due to intractable temporal lobe epilepsy. ECG recordings were performed before and twice (early and late) after surgery. The results were compared with age and sex matched controls. ResultsWhen compared with controls, all the time and frequency domain indices (SDRR, RMSSD, TP, LF and HF) were significantly lower in the patient group before surgery. Findings were similar in the early and late post-operative periods except that the LF/HF ratio increased in the patient group after the late post-operative period. Within the patient group, compared to pre-operative results, normalized HF was increased in the early post-operative period; however in the late post-operative period, LF/HF ratio was increased. ConclusionsThese findings show that in patients with intractable temporal lobe epilepsy, HRV is decreased globally in both sympathetic and parasympathetic domains. While the total HRV remains reduced throughout the postoperative periods, the LF/HF ratio, i.e., sympathovagal balance is altered, in favor of parasympathetic side early after surgery, but towards the sympathetic side after the first postoperative month.

AB0306 Tocilizumab therapy resulted in significantly increased heart rate variability and improved lipid profile in patients with rheumatoid arthritis

BackgroundInflammation plays a crucial role in rheumatoid arthritis (RA) pathogenesis. Tocilizumab (TCZ) is effective therapy in RA. One of the leading causes of death in RA is cardiovascular events (CVE)....

Cardiac autonomic control in Brugada syndrome patients during sleep: the effects of sleep disordered breathing.

Brugada syndrome is characterized by typical ECG features, ventricular arrhythmias and sudden cardiac death (SCD), more frequent during nighttime. Autonomic cardiovascular control has been implicated in triggering the ventricular arrhythmias. Sleep-disordered breathing (SDB) elicits marked autonomic changes during sleep and is also associated with an increased risk of nighttime SCD. Brugada patients may have a higher likelihood of SDB compared to controls. However, no data are available on cardiac autonomic control in Brugada patients, particularly with regard to the comorbidity of SDB. We evaluated autonomic cardiovascular control in Brugada patients with SDB (BRU-SDB, n=9), without SDB (BRU, n=9), in controls (CON, n=8) and in non-Brugada patients with SDB (n=6), during wakefulness and sleep (N2, N3 and REM). Linear spectral and entropy-derived measures of heart rate variability (HRV) were performed during apnea-free stable breathing epochs. Total HRV was attenuated in BRU-SDB compared to CON and BRU. During N2 and REM, in BRU-SDB patients sympathetic modulation decreased compared to BRU and CON, while during REM, they showed an increased parasympathetic modulation, compared to the other two groups. BRU-SDB and SDB were similar in terms of spectral components. Entropy-derived indices showed preserved dynamic changes in Brugada patients compared to controls through the different sleep stages. Brugada syndrome per se does not appear associated with an altered autonomic cardiovascular control during wakefulness and sleep. The comorbidity with SDB may contribute to disrupted autonomic cardiovascular regulation during sleep, possibly predisposing to the increased likelihood of sleep-related ventricular tachyarrhythmias and SCD.

Patent ductus arteriosus in preterm infants is associated with cardiac autonomic alteration and predominant parasympathetic stimulation

BackgroundHemodynamic disorders in patent ductus arteriosus (PDA) may alter the stimulation of the autonomic nervous system. AimThe objective of this study was to analyze the orthosympathetic–parasympathetic balance in preterm infants with PDA. Study design and subjectsPatients were included from consecutive admissions to Amiens University Hospital from 2009 to 2011. We defined a PDA group and a Control group (echographic criteria). For each patient, three 4-minutes segments of ECG were recorded during quiet sleep and the RR chronologic series were extracted, and spectral (Fourier Transform) and time-domain analyses were performed. For each parameter of heart rate variability (HRV), average of three measures was determined and analysed. ResultsForty-four patients were included for analysis. The total HRV power, LF/HF ratio and SDNN were lower in the PDA group (n=22, gestational age 28.2 w±1.9) than in the Control group (n=22, gestational age 28.8 w±2). The decrease in LF power destabilized the autonomic balance in favour of parasympathetic stimulation. After adjustment for postconceptional age, PDA was still associated with parameters of autonomic neural stimulation. ConclusionThese results suggest association of PDA with predominance of parasympathetic stimulation in preterm infants. The mechanisms of homeostasis in patients with PDA are very complex and involve both circulatory adaptations and control by autonomic pathway. If confirmed, our results could be interesting for future researches aiming to verify the interest of new targeted therapies for the management of PDA.

Autonomic effects of suggestive placebo interventions to increase or decrease blood pressure: A randomized controlled trial in healthy subjects

ObjectivePlacebo effects on pain and other subjective parameters are well-established, but the evidence for placebo effects on autonomic functions is scarce. Our randomized-controlled trial aimed to investigate autonomic responses after a suggestive placebo intervention intended to increase or decrease blood pressure (BP). Methods92 healthy subjects inhaled a placebo spray with the prior suggestion that it contained an effective drug to either increase or decrease BP, or the information that a placebo was administered (controls). BP, heart rate, stroke volume, peripheral resistance, heart rate variability and skin conductance level were monitored 30min before and after placebo administration. The expected and the subjectively perceived drug effect were measured by means of visual analog scales. ResultsWe found no statistically significant differences between the groups with respect to BP, heart rate, stroke volume, total peripheral resistance and heart rate variability responses to the verbal suggestions. Skin conductance response was more pronounced in the BP decrease group compared with controls (p=0.04), but this finding might be due to chance, given the multiple tests. Within the total study sample, BP, total peripheral resistance, low frequency power of heart rate variability and skin conductance were significantly higher after the placebo spray independent of the associated suggestions. Subjects in the BP increase and BP decrease condition had higher ratings of the expected and the subjectively perceived drug effect compared with controls (all p<0.05). ConclusionWe found no evidence that specific verbal suggestions during placebo interventions affect BP in healthy subjects.

Influence of Running Stride Frequency in Heart Rate Variability Analysis During Treadmill Exercise Testing

The analysis and interpretation of heart rate variability (HRV) during exercise is challenging not only because of the nonstationary nature of exercise, the time-varying mean heart rate, and the fact that respiratory frequency exceeds 0.4 Hz, but there are also other factors, such as the component centered at the pedaling frequency observed in maximal cycling tests, which may confuse the interpretation of HRV analysis. The objectives of this study are to test the hypothesis that a component centered at the running stride frequency (SF) appears in the HRV of subjects during maximal treadmill exercise testing, and to study its influence in the interpretation of the low-frequency (LF) and high-frequency (HF) components of HRV during exercise. The HRV of 23 subjects during maximal treadmill exercise testing is analyzed. The instantaneous power of different HRV components is computed from the smoothed pseudo-Wigner-Ville distribution of the modulating signal assumed to carry information from the autonomic nervous system, which is estimated based on the time-varying integral pulse frequency modulation model. Besides the LF and HF components, the appearance is revealed of a component centered at the running SF as well as its aliases. The power associated with the SF component and its aliases represents 22±7% (median±median absolute deviation) of the total HRV power in all the subjects. Normalized LF power decreases as the exercise intensity increases, while normalized HF power increases. The power associated with the SF does not change significantly with exercise intensity. Consideration of the running SF component and its aliases is very important in HRV analysis since stride frequency aliases may overlap with LF and HF components.

The Influence of New Colored Light Stimulation Methods on Heart Rate Variability, Temperature, and Well-Being: Results of a Pilot Study in Humans

Changes of light intensity of different colors can shift many physiological parameters and conditions like melatonin, alertness, body temperature, heart rate (HR), and heart rate variability (HRV). The aim of this pilot study was to investigate acute temperature, HR, HRV, and state of mind reactivities after illumination with red (631 nm) and blue (456 nm) light (illuminance 140 lux for both). Seven healthy volunteers (5 females, 2 males; mean age ± SD 34.1 ± 11.9 years) were investigated at the Medical University of Graz, using new color light panels. Significant decreases were found only after 10 min blue light stimulation in nose temperature (P = 0.046), HR (P < 0.05), and total HRV (P = 0.029), in association with a significant alteration of the emotional state (stress level score, P = 0.006). However, red light stimulation of the same persons did not induce the same effects in these parameters. The effect of blue light as environmental stimulation on human health is not clarified in detail and needs further investigations.

Effect of biofeedback training on operator's cognitive performance

Predominantly cognitive tasks assigned to the shop floor can lead to decreased cognitive functions problems, thereby increasing occupational accident risks. A potential approach to prevent such circumstances is by improving operator's cognitive performance. This study aimed to examine whether heart rate variability (HRV) biofeedback training could improve cognitive performance among electronic manufacturing's operators. Subjects consisted of 36 female operators who were randomly assigned as the experimental (n=19), and control group (n=17). The experimental participants received five session of weekly HRV biofeedback training of 30-50 minutes each. Physiological stress profiles and cognitive performance were assessed at pre and post-intervention. Significant group x time effects were observed for attention and memory (p< 0.01) but not present for cognitive flexibility. Significant higher total spectrum HRV and low frequency (LF) power also occurred during biofeedback sessions, in addition to slower respiration rate. Physiological stress profile showed that the biofeedback participants were able to increase their LF activity at baseline, stressor, and recovery periods from pre to post. This study demonstrates potential application of HRV biofeedback for operator's performance enhancement, associated with increases in HRV.

Ear acupressure, heart rate, and heart rate variability in patients with insomnia.

This high-tech “teleacupuncture study” describes a neurovegetative ear acupressure effect in patients with chronic insomnia by using heart rate variability analysis. Heart rate (HR) and heart rate variability (HRV) measurements in 31 patients (mean age ± SD: 54.3 ± 10.6 years) were performed under standardized conditions in Harbin, China, and the data analysis was performed in Graz, Austria. Similar to our previous clinical and basic teleacupuncture research works, the electrocardiograms (ECGs) were recorded by an HRV Medilog AR12 system during ear acupressure of the Shenmen point on the left ear. HR decreased significantly (P < 0.05) during and after acupressure stimulation. The effect was not visible after the first stimulation, rather it appeared in the phase following the second acupressure stimulation (10 min after the first stimulation). Total HRV showed significant stimulation-dependent increases (P < 0.05), immediately after each acupressure stimulation with a maximum after the third stimulation (20 min after the first stimulation), but there was no long-lasting effect. The present results can serve as a solid basis for the further investigations of auricular point stimulation for noninvasive complementary use in treating insomnia.

Laser Acupuncture: Two Acupoints (Baihui, Neiguan) and Two Modalities of Laser (658 nm, 405 nm) Induce Different Effects in Neurovegetative Parameters.

There are only few scientific publications dealing with the basic investigation of the effects of only one or two acupoints or comparing one single point with another single point, using different stimulation methods in the same persons. The aim of this needle-controlled, randomized crossover study was to investigate the neurovegetative parameters heart rate (HR) and heart rate variability (HRV) using two different acupoints, Baihui (GV20) and Neiguan (PC6), in separate sessions. We investigated 11 healthy volunteers (3 m, 8 f) with a mean age ± SD of 22.9 ± 2.8 years. The two acupoints were stimulated for 10 minutes each with manual needle acupuncture, red laser acupuncture (658 nm), and violet laser acupuncture (405 nm), in randomized order. Needle and red laser stimulation of the Baihui acupoint decreased HR significantly. Only violet laser stimulation at the Neiguan acupoint induced a significant increase of total HRV. Further studies using other neurovegetative parameters and more volunteers are necessary to confirm the preliminary results.

Relations between combined oral contraceptive therapy and indices of autonomic balance (baroreflex sensitivity and heart rate variability) in young healthy women

There are structural and functional links between autonomic nervous and endocrine systems. Derivatives of estrogens and gestagens applied in combined oral contraceptives (COC) reduce the production of endogenous sex steroids, but their effect on autonomic nervous system remains unknown. To compare indices of heart rate variability (HRV) and baroreflex sensitivity (BRS) among young healthy women taking vs. non-taking COC. We performed a cross-sectional study in a group of 53 healthy women (age: 23 +/- 3 years, BMI: 22.3 +/- 2.8 kg/m(2)) taking COC for > or = 3 months (COC-group) and in a group of 113 healthy women (age: 24 +/- 4 years, BMI: 22.0 +/- 3.1 kg/m(2)) not taking COC for > or = 3 months (n-COC-group). All examined women were between the 4th and the 8th day of menstrual (or pill-driven) cycle lasting from 21 to 35 days. Indices of autonomic balance was assessed based on the time- and frequency- domains of heart rate variability (HRV very low (VLF), low (LF), high (HF) frequencies and total HRV spectrum). BRS was evaluated using the sequence (BRS-Seq) and the controlled breathing (BRS-CtBr) methods. There were no differences in: age, weight, height, measures of adiposity and fat distribution, the menstrual (or pill-driven) cycle day on the day of examination, heart rate and HRV parameters between the two studied groups (all p > 0.1). BRS-CtBr was higher among n-COC-group as compared to COC-group (20.00 +/- 6.28 versus 18.07 +/- 6.57 ms/mmHg, p < 0.05). There was a trend towards higher BRS-Seq in the n-COC-group as compared to the COC-group (19.4 7 +/- 7.85 versus 16.95 +/- 5.76 ms/mmHg, p = 0.12). In the n-COC-group, BRS-CtBr and RMSSD were inversely related to age (r = -0.23, r = -0.19, p < 0.05). In the COC-group, SDNN was inversely related to waist circumference and WHR (respectively r = -0.34 and r = -0.35, both p < 0.05). COC impair the reflex regulation of cardiovascular system based on baroreflex, which may indicate unfavorable influence of COC use on women health. The exact mechanism of BRS impairment caused by COC remains unknown, also in the context of the different composition of various COC. Thus, it needs to be studied further

Intravenous Laser Blood Irradiation, Interstitial Laser Acupuncture, and Electroacupuncture in an Animal Experimental Setting: Preliminary Results from Heart Rate Variability and Electrocorticographic Recordings

This is the first study to investigate intravenous (i.v.) laser blood irradiation, interstitial (i.st.) laser acupuncture, and electroacupuncture (EA) in combination with heart rate variability (HRV) and electrocorticogram. We investigated 10 male anesthetized Sprague-Dawley rats under the three conditions mentioned previously in Beijing, China, and data analysis was performed in Graz, Europe. For i.v. laser stimulation in the femoral vein and i.st. laser acupuncture at Neiguan (PC6), we used a European system (Modulas needle, Schwa-Medico, Germany; 658 nm, 50 mW, continuous wave mode), and for EA at Neiguan, a Chinese system (Hanshi-100A; Nanjing Jisheng Medical Technology Company, China; 15 Hz, 1 mA). HR, HRV, and electrocorticogram were recorded using a biophysical amplifier AVB-10 (Nihon-Kohden, Japan). HR changed significantly during i.st. laser acupuncture stimulation of Neiguan in anesthetized rats. Total HRV increased insignificantly during i.v. and i.st. laser stimulation. The LF/HF ratio showed significant changes only during i.v. laser blood irradiation. Integrated cortical EEG (electrocorticogram) decreased insignificantly during EA and i.v. laser blood irradiation. Further studies concerning dosage-dependent alterations are in progress.

Neuropeptide Y polymorphism increases the risk for asthma in overweight subjects; protection from atherosclerosis in asthmatic subjects – The cardiovascular risk in young Finns study

AimsThe role of neuropeptide Y (NPY) and its gene polymorphisms in the development of atherosclerosis has become increasingly evident. In asthma, NPY has been shown to be involved as immunomodulator. In this study, we investigated the role of two functional NPY polymorphisms, NPY-Leu7Pro (rs16139) and NPY-399C/T (rs16147) and obesity for the development of asthma as well as atherosclerosis in asthmatic and non-asthmatic subjects. Also, we measured heart rate variability (HRV) and NPY in serum since these might contribute through these polymorphisms to both diseases. Methods and resultsThousand hundred and seventy six Finnish young adults were genotyped and three groups (G1–G3) were formed based on the observed diplotypes. The NPY-Pro7 allele always co-existed with the NPY-399T allele indicating complete linkage disequilibrium. Here we show that overweight (BMI⩾25kg/m2) was associated with 2.5-fold increased risk for asthma in subjects with the NPY-399T allele without NPY-Pro7 allele (G2, n=716). Overweight was also associated with increased atherosclerosis determined by carotid intima media thickness (cIMT), but asthma seemed to be more significant determinant than overweight in determing cIMT having a decreasing effect. NPY concentration in serum was diplotype-driven (G1=792.2(29.5), G2=849.0(18.9), G3=873.9(45.2) pg/ml) and correlated positively with cIMT in the group having NPY-Pro7 allele (G3, n=142). However, the subjects with asthma had a negative NPY-cIMT relationship. Total HRV was increased in asthma and correlated negatively with cIMT irrespective of the NPY genotype. ConclusionsOverweight together with the NPY-399T allele without NPY-Pro7 allele was associated with increased risk for asthma. Atherosclerosis was decreased in subjects with asthma depending on the NPY genotype. The results reveal novel insights into the genetics and biology of the relationship of atherosclerosis and asthma.

941 Autonomic Dysfunction in Infants with RSV Infection

BackgroundApnea can be a presenting symptom in respiratory Synctial Virus (RSV) infection. The incidence of apnea in RSV infected infants varies between 16 and 25% with a particularly high risk...

The Significance of Heart Rate Turbulence in Predicting Major Cardiovascular Events in Patients after Myocardial Infarction Treated Invasively

The role of heart rate turbulence (HRT) related to baroreflex sensitivity in predicting mortality after myocardial infarction (MI) has been confirmed by several investigators. However, the significance of HRT in predicting major adverse cardiovascular events (MACE) following acute MI is unknown. To analyze the prognostic value of HRT and other independent risk factors associated with autonomic regulation of MACE. HRT was assessed based on 24-hour Holter recordings in 500 patients (pts) with acute MI treated invasively (352 M, aged 60.58 years). Turbulence onset (TO,%), slope (TS, ms/RR interval) and timing (TT) were calculated. TO ≥ 0, TS ≤ 2.5 and TT ≥ 10 were considered abnormal; classic and own categories were defined. Time domain heart rate variability (HRV) parameters were also calculated. Within 30.1 ± 15.1 months of follow-up, MACE occurred in 116 pts. Abnormal TO, TS, and TT were significantly more frequent in patients with MACE (P < 0.05 for each parameter, classic and own categories). In long-term follow-up, the largest differences in MACE were observed in patients with own category comprising abnormal TO, TS, and TT. Combining HRT parameters with SDNN (total HRV index) augmented their predictive value. Independent risk factors for MACE were TT, SDNN and rMSSD (a parasympathetic activity index) (HR 2.44, 1.71 and 1.69 respectively; P < 0.05). Abnormal HRT distinguishes patients at risk of MACE after MI. Own category encompassing three abnormal HRT parameters best differentiates patients at risk of MACE. Turbulence timing is a strong independent risk factor for MACE following MI.

Low maternal vitamin B12 status during pregnancy is associated with reduced heart rate variability indices in young children

Vitamin B12 plays a vital role in neuronal development, particularly in myelinogenesis. Demyelination of the autonomic nervous system occurs early in vitamin B12 deficiency. However, the impact of maternal vitamin B12 deficiency during pregnancy on neuronal function in the offspring is poorly documented. The objective of this study was to assess cardiac autonomic nervous activity in children born to mothers with low vitamin B12 status during pregnancy using heart rate variability (HRV) indices in the frequency domain. Seventy-nine healthy children between 3 and 8 years of age were evaluated from an ongoing birth cohort. The blood sample of the mother had been stored and was analysed for plasma vitamin B12 following enrolment of the child. Subjects were divided, based on the median maternal first trimester vitamin B12 status (114 pmol L(-1)), into lower (n = 40) and higher (n = 39) vitamin B12 status groups. A lead II electrocardiogram was recorded in the supine posture and subjected to HRV analysis. Low-frequency HRV in absolute units was reduced significantly in children of the lower vitamin B12 status group (P = 0.03) and was 53% that of the higher vitamin B12 status group. There was a significant association between low-frequency and total power HRV with cord blood vitamin B12 levels (ρ = 0.31 and 0.30, both P = 0.03). In summary, children born to mothers with a lower vitamin B12 status have a reduced cardiac sympathetic activity. The long-term implication of this needs to be evaluated by follow-up studies.

Spectral Analyses of Cardiovascular Control in Rodents with Spinal Cord Injury

The severity of injury to cardiovascular autonomic pathways following clinical spinal cord injury (SCI) can be evaluated with spectral analyses. Whether this technique provides a translatable assessment of cardiovascular autonomic function in rodent SCI is unknown. Beat-to-beat blood pressure and pulse interval were measured in male rats 1 month after complete T3 or T10 SCI, and in uninjured control animals. Univariate autoregressive spectral analyses were performed and the power of the low frequency (LF), high frequency (HF), and very low frequency (VLF) peaks identified. Frequency domain variables were correlated with the severity of orthostatic hypotension (OH) and the severity of hypertension during autonomic dysreflexia (AD). Total heart rate variability (HRV) and blood pressure variability (BPV) were reduced in animals with T3, but not T10, SCI. VLF and LF HRV were reduced and HF HRV was increased in animals with T3 SCI compared to controls; there were no changes in animals with T10 SCI. BPV in the VLF and LF range was reduced in animals with T3 SCI, but not T10 SCI. In all animals with SCI, severity of OH was positively correlated with LF BPV, and negatively correlated with HF BPV. Severity of AD was positively correlated with HF BPV and HF HRV, and negatively correlated with VLF HRV. Spectral analyses can detect alterations in cardiovascular autonomic function in animals with SCI at rest. These parameters underscore the distinct cardiovascular ramifications of high- versus low-thoracic SCI, and correlate with the severity of AD and OH, clinically-relevant measures of abnormal blood pressure control.