Heart rate variability after complete autonomic blockade in man

Jokkel, Gabor; Bonyhay, Istvan; Kollai, Márk

doi:10.1016/0165-1838(95)80010-8

Cited by 69 publications

(41 citation statements)

References 13 publications

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“…A profound decrease in sympathetic tone was noted for control rats at T b 25°C, which was attenuated in CA rats, implying better preservation of autonomic control on acute cooling, as also indicated by the relatively preserved LF/HF ratio for CA vs control rats. Although LF/HF is readily accepted as a measure of sympathovagal balance, we do acknowledge that under different physiological conditions vagal modulation could significantly alter LF (Fazan et al, 2005;Jokkel et al, 1995;Chapleau and Sabharwal, 2011). However, in this study the changes in LF/HF are primarily the result of a reduction in T b , as on rewarming the ratio of LF/HF was returned to pre-cooling levels; this is further supported by blood pressure variability estimates showing similar restoration.…”

Section: Effects Of Casupporting

confidence: 52%

Cold-impaired cardiac performance in rats is only partially overcome by cold acclimation

Hui‐Kang

May

Sabharwal

et al. 2011

Journal of Experimental Biology

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SUMMARYThe consequences of acute hypothermia include impaired cardiovascular performance, ultimately leading to circulatory collapse. We examined the extent to which this results from intrinsic limitations to cardiac performance or physiological dysregulation/autonomic imbalance, and whether chronic cold exposure could ameliorate the impaired function. Wistar rats were held at a 12h:12h light:dark (L:D) photoperiod and room temperature (21°C; euthermic controls), or exposed to a simulated onset of winter in an environmental chamber by progressive acclimation to 1h:23h L:D and 4°C over 4 weeks. In vivo, acute cold exposure (core temperature, T b 25°C) resulted in hypotension (approximately -20%) due to low cardiac output (approximately -30%) accompanying a bradycardia (approximately -50%). Cold acclimation (CA) induced only partial compensation for this challenge, including increased coronary flow at T b 37°C (but not at T b 25°C), maintenance of ventricular capillarity and altered sympathovagal balance (increased low:high frequency in power spectral analysis, PSA), suggesting physiological responses alone were insufficient to maintain cardiovascular performance. However, PSA showed maintenance of cardiorespiratory coupling on acute cold exposure in both groups. Ex vivo cardiac performance revealed no change in intrinsic heart rate, but a mechanical impairment of cardiac function at low temperatures following CA. While CA involved an increased capacity for -oxidation, there was a paradoxical reduction in developed pressure as a result of adrenergic down-regulation. These data suggest that integrated plasticity is the key to cardiovascular accommodation of chronic exposure to a cold environment, but with the potential for improvement by intervention, for example with agents such as non-catecholamine inotropes. Supplementary material available online at

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Section: Effects Of Casupporting

confidence: 52%

Cold-impaired cardiac performance in rats is only partially overcome by cold acclimation

Hui‐Kang

May

Sabharwal

et al. 2011

Journal of Experimental Biology

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“…10 Other studies agree that LFP partly represents parasympathetic activity, suggesting it to be due to oscillations of the vagal outflow generated by the baroreceptor reflex, driven by sympathetically induced blood pressure low-frequency waves. 15 When comparing C1-C8, T1-T5 and T6-T12 patients, we found LFP was lower for C1-T5 lesions in all the recordings. This could be due to interruption of spinal pathways conveying supraspinal signals, and thus emphasise that sympathetic activity, either directly or through alterations in the sympathovagal balance, is important in the interpretation of LFP.…”

Section: Frequency Domain Analysismentioning

confidence: 81%

Assessment of autonomic function after acute spinal cord injury using heart rate variability analyses

et al. 2014

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Objectives: Spinal cord injury (SCI) often results in severe dysfunction of the autonomic nervous system. C1-C8 SCI affects the supraspinal control to the heart, T1-T5 SCI affects the spinal sympathetic outflow to the heart, and T6-T12 SCI leaves sympathetic control to the heart intact. Heart rate variability (HRV) analysis can serve as a surrogate measure of autonomic regulation. The aim of this study was to investigate changes in HRV patterns and alterations in patients with acute traumatic SCI. Methods: As soon as possible after SCI patients who met the inclusion criteria had 24 h Holter monitoring of their cardiac rhythm, additional Holter monitoring were performed 1, 2, 3 and 4 weeks after SCI. Results: Fifty SCI patients were included. A significant increase in standard deviation of the average normal-to-normal (SDANN) sinus intervals was seen in the first month after injury (P = 0.008). The increase was only significant in C1-T5 incomplete patients and in patients who did not experience one or more episodes of cardiac arrest. Significant lower values of Low Frequency Power, Total Power and the Low Frequency over High Frequency ratio were seen in the C1-T5 SCI patients compared with T6-T12 SCI patients. Conclusions: The rise in SDANN in the incomplete C1-T5 patients could be due to spontaneous functional recovery caused by synaptic plasticity or remodelling of damaged axons. That the autonomic nervous system function differs between C1-C8, T1-T5 and T6-T12 patients suggest that the sympathovagal balance in both the C1-C8 and T1-T5 SCI patients has yet to be reached. INTRODUCTIONSpinal cord injury (SCI) patients with tetraplegia and high level paraplegia are known to suffer from dysfunction of the autonomic nervous system (ANS) including the autonomic regulation of the heart. 1 The severity and the neurological level of the SCI have major impact on ANS function. 2 Patients with SCI above T1 often have intact efferent vagal and sympathetic neural pathways innervating the heart. However, they are deprived of the supraspinal control causing reduced sympathetic activity below the level of SCI. Furthermore, the loss of supraspinal control causes morphological changes in sympathetic preganglionic neurons and peripheral alpha-adrenoceptor hyperresponsiveness. 1 Patients with T1-T5 SCI lose cardiac sympathetic preganglionic neurons as the injury occurs corresponding to the sympathetic outflow to the heart, and likewise the postganglionic sympathetic innervation to the heart undergoes plastic changes. 3 Individuals with SCI at T6 and below have intact cardiac spinal sympathetic neurons and intact innervation of the heart.In tetraplegic individuals with complete lesions, the disconnection of the spinal sympathetic neurons from cerebral control represents a unique possibility for analysis of the sympathetic influence on the heart rate (HR) variability (HRV).

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“…Finally, PEP shows more specificity in response to autonomic blockade than the LF/HF ratio. Acute b-adrenergic blockade does not give rise to the expected reduction in LF power (Pagani et al, 1986) and may even cause an increase in LF power (Jokkel, Bonyhay, & Kollai, 1995) whereas cholinergic blockade by atropine causes a substantial reduction or even elimination of LF fluctuations (Akselrod et al, 1981;Jokkel et al, 1995). In contrast, acute 1088…”

Section: Discussionmentioning

confidence: 94%

Comparing low frequency heart rate variability and preejection period: Two sides of a different coin

et al. 2008

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It has been hypothesized that the ratio of heart rate variability in the low-(LF) and high-(HF) frequency bands may capture variation in cardiac sympathetic control. Here we tested the temporal stability of the LF/HF ratio in 24-h ambulatory recordings and compared this ratio to the preejection period (PEP), an established measure of cardiac sympathetic control. Good temporal stability was found across a period of 3.3 years (.46oro.78), but the LF/HF ratio did not show the expected negative correlation to PEP, either between or within subjects. We conclude that the evidence to support the LF/HF ratio as a potential marker of cardiac sympathetic control in epidemiology-scaled research is currently insufficient.

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Heart rate variability after complete autonomic blockade in man

Cited by 69 publications

References 13 publications

Cold-impaired cardiac performance in rats is only partially overcome by cold acclimation

Cold-impaired cardiac performance in rats is only partially overcome by cold acclimation

Assessment of autonomic function after acute spinal cord injury using heart rate variability analyses

Comparing low frequency heart rate variability and preejection period: Two sides of a different coin

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