scholarly journals Immediate changes in cardiac autonomic tone and stroke volume during microgravity simulation using head-down tilt

2021 ◽  
Vol 65 ◽  
pp. 86-93
Author(s):  
Vishwajeet Shankhwar ◽  
Dilbag Singh ◽  
K. K. Deepak
Keyword(s):  
Stroke Volume ◽  
Blood Volume ◽  
Sympathetic Activity ◽  
Cardiovascular Responses ◽  
Significant Rise ◽  
Vagal Activity ◽  
Autonomic Tone ◽  
Cardiac Sympathetic Activity ◽  
Microgravity Simulation ◽  
Frequency Power

Objectives: Gravity plays an important role in the day-to-day functioning of the cardiovascular system (CVS) in the human body. The absence of gravity severely affects CVS functioning. Out of existing simulation models of microgravity, the 6° head-down tilt (HDT) is frequently used analog to replicate the physiological effects of microgravity on earth. Materials and Methods: The present study has been designed to determine the specificity of 6° HDT usage as a microgravity simulation. The heart rate variability (HRV), blood pressure (BP), cardiac output (CO), and stroke volume (SV) responses to 5 min exposures were investigated for 4°, 6°, and 8° HDT. It was hypothesized that the graded HDT around 6° will demonstrate reversal of autonomic parameters. The study was conducted on 28 male subjects aged 20–30 years. Results: The study reveals that there was a significant rise in diastolic and mean BP at 6° and 8° HDT as compared to baseline. It was also observed that the high-frequency power in HRV was increased at 6° HDT (P = 0.026), with a concomitant reduction in the low-frequency power (P = 0.03) of HRV. The CO was increased at 6° and 8° HDT as compared to baseline (P = 0.037 and 0.021, respectively). There were no significant changes observed in any of the recorded parameters at 4° HDT. The cardiopulmonary volume receptors might have sensed the blood volume change in HDT as in microgravity simulation the blood passively shifts to cephalad. To overcome the low blood volume problem, the heart tried to pump extra blood through increased CO. At 8° HDT, it was observed that the cardiac sympathetic activity and CO were increased, which is not observed during microgravity exposures. Conclusion: The study suggests that 6° head-down-tilt is the best tilt level for producing microgravity on earth to study immediate cardiovascular parameters as it is a balanced compromise of increased vagal activity and CO without activation of cardiac sympathetic activity. Therefore, our data provide physiological evidence in support of 6° HDT microgravity simulation for the study of immediate cardiovascular responses.

scholarly journals The prognostic significance of cardiac sympathetic activity and dyssynchrony in cardiac resynchronization therapy in ischemic and non-ischemic heart failure patients

2021 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
A Mishkina ◽  
K Zavadovsky ◽  
V Saushkin ◽  
D Lebedev ◽  
Y Lishmanov
Keyword(s):  
Heart Failure ◽  
Cardiac Resynchronization Therapy ◽  
Sympathetic Activity ◽  
Gated Spect ◽  
Prognostic Significance ◽  
Cardiac Resynchronization ◽  
Resynchronization Therapy ◽  
Cardiac Sympathetic Activity ◽  
Heart Failure Patients ◽  
Crt Response

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Russian Foundation for Basic Research Introduction Impaired cardiac sympathetic activity and contractility are associated with poor prognosis in patients with heart failure after cardiac resynchronization therapy (CRT). There are few prognostic data of the cardiac sympathetic activity and dyssynchrony in patients with chronic heart failure of various etiologies. Purpose To examine the prognostic significance of scintigraphic cardiac sympathetic activity and contractility in predicting the response to CRT and to assess the differences between patients with ischemic (IHF) and non-ischemic (NIHF) heart failure. Methods This study included 38 heart failure patients (24 male; mean age of 56 ± 11 years; 16 patients with ischemic etiology), who were submitted to CRT. Before CRT all patients underwent 123I-metaiodobenzylguanidine (123I-MIBG) imaging for cardiac sympathetic activity evaluating: early and delay heart to mediastinum ratio (eH/M and dH/M), summed MIBG Score (eSMS and dSMS). Moreover all patients underwent gated SPECT with the assessments of left ventricle dyssynchrony indexes: standard deviation (SD) and histogram bandwidth (HBW). In addition, all patients underwent gated blood-pool SPECT (GBPS) to assessed ejection fraction (EF) and stroke volume (SV) of both ventricles. Results One year after CRT response defined as LV ESV decreased by≥15% and/or LV EF increase by≥5%. Baseline cardiac sympathetic activity parameters showed significant differences between responders and non-responders only in NIHF patients: eH/M: 2.27 (2.02–2.41) vs. 1.64 (1.32–2.16); dH/M: 2.18 (2.11–2.19) vs. 1.45 (1.23 – 1.61); eSMS: 7 (5-7) vs. 15.5 (10–28.5); dSMS: 10 (10–13) vs. 16.5 (15.5–29). Significant differences in baseline LV dyssynchrony indexes between responders and non-responders were in patients of both group: in NIHF patients - SD: 54.3 (43–58) degree vs. 65 (62–66) degree; HBW: 179.5 (140–198) degree vs. 211 (208-213) degree, p < 0.054 in IHF patients - HBW: 162 (115.2–180) degree vs.  115.2 (79.2–136.8) degree. Contractility of RV was significantly differed between responders and non-responders in IHF patients: RV EF: 54.5 (41-56) % vs. 44.5 (37–49.5) %; RV SV: 80 (69-101) ml vs. 55.5 (50–72.5) ml. According to univariate logistic regression analyses in IHF patients LV dyssynchrony indexes – SD (OR = 1.55; 95% CI 1.09-2.2; p < 0.5) and HBW (OR = 1.13; 95% CI 1.02-1.24; p < 0.5), as well as RV indexes – RV EF (OR = 1.11; 95% CI 1.001-1.23; p < 0.5), RV SV (OR = 1.07; 95% CI 1.003-1.138; p < 0.5) were predictors of CRT response. In the group of NIHF patients, dH/M (OR = 1.47; 95% CI 1.08-2; p < 0.5), SD (OR = 0.83; 95% CI 0.73-0.95; p < 0.5), HBW (OR = 0.96; 95% CI 0.93-0.99; p < 0.5) showed the predictive value in terms of CRT response. Conclusion  Scintigraphic methods can be used to select patients for CRT. Cardiac 123I-MIBG scintigraphy and gated SPECT may be used for predicting CRT response in NIHF patients. Whereas in IHF patients ECG-gated SPECT and GBPS may be valuable for predicting the response to CRT.

Control of arterial pressure in aquatic sea snakes

1983 ◽  
Vol 244 (1) ◽  
pp. R66-R73 ◽  
Author(s):  
H. B. Lillywhite ◽  
F. H. Pough
Keyword(s):  
Arterial Pressure ◽  
Blood Volume ◽  
Water Pressure ◽  
Cardiovascular Responses ◽  
Physiological Regulation ◽  
Sea Snakes ◽  
Head Up Tilt ◽  
External Water Pressure ◽  
External Water ◽  
Head Level

Cardiovascular responses to head-up tilt, acutely graded hemorrhage, and pharmacologic stimulation by principal autonomic drugs were studied in four species of marine snakes, principally Aipysurus laevis (family Hydrophiidae). Arterial pressure varied inversely with tilt angle and blood volume deficit in conscious snakes outside of water, indicating that physiological regulation was poor or lacking. Calculated arterial pressures at head level typically diminished to zero in A. laevis tilted to angles greater than or equal to 30 degrees. Arterial pressure (corrected for external water pressure) did not change when these snakes were tilted in seawater. Changes of arterial pressure induced by tilt, blood loss, or autonomic drugs elicited reflex adjustments in heart activity, but the magnitude of these responses was less than that observed in terrestrial species of snake. It is concluded that baroreflexes are present but comparatively ineffective in sea snakes. Snakes tolerated large losses of blood volume, and extravascular fluids were absorbed into the circulation during hemorrhage; both hemorrhage and estimated hemodilution volumes exceeded 100% of the initial blood volume in Acalyptophis peronii. Thus, in marine snakes major fluid shifts between nonvascular and vascular compartments significantly compensate hypovolemia but, because of minor autonomic adjustments, do not result in a well-regulated arterial pressure.

Long-term hemodynamic actions of atrial natriuretic factor (99-126) in conscious sheep

1988 ◽  
Vol 254 (4) ◽  
pp. H811-H815 ◽  
Author(s):  
D. G. Parkes ◽  
J. P. Coghlan ◽  
J. G. McDougall ◽  
B. A. Scoggins
Keyword(s):  
Blood Pressure ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Blood Volume ◽  
Total Peripheral Resistance ◽  
Atrial Natriuretic Factor ◽  
Peripheral Resistance ◽  
Natriuretic Factor ◽  
Atrial Natriuretic

The hemodynamic and metabolic effects of long-term (5 day) infusion of human atrial natriuretic factor (ANF) were examined in conscious chronically instrumented sheep. Infusion of ANF at 20 micrograms/h, a rate below the threshold for an acute natriuretic effect, decreased blood pressure by 9 +/- 1 mmHg on day 5, associated with a fall in calculated total peripheral resistance. On day 1, ANF reduced cardiac output, stroke volume, and blood volume, effects that were associated with an increase in heart rate and calculated total peripheral resistance and a small decrease in blood pressure. On days 4 and 5 there was a small increase in urine volume and sodium excretion. On day 5 an increase in water intake and body weight was observed. No change was seen in plasma concentrations of renin, arginine vasopressin, glucose, adrenocorticotropic hormone, or protein. This study suggests that the short-term hypotensive effect of ANF results from a reduction in cardiac output associated with a fall in both stroke volume and effective blood volume. However, after 5 days of infusion, ANF lowers blood pressure via a reduction in total peripheral resistance.

Plasma catecholamines, heart rate, and cardiac sympathetic activity in exercising dogs

1982 ◽  
Vol 14 (4) ◽  
pp. 281-285 ◽  
Author(s):  
FRANÇOIS PÉRONNET ◽  
RÉGINALD NADEAU ◽  
JACQUES de CHAMPLAIN ◽  
CLAUDE CHARTRAND
Keyword(s):  
Heart Rate ◽  
Sympathetic Activity ◽  
Plasma Catecholamines ◽  
Cardiac Sympathetic Activity

Differential contribution of central command to the cardiovascular responses during static exercise of ankle dorsal and plantar flexion in humans

2011 ◽  
Vol 110 (3) ◽  
pp. 670-680 ◽  
Author(s):  
Nan Liang ◽  
Tomoko Nakamoto ◽  
Seina Mochizuki ◽  
Kanji Matsukawa
Keyword(s):  
Stroke Volume ◽  
Total Peripheral Resistance ◽  
Plantar Flexion ◽  
Peripheral Resistance ◽  
Cardiovascular Responses ◽  
Central Command ◽  
Static Exercise ◽  
Maximum Increase ◽  
Arterial Blood ◽  
Differential Contribution

To examine whether central command contributes differently to the cardiovascular responses during voluntary static exercise engaged by different muscle groups, we encouraged healthy subjects to perform voluntary and electrically evoked involuntary static exercise of ankle dorsal and plantar flexion. Each exercise was conducted with 25% of the maximum voluntary force of the right ankle dorsal and plantar flexion, respectively, for 2 min. Heart rate (HR) and mean arterial blood pressure (MAP) were recorded, and stroke volume, cardiac output (CO), and total peripheral resistance were calculated. With voluntary exercise, HR, MAP, and CO significantly increased during dorsal flexion (the maximum increase, HR: 12 ± 2.3 beats/min; MAP: 14 ± 2.0 mmHg; CO: 1 ± 0.2 l/min), whereas only MAP increased during plantar flexion (the maximum increase, 6 ± 2.0 mmHg). Stroke volume and total peripheral resistance were unchanged throughout the two kinds of voluntary static exercise. With involuntary exercise, there were no significant changes in all cardiovascular variables, irrespective of dorsal or plantar flexion. Furthermore, before the force onset of voluntary static exercise, HR and MAP started to increase without muscle contraction, whereas they had no significant changes with involuntary exercise at the moment. The present findings indicate that differential contribution of central command is responsible for the different cardiovascular responses to static exercise, depending on the strength of central control of the contracting muscle.

scholarly journals Artifact Elimination in Impedance Cardiography using Gradient based Adaptive Signal Enhancement Techniques

2019 ◽  
Vol 8 (2) ◽  
pp. 598-606
Keyword(s):  
Stroke Volume ◽  
Blood Volume ◽  
Impedance Cardiography ◽  
Signal Enhancement ◽  
The Body ◽  
Body Segment ◽  
Volume Changes ◽  
The Real ◽  
Adaptive Techniques ◽  
Adaptive Signal

Impedance Cardiography (ICG) is a noninvasive method for indirect measurement of stroke volume, monitoring the cardiac output and observing the other hemodynamic parameters by the blood volume changes in the body. The blood volume changes inside a certain body segment due to a number of physiological processes are extracted in the form of the impedance variations of the body segment. The ICG analysis provides the heart stroke volume in sudden cardiac arrest. In the clinical environment desired ICG signals are influenced by several physiological and non-physiological artifacts.As these artifacts are not stationary in nature, we proposed adaptive filtering techniques to eliminate the artifacts. In this paper we used Least Mean Square (LMS), Least Mean Fourth (LMF), Median LMS (MLMS), Leaky LMS (LLMS), and Dead Zone (DZLMS) adaptive techniques to eliminate artifacts from the desired signals. Several adaptive signal enhancement units (ASEUs) are developed based on these adaptive techniques, and evaluated on the real ICG signal components. The ability of these algorithms is evaluated by performing the experiments to eliminate the various artifacts such as sinusoidal artifacts (SA), respiration artifacts (RA), muscle artifacts (MA) and electrode artifacts (EA). Among these techniques, the DZLMS based ASEU performs better in the filtering process. The signal to noise ratio improvement (SNRI) for this algorithm is calculated as 11.9140 dB, 7.3657 dB, 10.4060 dB and 10.5125 dB respectively for SA, RA, MA and EA. Hence, the DZLMS based ASEUs are well suitable for ICG filtering in the real time health care monitoring systems.

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