Impedance cardiography: Recent advancements

Effects of canagliflozin on cardiac remodeling and hemodynamic parameters in patients with type 2 diabetes mellitus

Sodium-glucose cotransporter type 2 (SGLT2) inhibitors have demonstrated to reduce cardiovascular risk in patients with type 2 diabetes mellitus (T2DM) in large trials independent of glycemic control. The mechanisms of this cardioprotective property remain uncertain. Evidence suggests positive hemodynamic changes and favorable cardiac remodeling contributing to the clinical outcomes but results were conflicting. We aim to investigate the potential impact on hemodynamic parameters, cardiac structure and functions. This prospective observational study included T2DM patients receiving canagliflozin 100 mg per day in addition to their antidiabetic treatment. We analyzed hemodynamic parameters assessed by echocardiographic measurements and impedance cardiography (ICG) to evaluate systolic and diastolic functions from baseline to 24 weeks after treatment. A total of 47 patients (25 males and 22 females) averaging 64.6 ± 10.9 years had a significant reduction in HbA1c, body weight, and systolic blood pressure. Hematocrit increased significantly, while NT-proBNP remained unchanged. E/e', left atrium (LA) volume, and LA stiffness were reduced, while left ventricle (LV) global longitudinal strain (GLS) and LA strain rates increased at 24 weeks by conventional and speckle tracking echocardiography. LV mass and ejection fraction showed no differences. ICG suggested significant improvement in hemodynamic parameters with increased stroke volume index and cardiac output index and decreased systemic vascular resistance index at 12 and 24 weeks. Canagliflozin improved hemodynamic parameters and had a favorable impact on LA and LV reverse remodeling. These changes may explain the beneficial effect on cardiovascular outcomes in large clinical trials.

Determination using impedance cardiograph of the chronic effects of different doses of radiotherapy on the cardiovascular system of rats

AIM

Cardiac damage caused by radiation in the long term varies according to the radiation dose received by the heart. In this study, it was aimed to evaluate the damage caused by different radiation doses in the heart, together with hemodynamic parameters, immunhistochemistry, and histopathological analyzes for long term.

METHOD AND MATERIALS

The animals were divided into four groups: The rats in control group (Group 1) were not irradiated; the rats in group 2 were irradiated with 5 Gy; the rats in group 3 were irradiated with 10 Gy and the rats in group 4 were irradiated with 20 Gy. Hemodynamic parameters and indices were determined from the impedance cardiography (ICG) recording in the whole groups before they were irradiated with RT and 180 days after RT. And then, interleukin-1β, interleukin-10, TNF-α, apopthosis were determined in all groups. In addition, histological changes of heart and aorta were evaluated.

RESULTS

Histopathologic, cytokine and hemodynamic findings supported that cardiac damage increased with increasing radiation dose.

CONCLUSION

it is important in terms of being an alternative and supportive method to other methods to be able to detect heart diseases caused by RT with the ICG method.

Wearable and Noninvasive Device for Integral Congestive Heart Failure Management in the IoMT Paradigm

Noninvasive remote monitoring of hemodynamic variables is essential in optimizing treatment opportunities and predicting rehospitalization in patients with congestive heart failure. The objective of this study is to develop a wearable bioimpedance-based device, which can provide continuous measurement of cardiac output and stroke volume, as well as other physiological parameters for a greater prognosis and prevention of congestive heart failure. The bioimpedance system, which is based on a robust and cost-effective measuring principle, was implemented in a CMOS application specific integrated circuit, and operates as the analog front-end of the device, which has been provided with a radio-frequency section for wireless communication. The operating parameters of the proposed wearable device are remotely configured through a graphical user interface to measure the magnitude and the phase of complex impedances over a bandwidth of 1 kHz to 1 MHz. As a result of this study, a cardiac activity monitor was implemented, and its accuracy was evaluated in 33 patients with different heart diseases, ages, and genders. The proposed device was compared with a well-established technique such as Doppler echocardiography, and the results showed that the two instruments are clinically equivalent.

A New Method of Identifying Characteristic Points in the Impedance Cardiography Signal Based on Empirical Mode Decomposition

The accurate detection of fiducial points in the impedance cardiography signal (ICG) has a decisive impact on the proper estimation of diagnostic parameters such as stroke volume or cardiac output. It is, therefore, necessary to find an algorithm that is able to assess their positions with great precision. The solution to this problem is, however, quite challenging with regard to the high sensitivity of the ICG technique to the noise and varying morphology of the acquired signals. The aim of this study is to propose a novel method that allows us to overcome these limitations. The developed algorithm is based on Empirical Mode Decomposition (EMD)-an effective technique for processing and analyzing various types of non-stationary signals. We find high correlations between the results obtained from the algorithm and annotated by an expert. This, in turn, implies that the difference in estimation of the diagnostic-relevant parameters is small, which suggests that the method can automatically provide precise clinical information.

The Lack of Systemic and Subclinical Side Effects of Botulinum Neurotoxin Type-A in Patients Affected by Post-Stroke Spasticity: A Longitudinal Cohort Study

Botulinum Neurotoxin type-A (BoNT-A) is the treatment of choice for focal post-stroke spasticity (PSS). Due to its mechanism of action and the administration method, some authors raised concern about its possible systemic diffusion leading to contralateral muscle weakness and autonomic nervous system (ANS) alterations. Stroke itself is a cause of motor disability and ANS impairment; therefore, it is mandatory to prevent any source of additional loss of strength and adjunctive ANS disturbance. We enrolled 15 hemiparetic stroke survivors affected by PSS already addressed to BoNT-A treatment. Contralateral handgrip strength and ANS parameters, such as heart rate variability, impedance cardiography values, and respiratory sinus arrythmia, were measured 24 h before (T0) and 10 days after (T1) the ultrasound (US)-guided BoNT-A injection. At T1, neither strength loss nor modification of the basal ANS patterns were found. These findings support recent literature about the safety profile of BoNT-A, endorsing the importance of the US guide for a precise targeting and the sparing of “critical” structures as vessels and nerves.

Signal processing techniques applied to impedance cardiography ICG signals - a review

Over the last decade, Computer-Aided Diagnosis (CAD) systems have been provided significant research focus by researchers. CAD systems have been developed in order to minimise visual errors, to compensate manual interpretation, and to help medical staff to take decisions swiftly. These systems have been considered as powerful tools for a reliable, automatic, and low-cost monitoring and diagnosis. CAD systems are based on analysis and classification of several physiological signals for detecting and assessing different diseases related to the corresponding organ. The implementation of these systems requires the application of several advanced signal processing techniques. Specifically, in cardiology, CAD systems have achieved promising results in providing an accurate and rapid detection of cardiovascular diseases (CVDs). Particularly, the number of works on signal processing field for impedance cardiography (ICG) signals starts to grow slowly in recent years. This paper presents a review study of signal processing techniques applied to the ICG signal for the denoising, the analysis, the classification and the characterisation purposes. This review is intended to provide researchers with a broad overview of the currently used signal processing techniques for ICG signal analysis, as well as to improve future research by applying other recent advanced methods.

Recent Academic Research on Clinically Relevant Digital Measures: Systematic Review

Background

Digital clinical measures collected via various digital sensing technologies such as smartphones, smartwatches, wearables, ingestibles, and implantables are increasingly used by individuals and clinicians to capture health outcomes or behavioral and physiological characteristics of individuals. Although academia is taking an active role in evaluating digital sensing products, academic contributions to advancing the safe, effective, ethical, and equitable use of digital clinical measures are poorly characterized.

Objective

We performed a systematic review to characterize the nature of academic research on digital clinical measures and to compare and contrast the types of sensors used and the sources of funding support for specific subareas of this research.

Methods

We conducted a PubMed search using a range of search terms to retrieve peer-reviewed articles reporting US-led academic research on digital clinical measures between January 2019 and February 2021. We screened each publication against specific inclusion and exclusion criteria. We then identified and categorized research studies based on the types of academic research, sensors used, and funding sources. Finally, we compared and contrasted the funding support for these specific subareas of research and sensor types.

Results

The search retrieved 4240 articles of interest. Following the screening, 295 articles remained for data extraction and categorization. The top five research subareas included operations research (research analysis; n=225, 76%), analytical validation (n=173, 59%), usability and utility (data visualization; n=123, 42%), verification (n=93, 32%), and clinical validation (n=83, 28%). The three most underrepresented areas of research into digital clinical measures were ethics (n=0, 0%), security (n=1, 0.5%), and data rights and governance (n=1, 0.5%). Movement and activity trackers were the most commonly studied sensor type, and physiological (mechanical) sensors were the least frequently studied. We found that government agencies are providing the most funding for research on digital clinical measures (n=192, 65%), followed by independent foundations (n=109, 37%) and industries (n=56, 19%), with the remaining 12% (n=36) of these studies completely unfunded.

Conclusions

Specific subareas of academic research related to digital clinical measures are not keeping pace with the rapid expansion and adoption of digital sensing products. An integrated and coordinated effort is required across academia, academic partners, and academic funders to establish the field of digital clinical measures as an evidence-based field worthy of our trust.

Assessing Patent Ductus Arteriosus (PDA) Significance on Cardiac Output by Whole-Body Bio-impedance

We evaluated the effectiveness of a whole-body bioimpedance device (NICaS®, NI Medical, Petach Tikva, Israel) to predict the presence of a hemodynamically significant patent ductus arteriosus (PDA) in premature infants. A total of 36 infants less than 35 week's gestation age and birth weights of less than 1750 g were included in the study. Using the NICaS® device, we obtained whole-body bioimpedance measurements of stroke volume index (SI), cardiac output index (CI) and total peripheral resistance index. A total of 61 measurements were taken together with echocardiograph imaging. The study population was divided into three groups according to the echocardiograph results: group 1-small PDA, group 2-moderate PDA, and group 3-large PDA. Both SI and CI significantly increased from a median value of 22.6 ml/m² and 3.4 l/min/m² to 23.8 and 3.7, to 39.8 and 5.4 between groups 1, 2 and 3 respectively. The difference was statistically significant between groups 1 and 3 (P = 0.005 for SI and P = 0.002 for CI) and between groups 2 and 3 (P = 0.037 for SI and P = 0.05 for CI). We found statistically significant differences in SI and CI between infants with large PDAs and infants with no or small and medium PDAs. We suggest that these differences can be used in real time, in addition to echocardiography, in assessing the presence of significant PDAs.

Difference in cardiovascular response during orthostatic stress in Parkinson's disease and multiple system atrophy

Although orthostatic hypotension is more prominent in multiple system atrophy (MSA) than in Parkinson's disease (PD), there is no study comparing the degree of decrease in total peripheral resistance and cardiac response during orthostatic stress between both diseases. In this study, we examined whether there is a difference in cardiovascular response between MSA and PD. We examined the results of the head-up tilt test in 68 patients with MSA, 28 patients with cardiac non-denervated PD, and 70 patients with cardiac denervated PD whose total peripheral resistance after 60° tilting was lower than the value at 0°. Differences in cardiac output and blood pressure changes were compared against the decrease in total peripheral resistance. There was no difference in the degree of decrease in total peripheral resistance among the three groups. However, the slope of the regression line revealed that the increase in cardiac output against the change in total peripheral resistance was significantly lower in the MSA group than in the cardiac non-denervated and denervated PD groups, and that the decrease in systolic blood pressure against the change in total peripheral resistance was significantly greater in the MSA group than in the cardiac non-denervated and denervated PD groups. In MSA, the cardiac response during orthostatic stress is lower than that in PD, possibly underlying the fact that orthostatic hypotension is more prominent in MSA than in PD.

Stroke volume and cardiac output measurement in cardiac patients during a rehabilitation program: comparison between tonometry, impedancemetry and echocardiography

Given the increasing use of noninvasive techniques for the assessment of cardiac function in clinical practice, the aim of this study was to evaluate if stroke volume (SV) and cardiac output (CO) measurements obtained by PhysioFlow impedance cardiography or HDI CR-2000 pulse wave analysis (Pulse) are interchangeable with measurements obtained by echocardiography in patients with coronary artery disease (CAD) or heart failure (HF). The study involved 48 men with heart disease (CAD or HF). We compared SV and CO measurements with the three devices at rest, as well as relative changes in SV and CO derived from a rehabilitation program. SV and CO measurements were carried out first by echocardiography and immediately after using tonometry and impedancemetry techniques simultaneously. The Bland-Altman analysis showed a significant bias in the measurement of absolute SV and CO values with Pulse and PhysioFlow. Four quadrant plot and polar plot analysis of relative change SV between Pulse and echocardiography show a rate of concordance of 77% (95% CI 60-88%) and 79% (95% CI 63-89%) respectively. The polar plot analysis showed a mean polar angle of 34° ± 22°, and a 30° radial sector containing 52% of the data points. Both Pulse and PhysioFlow devices overestimate absolute SV and CO values compared to values recorded using echocardiography. Similarly, neither Pulse nor PhysioFlow reliably track SV or CO changes after a rehabilitation program compared with echocardiography.

Cardiovascular Responses and Cardiac Work of Selected Daily Activities in Young Healthy Indian Participants

BACKGROUND

Studies suggest that habitual daily activities may result in significant cardiovascular responses that might have implications for individuals with coronary artery disease. This study determined the cardiac work for various activities of daily living among healthy young participants.

METHODS

We evaluated cardiovascular responses in 42 young adults (21 male, 21 female) to graded activities. Subjects were divided into three groups. In each group, one light, one moderate, and one heavy activity were performed based on published METS. Cardiovascular responses were evaluated using impedance cardiography (BOMED Instruments, USA) and automated blood pressure monitor (Welch Allyn, USA). Cardiac work was computed as the double product (heart rate × systolic blood pressure) and triple product (systolic blood pressure × cardiac output [stroke volume × heart rate]). Perceived exertion was evaluated using Borg's scale.

RESULTS

There was high inter-individual variability in cardiovascular responses for each activity. There were, by and large, no gender differences across the activities. Cardiac work was significantly higher with heavy activities than light activities using both indices; however, the triple product showed greater discriminatory ability in evaluating differences in cardiac work across all categories of activities.

CONCLUSION

The data suggest a need to develop a compendium of cardiac work related to habitual activities to guide doctors and patients.

Correlation between the left atrial low-voltage area and the cardiac function improvement after catheter ablation for paroxysmal atrial fibrillation

BACKGROUND

The impact of the left atrial low-voltage area (LVA) on the cardiac function improvement following ablation for atrial fibrillation (AF) is unclear.

METHODS

In 49 patients with paroxysmal AF who underwent ablation, the left ventricular stroke volume index (SVI) was repeatedly measured using an impedance cardiography until 6 months after ablation. We defined the cardiac function improvement as a 20% increase in the SVI. The LVA (the area with the voltage amplitude of <0.5 mV) was assessed before ablation.

RESULTS

The reduced baseline SVI (<33 mL/m2) was observed in 18 (37%) patients. The SVI increased following ablation (from 36 ± 5 to 39 ± 6 mL/m2, P < .001). We observed the cardiac function improvement in 14 (29%) patients. The LVA was smaller in patients with the improved cardiac function than in those without (8.3% ± 5.2% vs 14.0% ± 8.5%, P = .026). The multivariate analysis revealed that only the LVA was independently associated with the cardiac function improvement (odds ratio, 0.878; 95% confidence interval: 0.778-0.991, P = .036). Furthermore, LVAs of the anterior (7.9% ± 7.6% vs 18.2% ± 15.5%, P = .022), septal (12.0 ± 7.3% vs 20.7% ± 13.8%, P = .031), and roof walls (6.9% ± 6.0% vs 16.9% ± 15.2%, P = .022) were smaller in patients with the improved cardiac function than in those without.

CONCLUSIONS

The LVA was related to the cardiac function improvement following ablation in patients with paroxysmal AF.

The complexity of hemodynamic response to the tilt test with and without nitroglycerine provocation in patients with vasovagal syncope

The paper presents a comparison of vasovagal syndrome occurrence in a head up tilt table test between patients with a positive result of passive tilt test and those with a positive result after pharmacological provocation. The study group consisted of 80 patients: 57 patients who experienced syncope in the passive phase of the test (43 women (aged: 35.6 ± 16.2) and 14 men (aged: 41.7 ± 15.6) and 23 patients who experienced syncope after pharmacological provocation (17 women (age: 32.3 ± 12) and 6 men (age: 43 ± 15). The main investigation was based on the assessment of monitored signals complexity: heart rate, blood pressure and stroke volume. The analysis of complexity in chosen measurement phases was performed with Sample Entropy. The investigation showed that the reactions of autonomic nervous system during tilt test and before syncope are similar for positive result of passive tilt test and positive result of tilt test with provocation. The differences in supine position occurred only in analysis based on impedance measurement (SV: p = 0.01). Significant differences were denoted for all signals just before the syncope (RRI, sBP, dBP: p = 0,00001 and SV: p = 0.01). In analysis of signals complexity the significant differences occurred just before the syncope for Sample Entropy of blood pressure (SampEn (sBP): p = 0.0008, SampEn (dBP): p = 0,0001).

Improvement of Left Ventricular Ejection Time Measurement in the Impedance Cardiography Combined with the Reflection Photoplethysmography

Cardiac stroke volume (SV) is an essential hemodynamic indicator that can be used to assess whether the pump function of the heart is normal. Non-invasive SV measurement is currently performed using the impedance cardiography (ICG). In this technology, left ventricular ejection time (LVET) is an important parameter which can be determined from the ICG signals. However, the ICG signals are inherently susceptible to artificial noise interference, which leads to an inaccurate LVET measurement and then yields an error in the calculation of SV. Therefore, the goal of the study was to measure LVETs using both the transmission and reflection photoplethysmography (PPG), and to assess whether the measured LVET was more accurate by the PPG signal than the ICG signal. The LVET measured by the phonocardiography (PCG) was used as the standard for comparing with those by the ICG and PPG. The study recruited ten subjects whose LVETs were simultaneously measured by the ICG using four electrodes, the reflection PPG using neck sensors (PPG_neck) and the transmission PPG using finger sensors (PPG_finger). In each subject, ten LVETs were obtained from ten heartbeats selected properly from one-minute recording. The differences of the measured LVETs between the PCG and one of the ICG, PPG_neck and PPG_finger were −68.2 ± 148.6 ms, 4.8 ± 86.5 ms and −7.0 ± 107.5 ms, respectively. As compared with the PCG, both the ICG and PPG_finger underestimated but the PPG_neck overestimated the LVETs. Furthermore, the measured LVET by the PPG_neck was the closest to that by the PCG. Therefore, the PPG_neck may be employed to improve the LVET measurement in applying the ICG for continuous monitoring of SV in clinical settings.

Comparing square root method of measuring the cardiac output by means of aortic impedance change component to Kubicek's method

PURPOSE

The aim of this study is to explore a calculated method used to measure the cardiac output using the aortic impedance change component of reconstructed impedance cardiography.

METHODS

Routine impedance cardiography was measured using Kubicek's method with four ring electrodes. The thoracic mixed impedance changes were measured by six leads, which consisted of 15 electrodes. The aortic impedance change component was separated from six thoracic mixed impedance changes through waveform reconstruction. The square root formula used to calculate the cardiac output was deduced based on the thoracic impedance change equation and the aortic volume change hypothesis during the systole period. The cardiac outputs of 180 normal adults and 72 patients with cardiac insufficiency who could still walk freely were contrastively computed with both Kubicek's formula and the square root formula.

RESULTS

For 180 normal adults, the cardiac index (CI) computed with the square root formula was 3.60 ± 0.45 L/min/m2 , with normal values ranging from 2.7 to 4.5 L/min/m2 . A total of 163 cases (90.6%) had a CI in the standard range (2.7-4.3 L/min/m2 ) adopted in clinical applications. The CI computed with Kubicek's formula was 3.61 ± 0.86 L/min/m2 , with normal values ranging from 1.9 to 5.3 L/min/m2 , and only 115 cases (63.9%) had a CI in the above standard range. Among the 72 patients with cardiac insufficiency, 20 (27.8%) patients had a CI < 2.0 L/min/m2 with Kubicek's formula. Of these 20 cases, 9 cases had a CI < 1.5 L/min/m2 , and 4 cases had a CI < 1.1 L/min/m2 . In contrast, none of the 72 patients had a CI < 2.0 L/min/m2 with the square root formula. In addition, the influence of the chest circumference on the CI was lower for the square root formula than for Kubicek's formula.

CONCLUSIONS

The CI calculated with the square root formula had a better normal value range, was more accurate for the patients with cardiac insufficiency, and was less affected by the chest circumference than the CI calculated with Kubicek's formula.

Impedance cardiography as tool for continuous hemodynamic monitoring during cesarean section: randomized, prospective double blind study

BACKGROUND

Impedance Cardiography (ICG) is a non-invasive tool for continuous hemodynamic monitoring. Aims of our study were to assess the utility of ICG to evaluate the hemodynamic impact of 6 mg (GL6) vs 8 mg (GL8) levobupivacaine combined with fentanyl in healthy patients undergoing elective cesarean section; secondary, to compare the duration and quality of analgesia and anesthesia.

METHODS

Sixty-two women receiving combined spinal-epidural (CSE) for elective cesarean delivery were randomly allocated to GL6 or GL8 groups. Mean arterial pressure (MAP), cardiac index (CI), systemic vascular resistance index (SVRI), heart rate (HR), stroke volume index (SVI) were recorded from Tbaseline to 31 min after CSE by ICG. Sensory and motor blocks, patients and surgeons satisfaction, neonatal data were also recorded.

RESULTS

Fifteen of 32 patients in GL6 and 15 of 30 patients in GL8 experienced hypotension at T2 vs Tbaseline (P < .001) and SVRI reduction (P = .035 and P < .001 respectively). MAP, CI and SVRI were always slightly higher in GL6 vs GL8. HR and SVI remained stable until the end of surgery in all patients. Total ephedrine requirements was higher in GL8 (P = .010). The onset and offset time of sensory and motor block were similar in both groups, but the number of patients with motor block was lower in GL6 vs GL8 (P = .001). Patients and surgeon satisfaction scores, the number of patients needed systemic rescue doses, neonatal data were similar in both groups.

CONCLUSIONS

ICG is a useful noninvasive tool to monitor continuously hemodynamics during cesarean section. The hemodynamic stability, the satisfying sensory block and rapid mobilization provided by low levobupivacaine dose may be particularly advantageous in obstetric patients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03170427 . Retrospectively Registered (Date of registration: May 2017).

Systolic time ratio measured by impedance cardiography accurately screens left ventricular diastolic dysfunction in patients with arterial hypertension

Background

The use of impedance cardiography (ICG) may play a role in the assessment of cardiac effects of hypertension (HT), especially its hemodynamic features. Hypertensive heart disease involves structural changes and alterations in left ventricular geometry that end up causing systolic and/or diastolic dysfunction. The IMPEDDANS study aims to assess the usefulness of ICG for the screening of left ventricular diastolic dysfunction (LVDD) in patients with HT.

Methods

Patients with HT were assessed by echocardiography and ICG. Receiver-operating characteristic curve and the area under the curve were used to assess the discriminative ability of the parameters obtained by ICG to identify LVDD, as diagnosed by echocardiography.

Results

ICG derived pre-ejection period (PEP), left ventricle ejection time (LVET), systolic time ratio (STR) and D wave were associated (p < 0.001) with LVDD diagnosis, with good discriminative ability: PEP (AUC 0.81; 95% CI 0.74–0.89), LVET (AUC 0.82; 95% CI 0.75–0.88), STR (AUC 0.97; 95% CI 0.94–1.00) and presence of D wave (AUC = 0.87; 95% CI 0.82–0.93). STR ≥ 0.30 outperformed the other parameters (sensitivity of 98.0%, specificity of 90.2%, positive predictive value of 95.2%, and negative predictive value of 96.1%).

Conclusion

The ICG derived value of STR allows the accurate screening of LVDD in patients with HT. It might as well be used for follow up assessment.

Trial registration

The study protocol was retrospectively registered as IMPEDDANS on ClinicalTrials.gov (ID: NCT03209141) on July 6, 2017.

Hemodynamic changes caused by acupuncture in healthy volunteers: a prospective, single-arm exploratory clinical study

BACKGROUND

Radial pressure pulse wave (RPPW) examination has been a key diagnostic component of traditional Chinese medicine. The objective of this study was to investigate the changes in RPPW along with various hemodynamic variables after acupuncture stimulation and to examine the validity of pulse diagnosis as a modern diagnostic tool.

METHODS

We conducted acupuncture stimulation at both ST36 acupuncture points in 25 healthy volunteers. We simultaneously assessed the RPPW by pulse tonometry; heart rate variability (HRV) by electrocardiogram; photoplethysmogram (PPG) signals, respiration rate, peripheral blood flow velocity and arterial depth by ultrasonography; and cardiac output by impedance cardiography, before, during and after a session of acupuncture stimulation.

RESULTS

We observed consistent patterns of increased spectral energy at low frequency (<10 Hz) and pulse power using RPPW examination and in the amplitude and systolic area of the PPG signal during the entire acupuncture session. The low- and high-frequency domains of HRV increased and decreased, respectively, during the acupuncture session. The peripheral blood velocity rose shortly after needle insertion, reached a maximum in the middle of the session and decreased afterwards. The augmentation index (AIX) and pulse transit time (PTT) obtained from RPPW did not change significantly.

CONCLUSION

Acupuncture stimulation at ST36 in healthy subjects increased the peripheral pulse amplitudes (pressure pulse wave (PPW) and PPG), blood flow velocity (ultrasonography) and sympathetic nerve activity (HRV). The lack of changes in the AIX and PTT suggests that the increased pulse amplitudes and blood flow velocity may result from increased cardiac output.

TRIAL REGISTRATION

Clinical Research Information Service ( KCT0001663 ).

Impedance cardiography signal denoising using discrete wavelet transform

Impedance cardiography (ICG) is a non-invasive technique for diagnosing cardiovascular diseases. In the acquisition procedure, the ICG signal is often affected by several kinds of noise which distort the determination of the hemodynamic parameters. Therefore, doctors cannot recognize ICG waveform correctly and the diagnosis of cardiovascular diseases became inaccurate. The aim of this work is to choose the most suitable method for denoising the ICG signal. Indeed, different wavelet families are used to denoise the ICG signal. The Haar, Daubechies (db2, db4, db6, and db8), Symlet (sym2, sym4, sym6, sym8) and Coiflet (coif2, coif3, coif4, coif5) wavelet families are tested and evaluated in order to select the most suitable denoising method. The wavelet family with best performance is compared with two denoising methods: one based on Savitzky-Golay filtering and the other based on median filtering. Each method is evaluated by means of the signal to noise ratio (SNR), the root mean square error (RMSE) and the percent difference root mean square (PRD). The results show that the Daubechies wavelet family (db8) has superior performance on noise reduction in comparison to other methods.

Beyond catecholamines: Measuring autonomic responses to psychosocial context

Despite longstanding interest among human biologists in autonomic responses to socioecological context or culture change, the adoption of autonomic measures has been limited by methodological challenges. Catecholamine secretion is the most direct measure, but not all study designs are amenable to urinary sampling, and blood pressure lacks specificity to the parasympathetic or sympathetic division of the autonomic nervous system. This article reviews three alternative approaches for measuring autonomic responses: salivary α-amylase as a nonspecific autonomic marker, respiratory sinus arrhythmia as a specific parasympathetic marker, and the pre-ejection period as a specific sympathetic marker. Study design considerations are discussed in detail, including ambulatory sampling protocols that permit the evaluation of autonomic responses to everyday life. Researchers interested in how culture and social experience "get under the skin," as well as those concerned with the evolution of social engagement, can benefit from these well-validated biomarkers that are nevertheless relatively novel in human biology. Am. J. Hum. Biol. 28:309-317, 2016. © 2015 Wiley Periodicals, Inc.

Impaired peripheral vasoconstrictor response to orthostatic stress in patients with multiple system atrophy

BACKGROUND AND PURPOSE

Most patients with multiple system atrophy (MSA) develop autonomic dysfunction; however, orthostatic hypotension is not always present. Failure of the vasoconstrictor response is thought to be responsible for orthostatic hypotension, but the degree of impairment of this response in patients with MSA is unclear. We assessed autonomic function in patients with MSA by evaluating the vasoconstrictive response during a head-up tilt test and determining its relationship to orthostatic hypotension. As an additional examination, the efficacy of norepinephrine in treating orthostatic hypotension was also assessed.

METHODS

The study included 82 patients with MSA and 28 controls. Measures of total peripheral resistance were obtained during a head-up tilt test. Norepinephrine was administered to the patients lacking a vasoconstrictive response to evaluate its ability to treat orthostatic hypotension.

RESULTS

At a 60° tilt, orthostatic hypotension occurred in 47.6% of the patients and 0% of controls. Reduction in total peripheral resistance from baseline at a 60° tilt was observed in 69.5% of the patients and 0% of controls. In patients with MSA, changes in systolic blood pressure from the baseline at a 60° tilt correlated positively with changes in the total peripheral resistance (r = 0.69, p < 0.0001). Norepinephrine prevented the reduction of total peripheral resistance and development of orthostatic hypotension.

CONCLUSIONS

A large number of patients with MSA with and without orthostatic hypotension have an impaired peripheral vasoconstrictive response, suggesting a high frequency of cardiovascular dysautonomia with an associated risk of developing orthostatic hypotension. A norepinephrine infusion was effective for treating orthostatic hypotension.

Early hemodynamic response to the tilt test in patients with syncope

INTRODUCTION

Our aim was to evaluate the differences in the early hemodynamic response to the tilt test (HUTT) in patients with and without syncope using impedance cardiography (ICG).

MATERIAL AND METHODS

One hundred twenty-six patients (72 female/48 male; 37 ±17 years) were divided into a group with syncope (HUTT(+), n = 45 patients) and a group without syncope (HUTT(-), n = 81 patients). ECG and ICG signals were continuously recorded during the whole examination, allowing the calculation of heart rate (HR), stroke volume (SV), and cardiac output (CO) for every beat. The hemodynamic parameters (averaged over 1 min) were analyzed at the following points of the HUTT: the last minute of resting, the period immediately after the tilt (0 min), 1 min and 5 min after the maneuver. The absolute changes of HR, SV and CO were calculated for 0, 1, and 5 min after the maneuver in relation to the values at rest (ΔHR, ΔSV, ΔCO). Also, the percentage changes were calculated (HRi, SVi, COi).

RESULTS

There were no differences between the groups in absolute and percentage changes of hemodynamic parameters immediately after and 1 min after tilting. Significant differences between the HUTT(+) and HUTT(-) groups were observed in the 5(th) min of tilting: for ΔSV (-27.2 ±21.2 ml vs. -9.7 ±27.2 ml; p = 0.03), ΔCO (-1.78 ±1.62 l/min vs. -0.34 ±2.48 l/min; p = 0.032), COi (-30 ±28% vs. -0.2 ±58%; p = 0.034).

CONCLUSIONS

In the 5(th) min the decrease of hemodynamic parameters (ΔSV, ΔCO, COi) was significantly more pronounced in HUTT(+) patients in comparison to the HUTT(-) group.

Role of cardiac sympathetic nerves in preventing orthostatic hypotension in Parkinson's disease

PURPOSE

Cardiac sympathetic denervation is associated with orthostatic hypotension (OH) in Parkinson's disease (PD); however, the physiological role of cardiac sympathetic nerves has yet to be elucidated. To clarify the role of the heart in orthostatic stress, we evaluated whether cardiac sympathetic nerves can alter cardiac activity and systolic blood pressure (BP) in association with elevations or depressions of total peripheral resistance during the head-up tilt test.

METHODS

Ninety-five PD patients and 17 normal controls were enrolled. Using impedance cardiography, we measured total peripheral resistance, stroke volume, heart rate, and systolic BP during the head-up tilt test. Cardiac denervation was defined as a heart-to-mediastinum ratio <1.7 for cardiac (123)I-metaiodobenzylguanidine uptake on delayed images.

RESULTS

At 60° tilt, total peripheral resistance decreased from the initial value in 49 PD patients. Among these, 36 patients exhibited cardiac denervation with severe reductions in systolic BP but little change in stroke volume; among these patients 22 had OH. The remaining 13 patients without cardiac denervation exhibited significant increases in stroke volume and well-preserved systolic BP with no OH. On the other hand, 46 patients had elevations in total peripheral resistance and reduced stroke volume, but little change in systolic BP, regardless of the presence or absence of cardiac denervation. Only one of these patients experienced OH.

CONCLUSION

Under orthostatic stress, cardiac sympathetic denervation with failure to increase total peripheral resistance leads to large reductions in systolic BP. However, patients without cardiac denervation exhibited a positive inotropic response against vasodilatation, which may prevent OH.

Comparison of cardiac output derived from FloTrac™/Vigileo™ and impedance cardiography during major abdominal surgery

Objectives

Impedance cardiography (ICG) is a noninvasive technique that provides reasonably accurate measurements of cardiac output, but the usefulness of ICG in patients undergoing open abdominal surgery has not been validated.

Methods

Cardiac output was measured while patients underwent open gastrectomy using an ICG monitor ( niccomo™; ICG-CO); the results were compared with those measured using a FloTrac™/Vigileo™ monitor (Flo-CO), which measures cardiac output by analysing the arterial waveform. Data collection commenced at the beginning of anaesthetic induction and continued until the patient was awake. Data were compared using the Bland–Altman analysis, and the clinical significance of the difference between the two methods was evaluated by calculating the percentage error (%).

Results

Eleven patients were monitored during surgery. The bias of the Flo-CO and ICG-CO values was −0.45 l/min. The upper and lower limits of agreement were 0.96 l/min and −1.85 l/min, respectively. The percentage error was 28.5%. Electrocautery induced interference that transiently impaired the performance of the ICG monitor.

Conclusions

ICG provided useful information in evaluating the cardiac output of patients during abdominal surgery.