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BACKGROUND Blood pressure (BP) control can be difficult to attain due to multiple factors, including choosing and titrating antihypertensive medications. Measurement of hemodynamic parameters using impedance cardiography (ICG) at the point of care may allow better alignment of medication with the mechanism(s) underlying an individual's hypertension. We conducted a systematic review of randomized controlled trials of ICG compared to usual care for attainment of BP control. METHODS We searched Medline inclusive of the year 1946 to January 31, 2024, using a combination of MeSH terms and keywords. English-language articles were eligible for inclusion if they described results of a randomized controlled trial designed to compare ICG-guided BP-medication selection to usual care (i.e. clinician judgment/guidelines-based alone) among a sample of hypertensive patients. RESULTS Of 1,952 titles screened, 6 trials met inclusion criteria. The first was published in 2002 from a specialty clinic in the United States, and the most recent in 2021 from a specialty clinic in China. One trial was conducted in a primary care setting. Sample sizes ranged from 102 to 164. Participants randomized to ICG-guided antihypertensive medication had reduced BP in the short-term to a greater extent than those randomized to usual care, with odds ratios for BP control (<140/90 mm Hg) at 3 months ranging from 1.87 to 2.92. This effect was seen in both specialty clinics and in a primary care setting. CONCLUSIONS Incorporation of ICG in the clinical setting may facilitate medication selection that leads to a greater proportion of patients obtaining BP control in the short term. [ABSTRACT FROM AUTHOR]

Background/Objectives: Acromegaly-induced prolonged exposure to growth hormone and insulin-like growth factor 1 may have significant cardiovascular effects. The purpose of this study was to assess the relationship between hemodynamic parameters measured via impedance cardiography (ICG) and parameters of systolic left ventricular function measured via echocardiography in patients with acromegaly. Methods: The observational cohort study included 33 patients with newly diagnosed acromegaly, with a mean age of 47 years and without significant comorbidities. Correlation analysis (Spearman's rank correlation coefficient R) was performed on parameters obtained by ICG and left ventricular systolic function parameters obtained by echocardiography. ICG assessment included indices of (1) cardiac function as a pump: stroke volume index (SI), cardiac index (CI), Heather index (HI), velocity index (VI), and acceleration index (ACI); (2) afterload: systemic vascular resistance index (SVRI) and total arterial compliance index (TACI); and (3) thoracic fluid content (TFC). Echocardiographic examinations evaluated left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS). Results: A lower LVEF was associated with a lower SI (R = 0.38; p = 0.03) and a higher SVRI (R = −0.35; p = 0.046), whereas lower GLS was associated with lower SI (R = 0.43; p = 0.02), CI (R = 0.62; p < 0.001), VI (R = 0.59; p < 0.001), ACI (R = 0.38; p = 0.048), HI (R = 0.59; p < 0.001), and TACI (R = 0.50; p = 0.006) and a higher SVRI (R = −0.59; p < 0.001). No significant correlation was observed between either LVEF or GLS and TFC. Conclusions: In patients with acromegaly, poorer echocardiographic parameters of left ventricular systolic function are associated with impaired function of the heart as a pump and higher afterload as assessed via ICG. [ABSTRACT FROM AUTHOR]

Objective: Hyperthyroidism increases cardiovascular morbidity and mortality, but the underlying mechanisms are not fully understood. In this study, we compared non-invasive haemodynamics between 20 hyperthyroid patients and 60 euthyroid subjects. Methods: The measurements were performed median 6 days after the initiation of antithyroid medication when the patients were still hyperthyroid. Three controls matched for age, sex, body mass index, and smoking status were selected for each patient. Recordings were performed during rest and passive head-up tilt using whole-body impedance cardiography, radial pulse wave analysis, and finger blood pressure measurements. Results: Systolic and diastolic blood pressures in the aorta and radial artery were similar in hyperthyroid and euthyroid subjects, while finger blood pressure was 16/12 mm Hg lower in hyperthyroidism (P < 0.001). Pulse wave velocity and aortic pulse pressure were similar, but radial pulse pressure was ~5 mm Hg higher in hyperthyroidism (P = 0.040) due to augmented amplification (P = 0.045). Systemic vascular resistance was reduced (−18%), whereas heart rate (+19 beats/min), cardiac index (+28%), and left cardiac work (+31%) were increased in hyperthyroidism (P < 0.001). Subendocardial viability ratio, reflecting the balance between coronary perfusion and pressure load, was reduced by 19% in hyperthyroidism (P < 0.001). Compared with euthyroid subjects, hyperthyroid patients presented with reductions in systolic and diastolic finger blood pressures (P < 0.001), and a higher increase in heart rate (P = 0.014) during upright posture. Conclusions: Hyperthyroid patients exhibited hyperdynamic circulation, reduced vascular resistance, reduced peripheral but not central blood pressure, and higher pulse pressure amplification. Furthermore, the left cardiac workload was increased in parallel with unfavourable changes in coronary perfusion conditions.

Abstract Background The association of obstructive sleep apnea (OSA) with cardiovascular morbidity has been repeatedly reported in numerous studies and argues for treatment initiation even in the absence of significant day time sleepiness. While the long-term consequences of positive airway pressure (PAP) treatment on OSA related comorbidities like secondary hypertension are based on substantial clinical evidence, less is known about the immediate hemodynamic effects. Methods This study tried to investigate the impact of PAP treatment on different hemodynamic parameters in 48 patients with OSA by extending the standard polysomnographic assessment with non-invasive hemodynamic monitoring using impedance cardiography (ICG). On two consecutive nights under diagnostic and therapeutic conditions, polysomnographic and hemodynamic data were acquired. In addition, we subdivided the participants according to their treatment related change in stroke volume (SV) and assigned the hemodynamic measurements to the corresponding sleep stage. Results Comparing both conditions, a non-statistically significant decrease in SV and cardiac output (CO) was observed for all participants. Treatment initiation was associated with a statistically significant prolongation of the pre-ejection period (PEP) for the entire study population (p = 0.001) and the subgroup with decreasing SV (p = 0.008). In addition, systolic blood pressure (SBP) (p = 0.026) and pulse pressure (PP) (p = 0.041) were lowered significantly for patients with a therapeutically reduced SV under treatment conditions. A higher BMI (p = 0.020) and a more pronounced reduction of the respiratory distress index (RDI) (p = 0.030) and the arousal-index (p = 0.021) were observed for patients with decreasing SV. Correlational analysis revealed a negative relationship between the diagnostic values for both SBP (r=-0.324, p = 0.025) and PP (r=-0.407, p = 0.004) with the change in SV and a positive correlation with the change of the SBP (r = 0.317, p = 0.028) for all participants. Conclusions To conclude, our results indicate that treatment with a PAP device in patients with OSA can lead to a decrease in SV which is associated with a lowering of the SBP. This may be caused by a reduced sympathetic tone due to less respiratory events and an improved sleep profile.

The hemodynamic response during the transition from the supine to standing position in idiopathic atrial fibrillation (AF) patients is not completely understood. This study aimed to analyze the hemodynamic changes that occur during the head‐up tilt test in idiopathic AF patients. We investigated the hemodynamic changes during the head‐up tilt test with impedance cardiography in 40 AF patients (12 with AF rhythm‐AFr and 28 with sinus rhythm‐AFsr) and 38 non‐AF controls. Patients with AFr had attenuated SVI decrease after standing when compared to AFsr and non‐AF [ΔSVI in mL/m2: −1.3 (−3.4 to 1.7) vs. −6.4 (−17.3 to −0.1) vs. −11.8 (−18.7 to −8.0), respectively; p < 0.001]. PVRI decreased in AFr but increased in AFsr and non‐AF [ΔPVRI in dyne.seg.m2/cm5: −477 (−1148 to 82.5) vs. 131 (−525 to 887) vs. 357 (−29 to 681), respectively; p < 0.01]. Similarly, compared with non‐AF patients, AFr patients also had a greater HR and greater CI increase after standing. The haemodynamic response to orthostatic challenge suggests differential adaptations between patients with AF rhythm and those reverted to sinus rhythm or healthy controls. Characterizing the hemodynamic phenotype may be relevant for the individualized treatment of AF patients. [ABSTRACT FROM AUTHOR]

Prenatal opioid exposure has been associated with developmental problems, including autonomic nervous system dysregulation. However, little is known about the effects of prenatal opioid exposure on the autonomic nervous system beyond the first days of life, particularly across both the parasympathetic and sympathetic branches, and when accounting for exposure to other substances. The present study examined the effects of prenatal exposure to opioid agonist therapy (OAT, e.g., methadone) and other opioids on infant autonomic nervous system activity at rest and in response to a social stressor (the Still‐Face Paradigm) at six months among 86 infants varying in prenatal opioid and other substance exposure. Results indicated that OAT and other opioids have unique effects on the developing autonomic nervous system that may further depend on subtype (i.e., methadone versus buprenorphine) and timing in gestation. Results are discussed in the context of theoretical models of the developing stress response system. Prenatal opioid exposure (POE) is a major public health concern and impacts the fetal and neonatal autonomic nervous system (ANS). However, little is known about POE effects on the ANS beyond the neonatal period and accounting for other substance exposure. The present study describes the effects of POE on infant respiratory sinus arrhythmia and pre‐ejection period at six months of age and the differential effects of type and timing of exposure in the context of polysubstance exposure. [ABSTRACT FROM AUTHOR]

Background: Cushing's disease (CD) is associated with a specific form of metabolic syndrome that includes visceral obesity, which may affect cardiovascular hemodynamics by stimulating hypercortisolism-related metabolic activity. The purpose of this study was to evaluate the relationship between obesity and the hemodynamic profile of patients with CD. Methods: This prospective clinical study involved a hemodynamic status assessment of 54 patients newly diagnosed with CD with no significant comorbidities (mean age of 41 years). The assessments included impedance cardiography (ICG) to assess such parameters as stroke index (SI), cardiac index (CI), velocity index (VI), acceleration index (ACI), Heather index (HI), systemic vascular resistance index (SVRI), and total arterial compliance index (TACI) as well as applanation tonometry to assess such parameters as central pulse pressure (CPP) and augmentation index (AI). These assessments were complemented by echocardiography to assess cardiac structure and function. Results: Compared with CD patients without obesity, individuals with CD and obesity (defined as a body mass index ≥ 30 kg/m2) exhibited significantly lower values of ICG parameters characterizing the pumping function of the heart (VI: 37.0 ± 9.5 vs. 47.2 ± 14.3 × 1*1000−1*s−1, p = 0.006; ACI: 58.7 ± 23.5 vs. 76.0 ± 23.5 × 1/100/s2, p = 0.005; HI: 11.1 ± 3.5 vs. 14.6 ± 5.5 × Ohm/s2, p = 0.01), whereas echocardiography in obese patients showed larger heart chamber sizes and a higher left ventricular mass index. No significant intergroup differences in blood pressure, heart rate, LVEF, GLS, TACI, CPP, or AI were noted. Conclusions: Hemodynamic changes associated with obesity already occur at an early stage of CD and manifest via significantly lower values of the ICG parameters illustrating the heart's function as a pump, despite the normal function of the left ventricle in echocardiography. [ABSTRACT FROM AUTHOR]

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. 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. Histopathologic, cytokine and hemodynamic findings supported that cardiac damage increased with increasing radiation dose. 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. [ABSTRACT FROM AUTHOR]

Abstract The hemodynamic response during the transition from the supine to standing position in idiopathic atrial fibrillation (AF) patients is not completely understood. This study aimed to analyze the hemodynamic changes that occur during the head‐up tilt test in idiopathic AF patients. We investigated the hemodynamic changes during the head‐up tilt test with impedance cardiography in 40 AF patients (12 with AF rhythm‐AFr and 28 with sinus rhythm‐AFsr) and 38 non‐AF controls. Patients with AFr had attenuated SVI decrease after standing when compared to AFsr and non‐AF [ΔSVI in mL/m2: −1.3 (−3.4 to 1.7) vs. −6.4 (−17.3 to −0.1) vs. −11.8 (−18.7 to −8.0), respectively; p

Cardiovascular diseases are a leading global cause of mortality. The current standard diagnostic methods, such as imaging and invasive procedures, are relatively expensive and partly connected with risks to the patient. Bioimpedance measurements hold the promise to offer rapid, safe, and low-cost alternative diagnostic methods. In the realm of cardiovascular diseases, bioimpedance methods rely on the changing electrical conductivity of blood, which depends on the local hemodynamics. However, the exact dependence of blood conductivity on the hemodynamic parameters is not yet fully understood, and the existing models for this dependence are limited to rather academic flow fields in straight pipes or channels. In this work, we suggest two closely connected anisotropic electrical conductivity models for blood in general three-dimensional flows, which consider the orientation and alignment of red blood cells (RBCs) in shear flows. In shear flows, RBCs adopt preferred orientations through a rotation of their membrane known as tank-treading motion. The two models are built on two different assumptions as to which hemodynamic characteristic determines the preferred orientation. The models are evaluated in two example simulations of blood flow. In a straight rigid vessel, the models coincide and are in accordance with experimental observations. In a simplified aorta geometry, the models yield different results. These differences are analyzed quantitatively, but a validation of the models with experiments is yet outstanding. [ABSTRACT FROM AUTHOR]

Background: Acromegaly is a rare, chronic disease that involves structural and functional abnormalities of the cardiovascular system. Acromegaly likely affects interactions between the cardiovascular system and the autonomic nervous system (ANS). Therefore, assessing the relationship between sympathetic–parasympathetic balance by analyzing heart rate variability (HRV) and the hemodynamic profile via impedance cardiography (ICG) may be useful in learning the exact nature of interactions between the ANS and the cardiovascular system. The purpose of this study was to assess a possible association between HRV and ICG-based parameters of cardiac function in patients newly diagnosed with acromegaly. Methods: This observational cohort study was conducted on 33 patients (18 men, mean age of 47 years) newly diagnosed with acromegaly and no significant comorbidities. A correlation analysis (Spearman's rank coefficient R) of the parameters assessed via ICG and the HRV assessed via 24 h ambulatory electrocardiography was performed. ICG assessments included the following parameters: stroke volume index (SI), cardiac index (CI), acceleration index (ACI), velocity index (VI), and Heather index (HI). The analysis of HRV included both time-domain parameters (pNN50, SDNN, SDSD, rMSSD) and frequency-domain parameters (total power (TP) and its individual frequency bands: low-frequency (LF day/night), high-frequency (HF day/night), and the LF/HF ratio (day/night)). Results: Frequency-domain HRV analysis showed the following correlations: (1) lower nighttime LF values with higher ACI (R = −0.38; p = 0.027) and HI (R = −0.46; p = 0.007) values; (2) higher nighttime HF values with higher ACI (R = 0.39; p = 0.027) and HI (R = 0.43; p = 0.014) values; (3) lower nighttime LF/HF values with higher ACI (R = −0.36; p = 0.037) and HI (R = −0.42; p = 0.014) values; (4) higher nighttime TP values with higher SI values (R = 0.35; p = 0.049). Time-domain parameters of HRV showed a significant correlation only between the nighttime values of SDSD and SI (R = 0.35; p = 0.049) and between the daytime and nighttime values of SDNN and HR (R = −0.50; p = 0.003 and R = −0.35; p = 0.046). In multivariate regression, only ACI was revealed to be independently related to HRV. Conclusions: In patients newly diagnosed with acromegaly, the relationship between the sympathetic–parasympathetic balance assessed via HRV and the hemodynamic profile assessed via ICG was revealed. Better function of the left ventricle was associated with a parasympathetic shift in the autonomic balance. [ABSTRACT FROM AUTHOR]

Background: Pulmonary hypertension guidelines recommend invasive right heart catheterization for diagnosis and clinical follow-up. Our aim was to compare non-invasive impedance cardiography with invasive techniques for cardiac index measurements and mortality prediction in patients with pulmonary hypertension. Methods: Between 2008 and 2018, 284 right heart catheterizations were performed for the diagnosis of pulmonary hypertension in 215 patients with mean pulmonary artery pressure >25 mm Hg, and at least 2 methods used for cardiac output measurement were included in the study retrospectively. Patients were evaluated with Pearson's correlation in 3 groups: estimated Fick (eFick) method and thermodilution (group 1), eFick method and impedance cardiography (group 2), and thermodilution and impedance cardiography (group 3). We also compared the predictive power of cardiac index measured by different methods for 1-year overall mortality and hospitalizations. Results: There were strong and moderate positive correlations in groups 1 and 3, respectively (r = 0.634, P

Abstract Background Patients with fibromyalgia (FM) exhibit low peak oxygen uptake ( $$\dot{\text{V}}$$ V ˙ O2peak). We aimed to detect the contribution of cardiac output to ( $$\dot{\text{Q}}$$ Q ˙ ) and arteriovenous oxygen difference $$[\text{C}(\text{a-v})\text{O}_{2}]$$ [ C ( a-v ) O 2 ] to $$\dot{\text{V}}\text{O}_{2}$$ V ˙ O 2 from rest to peak exercise in patients with FM. Methods Thirty-five women with FM, aged 23 to 65 years, and 23 healthy controls performed a step incremental cycle ergometer test until volitional fatigue. Alveolar gas exchange and pulmonary ventilation were measured breath-by-breath and adjusted for fat-free body mass (FFM) where appropriate. $$\dot{\text{Q}}$$ Q ˙ (impedance cardiography) was monitored. $$\text{C}(\text{a-v})\text{O}_{2}$$ C ( a-v ) O 2 was calculated using Fick’s equation. Linear regression slopes for oxygen cost (∆ $$\dot{\text{V}}$$ V ˙ O2/∆work rate) and $$\dot{\text{Q}}$$ Q ˙ to $$\text{V}$$ V O2 (∆ $$\dot{\text{Q}}$$ Q ˙ /∆ $$\dot{\text{V}}$$ V ˙ O2) were calculated. Normally distributed data were reported as mean ± SD and non-normal data as median [interquartile range]. Results $$\dot{\text{V}}$$ V ˙ O2peak was lower in FM patients than in controls (22.2 ± 5.1 vs. 31.1 ± 7.9 mL∙min−1∙kg−1, P

Background: Heart failure (HF) is associated with high mortality, morbidity, and frequent hospitalizations due to acute HF (AHF) and requires immediate diagnosis and individualized therapy. Some differences between acutely decompensated chronic heart failure (ADCHF) and de novo HF (dnHF) patients in terms of clinical profile, comorbidities, and outcomes have been previously identified, but the hemodynamics related to both of these clinical states are still not well recognized. Purpose: To compare patients hospitalized with ADCHF to those with dnHF, with a special emphasis on hemodynamic profiles at admission and changes due to hospital treatment. Methods: This study enrolled patients who were at least 18 years old, hospitalized due to AHF (both ADCHF and dnHF), and who underwent detailed assessments at admission and at discharge. The patients' hemodynamic profiles were assessed by impedance cardiography (ICG) and characterized in terms of heart rate (HR), blood pressure (BP), systemic vascular resistance index (SVRI), cardiac index (CI), stroke index (SI), and thoracic fluid content (TFC). Results: The study population consisted of 102 patients, most of whom were men (76.5%), with a mean left ventricle ejection fraction (LVEF) of 37.3 ± 14.1%. The dnHF patients were younger than the ADCHF group and more frequently presented with palpitations (p = 0.041) and peripheral hypoperfusion (p = 0.011). In terms of hemodynamics, dnHF was distinguished by higher HR (p = 0.029), diastolic BP (p = 0.029), SVRI (p = 0.013), and TFC (only numeric, p = 0.194) but lower SI (p = 0.043). The effect of hospital treatment on TFC was more pronounced in dnHF than in ADCHF, and this was also true of N-terminal pro-brain natriuretic peptide (NT-proBNP) and body mass. Some intergroup differences in the hemodynamic profile observed at admission persisted until discharge: higher HR (p = 0.002) and SVRI (trend, p = 0.087) but lower SI (p < 0.001) and CI (p = 0.023) in the dnHF group. Conclusions: In comparison to ADCHF, dnHF is associated with greater tachycardia, vasoconstriction, depressed cardiac performance, and congestion. Despite more effective diuretic therapy, other unfavorable hemodynamic features may still be present in dnHF patients at discharge. [ABSTRACT FROM AUTHOR]

Background: Pulmonary hypertension guidelines recommend invasive right heart catheterization for diagnosis and clinical follow-up. Our aim was to compare non-invasive impedance cardiography with invasive techniques for cardiac index measurements and mortality prediction in patients with pulmonary hypertension. Methods: Between 2008 and 2018, 284 right heart catheterizations were performed for the diagnosis of pulmonary hypertension in 215 patients with mean pulmonary artery pressure >25 mm Hg, and at least 2 methods used for cardiac output measurement were included in the study retrospectively. Patients were evaluated with Pearson’s correlation in 3 groups: estimated Fick (eFick) method and thermodilution (group 1), eFick method and impedance cardiography (group 2), and thermodilution and impedance cardiography (group 3). We also compared the predictive power of cardiac index measured by different methods for 1-year overall mortality and hospitalizations. Results: There were strong and moderate positive correlations in groups 1 and 3, respectively (r=0.634, P < .001, r=0.534, P=.001), and the weakest correlation was in group 2 (r=0.390, P=.001). The mean difference (bias) between eFick method versus impedance cardiography, impedance cardiography vs. thermodilution, and eFick method vs. thermodilution was 0.6 mL/min, 0.47 mL/min, and −0.2 mL/min respectively, but limits of agreement were wide. In both groups, cardiac index <2.5 L/min/m² as measured by thermodilution significantly predicted 1-year mortality. Also, impedance cardiography was better than eFick method in predicting mortality (P=.02). Conclusions: Our single-center real-life data showed that for cardiac output and cardiac index measurements, impedance cardiography provides a moderate correlation with thermodilution and is fair with eFick method methods. Moreover, thermodilution appeared superior to both eFick method and impedance cardiography, while impedance cardiography was even better than eFick method in predicting 1-year adverse events, including total mortality and hospitalization, in patients with pulmonary hypertension. [ABSTRACT FROM AUTHOR]

Background: Cushing disease (CD) may lead to accelerated cardiovascular remodeling and increased mortality. There are suspected differences in the mechanism of cardiovascular dysfunction between males and females with CD. The purpose of this study was to assess the effect of patient sex on the hemodynamic profile assessed via impedance cardiography and echocardiography in patients newly diagnosed with CD. Material and methods: The 54 patients newly diagnosed with CD (mean age 41 years; 77.8% of females) who were included in this prospective clinical study underwent impedance cardiography to assess specific parameters (including systemic vascular resistance index [SVRI], total arterial compliance index [TACI], Heather index [HI], stroke index [SI], cardiac index [CI], velocity index [VI], and acceleration index [ACI]) and transthoracic echocardiography to assess heart chamber diameters and left ventricular systolic and diastolic function. Results: Males with CD exhibited higher afterload, with higher SVRI (3,169.3 ± 731.8 vs. 2,339.3 ± 640.8 dyn*s*cm-5*m² in males and females, respectively; p=0.002), lower TACI (0.80 ± 0.30 vs. 1.09 ± 0.30 mL/mmHg*m²; p=0.008), and lower hemodynamic parameters of left ventricular function, with lower HI (9.46 ± 2.86 vs. 14.1 ± 5.06 Ohm/s²; p=0.0007), lower VI (35.1 ± 11.9 vs. 44.9 ± 13.1 1*1000-1*s-1; p=0.009), lower SI (36.5 ± 11.7 vs. 43.6 ± 9.57mL/m²; p=0.04), lower CI (2.36 ± 0.46 vs. 3.17 ± 0.76 mL*m-2*min-1; p=0.0009), and lower ACI (50.4 ± 19.8 vs. 73.6 ± 25.0 1/100/s²; p=0.006). There were no significant differences between the sexes in left ventricular systolic or diastolic function assessed by echocardiography. Conclusion: In comparison with females with CD, males with CD have a less favorable hemodynamic profile, with higher afterload and worse left ventricular function. Sex differences in cardiovascular system function should be taken into consideration in designing personalized diagnostic and therapeutic management of patients with CD. [ABSTRACT FROM AUTHOR]

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Abstract Background Obesity-related hypertension and the associated metabolic abnormalities are considered as a distinct hypertensive phenotype. Here we examined how abdominal fat content, as judged by waist:height ratio, influenced blood pressure and hemodynamic profile in normotensive subjects and never-treated hypertensive patients. Methods The 541 participants (20–72 years) underwent physical examination and laboratory analyses and were divided into age and sex-adjusted quartiles of waist:height ratio. Supine hemodynamics were recorded using whole-body impedance cardiography, combined with analyses of radial tonometric pulse wave form and heart rate variability. Results Mean waist:height ratios in the quartiles were 0.46, 0.51, 0.55 and 0.62. Radial and aortic blood pressure, systemic vascular resistance, pulse wave velocity, markers of glucose and lipid metabolism, leptin levels and C-reactive protein were higher in quartile 4 when compared with quartiles 1 and 2 (p

BackgroundCushing disease (CD) may lead to accelerated cardiovascular remodeling and increased mortality. There are suspected differences in the mechanism of cardiovascular dysfunction between males and females with CD. The purpose of this study was to assess the effect of patient sex on the hemodynamic profile assessed via impedance cardiography and echocardiography in patients newly diagnosed with CD.Material and methodsThe 54 patients newly diagnosed with CD (mean age 41 years; 77.8% of females) who were included in this prospective clinical study underwent impedance cardiography to assess specific parameters (including systemic vascular resistance index [SVRI], total arterial compliance index [TACI], Heather index [HI], stroke index [SI], cardiac index [CI], velocity index [VI], and acceleration index [ACI]) and transthoracic echocardiography to assess heart chamber diameters and left ventricular systolic and diastolic function.ResultsMales with CD exhibited higher afterload, with higher SVRI (3,169.3 ± 731.8 vs. 2,339.3 ± 640.8 dyn*s*cm-5*m² in males and females, respectively; p=0.002), lower TACI (0.80 ± 0.30 vs. 1.09 ± 0.30 mL/mmHg*m2; p=0.008), and lower hemodynamic parameters of left ventricular function, with lower HI (9.46 ± 2.86 vs. 14.1 ± 5.06 Ohm/s2; p=0.0007), lower VI (35.1 ± 11.9 vs. 44.9 ± 13.1 1*1000-1*s-1; p=0.009), lower SI (36.5 ± 11.7 vs. 43.6 ± 9.57 mL/m2; p=0.04), lower CI (2.36 ± 0.46 vs. 3.17 ± 0.76 mL*m-2*min-1; p=0.0009), and lower ACI (50.4 ± 19.8 vs. 73.6 ± 25.0 1/100/s2; p=0.006). There were no significant differences between the sexes in left ventricular systolic or diastolic function assessed by echocardiography.ConclusionIn comparison with females with CD, males with CD have a less favorable hemodynamic profile, with higher afterload and worse left ventricular function. Sex differences in cardiovascular system function should be taken into consideration in designing personalized diagnostic and therapeutic management of patients with CD.

Impedance cardiography (ICG) is a low-cost, non-invasive technique that enables the clinical assessment of haemodynamic parameters, such as cardiac output and stroke volume (SV). Conventional ICG recordings are taken from the patient's thorax. However, access to ICG vital signs from the upper-arm brachial artery (as an associated surrogate) can enable user-convenient wearable armband sensor devices to provide an attractive option for gathering ICG trend-based indicators of general health, which offers particular advantages in ambulatory long-term monitoring settings. This study considered the upper arm ICG and control Thorax-ICG recordings data from 15 healthy subject cases. A prefiltering stage included a third-order Savitzky–Golay finite impulse response (FIR) filter, which was applied to the raw ICG signals. Then, a multi-stage wavelet-based denoising strategy on a beat-by-beat (BbyB) basis, which was supported by a recursive signal-averaging optimal thresholding adaptation algorithm for Arm-ICG signals, was investigated for robust signal quality enhancement. The performance of the BbyB ICG denoising was evaluated for each case using a 700 ms frame centred on the heartbeat ICG pulse. This frame was extracted from a 600-beat ensemble signal-averaged ICG and was used as the noiseless signal reference vector (gold standard frame). Furthermore, in each subject case, enhanced Arm-ICG and Thorax-ICG above a threshold of correlation of 0.95 with the noiseless vector enabled the analysis of beat inclusion rate (BIR%), yielding an average of 80.9% for Arm-ICG and 100% for Thorax-ICG, and BbyB values of the ICG waveform feature metrics A, B, C and VET accuracy and precision, yielding respective error rates (ER%) of 0.83%, 11.1%, 3.99% and 5.2% for Arm-IG, and 0.41%, 3.82%, 1.66% and 1.25% for Thorax-ICG, respectively. Hence, the functional relationship between ICG metrics within and between the arm and thorax recording modes could be characterised and the linear regression (Arm-ICG vs. Thorax-ICG) trends could be analysed. Overall, it was found in this study that recursive averaging, set with a 36 ICG beats buffer size, was the best Arm-ICG BbyB denoising process, with an average of less than 3.3% in the Arm-ICG time metrics error rate. It was also found that the arm SV versus thorax SV had a linear regression coefficient of determination (R2) of 0.84. [ABSTRACT FROM AUTHOR]

Background: Patients with fibromyalgia (FM) exhibit low peak oxygen uptake ( V ˙ O2peak). We aimed to detect the contribution of cardiac output to ( Q ˙ ) and arteriovenous oxygen difference [ C (a-v) O 2 ] to V ˙ O 2 from rest to peak exercise in patients with FM. Methods: Thirty-five women with FM, aged 23 to 65 years, and 23 healthy controls performed a step incremental cycle ergometer test until volitional fatigue. Alveolar gas exchange and pulmonary ventilation were measured breath-by-breath and adjusted for fat-free body mass (FFM) where appropriate. Q ˙ (impedance cardiography) was monitored. C (a-v) O 2 was calculated using Fick's equation. Linear regression slopes for oxygen cost (∆ V ˙ O2/∆work rate) and Q ˙ to V O2 (∆ Q ˙ /∆ V ˙ O2) were calculated. Normally distributed data were reported as mean ± SD and non-normal data as median [interquartile range]. Results: V ˙ O2peak was lower in FM patients than in controls (22.2 ± 5.1 vs. 31.1 ± 7.9 mL∙min−1∙kg−1, P < 0.001; 35.7 ± 7.1 vs. 44.0 ± 8.6 mL∙min−1∙kg FFM−1, P < 0.001). Q ˙ and C(a-v)O2 were similar between groups at submaximal work rates, but peak Q ˙ (14.17 [13.34–16.03] vs. 16.06 [15.24–16.99] L∙min−1, P = 0.005) and C(a-v)O2 (11.6 ± 2.7 vs. 13.3 ± 3.1 mL O2∙100 mL blood−1, P = 0.031) were lower in the FM group. No significant group differences emerged in ∆ V ˙ O2/∆work rate (11.1 vs. 10.8 mL∙min−1∙W−1, P = 0.248) or ∆ Q ˙ /∆ V ˙ O2 (6.58 vs. 5.75, P = 0.122) slopes. Conclusions: Both Q ˙ and C(a-v)O2 contribute to lower V ˙ O2peak in FM. The exercise responses were normal and not suggestive of a muscle metabolism pathology. Trial registration: ClinicalTrials.gov, NCT03300635. Registered 3 October 2017—Retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT03300635. [ABSTRACT FROM AUTHOR]

One of the crucial steps in assessing hemodynamic parameters using impedance cardiography (ICG) is the detection of the characteristic points in the dZ/dt ICG complex, especially the X point. The most often estimated parameters from the ICG complex are stroke volume and cardiac output, for which is required the left ventricular pre-ejection time. Unfortunately, for beat-to-beat calculations, the accuracy of detection is affected by the variability of the ICG complex subtypes. Thus, in this work, we aim to create a predictive model that can predict the missing points and decrease the previous work percentages of missing points to support the detection of ICG characteristic points and the extraction of hemodynamic parameters according to several existing subtypes. Thus, a time-series non-linear autoregressive model with exogenous inputs (NARX) feedback neural network approach was implemented to forecast the missing ICG points according to the different existing subtypes. The NARX was trained on two different datasets with an open-loop mode to ensure that the network is fed with correct feedback inputs. Once the training is satisfactory, the loop can be closed for multi-step prediction tests and simulation. The results show that we can predict the missing characteristic points in all the complexes with a success rate ranging between 75% and 88% in the evaluated datasets. Previously, without the NARX predictive model, the successful detection rate was 21%-30% for the same datasets. Thus, this work indicates a promising method and an accuracy increase in the detection of X, Y, O, and Z points for both datasets. [ABSTRACT FROM AUTHOR]

Background: Continuous blood pressure (BP) monitoring provides additional information about how changes in BP may correlate with daily activities and sleep patterns. Recommendations from the American Heart Association and American College of Cardiology strongly suggest confirming a diagnosis of hypertension with continuous BP monitoring. Non-invasive and non-intrusive detection of haemodynamic parameters is emerging as a norm, based on self-monitoring wearable medical devices. Researchers have carried out several studies using non-invasive and continuous BP measurements as an alternative to conventional cuff-based measurements. In this work, we proposed a novel method for cuffless estimation of BP using impedance cardiography (ICG). Methods: We conducted a single-centre, cross-sectional study of 104 subjects (of whom 30 were categorized as controls and the remaining 74 as the disease group) at the Medical College and Hospital, Kolkata. The disease group consisted of patients with confirmed coronary artery disease, while the individuals in the control group were deemed to be healthy. All subjects underwent electrocardiogram recording by on-duty doctors in order to determine their health status. A custom-made device based on the principle of impedance plethysmography was designed to record impedance changes due to subjects’ peripheral blood flow. The device was used to record ICG signals. In this study, we developed a novel auto-adaptive algorithm based on ICG signals for non-invasive, cuffless, continuous monitoring of BP and heart rate. Separate mathematical models were developed for all the estimated parameters (BP and heart rate) for both the study groups (control and disease). The developed models were auto-adaptive and did not require subject-specific calibration. Performance indicators including, r2, error percentage, standard deviation, and mean difference were used to quantify the performance of the models. Results: The ICG signal recorded by the device was used to extract features and compute the augmentation index. The calculated augmentation index values showed strong correlations with systolic BP (r=0.99, P

We present a nonconforming Finite Element (FE) formulation for the electro‐quasistatic case. The formulation allows a grid generation for each sub‐domain individually. At the nonconforming interfaces, we apply a Nitsche‐type mortaring, which can also be interpreted as a DG‐IP (Discontinuous Galerkin‐Internal Penalty) formulation. Thereby, the continuity of the electric potential and the electric flux in the discrete setting is guaranteed. The system matrix remains symmetric, and the necessary penalty factor can be chosen in a wide range without deteriorating the numerical solution. The application to impedance cardiography demonstrates the practical applicability, especially its advantage toward simplification of the grid generation. [ABSTRACT FROM AUTHOR]

To improve the outcomes of patients with chronic heart failure (CHF), it is important to identify reliable prognostic tools. Early repolarization pattern (ER) on 12‑lead electrocardiogram (ECG) is a predictor of worse outcomes, which has been widely researched in the general population but not in the CHF population. To evaluate the incidence and prognostic value of ER and compare its prognostic significance with other non-invasive diagnostic methods for CHF outcomes and hospital readmissions. The study included 301 patients (166 men and 135 women) hospitalized for CHF decompensation. CHF diagnosis was confirmed according to the current guidelines. The patients underwent standard tests and impedance cardiography (ICG) at enrollment and on the day of discharge. Thirty-one confirmed ER cases (10.3%) were enrolled. During a median follow-up period of 18 months, 128 cardiac-related deaths were observed (42.5%), with 23 (74.2%) and 105 (38.9%) patients in the ER and non-ER groups, respectively (p < 0.001). The ER group had more readmissions than the non-ER group did at 6-months (2 [1, 2] vs. 1 [1, 2]; p =0.04) and 12-months (3 [2–4] vs. 2 [1–3]; p <0.001). ER on ECG (hazard ratio [HR] 2.59; 95% confidence interval [CI] 1.64–4.07; p<0.001), N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels ≥425.5 pmoL/L (HR 5.1; 95% CI 3.33–7.83; p < 0.001), thoracic fluid content (TFC) ≥36.9 1/kΩ (HR 4.6; 95% CI 2.7–7.85, p < 0.001), and left ventricular ejection fraction (LVEF) ≤40% (HR 4.94; 95% CI 2.83–8.65; p < 0.001) were independently and significantly associated with cardiac death. The combination of ER, LVEF ≤40%, NT-proBNP, or TFC provides an incremental prognostic value for cardiac-related death in patients with CHF. • The early repolarization pattern may be utilized as a powerful predictor. • The early repolarization pattern is associated with worse outcomes. • Electrocardiography has great potential in chronic heart failure prognostication. • Impedance cardiography and electrocardiography combine for higher predictive values. • Electrocardiography is still the cornerstone in diagnosis and outcome prediction. [ABSTRACT FROM AUTHOR]

Background: Obesity-related hypertension and the associated metabolic abnormalities are considered as a distinct hypertensive phenotype. Here we examined how abdominal fat content, as judged by waist:height ratio, influenced blood pressure and hemodynamic profile in normotensive subjects and never-treated hypertensive patients. Methods: The 541 participants (20–72 years) underwent physical examination and laboratory analyses and were divided into age and sex-adjusted quartiles of waist:height ratio. Supine hemodynamics were recorded using whole-body impedance cardiography, combined with analyses of radial tonometric pulse wave form and heart rate variability. Results: Mean waist:height ratios in the quartiles were 0.46, 0.51, 0.55 and 0.62. Radial and aortic blood pressure, systemic vascular resistance, pulse wave velocity, markers of glucose and lipid metabolism, leptin levels and C-reactive protein were higher in quartile 4 when compared with quartiles 1 and 2 (p < 0.05 for all). Cardiac index was lower in quartile 4 versus quartile 1, while no differences were seen in heart rate variability, augmentation index, plasma renin activity, and aldosterone concentration between the quartiles. Linear regression analyses showed independent associations of abdominal obesity with higher aortic systolic and diastolic blood pressure, systemic vascular resistance, and pulse wave velocity (p < 0.05 for waist:height ratio in all regression models). Conclusion: Higher waist:height ratio was associated with elevated blood pressure, systemic vascular resistance, and arterial stiffness, but not with alterations in cardiac sympathovagal modulation or activation of the circulating renin-angiotensin-aldosterone system. Although obesity-related elevation of blood pressure has distinct phenotypic features, these results suggest that its main characteristics correspond those of primary hypertension. Trial registration: ClinicalTrails.gov NCT01742702 (date of registration 5th December 2012). [ABSTRACT FROM AUTHOR]

The explanation of physiological mechanisms involved in adaptation of the cardiovascular system to intrinsic and environmental demands is crucial for both basic science and clinical research. Computational algorithms integrating multivariable data that comprehensively depict complex mechanisms of cardiovascular reactivity are currently being intensively researched. Quantitative Complexity Theory (QCT) provides quantitative and holistic information on the state of multi-functional dynamic systems. The present paper aimed to describe the application of QCT in an integrative analysis of the cardiovascular hemodynamic response to posture change. Three subjects that underwent head-up tilt testing under beat-by-beat hemodynamic monitoring (impedance cardiography) were discussed in relation to the complexity trends calculated using QCT software. Complexity has been shown to be a sensitive marker of a cardiovascular hemodynamic response to orthostatic stress and vasodilator administration, and its increase has preceded changes in standard cardiovascular parameters. Complexity profiling has provided a detailed assessment of individual hemodynamic patterns of syncope. Different stimuli and complexity settings produce results of different clinical usability. [ABSTRACT FROM AUTHOR]

Introduction: Changes in autonomic nervous system (ANS) balance associated with endovascular interventions may potentially cause haemodynamic abnormalities that lead to periprocedural cardiovascular complications. This study aimed to determine the relationships between changes in ANS balance and impedance cardiography (ICG) parameters after endovascular leg revascularization. Material and methods: Before the procedure, and 1, 3 and 5h after the intervention, 5-min examinations of both ANS balance and ICG parameters were performed using a Task Force Monitor in 42 patients undergoing endovascular leg revascularization. Results: When compared to patients with intermittent claudication, individuals with chronic limb-threatening ischaemia had a significantly shorter R-R interval and lower stroke volume (SV) and left ventricle ejection time (LVET) at the beginning of the study. During the 5h after endovascular leg revascularization, significant fluctuations were noted in the following: heart rate, frequency-domain parameters of heart rate variability, baroreflex effectiveness indices, and ICG parameters, such as total peripheral resistance, SV, LVET, and ejection rate. The deltas of ANS parameters correlated with the deltas of ICG parameters in the respective periods of measurement. Conclusions: Dynamic fluctuations in ICG and ANS parameters that occurred in patients who had undergone endovascular leg revascularization might potentially affect the risk of the occurrence of a cardiovascular event in the periprocedural period. The correlations between the ANS and ICG parameters suggest that haemodynamic oscillations after endovascular leg revascularization are mediated by changes in ANS activity, most probably through a sympathoexcitatory effect of the procedure related to changes in skeletal muscle perfusion. [ABSTRACT FROM AUTHOR]

One of the crucial steps in assessing hemodynamic parameters using impedance cardiography (ICG) is the detection of the characteristic points in the dZ/dt ICG complex, especially the X point. The most often estimated parameters from the ICG complex are stroke volume and cardiac output, for which is required the left ventricular pre-ejection time. Unfortunately, for beat-to-beat calculations, the accuracy of detection is affected by the variability of the ICG complex subtypes. Thus, in this work, we aim to create a predictive model that can predict the missing points and decrease the previous work percentages of missing points to support the detection of ICG characteristic points and the extraction of hemodynamic parameters according to several existing subtypes. Thus, a time-series non-linear autoregressive model with exogenous inputs (NARX) feedback neural network approach was implemented to forecast the missing ICG points according to the different existing subtypes. The NARX was trained on two different datasets with an open-loop mode to ensure that the network is fed with correct feedback inputs. Once the training is satisfactory, the loop can be closed for multi-step prediction tests and simulation. The results show that we can predict the missing characteristic points in all the complexes with a success rate ranging between 75% and 88% in the evaluated datasets. Previously, without the NARX predictive model, the successful detection rate was 21%–30% for the same datasets. Thus, this work indicates a promising method and an accuracy increase in the detection of X, Y, O, and Z points for both datasets.

Cardiovascular diseases are a leading global cause of mortality. The current standard diagnostic methods, such as imaging and invasive procedures, are relatively expensive and partly connected with risks to the patient. Bioimpedance measurements hold the promise to offer rapid, safe, and low-cost alternative diagnostic methods. In the realm of cardiovascular diseases, bioimpedance methods rely on the changing electrical conductivity of blood, which depends on the local hemodynamics. However, the exact dependence of blood conductivity on the hemodynamic parameters is not yet fully understood, and the existing models for this dependence are limited to rather academic flow fields in straight pipes or channels. In this work, we suggest two closely connected anisotropic electrical conductivity models for blood in general three-dimensional flows, which consider the orientation and alignment of red blood cells (RBCs) in shear flows. In shear flows, RBCs adopt preferred orientations through a rotation of their membrane known as tank-treading motion. The two models are built on two different assumptions as to which hemodynamic characteristic determines the preferred orientation. The models are evaluated in two example simulations of blood flow. In a straight rigid vessel, the models coincide and are in accordance with experimental observations. In a simplified aorta geometry, the models yield different results. These differences are analyzed quantitatively, but a validation of the models with experiments is yet outstanding.

Marija Marjanovic,1 Vesna Stojanov,1,2 Ivan Marjanovic,2,3 Gordana Vukcevic-Milosevic,1 Nenad Radivojevic,1 Dragan Matic1,2 1Clinic for Cardiology, University Clinical Centre of Serbia, Belgrade, Serbia; 2Faculty of Medicine, University of Belgrade, Belgrade, Serbia; 3Ophthalmology Clinic, University Clinical Centre of Serbia, Belgrade, SerbiaCorrespondence: Dragan Matic, Clinic for Cardiology, University Clinical Centre of Serbia, Dr Koste Todorovi&cacute;a 8, Belgrade, 11000, Serbia, Tel +381 63 208 975, Email dragan4m@gmail.comPurpose: The aim of this study was to use non-invasive impedance cardiography (ICG) to determine the hemodynamic status of patients with grade 1 and grade 2 hypertension in relation to gender and age.Patients and Methods: We analyse prospectively collected data of 158 patients with grade 1 or grade 2 arterial hypertension. Patients were grouped according to age: 1) < 50 years and 2) ≥ 50 years. Hemodynamic status of patients was assessed by using non-invasive ICG. For the purpose of this study two hemodynamic parameters were used: a) systemic vascular resistance index (SVRI) and b) left cardiac work index (LCWI). The primary endpoint was the hemodynamic status of patients. The secondary endpoint was hypertension-mediated organ damage.Results: Increased SVRI was assessed in 80% of patients, more common in the ≥ 50 years group than in the < 50 years group (88.5% vs 64.8%; p < 0.01). The occurrence of increased systemic vascular resistance correlates hierarchically with increasing age. Elevated LCWI (hypervolemia and/or hyperinotropy) was present in 63% of patients, more often in males than females (70.3% vs 57.1%; p < 0.05) as well in those < 50 years than in older patients (70.4% vs 59.6%; p < 0.05). Patients with diabetes were less likely to have hypervolemia/hyperinotropy than those without diabetes (46.7% vs 67.2%; p < 0.01). Hypervolemia/hyperinotropy (46.7%) and hypovolemia/hypoinotropy (43.3%) were present in a similar percentage of diabetic patients. Left ventricular hypertrophy was found in 30 patients (19%). Patients with left ventricular hypertrophy were more commonly male (66.7% vs 42.2%; p = 0.016) and had increased systemic vascular resistance (96.7% vs 77.3%; p = 0.015) compared to the patients without left ventricular hypertrophy. Hypertensive retinopathy grade III was found in 14 patients (8.9%). Elevated daytime systolic pressure, diabetes and increased age are independent predictors of grade III hypertensive retinopathy. Patients with reduced renal function had higher mean systolic blood pressure (p < 0.05), were more commonly male (p < 0.01) and older (p < 0.01) than those without reduced renal function.Conclusion: Although there are certain correlations between hemodynamic disorders and age and gender, specific hemodynamic status of an individual patient with hypertension cannot reliably be predicted on the basis of age and gender. The measurement of hemodynamic parameters by ICG can guide the clinician to select appropriate antihypertensive therapy to the patients’ hemodynamic pathophysiologic condition.Keywords: hypertension, hemodynamics, impedance cardiography

Aortic dissection is caused by a tear on the aortic wall that allows blood to flow through the wall layers. Usually, this tear involves the intimal and partly the medial layer of the aortic wall. As a result, a new false lumen develops besides the original aorta, denoted then as the true lumen. The local hemodynamic conditions such as flow disturbances, recirculations and low wall shear stress may cause thrombus formation and growth in the false lumen. Since the false lumen status is a significant predictor for late‐dissection‐related deaths, it is of great importance in the medical management of patients with aortic dissection. The hemodynamic changes in the aorta also alter the electrical conductivity of blood. Since the blood is much more conductive than other tissues in the body, such changes can be identified with non‐invasive methods such as impedance cardiography. Therefore, in this study, the capability of impedance cardiography in monitoring thrombosis in the false lumen is studied by multiphysics simulations to assist clinicians in the medical management of patients under treatment. To tackle this problem, a 3D computational fluid dynamics simulation has been set up to model thrombosis in the false lumen and its impact on the blood flow‐induced conductivity changes. The electrical conductivity changes of blood have been assigned as material properties of the blood‐filled aorta in a 3D finite element electric simulation model to investigate the impact of conductivity changes on the measured impedance from the body's surface. The results show remarkable changes in the electrical conductivity distribution in the measurement region due to thrombosis in the false lumen, which significantly impacts the morphology of the impedance cardiogram. Thus, frequent monitoring of impedance cardiography signals may allow tracking the thrombus formation and growth in the false lumen. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Accurate and reliable determination of the characteristic points of the impedance cardiogram (ICG) is an important research problem with a growing range of applications in the cardiological diagnostics of patients with heart failure (HF). The shapes of the characteristic waves of the ICG signal and the temporal location of the characteristic points B, C, and X provide significant diagnostic information. On this basis, essential diagnostic cardiological parameters can be determined, such as, e.g., cardiac output (CO) or stroke volume (SV). Although the importance of this problem is obvious, we face many challenges, including noisy signals and the big variability in the morphology, which altogether make the accurate identification of the characteristic points quite difficult. The paper presents an effective method of ICG points identification intended for conducting experimental research in the field of impedance cardiography. Its effectiveness is confirmed in clinical pilot studies. [ABSTRACT FROM AUTHOR]

Hyperprolactinemia in males with prolactin-secreting adenomas, or prolactinomas, may be associated with endothelial dysfunction and co-existing cardiovascular risk factors. As a noninvasive technique of assessing cardiac function, impedance cardiography (ICG) may be useful in the early detection of hemodynamic dysfunction. The aim of the present study was to analyze and compare the hemodynamic profiles of patients with prolactinoma versus controls. A total of 20 men with prolactinoma (PR group) (mean age 43 years) and 20 men from the control group (CG) were evaluated in this prospective, observational comparative clinical study. The study subjects were propensity score-matched in terms of clinical characteristics—age, mean blood pressure [MBP], arterial hypertension [AH] rates, and body mass index [BMI]. ICG assessments of hemodynamic profiles were conducted with the use of a Niccomo™ device and included stroke volume index (SI), cardiac index (CI), systemic vascular resistance index (SVRI), velocity index (VI), acceleration index (ACI), Heather index (HI), and thoracic fluid content (TFC). AH was well-controlled in both study groups (116/76 mmHg PR vs. 119/76 mmHg CG). In comparison with CG patients, ICG revealed PR group patients to have higher rates of high thoracic fluid content (TFC) (>35 1/kOhm; p = 0.035) and lower SI values (<35 mL/m2, p = 0.072). There was a convergent tendency towards lower values of other cardiac function parameters (SI, CI, VI, ACI, and HI). Prolactinoma-associated endocrine abnormalities are related to hemodynamic profile alterations, including higher rates of increased TFC and the risk of worsened cardiac function. [ABSTRACT FROM AUTHOR]

Background: Wearable technologies for monitoring cardiovascular parameters, including electrocardiography (ECG) and impedance cardiography (ICG), propose a challenging research subject. The expectancy for wearable devices to be unobtrusive and miniaturized sets a goal to develop smarter devices and better methods for signal acquisition, processing, and decision-making. Methods: In this work, non-standard electrode placement configurations (EPC) on the thoracic area and single arm were experimented for ECG signal acquisition. The locations were selected for joint acquisition of ECG and ICG, targeted to suitability for integrating into wearable devices. The methodology for comparing the detected signals of ECG was developed, presented, and applied to determine the R, S, and T waves and RR interval. An algorithm was proposed to distinguish the R waves in the case of large T waves. Results: Results show the feasibility of using non-standard EPCs, manifesting in recognizable signal waveforms with reasonable quality for post-processing. A considerably lower median sensitivity of R wave was verified (27.3%) compared with T wave (49%) and S wave (44.9%) throughout the used data. The proposed algorithm for distinguishing R wave from large T wave shows satisfactory results. Conclusions: The most suitable non-standard locations for ECG monitoring in conjunction with ICG were determined and proposed. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases (CVDs) are one of the leading members of non-communicable diseases. An early diagnosis is essential for effective treatment, to reduce hospitalization time and health care costs. Nowadays, an exercise stress test on an ergometer is used to identify CVDs. To improve the accuracy of diagnostics, the hemodynamic status and parameters of a person can be investigated. For hemodynamic management, thoracic electrical bioimpedance has recently been used. This technique offers beat-to-beat stroke volume calculation but suffers from an artifact-sensitive signal that makes such measurements difficult during movement. We propose a new method based on a gated recurrent unit (GRU) neural network and the ECG signal to improve the measurement of bioimpedance signals, reduce artifacts and calculate hemodynamic parameters. We conducted a study with 23 subjects. The new approach is compared to ensemble averaging, scaled Fourier linear combiner, adaptive filter, and simple neural networks. The GRU neural network performs better with single artifact events than shallow neural networks (mean error −0.0244, mean square error 0.0181 for normalized stroke volume). The GRU network is superior to other algorithms using time-correlated data for the exercise stress test. [ABSTRACT FROM AUTHOR]

We aimed to continuously determine the stroke volume (SV) and blood volume (BV) during incremental exercise to evaluate the individual SV course and to correlate both variables across different exercise intensities. Twenty-six females with heterogeneous endurance capacities performed an incremental cycle ergometer test to continuously determine the oxygen uptake (V_O2), cardiac output (Q_) and changes in BV. Q_ was determined by impedance cardiography and resting cardiac dimensions by 2D echocardiography. Hemoglobin mass and BV were determined using a carbon monoxide-rebreathing method. V_O2max ranged from 32 to 62 mL·kg−1·min−1. Q_max and SVmax ranged from 16.4 to 31.6 L·min−1 and 90–170 mL, respectively. The SV significantly increased from rest to 40% and from 40% to 80% V_O2max. Changes in SV from rest to 40% V_O2max were negatively (r = −0.40, p = 0.05), between 40% and 80% positively correlated with BV (r = 0.45, p < 0.05). At each exercise intensity, the SV was significantly correlated with the BV and the cardiac dimensions, i.e., left ventricular muscle mass (LVMM) and end-diastolic diameter (LVEDD). The BV decreased by 280 ± 115 mL (5.7%, p = 0.001) until maximum exercise. We found no correlation between the changes in BV and the changes in SV between each exercise intensity. The hemoglobin concentration [Hb] increased by 0.8 ± 0.3 g·dL−1, the capillary oxygen saturation (ScO2) decreased by 4.0% (p < 0.001). As a result, the calculated arterial oxygen content significantly increased (18.5 ± 1.0 vs. 18.9 ± 1.0 mL·dL−1, p = 0.001). A 1 L higher BV at V_O2max was associated with a higher SVmax of 16.2 mL (r = 0.63, p < 0.001) and Q_max of 2.5 L·min−1 (r = 0.56, p < 0.01). In conclusion, the SV strongly correlates with the cardiac dimensions, which might be the result of adaptations to an increased volume load. The positive effect of a high BV on SV is particularly noticeable at high and severe intensity exercise. The theoretically expected reduction in V_O2max due to lower SV as a consequence of reduced BV is apparently compensated by the increased arterial oxygen content due to a higher [Hb]. [ABSTRACT FROM AUTHOR]

Ischemic preconditioning (IPC) involves brief, repeated bouts of limb occlusion and reperfusion capable of improving exercise performance at least partially by enhancing local skeletal muscle oxygenation. This study sought to investigate the effect of a lower limb IPC protocol, with either a 5-min or 45-min post-application delay, on vastus lateralis tissue saturation index (TSI) and systemic cardiac hemodynamics at rest and during short-duration intense cycling. Twelve young adults randomly completed four interventions: IPC (at 220 mmHg) with 5-min delay (IPC5), IPC with 45-min delay (IPC45), SHAM (at 20 mmHg) with 5-min delay (SHAM5), and SHAM with 45-min delay (SHAM45). Following IPC intervention and recovery delay, participants completed 5, 60-s high-intensity (100% Wpeak) cycle sprints separated by 120-sec of active recovery (30% Wpeak). Compared to baseline, TSI immediately following IPC5, but pre-exercise, remained lower than the equivalent for IPC45 (−5.9 ± 1.5%, p =.002). IPC, imposed at least 45-min before the completion of five 60-s sprint cycling efforts, significantly enhanced TSI during active recovery between sprint intervals compared to a 5-min delay (6.6 ± 2.4%, p =.021), and identical SHAM conditions (SHAM5: 5.8 ± 2.2%, p =.024; SHAM45: 6.2 ± 2.5%, p =.029). A 45-min delay following IPC appears to provide heightened skeletal muscle metabolic rebound prior to intense sprint cycling as compared to a 5-min delay. Furthermore, IPC followed by a 45-min delay enhanced recovery of skeletal muscle oxygenation during low intensity active sprint recovery, despite an unchanged decline in skeletal muscle oxygenation during near-maximal sprinting efforts. [ABSTRACT FROM AUTHOR]

Partner support for self-expansion has been associated with long-term health and retirement satisfaction, yet the underlying physiological correlates are unknown. We predicted that partner support for self-expansion would be associated with short-term physiology and behavior as well as long-term goal pursuit. And 100 couples with at least one retiree within 2 years of retirement visited the laboratory and had a discussion of the retirees' future goals for retirement. We recorded behaviors and physiological responses during the discussion, assessed immediate feelings of capability afterwards, and then assessed goal pursuit one year later. Laboratory results indicated that partner support for self-expansion was linked to increased stroke volume reactivity in the support-recipient (suggesting a greater challenge response), which in turn predicted greater feelings of capability of accomplishing the goal, particularly for males. In addition, decreasesin the support provider's pre-ejection period reactivity (greater sympathetic arousal) during the discussion were associated with greater partner support for self-expansion in the lab, suggesting that support providers offer greater levels of support when they exhibit greater physiological signs of task engagement. Longitudinal follow-up results indicated that immediate feelings of capability of accomplishing the goal following a discussion about that goal predicted goal pursuit 1 year later. This research leverages a dyadic design and a multi-method approach (involving physiology, observed behavior, and perceptions) to show that couple members' physiology during goal discussions has long-term implications for a support-recipient's ability to accomplish goals. [ABSTRACT FROM AUTHOR]

Impedance cardiography (ICG) is essential in evaluating cardiac function in patients with cardiovascular diseases. Aiming at the problem that the measurement of ICG signal is easily disturbed by motion artifacts, this paper introduces a de-noising method based on two-step spectral ensemble empirical mode decomposition (EEMD) and canonical correlation analysis (CCA). Firstly, the first spectral EEMD-CCA was performed between ICG and motion signals, and electrocardiogram (ECG) and motion signals, respectively. The component with the strongest correlation coefficient was set to zero to suppress the main motion artifacts. Secondly, the obtained ECG and ICG signals were subjected to a second spectral EEMD-CCA for further denoising. Lastly, the ICG signal is reconstructed using these share components. The experiment was tested on 30 subjects, and the results showed that the quality of the ICG signal is greatly improved after using the proposed denoising method, which could support the subsequent diagnosis and analysis of cardiovascular diseases.