Noninvasive Impedance Cardiography Research Articles

Impact of age and sex on heart rate variability and cardiometabolic function in healthy adults

Heart rate variability (HRV) is a non-invasive measure of cardiac autonomic function. A clearer understanding as to whether resting autonomic function represented by HRV could be associated with changes in peak exercise cardiac function remains unanswered. This study evaluated the effect of age and sex on HRV, cardiometabolic function, and determined the correlation between HRV and cardiac function in healthy individuals. Sixty-eight participants (age range: 19–78 years old, females, n = 28) were recruited. Participants were stratified according to age (younger (<40 years old, n = 43, females, n = 17) and older age groups (>55 years old, n = 25, females, n = 11). Firstly, HRV was measured using non-invasive impedance cardiography method (TaskForce, CNSystems, Graz, Austria) and recorded at rest (supine position) for 30 min. HRV measures included: low frequency (LF) power, high frequency (HF) power (both normalised (nu) and absolute units (ms2)) and LF/HF ratio. Participants then completed a progressive cardiorespiratory exercise test using a semi-recumbent cycle ergometer (Corival, Lode, Groningen, Netherlands) with simultaneous gas exchange measurements (Metalyzer 3B, Cortex, Leipzig, Germany). Cardiac function was represented by peak exercise cardiac power output index (CPO). After controlling for body mass index and physical activity, males had significantly higher mean vales of RR interval than females (males = 1043 ± 165; females = 952 ± 128 ms, p = 0.02). There was no significant main effect of age, sex or their interaction on any of the other HRV measures. In younger and older females, resting RR interval had a significant relationship with peak exercise CPO (young females: r = 0.54, p < 0.05; old females: r = 0.81, p < 0.01). There was also a significant relationship between resting HF power and peak exercise CPO in younger females (r = 0.70, p < 0.01). HRV was not influenced by age but RR interval was associated with peak exercise CPO in females regardless of age, whilst HF power was significantly associated with CPO in younger females only.

Optimal homeostatic stress to maximize the homogeneity of adaptations to interval interventions in soccer players.

This study examined the uniformity of adaptations in cardiorespiratory fitness and bio-motor abilities by analyzing individual responses to measures representing the mentioned qualities. Twenty-four male well-trained soccer players (Age = 26 ± 4years; stature = 181 ± 3.8; Weight = 84 ± 6.1) were randomized to two groups performing short sprint interval training [sSIT (3 sets of 10 × 4s all-out sprints with 20s of recovery between efforts and 3min of rest intervals between sets)] or a time-matched small-sided game [SSG (3 sets of 3 v 3 efforts in a 20 × 15m area with 3min of relief in-between)]. Before and after the 6-week training period, aerobic fitness indices, cardiac hemodynamics, and anaerobic power were assessed through a graded exercise test utilizing a gas collection system, noninvasive impedance cardiography, and a lower-body Wingate test, respectively. Also, sport-specific bio-motor abilities were determined by measuring linear speed, change of direction, and jumping ability. Comparing inter-individual variability in the adaptive changes by analyzing residuals in individual adaptations indicated that sSIT induces more uniform changes in the first and second ventilatory threshold (VT1 & VT2), stroke volume, and peak power output across team members than SSG. SSG also yielded lower proportions of responders in , VT1, VT2, peak, and average power output compared to sSIT. Additionally, the coefficient of variation in mean group changes in measures of aerobic fitness and bio-motor abilities in response to sSIT were lower than in SSG. Short sprint interval training induces more homogenized adaptations in measures of cardiorespiratory fitness and anaerobic power than small-sided games across team members.

Effect of cardiac function in patients with gastrointestinal cancer with or without acute kidney injury assessed using a non-invasive impedance cardiography: a case-control study

ObjectivesThis study aimed to analyze the possible causes of changes in cardiac function and investigate the feasibility of clinical assessment of gastrointestinal cancer in patients with or without acute kidney injury (AKI) assessed using a non-invasive impedance cardiography (ICG, Bioz. Cardio Dynamics, USA) to identify independent risk factors.MethodsPatients admitted to the Fourth Hospital of Hebei Medical University, China, between May 1, 2019, and February 15, 2022, were included in this study. A total of 51 patients with gastrointestinal cancer (31 men and 20 women, mean age 61.1 ± 10.9 years) with or without AKI were evaluated for ICG. A total of 19 patients underwent ultrasound cardiography (UCG) and ICG evaluations.ResultThere was a significant positive correlation between cardiac output (CO), cardiac index (CI), stroke volume (SV), left cardiac work index (LCWI), and ejection fraction (EF) measured using UCG and ICG. The relationship was observed between COICG and COUCG (r = 0.707, P = 0.001), CIICG and CIUCG (r = 0.718, P = 0.001), SVICG and SVUCG (r = 0.837, P < 0.001), and LCWIICG and EFUCG (r = 0.540, P = 0.017). Cardiac function parameters measured using ICG were statistically different between patients with gastrointestinal cancer with or without AKI (P ≤ 0.05). Multivariate analysis revealed that AKI independently affects cardiac function in patients with gastrointestinal cancer.ConclusionsUCG and ICG methods are significantly associated with cardiac function in patients with or without AKI, and patients with gastrointestinal cancer with AKI are worse than those without AKI. AKI is an independent risk factor for cardiac function in patients with gastrointestinal cancer.

Could Impedance Cardiography be a Non-Invasive Alternative Method of Measuring Cardiac Output in Patients with Pulmonary Hypertension?

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. 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. 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). 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.

Age- and Gender-Related Differences in the Hemodynamic Status of Patients with Mild or Moderate Hypertension.

PurposeThe 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 MethodsWe 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.ResultsIncreased 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.ConclusionAlthough 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.

The effect of impedance cardiography directed antihypertensive therapy on fetal growth restriction rates and perinatal mortality in women with chronic hypertension.

We sought to determine the effect of impedance cardiography directed medical antihypertensive therapy on fetal growth restriction and perinatal mortality in women with chronic hypertension. A retrospective study was conducted on 958 women referred to the Maternal Hypertension Center at Cabell Huntington Hospital between 2005 and 2014 for the indication of chronic hypertension. Serial assessments of maternal hemodynamics were obtained using non-invasive impedance cardiography. Vasodilators were initiated for increased systemic vascular resistance. Elevated cardiac output was treated with beta blockade. Blood pressure at initial visit was used to stratify patients into five groups. Initial blood pressure of <130 systolic or <80 diastolic had 24 cases of growth restriction (6.8%) and 6 perinatal deaths (1.7%), 130-139 systolic or 80-89 diastolic resulted in 29 cases of growth restriction (9.3%) and 9 perinatal deaths (2.9%), 140-149 systolic or 90-99 diastolic 14 cases of growth restriction (6.5%) and 3 perinatal deaths (1.4%), 150-159 systolic or 100-109 diastolic had 5 cases of growth restriction (8.6%) and 4 perinatal deaths (6.89%), and >160 systolic or >110 diastolic 3 cases of growth restriction (13%) with no perinatal deaths. There were no differences in growth restriction (p=.59) or perinatal death (p=.15) between the groups. The rates of IUGR and perinatal mortality did not increase even with increasing severity of maternal hypertension. This low cost and non-invasive test should be considered for optimizing rates of growth restriction and perinatal mortality in pregnancies complicated by chronic hypertension.

Performance evaluation of a portable bioimpedance cardiac output monitor for measuring hemodynamic changes in athletes during a head-up tilt test.

Cardiac output (CO) monitoring is useful for sports performance training, but most methods are unsuitable as they are invasive or hinder performance. The performance of PhysioFlow (PF), a portable noninvasive transthoracic bioimpedance CO monitor, was evaluated and compared with a reference Doppler CO monitor, USCOM, using a head-up tilt (HUT) test. With ethics committee approval, 20 healthy well-trained athletes were subjected to HUT in a fixed order of 0°, 70°, 30°, and 0° for 3 min each. Simultaneous hemodynamic measurements using PF and USCOM were made 30 s after a change in HUT and analyzed using t tests, ANOVA, and mountain plots. Heart rate (HR) and stroke volume (SV) from both monitors changed according to physiological expectation of tilt, but PF measurements of SV were higher with a positive bias (PF vs. USCOM, 0°: 87.3 vs. 54.0 mL, P < 0.001; 70°: 76.5 vs. 39.5 mL, P < 0.001; 30°: 81.4 vs. 50.1 mL, P < 0.001; 0°: 88.3 vs. 57.1 mL, P < 0.001). Relative changes in SV (∆SV) after each tilt measured using PF were lower with a negative bias (PF vs. USCOM, 0° to 70°: -12.3% vs. -26.3%, P = 0.002; 70° to 30°: +6.4% vs. +31.2%, P < 0.001; 30° to 0°: +9.2% vs. +15.8%, P = 0.280). CO measurements using PF at 70° were erroneous. Compared with USCOM, PF overestimated SV measurements but underestimated the ∆SV between HUT. Accuracy of the PF deteriorated at 70°, implying a gravitational influence on its performance. These findings suggested that the suitability of PF for sports use is questionable.NEW & NOTEWORTHY The use of impedance cardiography to monitor physiological changes in sports is rarely reported. Using head-up tilt test, we evaluated a portable noninvasive impedance cardiography device (PhysioFlow) by comparing it with a reference Doppler monitor (USCOM). Accuracy in tracking hemodynamic changes deteriorated with higher tilt, implying a gravitational influence on its performance. Stroke volume measurements were overestimated, but the changes were underestimated. Despite its convenient physical features, the suitability of PhysioFlow for sports use is questionable.

A Novel Non-Invasive Assessment of Cardiac Hemodynamics in Patients With Heart Failure and Atrial Fibrillation.

BackgroundHeart failure (HF) and atrial fibrillation (AF) often coexist. The hemodynamic alterations induced by AF in patients with HF are well studied; however we lack reliable and non-invasive means to study these hemodynamic alterations in ambulatory patients. We sought to evaluate the clinical utility of impedance cardiography (ICG) as a novel and non-invasive tool to evaluate cardiac hemodynamics in ambulatory patients with HF and AF.MethodsThis was a single-center observational study. A convenient sample of ambulatory patients with chronic HF underwent non-invasive electrocardiogram (ECG) and hemodynamic monitoring using BioZ Dx impedance cardiographer. Hemodynamics were automatically computed and ECG data were interpreted by an independent reviewer.ResultsA total of 32 patients (62 ± 14 years of age; 66% male; ejection fraction 33±13%) were enrolled. There were no baseline demographic or clinical differences between those with AF (28%) and those without AF (72%). However, patients with AF exhibited lower stroke volume (60 ± 7 vs. 89 ± 29, P = 0.008), left ventricular work (33 ± 9 vs. 45 ± 13, P = 0.016), cardiac contractility (30 ± 8 vs. 40 ± 13, P = 0.037), and arterial elasticity (13 ± 5 vs. 21 ± 5, P = 0.012), as well as higher cardiac afterload (203 ± 57 vs. 151 ± 49, P = 0.015).ConclusionsUsing non-invasive ICG, we have shown that it is feasible to characterize hemodynamics in ambulatory HF patients. We show that AF compromises left ventricular function in patients with HF and is associated with excess afterload and reduced arterial elasticity.

The utility of impedance cardiography in hemodynamic monitoring of patients with sepsis

BackgroundCommonly used biochemical indicators and hemodynamic and physiologic parameters of sepsis vary with regard to their sensitivity and specificity to the diagnosis. The aim of this preliminary study was to...

Acute Soy Supplementation Improves 20-km Time Trial Performance, Power, and Speed.

Isoflavones, a chemical class of phytoestrogens found in soybeans and soy products, may have biological functions similar to estradiol. After binding with ERβ or perhaps independently of estrogen receptors, isoflavones may augment vascular endothelial relaxation, contributing to improved limb blood flow. To determine if acute fermented soy extract supplementation influences 20-km time trial cycling performance and cardiac hemodynamics compared with a placebo. Subjects included 25 cyclists and triathletes (31 ± 8 yr, V˙O2peak: 55.1 ± 8.4 mL·kg·min). Each subject completed a V˙O2peak assessment, familiarization, and two 20-km time trials in randomized order after ingestion of a fermented soy extract supplement or placebo. The fermented soy extract consisted of 30 g powdered supplement in 16 fl. ounces of water. The placebo contained the same quantities of organic cocoa powder and water. Each trial consisted of 60 min of rest, 30 min at 55% Wpeak, and a self-paced 20-km time trial. Soy supplementation elicited a faster time to 20-km completion (-0.22 ± 0.51 min; -13 s), lower average HR (-5 ± 7 bpm), and significantly greater power (7 ± 3 W) and speed (0.42 ± 0.16 km·h) during the last 5 km of the time trial compared with placebo. Analysis of the results by relative fitness level (<57 vs ≥ 57 mL⋅kg⋅min) indicated that those with a higher level of fitness reaped the largest performance improvement alongside a reduced HR (-5 ± 7 bpm). Ingestion of a fermented soy extract supplement improved sprint-distance performance through improvements in both power and speed. For those with great aerobic fitness, soy supplementation may help to decrease cardiac demand alongside performance improvement.

The impedance cardiography technique in medical diagnosis

Background: Thoracic Electrical Bioimpedance (TEB) Technology sometimes called the Impedance Cardiography (ICG). In 1940, the Impedance Cardiography emerged; the studies of this technique are realized to the cardiovascular diseases detection which used hemodynamic parameters measurements based on the skin electrodes contact by injecting a low amplitude alternating signal. The objective of this article is to review the various studies based on this signal type and to present the multiple methods used for the treatment and to have a correct analysis.&#x0D; Methods: This ICG technique consists for applying an electric field longitudinally across a segment of the thorax with amplitude in mean, high frequency and low amplitude current. To analyze the ICG signal, the signal denoising is necessary that’s why a multiple filters are proposed, and the Discrete Wavelet Transform (DWT) denoising is also used.&#x0D; Results: The ICG is considered advantageous compared to other invasive conventional techniques; it gives a good correlation, and solves the Doppler ultrasound and Thermodilution problems. According to the studies, the Daubechies wavelet family (db8) is the best DWT to eliminate the noises. There are several algorithms for the signal characteristic point’s detection.&#x0D; Conclusion: For the purpose of cardiovascular disease diagnosis and monitoring, the non-invasive ICG technique comes to solve the complexity problem for measurement and analyzing heart disease based on the thoracic electrical impedance change assessment that is due to blood velocity and resistivity changes (blood volume changes) in order to estimate several hemodynamic parameters.&#x0D; Keywords: ICG, cardiovascular disease, hemodynamic parameters, diagnosis and monitoring, correct analysis.&#x0D;

Cardiopulmonary factors affecting 6-min walk distance in patients with idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies involve skeletal muscles and can be associated with interstitial lung disease and/or heart dysfunction, which may reduce exercise capacity. We aimed to clarify cardiopulmonary factors affecting the 6-min walk distance in patients who were able to walk without leg pain or fatigue. Twenty-three patients with inactive adult idiopathic inflammatory myopathies, and 18 age- and gender-matched healthy controls were evaluated for hemodynamic responses using noninvasive impedance cardiography during the 6-min walk test. The patients were also examined by the pulmonary function test for forced vital capacity and diffusing capacity for carbon monoxide (DLCO), and by echocardiography for left ventricular ejection fraction and right ventricular systolic pressure. Interstitial lung disease was diagnosed in 19 patients using high-resolution computed tomography. There was no difference in 6-min walk distance or cardiac output after walking between the patients and healthy controls. However, stroke volume during the 6-min walk test was significantly lower in the patients than in healthy controls, suggesting malfunction in the heart. Moreover, the increased heart rate matched the cardiac output. Spearman’s correlation analysis demonstrated a correlation between 6-min walk distance and stroke volume, cardiac output after walking and DLCO, but not left ventricular ejection fraction or right ventricular systolic pressure, as this study lacked the patients with pulmonary hypertension. In conclusion, impaired DLCO due to interstitial lung disease was suggested to be a fundamental parameter affecting exercise capacity, in addition to heart involvement, in patients with idiopathic inflammatory myopathies.

Hemodynamic and Body Fluid Response to Water Ingestion

Despite a paucity of information regarding the hemodynamic changes associated with moderate fluid ingestion, the popular, unsubstantiated recommendation for most adults to ingest 8 x 8 ounce glasses of water daily (1888 mL) remains prevalent. PURPOSE: The purpose of this study was to determine the hemodynamic and body fluid changes associated with consuming water at temperatures of 4° C & 37° C and two volumes of 7 & 21 mL/kg. METHODS: 10 subjects (age 22.3 ± 1.3 yr, ht. 1.74 ± .15 m., body mass(bm), 75.1 ± 18.5 kg, 4♂) reported to the lab in a euhydrated state and refrained from ingestion of food and beverage (except water) for 10 hrs and no water 2 hours pre- trial. 30 minutes of rest preceded venipuncture for hematocrit (H), plasma specific gravity (PSG), and plasma density (PD) analyzed by digital refractometry. Hemodynamic values of heart rate (HR), stroke volume (SV) and cardiac output (Q) were obtained by a non-invasive impedance cardiography system. All measures were obtained pre-water ingestion (PRE) and at 20 minute intervals following water ingestion (T1, T2, & T3). Immediately following the PRE, subjects ingested C7, C21, H7 or H21 with the volume calculated from individual bm at a mean of 526 and 1577 mL for 7 and 21 trials, respectively. Subjects served as their own control in the randomized assignment of trials. RESULTS: Statistical analysis by ANOVA was applied to these data and revealed NSD (p>.05) among all trials. Mean values for all four trials are depicted in the following table:Table: No title available.CONCLUSION: The ingestion of water in volumes and temperatures mimicking current practices among many adults results in minimal expansion of blood volume or changes in hemodynamic function. Apparently, consuming considerable water without excessive loss of fluid from either environmental conditions or exercise induced temperature regulation, is safe with no adverse impact on non-exercising individuals.

Cardiovascular Responses to Selected Cranial Osteopathic Manipulations in Hypertensive Patients

Background and PurposeOsteopathic cranial manipulations (CM) have been used as a part of therapeutic management of hypertensive patients. However, our knowledge about physiological responses to CM in cardiac patients is limited. A quantitative relationship between applied CM and cardiovascular parameters has not been well established. The purpose of this study was to measure changes in heart rate, autonomic input to the heart by using the heart rate variability test, cardiac contractility by using impedance cardiography, and systemic blood pressure in response to selected CM, namely occipital‐atlantal decompression, occipital‐mastoid decompression, and compression of the fourth ventricle.MethodHypertensive 65–75 year old subjects, three men and two women, were involved in this study. Hypertension was controlled by an angiotensin‐converting enzyme inhibitor (3 subjects), calcium channels blocker (1 subject) and beta‐blocker (1 subject). Each subject participated in the experimental (CM) and control (sham) groups. A non‐invasive impedance cardiography method was used to measure changes in cardiac parameters before and after manipulations. Data were recorded and analyzed using BIOPAC Systems, Inc. equipment and software. Blood pressure was measured before and after manipulations by using a sphygmomanometer. All manipulations were performed by the same osteopathic physician.ResultsCranial and sham manipulations resulted in different responses by the subjects. CM produced a decrease in systolic (5%) and mean arterial (6%) pressures, and revealed a trend towards an increase in sympathetic and decrease in parasympathetic cardiac activity based on heart rate variability test. Sham manipulations did not affect blood pressure and were associated with a trend towards a decrease in sympathetic and increase in parasympathetic cardiac activity. No changes in cardiac contractility were recorded for CM and sham manipulations.Discussion and conclusionIt appears that cranial manipulations may enhance the antihypertensive effect of medication through the effect on autonomic nervous system. The physiological effect of CM on autonomic control of systemic hemodynamics needs further investigation.Support or Funding InformationThis project was funded by the TUN Research Grant AwardThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Cardiac hemodynamic response to the 6-minute walk test in young adults and the elderly.

BackgroundExercise capacity is evaluated using the 6-minute walk test in various diseases. Variety in the distances walked was also shown in healthy subjects. Moreover, age-related influences on cardiac hemodynamic response to the 6-minute walk test have not been clarified. The purpose of this study was thus to investigate the hemodynamic response to the 6-minute walk test and to detect factors related to the distance walked in healthy subjects.MethodsThirteen young adults (age 20.5 ± 0.7 years, BMI 22.0 ± 4.3) and 26 elderly individuals (age 60.2 ± 6.1 years, BMI 21.7 ± 2.2) were enrolled to measure real-time hemodynamic responses using non-invasive impedance cardiography during the 6-minute walk test.ResultsStroke volume was higher in the young than in the elderly and reached a plateau within 30 s of starting to walk in all subjects. An increase in heart rate took more than 1 min in the elderly, while it took less than 30 s in the young, which resulted in slower increases in cardiac output and cardiac index in the elderly. There was no difference in the distance in the 6-minute walk test between the young and the elderly. The distance walked was correlated with heart rate, cardiac output, and cardiac index, but not with stroke volume, at the end of the 6-minute walk test.ConclusionsThe distance walked appeared to depend on increased cardiac output based on heart rate, but did not appear to be limited by stroke volume, in healthy subjects.

Maternal venous Doppler characteristics are abnormal in pre-eclampsia but not in gestational hypertension.

To compare functional characteristics of maternal thoraco-abdominal arteries and veins in proteinuric and non-proteinuric hypertension in pregnancy. This retrospective study included women with singleton pregnancies during the third trimester, which were either uncomplicated or complicated with different clinical types of hypertension: non-proteinuric gestational hypertension (GH), early-onset pre-eclampsia (PE) diagnosed < 34 weeks or late-onset PE diagnosed ≥ 34 weeks. Demographic maternal and neonatal data were recorded, together with maternal serum and urine analytes. All women underwent standardized automated blood-pressure measurement, together with non-invasive impedance cardiography (ICG), for measurement of cardiac output (CO), aortic flow velocity index (VI) and aortic flow acceleration index (ACI). A standardized combined Doppler-electrocardiography assessment of maternal venous hemodynamics was performed to measure renal interlobar vein impedance index (RIVI), hepatic vein impedance index (HVI) and venous pulse transit time (VPTT) in liver and kidneys. Finally, resistance index (RI), pulsatility index (PI) and arterial pulse transit time (APTT) were measured in the uterine arcuate arteries. Mann-Whitney U-tests and Fisher's exact tests were used for intergroup comparisons, and linear dependence between variables was assessed using Pearson's correlation coefficient (r). A total of 150 pregnancies were evaluated: 22 with uncomplicated pregnancy, 41 GH, 31 early PE and 56 late PE. Aortic VI and ACI were lower in GH, early PE and late PE than in uncomplicated pregnancy. Both early PE and late PE differed from GH by having shorter APTT in the uterine arcuate arteries and higher RIVI. Hemodynamic abnormalities were most pronounced in early PE, during which uterine arcuate artery RI was higher and VPTT in kidneys was shorter than in late PE. There was a significant correlation between degree of proteinuria and RIVI for the left (r = 0.381) and right (r = 0.347) kidney in late PE, but this was not true for early PE. There is a gradient of worsening arterial and venous hemodynamic abnormalities from GH to late PE and then to early PE. Venous hemodynamic abnormalities are present only in PE, with a linear correlation between proteinuria and RIVI in late PE. The role of the maternal venous compartment in the pathophysiology and etiology of PE-related symptoms may be much more important than considered at present.

Impedance cardiography assessed treatment of acute severe pregnancy hypertension: a randomized trial

Objective: Using noninvasive bedside impedance cardiography (ICG), we compared the effectiveness and the hemodynamic impact of intravenous labetalol versus hydralazine for the reduction of acute-onset severe hypertension to ACOG-recommended blood pressure levels (ACOG Committee Opinion 514).Study design: In this prospective randomized pilot study of acutely severe systolic hypertension (≥160 mmHg), pregnant women received either labetalol (L) or hydralazine (H) intravenously and underwent thoracic ICG before and after treatment. Data analysis were performed using STATA software (StataCorp LP, College Station, TX); data are expressed as mean ± SD.Results: About 29 patients completed the study. There was no significant difference in mean arterial pressure (MAP) between groups [H = 119.4 mmHg, L = 117.7 mmHg, mean difference (MD) = 1.73); the estimated MD between baseline and follow-up ICG was −9.17 (p = 0.001, 95% CI: −14.39 to −3.95). There were no significant differences in total peripheral resistance (TPR) between groups (H = 1771.3, L = 1976.97, MD = 205.62) or cardiac output (CO) between groups (H = 5.7, L = 5.1, MD = 0.64) or a significant MD between these at baseline and follow-up.Conclusion: Both drugs performed similarly to achieve ACOG-recommended initial blood pressure reduction safely without side effects or excessive acute hemodynamic profile correction toward normal pregnancy values.

Abstract 17638: Systemic Cardiovascular Effects of Intravenous Urocortin 2 and Urocortin 3 in Patients with Heart Failure and Healthy Volunteers

Introduction: Urocortin 2 (UCN 2) and urocortin 3 (UCN 3) are endogenous peptide hormones with an emerging role in the pathophysiology and treatment of heart failure. For the first time, we examined the systemic cardiovascular effects of both UCN 2 and UCN 3 in healthy volunteers and patients with heart failure. Methods: Seven healthy volunteers (Group A) and nine patients with stable chronic heart failure (Group B, New York Heart Association class II and III, left ventricular ejection fraction &lt;35%) on optimal medical therapy underwent non-invasive oscillometric sphygmomanometry and impedance cardiography during incremental intravenous infusions of sodium nitroprusside (0.15/0.5/1.5 μg/kg/min), UCN 2 (0.16/0.48/1.6 μg/min), UCN 3 (5/15/50 μg/min) and saline placebo in a randomised double blind two-way cross over study. Results: Other than diastolic blood pressure (78 vs 72 mmHg for Group A and B respectively, p&lt;0.05), haemodynamic variables were similar at baseline of each infusion and were unchanged by saline placebo infusion (p&gt;0.05 for all). SNP, UCN2 and UCN 3 infusions increased heart rate and cardiac index, and reduced systolic and diastolic blood pressure and peripheral vascular resistance index (PVRI) in both healthy volunteers and patients with heart failure (p&lt;0.05 for all; see Figure 1). There were no significant differences in the changes in cardiac index or PVRI between healthy volunteers and patients with heart failure during either UCN 2 or UCN 3 infusions (p&gt;0.05). Conclusion: Intravenous UCN 2 and especially UCN 3 increase cardiac output and reduce peripheral vascular resistance. This favourable haemodynamic profile suggests that UCN 2 and UCN 3 hold exciting therapeutic potential for the treatment of acute heart failure.

Cardiac responses to selected cranial osteopathic manipulations in healthy young men (LB656)

Background and Purpose: Cranial manipulations (CM) as a part of osteopathic manipulative treatment have been used to treat patients. However, physiological responses to CM are not well defined in literature. The purpose of this study was to measure changes in heart rate (HR), heart rate variability (HRV), stroke volume index (SI), and cardiac index (CI) in response to selected CM and sham manipulation.Method: Healthy 25‐35 year old men participated in this study. Non‐invasive impedance cardiography method was used to measure changes in cardiac parameters before and after manipulations. Data were recorded and analyzed using BIOPAC Systems, Inc. equipment and software. All manipulations were performed by the same osteopathic physician.Results: CM increased parasympathetic input (70%) to the heart resulting in decreased HR (5%) and CI (7%) without significant effect on SI. These changes were not seen in sham manipulation.Conclusion: Selected CM decreased CI by decreasing HR without significant effect on cardiac contractility in healthy young men. Future studies will compare gender and age differences in response to osteopathic techniques.Grant Funding Source: This project was funded by the TUN Research Grant Award

339: A pilot study of hemodynamic parameters by noninvasive advanced impedance cardiography (NAIC) in pregnant women in Urban India: a prelude to preeclampsia, low birth weight and future development of metabolic syndrome

339: A pilot study of hemodynamic parameters by noninvasive advanced impedance cardiography (NAIC) in pregnant women in Urban India: a prelude to preeclampsia, low birth weight and future development of metabolic syndrome