Thoracic Fluid Content Index Research Articles

#3050 Hemodynamic study of hypertensive disorders in pregnancy using cardiothoracic bioimpedance

Abstract Background and Aims Hypertensive disorders in pregnancy (HDP) are a major cause of maternal and perinatal morbidity and mortality. There is still a need for the development of biomarkers for early diagnosis of the severity of the condition. Thoracic electrical bioimpedance (TEB) is a non-invasive hemodynamic technique based on the resistance to the flow of electrical current. We investigated hemodynamic changes in pregnant/postpartum women with HDP using TEB. Method A retrospective observational study was conducted in pregnant and postpartum women with hypertension monitored by TEB. Indirect changes were analyzed in: cardiac work, left cardiac work index (LCWI kg⋅m/m2) and calculated cardiac output (CO ml/min=systolic volume -SV ml- × heart rate -HR bpm-); fluid status, thoracic fluid content index (TFCI l/kOhm/m2); and resistances, systemic vascular resistance index (SVRI dyn.s.cm-5.m2). Normality of variables was assessed by Shapiro-Wilk test and correlation analysis was performed by Pearson/Spearman tests. Statistical inference between the hypertension-preeclampsia and pregnancy-postpartum groups was performed using Student's/Mann-Whitney U tests. Analysis was performed using STATA 12. Results Fifty-five patients were included with a mean age of 36.5 years (SD 4.54), 69% were older than 35 years. Pregnant women accounted for 86% of the TEB evaluations, the majority (93.6%) in the third trimester. There was chronic hypertension in 7.27% and pre-eclampsia in 18.18% of previous pregnancies. The diagnoses were: pre-eclampsia (56.36%), gestational hypertension (40%) and HELLP syndrome (3.64%). The mean blood pressure was 144/89 (SD 16/11) mmHg. Mean proteinuria was 363.2 (range: 10.3-23220) mg/g. The median values were as follow: LCWI: 5.05 (IQR: 1.4) kg⋅m/m2; CO: 6352 (IQR: 2345) ml/min; TFCI: 17.9 (IQR: 6.3) l/kOhm/m2; SVRI: 2167.63 (SD: 462.87) dyn.s.cm-5.m2. LCWI showed a weak positive correlation with systolic blood pressure (SBP) and a strong correlation with diastolic blood pressure (DBP) (Rho 0.2899 and 0.5176, respectively). There was also a positive and moderate correlation between SVRI and SBP and DBP (r 0.4265 and 0.4019, respectively). There was no correlation between CO or TFCI and SBP or DBP. No statistically significant differences in hemodynamic parameters were found between gestational hypertension and pre-eclampsia, nor between pregnant and postpartum women. Conclusion Increased blood pressure in the setting of HDP correlates with increased LCWI and systemic resistance independent of fluid retention. An increase in systemic vascular resistance measured by TEB (which decreases in normal pregnancy) may be an early diagnostic marker of HDP. These findings require further validation in a larger cohort, including a control group of pregnant women without hypertension.

Independent prognostic value of the congestion and renal index in patients with acute heart failure.

Clinical outcomes are poor if patients with acute heart failure (AHF) are discharged with residual congestion in the presence of renal dysfunction. However, there is no single indication to reflect the combined effects of the two related pathophysiological processes. We, therefore, proposed an indicator, congestion and renal index (CRI), and examined the associations between the CRI and one-year outcomes and the incremental prognostic value of CRI compared with the established scoring systems in a multicenter prospective cohort of AHF. We enrolled AHF patients and calculated the ratio of thoracic fluid content index divided by estimated glomerular filtration rate before discharge, as CRI. Then we examined the associations between CRI and one-year outcomes. A total of 944 patients were included in the analysis (mean age 63.3 ± 13.8 years, 39.3% women). Compared with patients with CRI ≤ 0.59 mL/min per kΩ, those with CRI > 0.59 mL/min per kΩ had higher risks of cardiovascular death or HF hospitalization (HR = 1.56 [1.13-2.15]) and all-cause death or all-cause hospitalization (HR = 1.33 [1.01-1.74]). CRI had an incremental prognostic value compared with the established scoring system. In patients with AHF, CRI is independently associated with the risk of death or hospitalization within one year, and improves the risk stratification of the established risk models.

Single-Center Study in Lithuania to Evaluate the Role of Transthoracic Impedance Cardiography in the Diagnosis and Outcome Evaluation of 301 Patients with Chronic Heart Failure Exacerbation.

BACKGROUND Scientific data regarding transthoracic impedance cardiography (ICG) parameters and its utility in patients with heart failure (HF) remains controversial. This study from a single center in Lithuania aimed to evaluate the role of ICG in the diagnosis and outcome evaluation of patients who were admitted to the hospital due to HF exacerbation. MATERIAL AND METHODS The sample consisted of 301 consecutive patients with a previous chronic HF diagnosis (166 men, 135 women) hospitalized for HF flare-ups. ICG data were compared to other noninvasive HF diagnostic tests. Data about patient outcomes were gathered from the Lithuanian Medical Record Database. RESULTS A weak correlation of amino-terminal pro-brain natriuretic peptide (NT-proBNP) with thoracic fluid content (TFC) and thoracic fluid content index (TFCI) was found (r=0.204, P<0.001 and r=0.207, P<0.001, respectively). There was weak to moderate correlation of 6-min walk distance with main ICG data. There was weak correlation between left ventricular ejection fraction (LVEF) with TFCI (r=-0.163, P=0.005), systolic index (r=-0.137, P=0.017), and systolic time ratio (r=0.236, P<0.001). By multivariate Cox proportional analysis, the following parameters were independently associated with cardiac death (P<0.001): NT-proBNP ≥425.5 pmoL/L (hazard ratio (HR), 5.104, 95% confidence interval (CI) 3.326-7.832), TFC ≥36.9 1/kOhm (HR, 4.604, 95% CI 2.701-7.849), LVEF ≤40% (HR, 4.942, 95% CI 2.8256-8.647). CONCLUSIONS The combination of non-invasively measured TFC, LVEF, and NT-proBNP showed great prognostic value for predicting readmissions and cardiac death in patients with HF.

The non-invasive evaluation of heart function in patients with an acute myocardial infarction: The role of impedance cardiography.

The purpose of this study was to analyze hemodynamic changes in patients treated with percutaneous coronary intervention (PCI) at an early stage of acute myocardial infarction (AMI) and at 1-month follow-up. Patients with AMI (n = 27) who underwent PCI were analyzed using impedance cardiography (ICG). ICG data were collected continuously (beat by beat) during the whole PCI procedure and thereafter at every 60 s for the next 24 h. Blood pressure was taken every 10 min and stored for analysis. Additionally the following parameters were measured: cardiac index (CI), stroke volume index (SVi), left cardiac work index (LCWi), contractility index (CTi), ventricular ejection time (VET), systemic vascular resistance index (SVRi), thoracic fluid content index (TFCi) and heart rate (HR). In the first 24 h after PCI all the contractility parameters including CI, SVi, LCWi, CTi and VET significantly decreased, whereas HR, SVRi and TFCi increased compared to baseline. All of the parameters examined got normalized at 1 month. The CI, SVi, LCWi, CTi, SVRi did not significantly differ from baseline, however the HR and VET were significantly lower compared to first day after PCI CONCLUSIONS: Cardiac performance deteriorates early after PCI and normalizes after 1 month in patients with an AMI. ICG is useful for hemodynamic monitoring of AMI patients during and after invasive therapy.

Nocturnal thoracic volume overload and post‐discharge outcomes in patients hospitalized for acute heart failure

AimsVolume overload and perturbations of pulsatile haemodynamics may precipitate acute heart failure (AHF). Nocturnal thoracic volume overload due to rostral fluid shift during recumbency undetected by daytime measures may impact nighttime haemodynamics and post‐discharge outcomes.Methods and resultsA total of 63 patients (median 60 years, 79.4% men, and left ventricular ejection fraction 29.4%) hospitalized for AHF were enrolled. Once clinical euvolaemia was achieved, noninvasive pulsatile haemodynamics were assessed during daytime followed by circadian monitoring (6 p.m. to 5 a.m.) of thoracic fluid content and thoracic fluid content index (TFCi) using impedance cardiography, normalized electromechanical activation time ratio (EMAT%) using acoustic cardiography, and mean blood pressure using ambulatory blood pressure monitoring before discharge. The primary endpoints were composited of the first hospitalization for heart failure and death from any cause. Patients were also followed for the repeated heart failure hospitalizations. During a median follow‐up duration of 16 months, 33 patients encountered primary composite endpoints (52.4%), and there were 42 hospitalizations developed among 25 patients. An overnight increase in TFCi along with persistently prolonged EMAT% and low mean blood pressure was observed in the eventful group. Overnight increase in TFCi (ΔTFCi, the difference between the measures at 4 a.m. and 6 p.m.) was an independent predictor of primary composite events (hazard ratio and 95% confidence interval: 1.58, 1.07–2.33; P = 0.022) and recurrent composite events (2.22, 1.51–3.26; P < 0.001), after adjusting for potential confounding factors. A high ΔTFCi (≥0.5/kΩ/m2) significantly correlated with higher post‐discharge events (hazard ratio 6.25; 95% confidence interval 2.30–16.96; P < 0.001) in comparison with a low ΔTFCi (<0.5/kΩ/m2). ΔTFCi was significantly associated with EMAT%, estimated glomerular filtration rate, and left ventricular ejection fraction, but not with parameters of pulsatile haemodynamics.ConclusionsNocturnal thoracic volume overload in AHF before discharge, indicating the presence of residual volume overload unidentified by daytime measures, may predict post‐discharge outcomes.

Cardiovascular testing of seasickness in healthy volunteers on life rafts.

The role of the cardiovascular system in the development of seasickness remains uncertain. Overall, 18 healthy students (10 males and 8 females) aged 18-24 years volunteered in the project, spending 2-7 h on life rafts. The cardiovascular system was examined with impedance cardiography. Susceptibility and symptoms of seasickness were evaluated by the Motion Sickness Susceptibility Questionnaire Shortform (MSSQ-Short) and the Motion Sickness Assessment Questionnaire (MSAQ). The Visual Analogue Scale (VAS), ranging 0-10, was used to assess nausea, dizziness and mood. The parameters were assessed at 2 time points. Differences in the heart rate (HR), the thoracic fluid content index (TFCI), the stroke index (SI) and the Heather index (HI) before launching the life rafts and after leaving them were observed (78.6, 20.8, 55.6 and 15.9 vs. 70.1, 19.7, 60.5 and 17.9, with p-values of 0.002, <0.001, 0.003 and 0.004, respectively). Females reacted with changes in SI and HR more vividly, whereas males regulated more HI and TFCI. In addition, HR correlated significantly with the central and peripheral symptoms in MSAQ, stroke volume (SV) with peripheral and sopite-related ones, SI with overall ones, and pulse pressure with overall, gastrointestinal and central ones (Spearman's rank correlation coefficient [ρ] was -0.478, -0.711, 0.476, 0.472, 0.525, -0.476, -0.579 and -0.584, respectively). As regards MSSQ-Short, it correlated negatively with sopite-related symptoms in MSAQ (ρ= -0.486). Mood in VAS correlated significantly with gastrointestinal symptoms, SI and the cardiac index (CI) (ρ = -0.752, -0.492 and -0.489, respectively). It was found that HR correlated negatively, and SV/SI correlated positively, with the severity of seasickness symptoms measured with MSAQ. Gender is probably an independent factor influencing reactions to motion. Women react with SI increase whereas men react with increased heart contractility (HI rise). Negative mood in seasickness evaluated with VAS seems to be mostly determined by gastrointestinal symptoms assessed with MSAQ and diminished cardiovascular indices (both CI and SI). Int J Occup Med Environ Health. 2020;33(4):467-77.

Non-invasive assessment of haemodynamic parameters in patients after Fontan procedure.

Single ventricle anomaly is one of the complex congenital heart defects. A dependable non-invasive method of evaluation of Fontan circulation haemodynamics for early diagnosing unstable patients is hardly available in routine clinical practice. The aim of the study is non-invasive evaluation of the haemodynamic parameters in patients after Fontan operation. The study involved 11 participants (age 24.4±4.3 years) with functionally univentricular hearts after Fontan operation. Evaluation of haemodynamic parameters was performed in supine and sitting positions using the impedance cardiography method. In comparative analysis, heart rate (70.1 vs.78.3 1/min; p=0.001), diastolic blood pressure (73.9 vs. 76.7 mm Hg; p=0.026), mean arterial blood pressure (84.5 vs. 88.0 mm Hg; p=0.013), systemic vascular resistance (1284.8 vs. 1334.9 dyn*s*cm-5; p=0.024), systemic vascular resistance index (2178.7 vs. 2272.8 dyn*s*cm-5*m2 ; p=0.018), pre-ejection period (124.2 vs. 136.2 ms; p=0.009), systolic time ratio (0.43 vs. 0.53; p=0.0001), and Zo (26.2 vs. 28.7 Ω; p<0.00001), were significantly higher in the sitting position. Stroke volume (75.4 vs. 68.5 ml; p=0.013), stroke index (42.7 vs. 39.0 ml*m-2; p=0.014), thoracic fluid content (38.5 vs. 35.4 1*kΩ-1; p=<0.00001), thoracic fluid content index (22.8 vs. 21.0 1*kΩ-1*m-2; p=<0.00001), and leftventricular ejection time 291.1 vs. 260.1 ms; p <0.00001, were significantly higher in the supine position. In patients after Fontan procedure, impedance cardiography can be a useful tool the assessment of shortterm haemodynamic changes provoked by postural changes. Its clinical value in patients with congenital heart defects should be further investigated.

Diagnostic and Outcome Prediction Value of Transthoracic Impedance Cardiography in Heart Failure Patients During Heart Failure Flare-Ups.

BackgroundThis study aimed at evaluating the diagnostic and outcome prediction value of transthoracic impedance cardiography (ICG) in heart failure (HF) patients admitted for in-hospital treatment due to flare-ups of their condition.Material/MethodsIn total, 120 patients of intensive care units who were admitted due to HF flare-ups were involved to the study. The findings of ICG were compared to data obtained by other methods used for diagnosing HF.ResultsStatistically significant (p<0.001) results were obtained when evaluating differences in ICG data between admission and discharge from the intensive care unit. In addition, a correlation was detected between brain natriuretic peptide (BNP) and thoracic fluid content index (r=0.4, p<0.001). Differences in ICG values, and BNP data emerged after the participants were grouped according to NYHA classes (p<0.05). The evaluation of lethal outcome during 6 months after the discharge yielded statistically significant results: BNP ≥350 pg/mL (Odds Ratio (OR) 4.4), thoracic fluid content ≥34 1/kOhm (OR 4.3), and systolic time ratio ≥0.55 (OR 2.9), p<0.05.ConclusionsICG data might be applied for the diagnosis and prognosis of HF, although the links between ICG and HF need further evaluation.

PP.20.18] DETERMINANTS OF CAROTID ATHROSCLEROSIS IN PATIENTS WITH RHEUMATOID ARTHRITIS

Objective: Cardiovascular risk factors are of profound importance for the development of atherosclerosis. However, it remains unclear whether they exert the same impact on patients with chronic inflammatory background, as is the case in rheumatoid arthritis (RA) patients, compared to hemodynamic or disease-related parameters. Design and method: Consecutive RA patients attending our Rheumatology Outpatient Unit were assessed for carotid atherosclerosis by estimating carotid intima-media thickness (cIMT) using ultrasound (ALOKA e-tracking software). Impedance cardiography (ICG) was used to evaluate hemodynamic parameters, including systemic vascular resistance index (SVRI); stroke index (SI); cardiac index (CI), and thoracic fluid content index (TFCI). Disease activity was assessed by the treating rheumatologist using the Disease Activity Score in 28 joints (DAS28). The Health Assessment Questionnaire Disability Index (HAQ-DI) and the HAQ Pain Visual Analogue Scale (VAS) were completed to evaluate physical function and arthritis-related pain, respectively. Inflammatory markers and lipid fractions were measured in blood samples. Results: Among 92 RA patients aged 61.9 ± 11.5 years (females: 79.3%), cIMT was 0.69 ± 0.13 mm and correlated with age (r = 0.610, p < 0.001), systolic blood pressure (r = 0.277, p = 0.008) and body mass index (r = 0.312, p = 0.003). Males exhibited higher cIMT compared to females (0.76 ± 0.15 vs 0.68 ± 0.11 mm, p = 0.012), and the same was observed for diabetic compared to non-diabetic patients (0.78 ± 0.17 vs 0.69 ± 0.12 mm, p = 0.044). A significant association was found between cIMT and erythrocyte sedimentation rate (r = 0.037, p = 0.037), as well as triglycerides (r = 0.289, p = 0.009), but not with other lipid fractions. Regarding disease-related factors, cIMT correlated with HAQ-DI (r = 0.299, p = 0.010) and HAQ-VAS pain (r = 0.312, p = 0.010) scores but not with disease duration or DAS28. Of the ICG-derived hemodynamic parameters, cIMT significantly correlated with SVRI (r = 0.343, p = 0.001) and CI (r = –0.244, p = 0.020). After adjusting for anthropometric, hemodynamic and inflammatory factors in the linear regression analysis, age (p < 0.001), sex (p = 0.029) and diabetes mellitus (p = 0.024) remained independent predictors of cIMT in our population. Conclusions: Although several anthropometric, hemodynamic and inflammatory parameters may be implicated in the development of carotid atherosclerosis, factors associated with an unfavorable cardiovascular risk profile remain major predictors of impaired cIMT, especially in relatively well-controlled patients with RA treated on an outpatient basis.

Hemodynamic Determinants of the Biologic Variation of N-Terminal Pro–B-Type Natriuretic Peptide in Patients With Stable Systolic Chronic Heart Failure

Background ContextBiologic variation of N-terminal pro–B-type natriuretic peptide (NT-proBNP) in chronic heart failure (CHF) may affect blood levels and risk stratification. The sources of NT-proBNP variation are unknown. Methods and ResultsWe performed NT-proBNP measurements and clinical and hemodynamic assessments in 50 patients with heart failure with reduced ejection fraction (HFrEF) who met criteria for clinical stability over 2 time intervals. Hemodynamic variables were measured with the use of inert gas rebreathing and impedance cardiography. Heart rhythm was monitored with the use of external electrocardiographic event recorders throughout the study. Determinants of NT-proBNP-levels and both absolute (ΔNT-proBNPabs) and relative (ΔNT-proBNP%) changes at 1-week and 2-week intervals were identified with the use of univariable and multivariable linear mixed-effects models and linear regression analyses, respectively.Clinical and hemodynamic variables did not significantly change between study visits. The individual variation of NT-proBNP at 2 weeks was 9.2% (range 3.9%–18.6%). Weight and glomerular filtration rate were independently associated with baseline NT-proBNP concentrations (P = .01 and P = .005, respectively). There was no relationship between absolute and relative changes of NT-proBNP at 1-week intervals and changes in clinical and hemodynamic variables. Absolute change of NT-proBNP at 2-week intervals was associated with absolute change in left cardiac work index (P = .008), and relative change in NT-proBNP at 2-week intervals was determined by relative change of thoracic fluid content index (P = .008) and diastolic blood pressure (P = .01). The coefficients of determination (R2) for the multivariable models with Δ1wkNT-proBNPabs, Δ2-weeksNT-proBNPabs, Δ1wkNT-proBNP%, and Δ2wksNT-proBNP% as dependent variables were 0.21, 0.19, 0.10, and 0.32, respectively. ConclusionsIn patients with stable HFrEF, changes in clinical and hemodynamic variables only marginally contribute to the variation of NT-proBNP.

Applicability of Impedance Cardiography During Heart Failure Flare-Ups.

BackgroundHeart failure (HF) accounts for about 5% of all causes of urgent hospital admissions, and the overall mortality of HF patients within 1 year after hospitalization is 17–45%. Transthoracic impedance cardiography (ICG) is a safe, non-invasive diagnostic technique that helps to detect various parameters that define different cardiac functions. The aim of this study was to investigate the value of ICG parameters in patients hospitalized due to HF flare-ups.Material/MethodsThe study included 60 patients (24 women and 36 men) who were admitted to intensive care units because of an acute episode of HF without signs of myocardial infarction. The diagnosis of HF as the main reason for hospitalization was verified according to the universally accepted techniques. ICG data were compared to those obtained via other HF diagnostic techniques.ResultsA moderately strong relationship was found between the ejection fraction (EF) and the systolic time ratio (STR) r=−0.4 (p=0.002). Findings for STR and thoracic fluid content index (TFCI) differed after dividing the subjects into groups according to the EF (p<0.05). A moderately strong relationship was found between brain natriuretic peptide and TFCI r=0.425 (p=0.001), left cardiac work index (LCWI) r=−0.414 (p=0.001). Findings for TFCI, LCWI, and cardiac output differed after dividing the subjects into groups according to HF NYHA classes (p<0.05).ConclusionsTransthoracic impedance cardiography parameters could be applied for the diagnostics and monitoring of HF, but further studies are required to evaluate the associations between ICG findings and HF.

Genomic ancestry as a predictor of haemodynamic profile in heart failure

ObjectiveThe aim of this study is to assess the association between genetic ancestry, self-declared race and haemodynamic parameters in patients with chronic heart failure (HF).MethodsObservational, cross-sectional study. Eligible participants were...

Determination of the effects of pulmonary arterial hypertension and therapy on the cardiovascular system of rats by impedance cardiography.

AimTo evaluate the effects of bosentan, sildenafil, and combined therapy on the cardiovascular system using impedance cardiography (ICG) in rats with monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH).MethodsSeventy male Wistar-albino rats were randomized into five groups. A single dose of MCT was given to all rats, except to the control group. After 4 weeks, bosentan, sildenafil, and combined treatment was started and lasted for 3 weeks. The last group that developed PAH did not receive any medication. Echocardiographic evaluation was performed to determine the PAH development. Thoracic fluid content index (TFCI), stroke volume index (SI), heart rate (HR), cardiac index (CI), and myocardial contractility index (IC) were determined. All procedures were performed at the baseline and after 4 and 7 weeks.ResultsEchocardiographic parameters showed that the all MCT-injected rats developed PAH. There were no significant inter- and intra-group differences in TFCI, SI, and IC (P > 0.05), but at the 7th week, CI value in the sildenafil-treated PAH rats was significantly higher than in other groups and HR of PAH rats with combined therapy was significantly lower than in other groups.ConclusionPAH did not have an effect on LV function of rats, or if it did, the effect was compensated by physiological processes. Also, sildenafil treatment deteriorated the LV cardiac index.

Non‐invasive cardiovascular profiling using combined electrocardiogram–Doppler ultrasonography and impedance cardiography: An experimental approach

In the present study, the feasibility of cardiovascular profiling using both combined electrocardiogram (ECG)-Doppler ultrasonography and impedance cardiography (ICG) was evaluated. Fourteen non-pregnant healthy women received 500mL saline solution (NaCl 0.9% at 999mL/h) intravenously by steady state infusion. Before and after this acute volume loading, we measured orthostatic-challenged cardiac and arterial characteristics using ICG and assessed venous characteristics by combined ECG-Doppler before and during the Valsalva manoeuvre. Changes are expressed as the mean±SEM and were evaluated by the one-sample Wilcoxon signed-rank test. After volume loading, the observed fall in stroke volume after postural change from supine to standing decreased (-14±3 vs -23±2%; P=0.011). Hepatic A wave velocity increased 63±28% after volume loading (P=0.007) and decreased during the Valsalva manoeuvre (-205±21%; P=0.001). Volume loading raised the thoracic fluid content index in both the supine and standing positions (7±2% and 10±1%, respectively; P≤0.014). Combined ECG-Doppler ultrasonography and ICG enables the non-invasive identification of concomitant haemodynamic changes at the level of the heart, the arterial bed and the venous compartment. Our data support the view that non-invasive cardiovascular profiling is feasible, which seems particularly useful for the evaluation of patients who are not critically ill, such as pregnant women.

Diurnal and position-induced variability of impedance cardiography measurements in healthy subjects

Cardiovascular (CV) parameters and their measurements are subject to variation. In this study, we evaluated the reproducibility of impedance cardiography (ICG) measurements following orthostatic and diurnal challenges for a set of 22 CV parameters in ten randomly selected healthy nonpregnant women. A standard protocol was used to record a consecutive series of measurements for each parameter before and after three position changes. This series of measurements was performed twice (AM and PM sessions). For each parameter, measurement-shift following position change was evaluated at 5% cutoff and compared between sessions. Intra- and intersession intraclass correlation (ICC) was calculated for individual measurements per position using repeated-measures analysis of variance. Intra- and intersession Pearson's correlation coefficient (PCC) was calculated for mean values per position. Intersession correlation for measurement-shift following position change was 0·42 (5/12) for pressure parameters, whereas this was 0·96 (52/54) for other parameters. Inter- and intrasession ICC for individual measurements varied between 0·02 and 1 for all parameters, however inter- and intrasession PCC for mean values was consistently >0·80 for stroke volume (SV), stroke index (SI), cardiac output (CO), acceleration and velocity index (ACI and VI), thoracic fluid content (TFC), TFC index (TFCI) and heart period duration (HPD). We conclude that in healthy subjects under standardised conditions, reproducibility of means of multiple ICG measurements is high for SV, SI, CO, ACI, VI, TFC, TFCI and HPD. From our data, we cannot draw conclusions on trends in diseased subjects.

The Effect of Posture on Cheyne-Stokes Respirations and Hemodynamics in Patients with Heart Failure

Cheyne-Stokes respirations occur in 40% of patients with heart failure. Orthopnea is a cardinal symptom of heart failure and may affect the patient's sleeping angle. The objective of this study was to assess the respiratory and hemodynamic response to sleeping angle in a group of subjects with stable heart failure. Twenty-five patients underwent overnight polysomnography with simultaneous and continuous impedance cardiographic monitoring. Sleeping polysomnographic and impedance cardiographic data were recorded. The study was conducted in a sleep center. All 25 patients had clinically stable heart failure and left ventricular ejection fractions < 40%. The patients slept at 0 degrees, 15 degrees, 30 degrees, and 45 degrees in random order. Seventeen patients had Cheyne-Stokes apneas (index > 5/h) and 23 patients had hypopneas (index > 5/h). The hypopnea index showed no response to sleeping angle. The Cheyne-Stokes apnea index decreased with increasing sleeping angle (P < 0.001). This effect was seen only during supine sleep and non-rapid eye movement sleep and was absent in non-supine sleep, rapid eye movement sleep, and during periods of wakefulness. Thoracic fluid content index and left ventricular hemodynamics measured by impedance cardiography showed no response to sleeping angle. Changing the heart failure patient's sleeping angle from 0 degrees to 45 degrees results in a significant decrease in Cheyne-Stokes apneas. This decrease occurs on a constant base of hypopneas. The changes in Cheyne-Stokes apneas are not related to changes in lung congestion and left ventricular hemodynamics.

Forthcoming Issues

This study sought to assess the potential utility of impedance cardiography (ICG) in predicting clinical deterioration in ambulatory patients with heart failure (HF).Impedance cardiography uses changes in thoracic electrical impedance to estimate hemodynamic variables, but its ability to predict clinical events has not been evaluated.We prospectively evaluated 212 stable patients with HF and a recent episode of clinical decompensation who underwent serial clinical evaluation and blinded ICG testing every 2 weeks for 26 weeks and were followed up for the occurrence of death or worsening HF requiring hospitalization or emergent care.During the study, 59 patients experienced 104 episodes of decompensated HF (16 deaths, 78 hospitalizations, and 10 emergency visits). Multivariate analysis identified 6 clinical and ICG variables that independently predicted an event within 14 days of assessment. These included three clinical variables (visual analog score, New York Heart Association functional class, and systolic blood pressure) and three ICG parameters (velocity index, thoracic fluid content index, and left ventricular ejection time). The three ICG parameters combined into a composite score was a powerful predictor of an event during the next 14 days (p = 0.0002). Visits with a high-risk composite score had 2.5 times greater likelihood and those with a low-risk score had a 70% lower likelihood of a near-term event compared with visits at intermediate risk.These results suggest that when performed at regular intervals in stable patients with HF with a recent episode of clinical decompensation, ICG can identify patients at increased near-term risk of recurrent decompensation.

Utility of Impedance Cardiography for the Identification of Short-Term Risk of Clinical Decompensation in Stable Patients With Chronic Heart Failure

This study sought to assess the potential utility of impedance cardiography (ICG) in predicting clinical deterioration in ambulatory patients with heart failure (HF). Impedance cardiography uses changes in thoracic electrical impedance to estimate hemodynamic variables, but its ability to predict clinical events has not been evaluated. We prospectively evaluated 212 stable patients with HF and a recent episode of clinical decompensation who underwent serial clinical evaluation and blinded ICG testing every 2 weeks for 26 weeks and were followed up for the occurrence of death or worsening HF requiring hospitalization or emergent care. During the study, 59 patients experienced 104 episodes of decompensated HF (16 deaths, 78 hospitalizations, and 10 emergency visits). Multivariate analysis identified 6 clinical and ICG variables that independently predicted an event within 14 days of assessment. These included three clinical variables (visual analog score, New York Heart Association functional class, and systolic blood pressure) and three ICG parameters (velocity index, thoracic fluid content index, and left ventricular ejection time). The three ICG parameters combined into a composite score was a powerful predictor of an event during the next 14 days (p = 0.0002). Visits with a high-risk composite score had 2.5 times greater likelihood and those with a low-risk score had a 70% lower likelihood of a near-term event compared with visits at intermediate risk. These results suggest that when performed at regular intervals in stable patients with HF with a recent episode of clinical decompensation, ICG can identify patients at increased near-term risk of recurrent decompensation.