Bioimpedance Cardiography Research Articles

Non-invasive assessment of stroke volume and cardiovascular parameters based on peripheral pressure waveform.

Cardiovascular diseases are the leading cause of death globally, making the development of non-invasive and simple-to-use tools that bring insights into the state of the cardiovascular system of utmost importance. We investigated the possibility of using peripheral pulse wave recordings to estimate stroke volume (SV) and subject-specific parameters describing the selected properties of the cardiovascular system. Peripheral pressure waveforms were recorded in the radial artery using applanation tonometry (SphygmoCor) in 35 hemodialysis (HD) patients and 14 healthy subjects. The pressure waveforms were then used to estimate subject-specific parameters of a mathematical model of pulse wave propagation coupled with the elastance-based model of the left ventricle. Bioimpedance cardiography measurements (PhysioFlow) were performed to validate the model-estimated SV. Mean absolute percentage error between the simulated and measured pressure waveforms was 4.0% and 2.8% for the HD and control group, respectively. We obtained a moderate correlation between the model-estimated and bioimpedance-based SV (r = 0.57, p<0.05, and r = 0.58, p<0.001, for the control group and HD patients, respectively). We also observed a correlation between the estimated end-systolic elastance of the left ventricle and the peripheral systolic pressure in both HD patients (r = 0.84, p<0.001) and the control group (r = 0.70, p<0.01). These preliminary results suggest that, after additional validation and possibly further refinement to increase accuracy, the proposed methodology could support non-invasive assessment of stroke volume and selected heart function parameters and vascular properties. Importantly, the proposed method could be potentially implemented in the existing devices measuring peripheral pressure waveforms.

Chronic Heart Failure Management: Monitoring Patients and Intercepting Exacerbations.

Despite significant progress in the field of therapy and management, chronic heart failure (CHF) still remains one of the most common causes of morbidity and mortality, especially among the elderly in Western countries. In particular, frequent episodes of decompensation and, consequently, repeated hospitalizations represent an unsustainable burden for national health systems and the cause of worsening quality of life. CHF is more prevalent in elderly women, who often have "peculiar" clinical characteristics and a more preserved ejection fraction caused by endothelial dysfunction and micro-vessel damage. At the moment, noninvasive technologies that are able to remotely monitor these patients are not widely available yet, and clinical trials are underway to evaluate invasive remote sensors. Unfortunately, implantable devices for identifying decompensation are not the most practical solution in the majority of of patients with chronic heart failure. In particular, they are hypothesized to have the possibility of monitoring patients by pro-B-type natriuretic peptide, ventricular repolarization variability, and bioimpedance cardiography at the first point of care, but new technology and clinical trials must be planned to address the development and spread of these emergent possibilities.

Distinct Hemodynamic Responses That Culminate With Postural Orthostatic Tachycardia Syndrome

It is of paramount importance to characterize the individual hemodynamic response of patients with postural orthostatic tachycardia syndrome (POTS) to select the best therapeutic intervention. Our aim in this study was to describe the hemodynamic changes in 40 patients with POTS during the head-up tilt test and compare them with 48 healthy patients. Hemodynamic parameters were obtained by cardiac bioimpedance. Patients were compared in supine position and after 5, 10, 15, and 20minutes of orthostatic position. Patients with POTS demonstrated higher heart rate (74beats per minute [64 to 80] vs 67 [62 to 72], p <0.001) and lower stroke volume (SV) (83.0ml [72 to 94] vs 90 [79 to 112], p <0.001) at supine position. The response to orthostatic challenge was characterized by a decrease in SV index (SVI) in both groups (ΔSVI in ml/m2: -16 [-25 to -7.] vs -11 [-17 to -6.1], p=NS). Peripheral vascular resistance (PVR) was reduced only in POTS (ΔPVR in dyne.seg/cm5:-52 [-279 to 163] vs 326 [58 to 535], p <0.001). According to the best cut-off points obtained using the receiver operating characteristic analysis for the variation of SVI (-15.5%) and PVR index (PVRI) (-5.5%), we observed 4 distinct groups of POTS: 10% presented an increase in both SVI and PVRI after the orthostatic challenge, 35% presented a PVRI decrease with SVI maintenance or increase, 37.5% presented an SVI decrease with PVRI maintenance or elevation, and 17.5% presented a reduction in both variables. Body mass index, ΔSVI, and ΔPVRI were strongly correlated with POTS (area under the curve=0.86 [95% confidence interval 0.77 to 0.92], p <0.0001). In conclusion, the use of appropriate cut-off points for hemodynamic parameters using bioimpedance cardiography during the head-up tilt test could be a useful strategy to identify the main mechanism involved and to select the best individual therapeutic strategy in POTS.

PS-R01-4: SAME, SAME BUT DIFFERENT: WHY ABSOLUTE BLOOD PRESSURE VALUES DO NOT ALWAYS PROVIDE AN ABSOLUTELY TRUE PICTURE

A 45 year old woman was hospitalised for acute, symptomatic Dengue Fever with thrombopenia. Besides body ache and pruritus, she complained of non- postural giddiness. Her blood pressure throughout was in the hypotensive range, hovering between 80- 90 mm Hg systolic and 45–65 mm Hg diastolic. This raised concerns for Dengue- virus mediated endothelial dysfunction and shock. Symptomatic swelling of hands and feet were suspicious for capillary leak syndrome, which would be a relative contraindication for crystalline volume substitution. At the same time, however, the heart rate remained bradycardic, ranging from 52- 74 beats per minute despite febrile temperatures. With incipient thrombocyte recovery, patient requested discharge but agreed to outpatient follow up. In clinic, she revealed that she had had known low blood pressure and bradycardic heart rate for all her adult life. She had been a competitive swimmer in her youth with up to 10 weekly training sessions until age 17. Given thyroid function and cortisol levels were normal, we carried out two non- invasive cardiac assessments using the NICAs device (NIMedical), which evaluates cardiac function via bioimpedance cardiography. At rest, NICAs showed hypotension (86/47 mm Hg), bradycardia 58 bpm and subnormal cardiac output (3.8 L/min) and cardiac index (2.4 L/min/m2). NICAs was repeated after brief aerobic exercise (50 squats, 20 push-ups, 30 straight leg raises). This brought heart rate into the low normal range, averaging at 61bpm. Systolic blood pressure could be normalised to 92 mm Hg, but diastolic pressure remained low at 51 mm Hg. At the same time, cardiac output and cardiac index moved into the normal range at 4.0 L/min and 2.6 L/min/m2, respectively. While still suffering from mild giddiness, symptoms improved on exercise. While the measured absolute blood pressure values were in the hypotensive range, the patient was haemodynamically stable. The improved cardiac parameters after exercise and her personal exercise history suggest a permanent set-point to lower sympathetic drive. As such, medical alerts for this patient needed to be individually adjusted, and a personalised approach to treatment is likely to yield better outcomes. The case serves as a reminder that our guidelines are based on studies on large populations, while our patients need to be assessed as individuals if we aim to provide optimal care.

Left Ventricular Inotropic Response To An Exertional Challenge After Sympathetic Decentralization In Humans

Purpose: Cardiac sympathetic decentralization is a phenomenon in which supraspinal sympathoadrenal control to the heart is deprived. Dysfunction of the sympathetic nervous system is known to contribute to blood pressure abnormalities, arrhythmias, diminished heart rate variability, restricted peak heart rate, and decreased venous return and stroke volume. Cardiac inotropic insufficiency as a result of sympathetic dysfunction has been less frequently studied. This study aimed to characterize the change in left ventricular (LV) inotropicity from rest to a severe exercise challenge in the sympathetically decentralized heart using complete spinal cord injury (cSCI) as a model. Methods: We present two male cases with cSCI (age: 45 and 30 years, BMI 21.8 and 29.5 kg/m2) and compared them with two male sedentary otherwise healthy individuals (age: 43 and 29 years, BMI 29.2 and 25.6 kg/m2). Subjects underwent an incremental arm-ergometer exercise (iAEE) test to peak volitional exhaustion. All indices of LV inotropicity and hemodynamic loading conditions were assessed at rest, during iAEE and at peak iAEE using bioimpedance cardiography (PhysioFlow® Enduro, Manatec, France). LV inotropic response was characterized by observing the response of the acceleration index (dZ/dt2) in all subjects. Results: dZ/dt2 was observed to be impaired in subjects with cSCI compared to the healthy control counterparts (baseline: 0.39 and 0.44 vs .41 and 0.48; peak; 0.55 and 1.073. vs 0.96 and 0.97, respectively). Concomitant differences in the heart rate (HR) and cardiac output (Q) responses to maximal exercise between the cSCI and control subjects were also observed. HR baseline: 57 and 73 vs 97 and 63 bpm; peak: 123 and 99 vs 176 and 151 bpm, respectively. Q baseline: 4.38 and 6.04. vs 6.93 and 5.35 L/m; peak: 11.3 and 10.3 vs 17.06 and 13.94 L/m, respectively. Conclusions: A dichotomy in both the inotropic and chronotropic responses to exercise was apparent in the subjects with decentralizing cSCI. This preliminary data could underscore a critical dependency on heterometric autoregulation for mechanizing increases in cardiac function response to exercise in complete high-level SCI.

A Novel Hypertension Management Algorithm Guided by Hemodynamic Data

A Novel Hypertension Management Algorithm Guided by Hemodynamic Data

Can bioimpedance cardiography assess hemodynamic response to passive leg raising in critically ill patients: A STROBE-compliant study.

Passive leg raising (PLR) is a convenient and reliable test to predict fluid responsiveness. The ability of thoracic electrical bioimpedance cardiography (TEB) to monitor changes of cardiac output (CO) during PLR is unknown.In the present study, we measured CO in 61 patients with shock or dyspnea by TEB and transthoracic echocardiography (TTE) during PLR procedure. Positive PLR responsiveness was defined as the velocity-time integral (VTI) ≥10% after PLR. TTE measured VTI in the left ventricular output tract. The predictive value of TEB parameters in PLR responders was tested. Furthermore, the agreement of absolute CO values between TEB and TTE measurements was assessed.Among the 61 patients, there were 28 PLR-responders and 33 non-responders. Twenty-seven patients were diagnosed with shock and 34 patients with dyspnea, with 55.6% (15/27) and 54.6% (18/34) non-responders, respectively. A change in TEB measured CO (ΔCO) ≥9.8% predicted PLR responders with 75.0% sensitivity and 78.8% specificity, the area under the receiver operating characteristic curve (AUROC) was 0.79. The Δd2Z/dt2 (a secondary derivative of the impedance wave) showed the best predictive value with AUROC of 0.90, the optimal cut point was −7.1% with 85.7% sensitivity and 87.9% specificity. Bias between TEB and TTE measured CO was 0.12 L/min, and the percentage error was 65.8%.TEB parameters had promising performance in predicting PLR responders, and the Δd2Z/dt2 had the best predictive value. The CO values measured by TEB were not interchangeable with TTE in critically ill settings.

Modulation of left ventricular diastolic filling during exercise in persons with cervical motor incomplete spinal cord injury.

To characterize left ventricular diastolic function during an exertional challenge in adults with incomplete cervical spinal cord Injury (icSCI). In this cross-sectional study, a two-group convenience sample was used to compare left ventricular LV diastolic performance during a 5-10 W·min-1 incremental arm ergometer exercise protocol, using bioimpedance cardiography. Subjects were eight males with cervical incomplete spinal cord injury (icSCI; C5-C7: age 39 ± 14 years) versus eight able-bodied males (CON: age 38 ± 13 years). Left ventricular (LV) diastolic indices included end-diastolic volume (EDV) and early diastolic filling ratio (EDFR). LV ejection time (LVET), inotropic index (dZ/dT2) and stroke volume (SV) were compared between the groups at peak exercise, and maximum workload for the icSCI group (isomax). EDV (at peak exercise:131.4 ± 7.3 vs 188.78 ± 9.4, p < 0.001; at isomax: 131.4 ± 7.3 vs 169 ± 23, p = 0.0009) and EDFR (at peak exercise 73 ± 14% vs 119 ± 11%, p = 0.006; at isomax 94 ± 10; p = 0.009) were significantly reduced in icSCI compared to CON, respectively. Significant differences in LVET (icSCI: 273 ± 48 vs CON: 305 ± 68; p = 0.1) and dZ/dT2 (icSCI: 0.64 ± 0.11 vs CON: 0.85 ± 0.31; p = 0.1) were not observed at isomax, despite a significant decrease in SV in the subjects with icSCI (77.1 ± 6.05mL vs 105.8 ± 9.2mL, p < 0.00) CONCLUSION: Left ventricular filling was impaired in the subjects with icSCI as evidenced at both peak exercise and isomax. It is likely that restrictions on the skeletal muscle pump mechanized the impairment but increased left ventricular wall stiffness could not be excluded as a mediator.

The value of non-invasive measurement of cardiac output and total peripheral resistance to categorize significant changes of intradialytic blood pressure: a prospective study

BackgroundBlood pressure (BP) is currently the main hemodynamic parameter used to assess the influence of fluid removal during hemodialysis session. Since BP is dependent on cardiac output (CO) and total peripheral resistance (TPRI), investigating these parameters may help to better understand the influence of fluid removal on patient’s hemodynamics. We used a novel non-invasive whole-body bio-impedance cardiography device, recently validated in hemodialysis patients, to examine mechanisms of intradialytic hemodynamics in a Chinese dialysis population.MethodsChronic hemodialysis patients in Sichuan Provincial People’s Hospital were enrolled. Demographic data and dialysis prescriptions were collected. Hemodynamic measurements were made pre-treatment, every 20 min during treatment and immediately after treatment in each random dialysis session. These included blood pressure, cardiac index (CI), total peripheral resistance (TPRI) and cardiac power index (CPI). Patients were divided into 5 hemodynamic groups as per their major hemodynamic response to fluid removal: low CPI, low TPRI, high TPRI, High CPI and those with normal hemodynamics.ResultsTwenty-seven patients were enrolled, with 12 (44.4%) males. The average age was 65 ± 12 y. The average body mass index (BMI) was 23.7 ± 3.9 kg/m2. 12 (44.4%) patients were diabetic. Three hundred twenty-four hemodynamic measurements were made. Weight, BMI, total fluid removal, pretreatment systolic BP, CI, TPRI and CI differed significantly among the 5 hemodynamic groups.11.1% of patients had low CPI, 25.9% had low TPRI, 18.5% had high CPI, 3.7% had high TPRI and 40.7% had normal hemodynamics. Hemodynamic differences among the 5 subgroups were significant.ConclusionThis technology provides multi-dimensional insight into intradialytic hemodynamic parameters, which may be more informative than blood pressure only. Using hemodynamic parameters to describe patients’ status is more specific and accurate, and could help to work out specific and effective therapeutic actions according to underlying abnormalities.

Comparison of stroke volume measurements during hemodialysis using bioimpedance cardiography and echocardiography.

Fluid management remains a major challenge of hemodialysis (HD) care, with serious implications for morbidity and mortality. Intradialytic fluid management is typically guided by blood pressure, an indirect resultant of hemodynamics status. Direct measurements of hemodynamic parameters may improve cardiovascular outcomes by providing rational bases for intervention. We compare stroke volume (SV) measurements using a noninvasive, regional biompedance cardiography device (NiCaS) with Doppler echocardiography (Echo) in HD setting. Stroke volumes were simultaneously measured using the devices in 17 patients receiving maintenance HD. Measurements were made during 2 weekly HD treatments, and twice within each HD treatment during the first and last hour of each treatment, for a total of 64 SV measurements. Agreement between devices was assessed using linear regression, a Pearson's correlation coefficient, and a Bland-Altman plot all adjusted for repeated measures within patients. Echo and NiCaS SV mean and 95% CIs were 58.0 (50.1, 65.8) and 56.7 (49.4, 64.0) mL, respectively. NiCaS SV correlated strongly with Echo SV during the first and last hours of treatments (r = 0.93, P < 0.001 and r = 0.92, P < 0.001, respectively). Linear regression of NiCaS on Echo showed a slope of 0.97, 95% CI (0.91, 1.02) which did not differ from 1, P = 0.20. A Bland-Altman plot and 4-Quadrant plot confirmed that the 2 methods produced comparable measurements. NiCaS SV measurements are similar to and strongly correlated with Echo SV measurements. This suggests that noninvasive NiCaS technology may be a practical method for measuring SV during HD.

Higher exercise intensity delays postexercise recovery of impedance-derived cardiac sympathetic activity.

Systolic time intervals (STIs) provide noninvasive insights into cardiac sympathetic neural activity (cSNA). As the effect of exercise intensity on postexercise STI recovery is unclear, this study investigated the STI recovery profile after different exercise intensities. Eleven healthy males cycled for 8 min at 3 separate intensities: LOW (40%-45%), MOD (75%-80%), and HIGH (90%-95%) of heart-rate (HR) reserve. Bio-impedance cardiography was used to assess STIs - primarily pre-ejection period (PEP; inversely correlated with cSNA), as well as left ventricular ejection time (LVET) and PEP:LVET - during 10 min seated recovery immediately postexercise. Heart-rate variability (HRV), i.e., natural-logarithm of root mean square of successive differences (Ln-RMSSD), was calculated as an index of cardiac parasympathetic neural activity (cPNA). Higher preceding exercise intensity elicited a slower recovery of HR and Ln-RMSSD (p < 0.001), and these measures did not return to baseline by 10 min following any intensity (p ≤ 0.009). Recovery of STIs was also slower following higher intensity exercise (p ≤ 0.002). By 30 s postexercise, higher preceding intensity resulted in a lower PEP (98 ± 14 ms, 75 ± 6 ms, 66 ± 5 ms for LOW, MOD, and HIGH, respectively, p < 0.001). PEP recovered to baseline (143 ± 11 ms) by 5 min following LOW (139 ± 13 ms, p = 0.590) and by 10 min following MOD (145 ± 17 ms, p = 0.602), but was still suppressed at 10 min following HIGH (123 ± 21 ms, p = 0.012). Higher preceding exercise intensity attenuated the recovery of indices for cSNA (from STIs) and cPNA (from HRV) in a graded dose-response fashion. While exercise intensity must be considered, acute recovery may be a valuable period during which to concurrently monitor these noninvasive indices, to identify potentially abnormal cardiac autonomic responses.

Endotracheal bioimpedance cardiography improves immediate postoperative outcome: a case-control study in off-pump coronary surgery

The feasibility and clinical utility of the endotracheal cardiac output monitor (ECOM) to optimize intraoperative hemodynamics and improve short-term outcome in off-pump coronary artery bypass grafting (OPCAB) is unknown. We aimed to compare ECOM with a standard of care in that specific surgical setting. Twenty consecutive adult ECOM-monitored patients undergoing OPCAB were prospectively included (ECOM group) and retrospectively compared to 42 patients scheduled for similar surgery without ECOM monitoring (Control group). The primary endpoint was the global rate of postoperative admission to the intensive care unit (ICU). Secondary endpoints were the time to extubation, the length of stay in ICU and in hospital, the postoperative levels of lactate and troponin and the feasibility of ECOM. The rate of postoperative admission to the ICU was 38/42 (90%) in the Control group versus 11/20 (55%) in the ECOM group, P = 0.008. None unexpected admission for hemodynamic instability was observed in the ECOM group. The time to extubation, the length of stay in ICU, and both troponin level at admission and lactate level at H6 were all significantly decreased in the ECOM group. On a scale ranging from 0 to 5, convenience and satisfaction regarding ECOM were 4.30 ± 1.17 and 3.45 ± 0.68, respectively. The systematic use of ECOM is associated with a significant reduction in the rate of admission to the ICU and an improvement in immediate outcome in OPCAB.

Bioimpedance cardiography in pregnancy: A longitudinal cohort study on hemodynamic pattern and outcome.

BackgroundPregnancy associated cardiovascular pathologies have a significant impact on outcome for mother and child. Bioimpedance cardiography may provide additional outcome-relevant information early in pregnancy and may also be used as a predictive instrument for pregnancy-associated diseases.MethodsWe performed a prospective longitudinal cohort trial in an outpatient setting and included 242 pregnant women. Cardiac output and concomitant hemodynamic data were recorded from 11th–13th week of gestation every 5th week as well as at two occasions post partum employing bioimpedance cardiography.ResultsCardiac output increased during pregnancy and peaked early in the third trimester. A higher heart rate and a decreased systemic vascular resistance were accountable for the observed changes. Women who had a pregnancy-associated disease during a previous pregnancy or developed hypertension or preeclampsia had a significantly increased cardiac output early in pregnancy. Furthermore, an effect of cardiac output on birthweight was found in healthy pregnancies and could be confirmed with multiple linear regression analysis.ConclusionsCardiovascular adaptation during pregnancy is characterized by distinct pattern described herein. These may be altered in women at risk for preeclampsia or reduced birthweigth. The assessment of cardiac parameters by bioimpedance cardiography could be performed at low costs without additional risks.

The predictive value of non-invasive cardiac output at rest in discharged heart failure patients

Risk stratification in patients suffering from chronic congestive heart failure (CHF) is based on a variety of clinical and laboratory variables. Indeed, several prognostic parameters have been identified, including age, New York Heart Association (NYHA) class, renal function, comorbidity such as atrial fibrillation, diabetes mellitus and ischemic heart disease [ [1] Swedberg K. Cleland J. Dargie H. et al. Guidelines for the diagnosis and treatment of chronic heart failure: executive summary (update 2005): the Task Force for the Diagnosis and Treatment of Chronic Heart Failure of the European Society of Cardiology. Eur. Heart J. 2005; 26: 1115-1140 Crossref PubMed Scopus (246) Google Scholar ]. In acute decompensated heart failure (ADHF) episodes, the degree of renal dysfunction and arterial hypotension easily stratified patients with worst clinical outcome [ [2] Fonarow G.C. Adams K.F. Abraham W.T. Yancy C.W. Boscardin W.J. for the ADHERE Scientific Advisory Committee Risk stratification for in-hospital mortality in acutely decompensated heart failure. JAMA. 2005; 293: 572-580 Crossref PubMed Scopus (1308) Google Scholar ]. A single determination of Brain Natriuretic Peptide (BNP) plasma level represents a reliable risk stratification procedure and its increase is considered a sensitive diagnostic marker of left ventricular dysfunction [ 3 Boland D.G. Abraham W.T. Natriuretic peptides in heart failure. Congest. Heart Fail. 1998; 4: 23-33 Google Scholar , 4 McDonagh T.A. Robb S.D. Murdoch D.R. et al. Biochemical detection of left-ventricular systolic dysfunction. Lancet. 1998; 351: 9-13 Abstract Full Text Full Text PDF PubMed Scopus (909) Google Scholar ] having a clear prognostic relevance in predicting cardiovascular events in congestive heart failure (CHF) patients [ 5 Maisel A.S. Krishnaswamy P. Nowak R.M. et al. Rapid measurement of B-type natriuretic peptide in the emergency diagnosis of heart failure. N. Engl. J. Med. 2002; 347: 161-167 Crossref PubMed Scopus (2785) Google Scholar , 6 Berger R. Huelsman M. Strecker K. et al. B-type natriuretic peptide predicts sudden death in patients with chronic heart failure. Circulation. 2002; 105: 2392-2397 Crossref PubMed Scopus (616) Google Scholar , 7 Feola M. Aspromonte N. Canali C. et al. Prognostic value of plasma brain natriuretic peptide, urea nitrogen and creatinine in outpatients >70 years of age with heart failure. Am. J. Cardiol. 2005; 96: 705-709 Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar ]. In discharged HF patients both right or left ventricular function proved to play a prognostic role [ 8 Kamath S.A. Drazner M.H. Tasissa G. Rogers J.G. Stevenson L.W. Yancy C.W. Correlation of impedance cardiography with invasive hemodynamic measurements in patients with advanced heart failure: the Bioimpedance CardioGraphy (BIG) Substudy of the ESCAPE Trial. Am. Heart J. 2009; 158: 217-223 Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar , 9 Zornoff L.A.M. Skali H. Pfeffer M.A. et al. Right ventricular dysfunction and risk of heart failure and mortality after myocardial infarction. J. Am. Coll. Cardiol. 2002; 39: 1450-1455 Abstract Full Text Full Text PDF PubMed Scopus (366) Google Scholar ]. In particular, in HF patients developed after an MI each reduction of 5% in right ventricular function correlated with a 16% increased in mortality [ [9] Zornoff L.A.M. Skali H. Pfeffer M.A. et al. Right ventricular dysfunction and risk of heart failure and mortality after myocardial infarction. J. Am. Coll. Cardiol. 2002; 39: 1450-1455 Abstract Full Text Full Text PDF PubMed Scopus (366) Google Scholar ]. In the substudy of the ESCAPE trial, the invasive measurement of pulmonary wedge pressure was significantly associated with death at 6-month follow-up [ [8] Kamath S.A. Drazner M.H. Tasissa G. Rogers J.G. Stevenson L.W. Yancy C.W. Correlation of impedance cardiography with invasive hemodynamic measurements in patients with advanced heart failure: the Bioimpedance CardioGraphy (BIG) Substudy of the ESCAPE Trial. Am. Heart J. 2009; 158: 217-223 Abstract Full Text Full Text PDF PubMed Scopus (71) Google Scholar ].

Impedance cardiography - Old method, new opportunities. Part I. Clinical applications.

Monitoring of cardiovascular hemodynamic changes requires a very expensive and highly specialized equipment and skilled medical personnel. Up to the present time, an inexpensive, non-invasive and easy-to-use method which, like Doppler echocardiography, magnetic resonance angiography or radionuclide imaging, would assess hemodynamics of the cardiovascular system was not available. A method known as impedance cardiography (ICG) or thoracic electrical bioimpedance cardiography (TEBC) meets those criteria. It is non-invasive, which is of a particular advantage over the conventional methods that require catheterization. As a result, the patient is not at risk of possible complications and the procedure is less expensive and easier. Impedance cardiography, despite its non-invasive character, has not been so far extensively used for monitoring of hemodynamic parameters in hospitalized patients. Various authors report that attempts have been continued to compare the results from ICG and those obtained by other diagnostic methods. This paper presents the use of impedance cardiography in diagnosis of hypertension, cardiac insufficiency, differentiating the causes of acute dyspnea, as well as in assessing the effects of cardiac rehabilitation in patients with heart failure.

Cardiorespiratory function before and after aerobic exercise training in patients with interstitial lung disease.

To characterize the cardiorespiratory response to exercise before and after aerobic exercise training in patients with interstitial lung disease. We performed a clinical study, examining 13 patients (New York Heart Association/World Health Organization Functional class II or III) before and after 10 weeks of supervised treadmill exercise walking, at 70% to 80% of heart rate reserve, 30 to 45 minutes per session, 3 times a week. Outcome variables included measures of cardiorespiratory function during a treadmill cardiopulmonary exercise test, with additional near infrared spectroscopy measurements of peripheral oxygen extraction and bioimpedance cardiography measurements of cardiac output. Six-minute walk test distance was also measured. All subjects participated in at least 24 of their 30 scheduled exercise sessions with no significant adverse events. After training, the mean 6-minute walk test distance increased by 52 ± 48 m (P = .001), peak treadmill cardiopulmonary exercise test time increased by 163 ± 130 s (P = .001), and time to achieve gas exchange threshold increased by 145 ± 37 s (P < .001). Despite a negligible increase in peak (Equation is included in full-text article.)o2 with no changes to cardiac output, the overall work rate/(Equation is included in full-text article.)o2 relationship was enhanced after training. Muscle O2 extraction increased by 16% (P = .049) after training. Clinically significant improvements in cardiorespiratory function were observed after aerobic exercise training in this group of subjects with interstitial lung disease. These improvements appear to have been mediated by increases in the peripheral extraction of O2 rather than changes in O2 delivery.

Early goal-directed therapy based on endotracheal bioimpedance cardiography: a prospective, randomized controlled study in coronary surgery.

The objective was to compare the impact of an early goal-directed hemodynamic therapy based on cardiac output monitoring (Endotracheal Cardiac Output Monitor, ECOM) with a standard of care on postoperative outcome following coronary surgery. This prospective, controlled, parallel-arm trial randomized 100 elective primary coronary artery bypass grafting patients to a study group (ECOM; n = 50) or a control group (control; n = 50). In the ECOM group, hemodynamic therapy was guided by respiratory stroke volume variation and cardiac index given by the ECOM system. A standard of care was used in the control. Goal-directed therapy was started immediately after induction of anesthesia and continued until arrival in the intensive care unit (ICU). The primary endpoint was the time when patients fulfilled discharge criteria from hospital (possible hospital discharge). Secondary endpoints were the hospital discharge, the time to reach extubation, the length of stay in ICU, the number of major adverse cardiac events, and in-hospital mortality. Patients in the ECOM group received more often fluid loading and dobutamine. The time to reach extubation was reduced in the ECOM group: 510 min [360-1,110] versus 570 min [320-1,520], P = 0.005. No significant differences were found between both groups for possible hospital discharge [Hazard Ratio = 0.96 (95 % CI 0.64-1.45)] and hospital discharge [Hazard Ratio = 1.20 (95 % CI 0.79-1.81)]. A mini-invasive early goal-directed hemodynamic therapy based on ECOM can reduce the time to reach extubation but fails to significantly reduce the length of stay in hospital and the rate of major cardiac morbidity.

Electrical bioimpedance cardiography: an old technology with new hopes for the future.

THE POSITIVE IMPACT of early goal-directed hemodynamic therapy on postoperative outcome increasingly has been investigated over the last few years in high-risk patients undergoing noncardiac and cardiac surgeries. 1 Phan T.D. Ismail H. Herior A.G. et al. Improving perioperative outcomes: Fluid optimization with the esophageal Doppler monitor, a meta-analysis and review. J Am Coll Surg. 2008; 207: 935-941 Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar , 2 Hamilton M. Cecconi M. Rhodes A. A systematic review and meta-analysis on the use of preemptive hemodynamic intervention to improve postoperative outcomes in moderate and high-risk surgical patients. Anesth Analg. 2011; 112: 1392-1402 Crossref PubMed Scopus (593) Google Scholar , 3 Aya H.D. Cecconi M. Hamilton M. et al. Goal-directed therapy in cardiac surgery: A systematic review and meta-analysis. Br J Anaesth. 2013; 110: 510-517 Crossref PubMed Scopus (156) Google Scholar , 4 Goepfert M.S. Richter H.P. Eulenburg C.Z. et al. Individually optimized hemodynamic therapy reduces complications and length of stay in the intensive care unit: A prospective, randomized controlled study. Anesthesiology. 2013; 119: 824-836 Crossref PubMed Scopus (120) Google Scholar However, these preemptive strategies require advanced hemodynamic monitoring to assess cardiac output and stroke volume. The classic available tools (intermittent pulmonary arterial or transpulmonary thermodilution or esophageal Doppler), either invasive or operator-dependent and necessitating a learning curve, are not convenient for routine practice. Therefore, they remain insufficiently used among North American and European anesthesiologists. 5 Cannesson M. Pestel G. Ricks C. et al. Hemodynamic monitoring and management in patients undergoing high risk surgery: A survey among North American and European anesthesiologists. Crit Care. 2011; 15: R197 Crossref PubMed Scopus (208) Google Scholar Besides, new mini-invasive cardiac output devices have been developed commercially over the last decade. 6 Marik P.E. Noninvasive cardiac output monitors: A state-of the-art review. J Cardiothorac Vasc Anesth. 2013; 27: 121-134 Abstract Full Text Full Text PDF PubMed Scopus (205) Google Scholar Less accurate but more convenient and easy to use, they potentially could help the practitioners in promoting advanced hemodynamic monitoring and early goal-directed therapy at the bedside in high-risk patients in an attempt to further improve postoperative outcome. Among these mini-invasive technologies, thoracic electrical bioimpedance (TEB) has major theoretical advantages and could be of great clinical utility in the settings of anesthesiology, cardiology, and perioperative medicine. Despite extensive literature published over the last 50 years, TEB remains scarcely used by practitioners.

Early goal-directed therapy based on endotracheal bioimpedance cardiography: a prospective, randomized controlled study in coronary surgery

Early goal-directed therapy based on endotracheal bioimpedance cardiography: a prospective, randomized controlled study in coronary surgery

Alternative index for Lactate Threshold -Preliminary study using a non-invasive bioimpedance cardiography-

Alternative index for Lactate Threshold -Preliminary study using a non-invasive bioimpedance cardiography-