Non-invasive Assessment Of Cardiac Output Research Articles

Non-Invasive Cardiac Output Measurement Using Inert Gas Rebreathing Method during Cardiopulmonary Exercise Testing-A Systematic Review.

The use of inert gas rebreathing for the non-invasive cardiac output measurement has produced measurements comparable to those obtained by various other methods. However, there are no guidelines for the inert gas rebreathing method during a cardiopulmonary exercise test (CPET). In addition, there is also a lack of specific standards for assessing the non-invasive measurement of cardiac output during CPET, both for healthy patients and those suffering from diseases and conditions. This systematic review aims to describe the use of IGR for a non-invasive assessment of cardiac output during cardiopulmonary exercise testing and, based on the information extracted, to identify a proposed CPET report that includes an assessment of the cardiac output using the IGR method. This systematic review was conducted by PRISMA (Preferred Reporting Items for Systematic Reviews and Meta Analyses) guidelines. PubMed, Web of Science, Scopus, and Cochrane Library databases were searched from inception until 29 December 2022. The primary search returned 261 articles, of which 47 studies met the inclusion criteria for this review. This systematic review provides a comprehensive description of protocols, indications, technical details, and proposed reporting standards for a non-invasive cardiac output assessment using IGR during CPET. It highlights the need for standardized approaches to CPET and identifies gaps in the literature. The review critically analyzes the strengths and limitations of the studies included and offers recommendations for future research by proposing a combined report from CPET-IGR along with its clinical application.

Toward smartphone-based blood pressure monitoring

A single-centre, prospective longitudinal study to assess changes in maternal arterial stiffness and cardiac output parameters among low-risk healthy pregnant women.Thirty low-risk, healthy, pregnant women attending their routine antenatal dating ultrasound scan were recruited. Non-invasive assessment of arterial stiffness and cardiac output was undertaken at five gestational windows from 11 to 40 weeks of pregnancy. Data were analysed using a linear mixed model incorporating time and other relevant predictors as fixed effects, and patient as a random effect.Gestational age had a significant effect on all arterial stiffness parameters, including brachial augmentation index (AIx) (p = .001), aortic AIx (p = .002) and aortic pulse wave velocity (p = .002). The aortic AIx (%) reduced during pregnancy: the lowest mean (standard error, SE) was 4.07 (1.01) at 28 weeks before it increased to 7.04 (SE 1.64) at 40 weeks.Similarly, non-invasive assessments of cardiac output (p < .001), stroke volume (p = .014), heart rate (p < .001) and total peripheral resistance (p < .001) demonstrated significant changes with gestational age. Mean cardiac output (l/m) increased during pregnancy reaching a peak at 28 weeks gestation 6.66 (SE 0.28), but dropped thereafter to reach 5.71 (SE 0.25) around term.The current study provides pregnancy normograms for gestational changes in arterial stiffness and cardiac output parameters among low-risk, healthy pregnant women. Further work will be required to assess the risk of placental mediated diseases and pregnancy outcome among pregnant women with parameters outside the normal range.

Feasibility, reproducibility and accuracy of electrical velocimetry for cardiac output assessment in congenital heart disease

BackgroundNoninvasive cardiac output assessment is important for prognostication in patients with heart failure. Electrical velocimetry (EV), an impedance cardiography technique, can be used for noninvasive cardiac output assessment. The purpose of this study was to determine the feasibility, reproducibility and accuracy of cardiac output assessment by EV in adults with congenital heart disease (CHD). MethodsCross-sectional study of CHD patients that had simultaneous cardiac output assessment by Fick and EV (using Cardiotronic monitor, Osypka Medical). We divided the cohort into: Group 1 patients (n = 54) had hemodynamic assessment at rest only, while Group 2 patients (n = 7) had assessment both at rest and peak exercise. ResultsEV cardiac output assessment was feasible in 100% of the patients. There was good correlation between Fick-derived and EV-derived cardiac index (r = 0.89, p < 0.001) in Group 1. Among 26 patients in Group 1 that underwent cardiac output assessment pre- and post-intervention, there was no difference in the strength of correlation of Fick and EV cardiac output pre- and post-intervention (p-interaction 0.244) indicating good reproducibility of the technique. There was also modest correlation between Fick-derived and EV-derived cardiac index at rest (r = 0.68, p = 0.032), and peak exercise (r = 0.62, p = 0.055), in Group 2. ConclusionIn this study, we demonstrated the feasibility and accuracy of EV cardiac output assessment in adults with CHD. We also demonstrated, for the first time, that EV cardiac output assessment was reproducible under different loading conditions, and that EV can be used for the assessment of cardiac output augmentation at peak exercise.

Advanced hemodynamic monitoring in critically ill neonates

The neonatal circulation is unique due to the presence of fetal shunts. With the advances in biomedical technology, the assessment of sick newborn infants has improved significantly. It allows to collect, store and analyze the complex physiometric data and provides a foundation for advances in diagnosis and management of neonatal cardiovascular compromise. This could allow the clinician to have objective information to compliment the clinical assessment. Additionally, serial assessments and trending of measured parameters provides longitudinal information on disease pathophysiology and the response to treatment.The advanced hemodynamic monitoring however has to be structured and focussed to get the relevant information to compliment clinical signs and symptoms. It however has an inherent risk of inappropriate or over-treatment leading to a state of confusion. The following questions should thus be addressed at the outset:1. Objectives of assessment and goal of therapy2. Available techniques and processing information3. Point assessment vs continuous assessment4. Invasive monitoring vs non-invasive monitoringThe goal of hemodynamic monitoring is to optimise end-organ perfusion. The delivery of oxygen (DO2) depends on gas exchange, haematocrit, macrocirculation (preload, cardiac function and afterload) and microcirculation (capillary and end organ perfusion) (Table 1)1. The point-of-care functional echocardiography is helpful for initial assessment to complement continuous assessment techniques such as non-invasive continuous hemodynamic monitoring and in emergency situations of hemodynamic instability.When utilising these techniques, the limitations of individual devices and the interaction between them should be known. As compared to point-of-care assessment, when non-invasive monitoring devices are used, the trending of data from them with simultaneous single screen longitudinal display of values is helpful for diagnosis of disease and assessing response to treatment (Figure 1).2 The examples are continuous cardiac output, blood pressure, central venous pressure, pulse oximetry and near infrared spectroscopy. The trending of heart rate monitoring has already been utilised for early detection of sepsis using HeRO monitor. There has been interest in continuous amplitude integrated EEG but so far it is limited to research trials.We compared measurement of cardiac output with echocardiography with non-invasive cardiac output monitoring. We observed that absolute values were different but the trend on longitudinal assessment was comparable. This could be due to the fact that non-invasive cardiac output assessment methods utilise indirect techniques such as electric velocimetry, arterial pulse contour analysis etc. Using an example of a baby with septic shock, one can understand how the hemodynamic monitoring can guide initial management.3 BP = cardiac output (CO) x systemic vascular resistance (SVR) (Figure 2) 4 If a patient has low CO, high SVR and normal BP, the choice of treatment is inodilators e.g., milrinone. If CO, SVR and BP are all low, commence treatment with norepinephrine and add epinephrine. If high CO and low BP and SVR, give fluid bolus initially and titrate therapy.The integration of advanced hemodynamic monitoring in clinical care is akin to whole genome sequencing where a large amount of information is gathered which requires processing. Utilising this information is a challenge at present but it has the potential to open gateways for precision medicine.5

5941Improvement of cardiac output after transcatheter repair of severe tricuspid regurgitation impacts all-cause mortality

Abstract Background Severe tricuspid regurgitation (TR) impairs right-ventricular forward stroke volume and left-ventricular preload leading to a reduction of cardiac output (CO). Transcatheter tricuspid valve repair (TTVR) is a novel experimental treatment strategy for TR and an alternative to surgery in fragile patients. The clinical impact of improved CO after TTVR on the prognosis of chronic heart failure patients is currently unknown. Purpose This study has been designed to analyze the impact of TTVR on CO and the association to post-interventional hospitalization for congestive heart failure (CHF) and all-cause mortality. Methods Between February 2017 and October 2018 we prospectively enrolled 70 patients suffering from chronic heart failure (median age 78 years; 54% female; 90% NYHA III or IV; median NT-pro-BNP of 3,540 ng/ml) due to severe TR (all ≥ grade 3 of 4). All patients underwent TTVR with isolated intervention to the tricuspid valve (n=41) or combined mitral and tricuspid intervention due to concomitant mitral regurgitation (n=29). Invasive CO was measured shortly before TTVR under general anesthesia using transpulmonary thermodilution. For a more physiologic assessment, non-invasive CO was measured using the inert gas rebreathing technique (Innocor, Innovision, Glamsbjerg, Denmark). Non-invasive CO was assessed 2 weeks prior TTVR (baseline), at the day of discharge from the hospital (post-procedural) and after a median of 193 days (interquartile range, IQR 53 to 360 days; follow-up). Results Invasive CO significantly correlated to non-invasive assessment of CO at baseline (Pearsons correlation coefficient r=0.36, p&lt;0.01). Baseline median non-invasive CO (3.3 l/min, IQR 2.4 to 4.2 l/min) improved with TTVR in the post-procedural analysis (4.0 l/min, IQR 2.8 to 5.1 l/min, p&lt;0.001). At follow-up, median non-invasive CO improved by 0.5 l/min (IQR 0.0 to 1.6 l/min). CO changed ≤0.5 l/min in 37 patients (low ΔCO) and &gt;0.5 l/min in 33 patients (high ΔCO). Hospitalization for CHF was significantly lower with high ΔCO (18%), when compared to low ΔCO (54%; p&lt;0.01). Furthermore, all-cause mortality was significantly reduced in the high ΔCO-group (3%), when compared to the low ΔCO-group (43%; p&lt;0.001). Significant differences in mortality were also observed in the subgroup of patients with isolated tricuspid intervention (10% vs. 45%, p=0.016). Conclusion Successful TTVR with maintenance of improved CO impacts patient prognosis and is associated to a reduced rate of hospitalization and all-cause mortality.

Longitudinal study to assess changes in arterial stiffness and cardiac output parameters among low-risk pregnant women

A single-centre, prospective longitudinal study to assess changes in maternal arterial stiffness and cardiac output parameters among low-risk healthy pregnant women. Thirty low-risk, healthy, pregnant women attending their routine antenatal dating ultrasound scan were recruited. Non-invasive assessment of arterial stiffness and cardiac output was undertaken at five gestational windows from 11 to 40 weeks of pregnancy. Data were analysed using a linear mixed model incorporating time and other relevant predictors as fixed effects, and patient as a random effect. Gestational age had a significant effect on all arterial stiffness parameters, including brachial augmentation index (AIx) (p = .001), aortic AIx (p = .002) and aortic pulse wave velocity (p = .002). The aortic AIx (%) reduced during pregnancy: the lowest mean (standard error, SE) was 4.07 (1.01) at 28 weeks before it increased to 7.04 (SE 1.64) at 40 weeks. Similarly, non-invasive assessments of cardiac output (p < .001), stroke volume (p = .014), heart rate (p < .001) and total peripheral resistance (p < .001) demonstrated significant changes with gestational age. Mean cardiac output (l/m) increased during pregnancy reaching a peak at 28 weeks gestation 6.66 (SE 0.28), but dropped thereafter to reach 5.71 (SE 0.25) around term. The current study provides pregnancy normograms for gestational changes in arterial stiffness and cardiac output parameters among low-risk, healthy pregnant women. Further work will be required to assess the risk of placental mediated diseases and pregnancy outcome among pregnant women with parameters outside the normal range.

An update on carbon nanotube-enabled X-ray sources for biomedical imaging.

A new imaging technology has emerged that uses carbon nanotubes (CNT) as the electron emitter (cathode) for the X-ray tube. Since the performance of the CNT cathode is controlled by simple voltage manipulation, CNT-enabled X-ray sources are ideal for the repetitive imaging steps needed to capture three-dimensional information. As such, they have allowed the development of a gated micro-computed tomography (CT) scanner for small animal research as well as stationary tomosynthesis, an experimental technology for large field-of-view human imaging. The small animal CT can acquire images at specific points in the respiratory and cardiac cycles. Longitudinal imaging therefore becomes possible and has been applied to many research questions, ranging from tumor response to the noninvasive assessment of cardiac output. Digital tomosynthesis (DT) is a low-dose and low-cost human imaging tool that captures some depth information. Known as three-dimensional mammography, DT is now used clinically for breast imaging. However, the resolution of currently-approved DT is limited by the need to swing the X-ray source through space to collect a series of projection views. An array of fixed and distributed CNT-enabled sources provides the solution and has been used to construct stationary DT devices for breast, lung, and dental imaging. To date, over 100 patients have been imaged on Institutional Review Board-approved study protocols. Early experience is promising, showing an excellent conspicuity of soft-tissue features, while also highlighting technical and post-acquisition processing limitations that are guiding continued research and development. Additionally, CNT-enabled sources are being tested in miniature X-ray tubes that are capable of generating adequate photon energies and tube currents for clinical imaging. Although there are many potential applications for these small field-of-view devices, initial experience has been with an X-ray source that can be inserted into the mouth for dental imaging. Conceived less than 20 years ago, CNT-enabled X-ray sources are now being manufactured on a commercial scale and are powering both research tools and experimental human imaging devices. WIREs Nanomed Nanobiotechnol 2018, 10:e1475. doi: 10.1002/wnan.1475 This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Noninvasive assessment of cardiac output by brachial occlusion-cuff technique: comparison with the open-circuit acetylene washin method.

Cardiac output (CO) assessment as a basic hemodynamic parameter has been of interest in exercise physiology, cardiology, and anesthesiology. Noninvasive techniques available are technically challenging, and thus difficult to use outside of a clinical or laboratory setting. We propose a novel method of noninvasive CO assessment using a single, upper-arm cuff. The method uses the arterial pressure pulse wave signal acquired from the brachial artery during 20-s intervals of suprasystolic occlusion. This method was evaluated in a cohort of 12 healthy individuals (age, 27.7 ± 5.4 yr, 50% men) and compared with an established method for noninvasive CO assessment, the open-circuit acetylene method (OpCirc) at rest, and during low- to moderate-intensity exercise. CO increased from rest to exercise (rest, 7.4 ± 0.8 vs. 7.2 ± 0.8; low, 9.8 ± 1.8 vs. 9.9 ± 2.0; moderate, 14.1 ± 2.8 vs. 14.8 ± 3.2 l/min) as assessed by the cuff-occlusion and OpCirc techniques, respectively. The average error of experimental technique compared with OpCirc was -0.25 ± 1.02 l/min, Pearson's correlation coefficient of 0.96 (rest + exercise), and 0.21 ± 0.42 l/min with Pearson's correlation coefficient of 0.87 (rest only). Bland-Altman analysis demonstrated good agreement between methods (within 95% boundaries); the reproducibility coefficient (RPC) = 0.84 l/min with R2 = 0.75 at rest and RPC = 2 l/min with R2 = 0.92 at rest and during exercise, respectively. In comparison with an established method to quantify CO, the cuff-occlusion method provides similar measures at rest and with light to moderate exercise. Thus, we believe this method has the potential to be used as a new, noninvasive method for assessing CO during exercise.

Non-invasive cardiac output assessment in critically ill paediatric patients

Objective Recently, non-invasive methods for cardiac output (CO) assessment have been developed including the ultrasonic cardiac output monitor (USCOM). This technique uses the same concept as Doppler echocardiography but differs in two aspects including continuous wave (CW) Doppler and estimated outflow tract diameter (OTD) used in USCOM compared to pulsed wave Doppler and directed measurement of OTD used in echocardiography. We sought to assess the agreement between CO assessment by USCOM and echocardiography in critically ill paediatric patients.Methods Paired measurements of CO in critically ill paediatric patients were simultaneously and independently obtained by USCOM and echocardiography. Agreement between OTD, velocity time integral (VTI), CO, and cardiac index (CI) were assessed by percentage error and Bland-Altman analysis.Results Thirty-four children (aged 7.86 ± 5.78 years, 44.1% male) had a mean OTD (1.47 ± 0.38, 1.41 ± 0.40), VTI (19.13 ± 6.06, 23.53 ± 7.31 cm), CO (3.88 ± 2.19, 4.41 ± 2.83 l/min) and CI (4.23 ± 1.19, 4.77 ± 1.43 l/min/m2) by echocardiography and USCOM, respectively. Bias ± precision and percentage of error of OTD, VTI, CO, and CI were -0.07 ± 0.20 cm, 27.80%; -4.40 ± 3.84 cm, 31.99%; –0.53 ± 1.23 l/min, 54.66%; and 0.54 ± 1.03 l/min/m2, 42.32%, respectively. The bias ± precision and percentage error were more important in patients with septic shock (n = 16).Conclusion USCOM was an unreliable tool for absolute value measurement of CO and CI due to the errors of VTI by CW Doppler.

Non-invasive assessment of cardiac output at rest and during exercise by finger plethysmography

We sought to determine the accuracy of finger plethysmography using pulse waveform analysis with brachial calibration for measurement of cardiac output during submaximal exercise by comparing it against an acetylene (C2H2) uptake technique. The study included 24 healthy volunteers (12 males, age 35 ± 8 years). Testing was performed on an upright cycle ergometer using an incremental protocol. Cardiac output measurements were performed at rest and during sub-maximal exercise using a single breath C2H2 uptake technique and continuously using finger plethysmography with brachial calibration. Valid results at rest and during sub-maximal exercise were achieved in 20 of 24 participants. Cardiac output at rest was 5.3 ± 1.1 and 5.2 ± 1.2 l min(-1) for finger plethysmography and C2H2, respectively, P = 0.712. Mean difference between techniques was -0.1 ± 0.5 l min(-1). Cardiac output during submaximal exercise was 10.2 ± 2.3 and 10.3 ± 2.1 l min(-1) for finger plethysmography and C2H2, respectively, P = 0.898. Mean difference between techniques was 0.1 ± 1.5 l min(-1). The overall correlation between finger plethysmography and C2H2 data obtained during rest and exercise was r(2) = 0.872, P<0.0001. Mean rise in cardiac output during exercise was 4.9 ± 1.5 (finger plethysmography) and 5.1 ± 1.5 l min(-1) (C2H2), P = 0.64. Finger plethysmography determined cardiac output values both at rest and during sub-maximal exercise are comparable with those obtained using a single breath C2H2 uptake technique.

Noninvasive cardiac output monitoring during exercise testing: Nexfin pulse contour analysis compared to an inert gas rebreathing method and respired gas analysis

Exercise testing is often used to assess cardiac function during physical exertion to obtain diagnostic information. However, this procedure is limited to measuring the electrical activity of the heart using electrocardiography and intermittent blood pressure (BP) measurements and does not involve the continuous assessment of heart functioning. In this study, we compared continuous beat-to-beat pulse contour analysis to monitor noninvasive cardiac output (CO) during exercise with inert gas rebreathing and respired gas analysis. Nineteen healthy male volunteers were subjected to bicycle ergometry testing with increasing workloads. Cardiac output was deter- mined noninvasively by continuous beat-to-beat pulse contour analysis (Nexfin) and by inert gas rebreathing, and estimated using the respired gas analysis method. The effects of the rebreathing maneuver on heart rate (HR), stroke volume (SV), and CO were evaluated. The CO values derived from the Nexfin- and inert gas rebreathing methods were well correlated (r=0.88, P < 0.01) and the limits of agreement were 30.3% with a measurement bias of 0.4 ± 1.8 L/min. Nexfin- and respired gas analysis-derived CO values correlated even better (r=0.94, P < 0.01) and the limits of agreement were 21.5% with a measurement bias of -0.70 ± 1.6 L/min. At rest, the rebreathing maneuver increased HR by 13 beats/min (P < 0.01), SV remained unaffected (P=0.7), while CO increased by 1.0 L/min (P < 0.01). Rebreathing did not affect these parameters during exercise. Nexfin continuous beat-to-beat pulse contour analysis is an appropriate method for noninvasive assessment of CO during exercise.

A comparative evaluation of electrical velocimetry and inert gas rebreathing for the non-invasive assessment of cardiac output

When assessing the function of the cardiovascular system, cardiac output (CO) is a substantial parameter. For its determination, numerous non-invasive techniques have been proposed in the recent years including inert gas rebreathing (IGR) and impedance cardiography (ICG). The aim of our study was to evaluate whether a novel ICG algorithm (electrical velocimetry) and IGR can be used interchangeably in the clinical setting. A total of 120 consecutive stable patients were included resulting in two pairs of repeated non-invasive cardiac output measurements. The mean CO was 5.0±1.2l/min (range 2.6-8.6l/min) using IGR and 4.4±1.1l/min (1.7-7.4l/min) using ICG, respectively. Bland-Altman analysis revealed an acceptable agreement with a mean bias of 0.6±1.2l/min. We found a high reproducibility with a mean bias of 0.2±0.7l/min for IGR and 0.0±0.3l/min for ICG (p<0.001), respectively. There was a statistically significant difference for unphysiological circulatory conditions represented by values of 2.6-4.1l/min and 5.6-8.6l/min. Both non-invasive techniques are associated with low operating costs and require only a few expendable items for the rapid determination of cardiac function. We found an acceptable agreement between IGR and ICG as well as a high reproducibility, which was statistically significant higher for ICG. For cardiac output states exceeding the physiological range, we found a statistically significant difference. Consequently, values of cardiac function determined by either method should not be used interchangeably in the clinical setting.

Retraction Note: Noninvasive assessment of cardiac output using thoracic electrical bioimpedance in hemodynamically stable and unstable patients after cardiac surgery: a comparison with pulmonary artery thermodilution

Retraction Note: Noninvasive assessment of cardiac output using thoracic electrical bioimpedance in hemodynamically stable and unstable patients after cardiac surgery: a comparison with pulmonary artery thermodilution

673 Impedance Cardiography Is Inaccurate in the Assessment of Cardiac Output in Pulmonary Arterial Hypertension in Comparison to Left Ventricular Heart Failure

Cardiac output (CO) is the best predictor of prognosis in patients with pulmonary arterial hypertension (PAH). There is a need of accurate noninvasive assessment of CO in PAH patients (pts). The role of ICG in PAH pts has not been clarified yet. The aim of the study was to compare the measurement of CO using ICG (COI) and thermodilution methods (COT) in pts with PAH and in pts with left ventricular heart failure and pulmonary venous hypertension (PVH).

Non-invasive assessment of cardiac output during mechanical ventilation – a novel approach using an inert gas rebreathing method

Measurement of cardiac output (CO) is of importance in the diagnostic of critically ill patients. The invasive approach of thermodilution (TD) via pulmonary artery catheter is clinically widely used. A new non-invasive technique of inert gas rebreathing (IGR) shows a good correlation with TD measurements in spontaneously breathing individuals. For the first time, we investigated whether IGR can also be applied to sedated and mechanically ventilated subjects with a clinical point of care device. CO data from IGR were compared with TD in six healthy mongrel dogs. Data sampling was repeated under baseline conditions (rest) and under stress challenge by applying 10 μg/kg/min of dobutamine intravenously. Switching from mechanical ventilation to IGR, as well as the rebreathing procedures, were carried out manually. Cardiac output data from IGR and TD correlated with a coefficient of r=0.90 (95% confidence interval [0.81; 0.95]). The Bland-Altman analysis showed a bias of 0.46 l/min for the IGR CO measurements. Ninety-five percent of all differences fall in the interval [-1.03; 1.95], being the limit of the ± 1.96 standard deviation lines. IGR is a new approach for non-invasive cardiac output measurement in mechanically ventilated individuals, but requires further investigation for clinical use.

Evaluation of noninvasive exercise cardiac output determination in chronic heart failure patients: a proposal of a new diagnostic and prognostic method

Peak oxygen consumption (VO2) and various parameters of cardiopulmonary response to exercise are of important prognostic value in chronic heart failure patients. However, all the available parameters only indirectly reflect left-ventricular dysfunction and hemodynamic adaptation to an increased demand. Noninvasive assessment of cardiac output, especially during an incremental exercise test, would allow the direct measurement of cardiac reserve and may become the gold standard for prognostic evaluation of chronic heart failure patients.

Non-Invasive Measurement of Cardiac Output during Atrial Fibrillation: Comparison between Cardiac Magnetic Resonance Imaging and Inert Gas Rebreathing

Objectives: Atrial fibrillation (AF) is one of the most frequent heart rhythm disorders. It potentially influences cardiac function and its measurement. Cardiac magnetic resonance imaging (CMR) has become the new gold standard for non-invasive assessment of cardiac output (CO). A novel inert gas rebreathing (IGR) device based on the Fick Principle also proved promising in patients in sinus rhythm (SR). The aim of our study was to compare the agreement of non-invasive CO measurements between CMR and IGR in AF patients. Methods: A total of 68 patients, 34 with AF and 34 pair-matched controls in SR, were included. Results: Bland-Altman analysis showed good agreement between both methods, with an average deviation of 0.2 ±1.2 l/min in the AF group versus 0.3 ±1.0 l/min in the SR group (p = 0.77). IGR demonstrated good agreement for CO between 2.0 and 5.4 l/min. However, in hyperdynamic circulatory conditions (CO >5.5 l/min), the increasing disagreement of IGR and CMR measurements reached statistical significance. Conclusions: Non-invasive CO measurements using CMR and IGR are feasible in patients suffering from AF. Good agreement was found between the two methods in an unselected cohort. Hyperdynamic circulatory conditions can lead to significant measurement differences which, however, do not affect the reproducibility of IGR.

529: A Non-Invasive Assessment of Cardiac Output in Pediatric Heart Transplant Patients

Pediatric patients who undergo heart transplantation (OHT) have routine invasive and non-invasive procedures to monitor for signs of graft rejection. The USCOM device (Ultrasonic Cardiac Output Monitor) is a non-invasive tool that utilizes ultrasound to measure cardiac output (CO). We sought to determine the accuracy and utility of a non-invasive measurement of CO against the current standard of invasive measurement by Swan-Ganz thermodilution in pediatric OHT patients.

Noninvasive Measurement of Cardiac Output During Exercise by Inert Gas Rebreathing Technique

Reduced exercise tolerance and dyspnea during exercise are hallmarks of heart failure syndrome. Exercise capacity and various parameters of cardiopulmonary response to exercise are of important prognostic value. All the available parameters only indirectly reflect left ventricular dysfunction and hemodynamic adaptation to an increased demand. Noninvasive assessment of cardiac output, especially during an incremental exercise stress test, would allow the direct measure of cardiac reserve and may become the gold standard for prognostic evaluation in the future.

Modelflow: a new method for noninvasive assessment of cardiac output in pregnant women

Estimation of cardiac output by continuous finger arterial pressure waveform analysis with Modelflow is a noninvasive technique for beat-to-beat hemodynamic assessment. The purpose of this study was to compare this method in pregnant women with the more commonly used Doppler echocardiography. In 16 primigravid women, stroke volume was measured serially in first, second, and third trimester and after pregnancy by the Modelflow method and by Doppler echocardiography. Aortic diameter and compliance were assessed serially by echocardiography and pulse wave velocity measurements. Aortic compliance was increased significantly in pregnancy compared with nonpregnant values, but aortic diameter did not change. After adjustment for pregnancy-related changes in pulse wave velocity, blood pressure, and heart rate, Modelflow stroke volume measurements gave comparable results to Doppler echocardiography during and after pregnancy. The observed variation was similar to reported comparisons of Doppler echocardiography with thermodilution. After adjustment for pregnancy the Modelflow method is a useful research tool for assessment of stroke volume in pregnant women and offers the advantage of continuous measurement and convenience of application.