Calculation Of Cardiac Output Research Articles

Pulmonary hypertension in patients on chronic hemodialysis

Abstract Introduction Pulmonary hypertension (PH) is a common condition in patients with advanced chronic kidney disease and is associated with higher morbidity and mortality. High arteriovenous fistula (AVF) flow is one of known etiological factors, but the association of AVF flow within the acceptable range and PH has not been tested. Moreover, the prevalence of PH differed among various studies. Purpose The aims of this study were: 1. to describe the prevalence of PH in the Czech hemodialysis population; 2. to analyze the relation between dialysis fistula flow and PH; 3. to reveal other etiology of PH in a cross-sectional non-invasive trial. Methods We analyzed index visits of the cohort CZecking HF-CKD study (ISRCTN 18275480). Thus, this is a cross-sectional analysis based on detailed echocardiography with cardiac output (CO) calculation, evaluation of the central venous pressure (CVP) and AVF flow, bio-impedance and basic laboratory tests. All these measurements were done within an hour. The presence of PH was based on the peak systolic pulmonary arterial pressure (PASP) estimation above 35 mmHg. Results We analyzed data of 162 patients. They were 73,2 ± 12,6 years old, dialysis vintage 30 ± 69 months. Pulmonary hypertension was present in 35 % of analyzed patients. Among these patients, mild PH was present in 35 %, moderate in 53 % and severe in 12 %. There was no significant impact of AVF/AVG flow on the presence of PH or PASP value (Table 1.). However patients with PH had higher prevalence of heart failure (HF), which was present in 86 % of patients with PH and only in 46 % without PH (p<0.00001), see Figure 1. This and other differences presented in Table 1. document significant contribution of postcapillary PH. Patients with PH were also more overhydrated when considered by CVP, by overhydration measurement using bioelectrical impedance analysis and had higher N-terminal pro brain natriuretic peptide (NTproBNP) (Table 1.). There was a positive correlation between systemic vascular resistance (SVR) and PASP (R=0,333, p= .001). Conclusions PH is present in approximately one third of the dialysis patients. The presence of heart failure and changes of left heart chambers show for the postcapillary etiology of PH. Neither the prevalence nor the severity of PH were significantly related to arteriovenous access flow.

321 Application of the Fick Principle for the study of visceral nutrient absorption and metabolism

Abstract In 1870, Adolf Fick introduced the concept for the calculation of cardiac output by measuring gas exchange in the lungs at a meeting of the Würzburg Physiology and Medical Society. It was not until around 1930 after the development of cardiac catheterization that it was fully verified. Fick’s equation also serves as the basis for all indicator dilution methods for measuring blood flow and has been applied to several tissues throughout the body. By measuring the blood concentration of nutrients supplying and draining a tissue bed, coupled with the flow of blood, the net nutrient exchange can be calculated. Researchers first began investigating the movement of nutrients into the portal system of ruminants in the 1950s and the first method for measuring nutrient exchange in small ruminants was published in the 1960s. This approach requires the implantation of vascular catheters into an artery and the hepatic portal vein which drains the stomach, intestines, and spleen. An additional catheter is implanted upstream in a mesenteric vein for infusion of a blood flow marker, and the addition of a catheter in a hepatic vein allows the measure of blood flow and nutrient transfer in the liver. These methods were adapted for calves and dairy cows in the 1970s. The 1980s brought further refinement of the methodologies such as improved catheter materials allowing animals to be maintained for extended periods and, several researchers published data from cattle, sheep, and goats. These methods have been coupled with measures of ruminal and intestinal disappearance as well as isotopic tracers to examine nutrient exchange and metabolism by tissues. The goal of this presentation is to review the development of this approach for studying nutrient absorption in vivo, and to highlight specific advancements in its application.

Non-arterial line cardiac output calculation misclassifies exercise pulmonary hypertension and increases risk of data loss particularly in black, scleroderma and Raynaud's patients during invasive exercise testing.

The direct Fick principle is the standard for calculating cardiac output (CO) to detect CO-dependent conditions like exercise pulmonary hypertension (ePH). Fick COarterial incorporates arterial haemoglobin (Hba) and oxygen saturation (S aO2 ) with oxygen consumption from exercise testing, while Fick COnon-arterial substitutes mixed venous haemoglobin (Hbmv) and peripheral oxygen saturation (S pO2 ) in the absence of an arterial line. The decision to employ an arterial catheter for exercise testing varies, and discrepancies in oxygen saturation and haemoglobin between arterial and non-arterial methods may lead to differences in Fick CO, potentially affecting ePH classification. We performed a retrospective analysis of 296 consecutive invasive cardiopulmonary exercise testing (iCPET) studies comparing oxygen saturation from pulse oximetry (S pO2 ) and radial arterial (S aO2 ), Hba and Hbmv, and CO calculated with arterial (COarterial) and non-arterial (COnon-arterial) values. We assessed the risk of misclassification of pre- and post-capillary ePH and data loss due to inaccurate S pO2 . When considering all stages from rest to peak exercise, Hba and Hbmv demonstrated high correlation, while S pO2 and S aO2 as well as COarterial and COnon-arterial demonstrated low correlation. Data loss was significantly higher across all stages of exercise for S pO2 (n=346/1926 (18%)) compared to S aO2 (n=17/1923 (0.88%)). We found that pre- and post-capillary ePH were misclassified as COnon-arterial data (n=7/41 (17.1%) and n=2/23 (8.7%), respectively). Patients with scleroderma and/or Raynaud's (n=11/33 (33.3%)) and black patients (n=6/19 (31.6%)) had more S pO2 data loss. Reliance upon S pO2 during invasive exercise testing results in the misclassification of pre- and post-capillary ePH, and unmeasurable S pO2 for black, scleroderma and Raynaud's patients can preclude accurate exercise calculations, thus limiting the diagnostic and prognostic value of invasive exercise testing without an arterial line.

Cardiac output calculation using the Liljestrand and Zander formula: is this method applicable during immediate transition after birth? — A post hoc analysis

The transition from intrauterine to extrauterine life is a critical period for neonates. Assessing the cardiovascular transition during this period immediately after birth is crucial but challenging. The present study compares adjusted estimated cardiac output values calculated by the Liljestrand and Zander formula (COest/adj LaZ) with non-invasively measured cardiac output values (CO-bioimpedance) during immediate transition after birth. We performed a secondary outcome analysis of a prospective observational study in preterm and term neonates. Ten and 15 min after birth, arterial blood pressure and heart rate were assessed, and CO-bioimpedance was measured using electrical bioimpedance method (Aesculon monitor, Osypka, Germany). We calculated COest/adj LaZ and compared it to CO-bioimpedance. Further, we performed a correlation analysis. Thirty-two neonates with a median (IQR) gestational age of 37.0 (32.0–39.4) weeks were included. Mean ± SD CO-bioimpedance was 0.62 ± 0.15 l/min, and COest/adj LaZ was calculated to be 0.64 ± 0.10 l/min, whereby both correlated significantly (p = 0.025, r = 0.359) with each other. Conclusion: The present study demonstrates high comparability of COest/adj LaZ and CO-bioimpedance in neonates during immediate transition after birth, suggesting that cardiac output can be derived in a cost-effective and feasible manner if other methods are not available.What is Known:• Echocardiography is considered the gold standard for non-invasive CO evaluation, but its feasibility during the immediate transition period is limited.What is New:• Non-invasive methods such as CO-bioimpedance for cardiac output (CO) measurement and the Liljestrand and Zander (LaZ) formula for estimating CO offer promising alternatives during the immediate transition period.

A primer for the student joining the adult cardiac surgery service tomorrow: Primer 1 of 7

A primer for the student joining the adult cardiac surgery service tomorrow: Primer 1 of 7

Right heart catheterization in Italian catheterization laboratories: results of the SICI-GISE national survey promoted by the GISE Young Committee

Over the past decades, the improvements in the diagnostic power and availability of non-invasive cardiac imaging techniques have led to a decline of right heart catheterization (RHC) performance. However, RHC remains the gold standard for diagnosing pulmonary hypertension and an essential tool for the evaluation of patient candidacy to heart transplantation. This survey was carried out jointly by the Young Committee of GISE, with the support of the SICI-GISE Society, and the ICOT group, with the aim of evaluating how the interventional cardiology community perform RHC. A web-based questionnaire based on 20 questions was distributed to SICI-GISE members. The survey was distributed to 1550 physicians with 174 (11%) responses. Most centers perform few procedures per year (<10 RHC/year) and a dedicated cardiologist is usually lacking. Patients were frequently admitted as ordinary hospitalization regimen and the most frequent indication for RHC was the hemodynamic assessment of pulmonary hypertension, followed by diagnostics of valvular diseases and advanced heart failure/heart transplantation. Indeed, the majority of participants (86%) are involved in transcatheter procedures for structural heart disease. The average time taken to perform the RHC was approximately 30-60 min. The femoral access (60%) was the most frequently used, usually by an echo-guided approach. Two-thirds of participants discontinued oral anticoagulant therapy before RHC. Only 27% of centers assess wedge position from an integrated analysis. Furthermore, the edge pressure is detected in the end-diastolic cardiac phase in half cases and in the end-expiratory phase in only 31%. The most commonly used method for cardiac output calculation was the indirect Fick method (58%). Guidance on the best practice for performing RHC is currently lacking. A more precise standardization of this demanding procedure is warranted.

Potentiation of GABAergic synaptic transmission by diazepam acutely increases resting beat‐to‐beat blood pressure variability in young adults

IntroductionResting beat‐to‐beat blood pressure (BP) variability is a powerful predictor of cardiovascular events and end‐organ damage. Recent studies indicate that resting beat‐to‐beat BP variability possesses greater prognostic value when compared with traditional 24‐h ambulatory or home‐based BP monitoring. However, despite the well‐recognized clinical significance of resting beat‐to‐beat BP variability, its underlying mechanisms remain incompletely understood. The sympathetic nervous system is critical for BP regulation. Given that the sympathetic pre‐motor neurons are highly regulated by inhibitory GABAergic interneurons, it is reasonable to speculate that GABA receptors may contribute to the beat‐to‐beat BP variability. However, this hypothesis has not been tested experimentally before. Therefore, in this study, we tested the hypothesis that a potentiation of GABAergic synaptic transmission by diazepam would acutely increase resting beat‐to‐beat blood pressure variability in humans.MethodsIn 40 (17 females) young, normotensive adults, resting beat‐to‐beat BP (finger photoplethysmography) was continuously measured for 5‐10 min, 60 min after the oral administration of either diazepam (10 mg) or placebo. The experiments were conducted in a randomized, double‐blinded, placebo‐controlled and crossover design. Stroke volume was estimated from the BP waveform (ModelFlow) permitting the calculation of cardiac output (CO) and total peripheral resistance (TPR). Parameters of variability included the standard deviation, range, interquartile range (the difference between the 25th and 75th percentiles within‐subject), the coefficient of variation [(SD/mean) x 100], and the average real variability. Additionally, direct recordings of muscle sympathetic nerve activity (MSNA, microneurography) were obtained in a subset of subjects (n=13) and the gain of arterial baroreflex control of MSNA (sympathetic baroreflex) and heart rate (cardiac baroreflex), as well as signal‐averaged sympathetic transduction of blood pressure calculated.ResultsCompared to placebo, diazepam significantly increased the standard deviation of systolic (4.7 ± 1.4 vs. 5.7 ± 1.5 mmHg, P = 0.001), diastolic (3.8 ± 1.2 vs. 4.5 ± 1.2 mmHg, P = 0.007) and mean BP (3.8 ± 1.1 vs. 4.5 ± 1.1 mmHg, P = 0.002), as well as CO (469 ± 149 vs. 626 ± 259 ml/min, P &lt; 0.001) and TPR (1.0 ± 0.3 vs. 1.4 ± 0.6 mmHg/l/min, P &lt; 0.001). Similar results were found using all indices of variability. Furthermore, diazepam reduced resting MSNA burst frequency (placebo: 22 ± 6 bursts/min vs. diazepam: 18 ± 8 bursts/min, P = 0.025) without affecting cardiac or sympathetic baroreflex sensitivity. However, the peak increase in mean BP following a spontaneous burst of MSNA (i.e., sympathetic transduction) was accentuated after diazepam administration.ConclusionThis is the first study to indicate that GABAA receptors may play a role in resting beat‐to‐beat BP variability. These findings advance our current understanding of the neural network mechanisms contributing to the resting beat‐to‐beat BP variability in young adults.

Noninvasive Assessment Of Cardiovascular Hemodynamics During Exercise Using Systolic Time Intervals

Noninvasive Assessment Of Cardiovascular Hemodynamics During Exercise Using Systolic Time Intervals

Potentiation of GABAergic synaptic transmission by diazepam acutely increases resting beat-to-beat blood pressure variability in young adults.

Resting beat-to-beat blood pressure variability is a powerful predictor of cardiovascular events and end-organ damage. However, its underlying mechanisms remain unknown. Herein, we tested the hypothesis that a potentiation of GABAergic synaptic transmission by diazepam would acutely increase resting beat-to-beat blood pressure variability. In 40 (17 females) young, normotensive subjects, resting beat-to-beat blood pressure (finger photoplethysmography) was continuously measured for 5-10 min, 60 min after the oral administration of either diazepam (10 mg) or placebo. The experiments were conducted in a randomized, double-blinded, and placebo-controlled design. Stroke volume was estimated from the blood pressure waveform (ModelFlow) permitting the calculation of cardiac output and total peripheral resistance. Direct recordings of muscle sympathetic nerve activity (MSNA, microneurography) were obtained in a subset of subjects (n = 13), and spontaneous cardiac and sympathetic baroreflex sensitivity were calculated. Compared with placebo, diazepam significantly increased the standard deviation of systolic blood pressure (4.7 ± 1.4 vs. 5.7 ± 1.5 mmHg, P = 0.001), diastolic blood pressure (3.8 ± 1.2 vs. 4.5 ± 1.2 mmHg, P = 0.007), and mean blood pressure (3.8 ± 1.1 vs. 4.5 ± 1.1 mmHg, P = 0.002), as well as cardiac output (469 ± 149 vs. 626 ± 259 mL/min, P < 0.001) and total peripheral resistance (1.0 ± 0.3 vs. 1.4 ± 0.6 mmHg/L/min, P < 0.001). Similar results were found using different indices of variability. Furthermore, diazepam reduced MSNA (placebo: 22 ± 6 vs. diazepam: 18 ± 8 bursts/min, P = 0.025) without affecting the arterial baroreflex control of heart rate (placebo: 18.6 ± 6.7 vs. diazepam: 18.8 ± 7.0 ms/mmHg, P = 0.87) and MSNA (placebo: -3.6 ± 1.2 vs. diazepam: -3.4 ± 1.5 bursts/100 Hb/mmHg, P = 0.55). Importantly, these findings were not impacted by biological sex. We conclude that GABAA receptors modulate resting beat-to-beat blood pressure variability in young adults.

Deep learning for automated left ventricular outflow tract diameter measurements in 2D echocardiography

Abstract Background Left ventricular outflow tract diameter (LVOTd) is routinely measured to calculate stroke volume and estimate aortic valve area by the continuity equation. Despite LVOTd being regularly measured clinically, significant inter- and intraobserver variability is evident. This variability is highly impactful on both aortic stenosis evaluation and cardiac output calculation due to the squaring of the LVOT radius. Purpose We aimed to investigate if LVOTd measurements from clinical echocardiographic examinations could be used in a deep learning (DL) model to automatically perform LVOTd measurements with equivalent accuracy and improved consistency compared to current practice. Methods Data was collected from clinical echocardiographic examinations performed on 656 consecutive patients admitted to the cardiac catheterization laboratory at a university hospital in January – December 2018. Parasternal views with cardiologist annotated LVOTd coordinates were assessed for 1314 echocardiographic still images. The quality of the still image and annotated LVOT ground truth were individually graded as high, medium and low by experienced cardiologists to establish a rigorous training basis. Spatial geometry data was preserved for each still image in order to distinguish between different degrees of image zoom. Data was randomly split into training, validation and testing sets (68%, 17%, 15%). A fully convolutional network based on the Resnet50 architecture was used with a custom loss function with heatmap regression. Image augmentations were added to extend the dataset. Results When including echocardiographic images of any quality (n=1314) in the model training and inference, the median absolute difference between cardiologist LVOTd and DL LVOTd was 0.97 mm (95% Confidence interval (CI) 0.79–1.14). Using only high and medium quality still images and ground truth (n=869) in the training and inference, median absolute difference decreased to 0.81 mm (95% CI 0.60–0.96). Adding image augmentations to this dataset further improved the model, resulting in a median LVOTd absolute difference of 0.66 mm (95% CI 0.51–0.78). The LVOTd error in inference increased with decreasing image quality, as shown in Figure 1, with two predictions (0.9%) failing completely. Conclusion Deep learning models are capable of measuring LVOTd with comparable accuracy to cardiologists when trained on clinical data. Data quality affects both training and inference. Even with a slightly lower accuracy when used on lower quality echocardiographic images, DL-assisted LVOT measurement has a clear potential to increase repeatability and consistency of LVOTd measurements. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Research Council of Norway (Norges forskningsråd) Figure 1

Oil induced cardiac effects in embryonic sheepshead minnows, Cyprinodon variegatus

Following the Deepwater Horizon oil spill in April 2010, much research has been conducted on the cardiotoxic effects of oil on fish. Sensitive life history stages, such as the embryonic period, have been targeted to elucidate the effects of polycyclic aromatic hydrocarbons (PAHs) on the developing cardiovascular systems of fish. However, much of this research has focused on rapidly developing pelagic species, with little emphasis on estuarine species with longer embryological periods. Moreover, previous studies have used heart rate as the primary endpoint to measure cardiac performance in embryos and larvae; an endpoint that on its own may overlook impairment in cardiac performance. This study aims to fill these knowledge gaps and provide a more holistic approach for assessing the effects of PAHs on cardiac function by exposing sheepshead minnow (Cyprinodon variegatus) embryos to two oil doses (150 and 300 μg/L tPAH nominally) throughout embryonic development and measuring cardiac responses through the identification of cardiotoxic phenotypes (pericardial edema) as well as calculation of cardiac output at 4 days post fertilization. Results of this study show significant increases in pericardial edema at both oil doses relative to controls as well as significantly reduced cardiac output – driven by reductions in ventricular stroke volume. This study is one of the first to assess cardiac output in embryonic fish exposed to oil and methods described here allow for more physiologically relevant measures of cardiac performance in early life stages through established and non-invasive measures.

Non-invasive Oscillometry-Based Estimation of Cardiac Output - Can We Use It in Clinical Practice?

While invasive thermodilution techniques remain the reference methods for cardiac output (CO) measurement, there is a currently unmet need for non-invasive techniques to simplify CO determination, reduce complications related to invasive procedures required for indicator dilution CO measurement, and expand the application field toward emergency room, non-intensive care, or outpatient settings. We evaluated the performance of a non-invasive oscillometry-based CO estimation method compared to transpulmonary thermodilution. To assess agreement between the devices, we used Bland–Altman analysis. Four-quadrant plot analysis was used to visualize the ability of Mobil-O-Graph (MG) to track CO changes after a fluid challenge. Trending analysis of CO trajectories was used to compare MG and PiCCO® calibrated pulse wave analysis over time (6 h). We included 40 patients from the medical intensive care unit at the Charité – Universitätsmedizin Berlin, Campus Benjamin Franklin between November 2019 and June 2020. The median age was 73 years. Forty percent of the study population was male; 98% was ventilator-dependent and 75% vasopressor-dependent at study entry. The mean of the observed differences for the cardiac output index (COI) was 0.7 l∗min–1*m–2 and the lower, and upper 95% limits of agreement (LOA) were -1.9 and 3.3 l∗min–1*m–2, respectively. The 95% confidence interval for the LOA was ± 0.26 l∗min–1*m–2, the percentage error 83.6%. We observed concordant changes in CO with MG and PiCCO® in 50% of the measurements after a fluid challenge and over the course of 6 h. Cardiac output calculation with a novel oscillometry-based pulse wave analysis method is feasible and replicable in critically ill patients. However, we did not find clinically applicable agreement between MG and thermodilution or calibrated pulse wave analysis, respectively, assessed with established evaluation routine using the Bland–Altman approach and with trending analysis methods. In summary, we do not recommend the use of this method in critically ill patients at this time. As the basic approach is promising and the CO determination with MG very simple to perform, further studies should be undertaken both in hemodynamically stable patients, and in the critical care setting to allow additional adjustments of the underlying algorithm for CO estimation with MG.

Cardiac output estimation based on arterial and venous blood gas analysis: proposal of amonitoring method.

Hemodynamic optimization is vital in high risk surgical patients or in high risk surgical procedures. The main objective of hemodynamic management is to maintain tissue perfusion and preserve aerobic metabolism through acardiac output coupled with the metabolic demand. The technologies used for cardiac output monitoring use special techniques (e.g. lithium dilution or transpulmonary thermodilution) or implementation of dedicated devices with considerable rates of potential complications (pulmonary artery catheter). Thus, we propose anovel method to estimate cardiac output through the analysis of arteriovenous blood gases which could be an alternative to more expensive methods (minimally invasive devices, pulmonary artery catheter). Areview of several formulas described in the literature to compute the variables needed to calculate cardiac output with the Fick principle was carried out. These formulas estimate the oxygen consumption using the O2 sensor integrated in the anesthesia workstation. The other variables in the Fick equation are derived from the arterial and venous blood gas analysis and parameters obtained from mechanical ventilators. By integrating the data gathered from the publications found, the authors created acomprehensive formula for calculation of cardiac output and the cardiac index using the parameters obtained from blood gas analysis. The presented method provides amore accessible and affordable way to monitor cardiac output in surgical high-risk patients in an environment with limited resources.

Adolf Eugen Fick (1829-1901) – The Man Behind the Cardiac Output Equation

Adolf Fick was a German physiologist, born in Kassel in 1829, who studied medicine at the University of Marburg and graduated in 1851. He worked first in Zurich and then in Wurzburg. Most of his studies were based on physics and mathematics, and deep analysis, and only later were proven by experiments. Fick's name in physics is associated to the laws of diffusion of solutions, and in medicine to the principle of cardiac output calculation. In 1855, he proposed Fick's laws on gas diffusion. In 1870, he devised Fick's principle, which allows the measurement of cardiac output and calculations of intracardiac shunts from the arteriovenous oxygen difference. The method was later generalized to the Fick principle, according to which the flow of an indicator taken up or released by an organ corresponds to the difference between the indicator flows in the inflow and outflow tracts. Fick invented several devices most of them aimed to improve precision in his physiologic experiments. In 1868, he invented the plethysmograph, for recording the speed of blood in the human artery. In 1888, the tonometer for measuring from outside the hydrostatic pressure inside the eyeball. After 3 decades as Professor in Wurzburg, he retired. Fick died at Blankenberge, Belgium in 1901 age 71 years old.

The Effect of Dietary Inorganic Nitrate Supplementation on Cardiac Function during Submaximal Exercise in Men with Heart Failure with Reduced Ejection Fraction (HFrEF): A Pilot Study.

Heart failure with reduced ejection fraction (HFrEF) is a common end point for patients with coronary artery disease and it is characterized by exercise intolerance due, in part, to a reduction in cardiac output. Nitric oxide (NO) plays a vital role in cardiac function and patients with HFrEF have been identified as having reduced vascular NO. This pilot study aimed to investigate if nitrate supplementation could improve cardiac measures during acute, submaximal exercise. Five male participants (61 ± 3 years) with HFrEF (EF 32 ± 2.2%) completed this pilot study. All participants supplemented with inorganic nitrate (beetroot juice) or a nitrate-depleted placebo for ~13 days prior to testing. Participants completed a three-stage submaximal exercise protocol on a recumbent cycle ergometer with simultaneous echocardiography for calculation of cardiac output (Q), stroke volume (SV), and total peripheral resistance (TPR). Heart rate and blood pressure were measured at rest and during each stage. Both plasma nitrate (mean = ~1028%, p = 0.004) and nitrite (mean = ~109%, p = 0.01) increased following supplementation. There were no differences between interventions at rest, but the percent change in SV and Q from rest to stage two and stage three of exercise was higher following nitrate supplementation (all p > 0.05, ES > 0.8). Both interventions showed decreases in TPR during exercise, but the percent reduction TPR in stages two and three was greater following nitrate supplementation (p = 0.09, ES = 0.98 and p = 0.14, ES = 0.82, respectively). There were clinically relevant increases in cardiac function during exercise following supplementation with nitrate. The findings from this pilot study warrant further investigation in larger clinical trials.

Effects of the estrous cycle and pregnancy status on cardiovascular variables in healthy bitches

IntroductionThe aim of the study was to characterize changes in maternal cardiovascular variables throughout the reproductive cycle in healthy bitches and determine whether magnitude of pregnancy-induced changes correlates to litter size. AnimalsEleven client-owned breeding bitches were included in the study. Materials and methodsBitches were enrolled prospectively and followed up longitudinally throughout a single reproductive cycle. Physical examination, echocardiography, blood pressure analysis, and plasma volume estimation were performed during proestrus, diestrus (early and late pregnancy), and anestrus. Fetal echocardiography was performed during late pregnancy. Data were compared across visits using a linear mixed-effects model, and correlation between variables was assessed. ResultsCompared with proestrus, no significant changes were observed at any phase of the cycle in heart rate, blood pressure, echocardiographic measurements of left ventricular size or function, or echocardiographic calculations of stroke volume or cardiac output. Estimated plasma volume increased by 29.6% in early pregnancy (p < 0.001) and 70.7% in late pregnancy (p < 0.001). Fetal echocardiography was feasible in a subset of fetuses for each bitch. There was a significant correlation between estimated total fetal cardiac output and late pregnancy increase in maternal cardiac output (p = 0.0025). The incidence of physiologic heart murmurs ranged from 5 of 11 (45%) bitches in proestrus to 2 of 11 (18%) bitches in late pregnancy, attributed to variations in aortic outflow velocity. ConclusionsHemodynamic alterations in pregnant bitches do not result in consistently detectable echocardiographic changes, suggesting that cardiac screening could be diagnostic at any time during a reproductive cycle. Physiologic heart murmurs were common in this study population and not obviously associated with the reproductive cycle.

Dynamic Modulation of Device-Arterial Coupling to Determine Cardiac Output and Vascular Resistance.

Clinical adoption of mechanical circulatory support for shock is rapidly expanding. Achievingoptimal therapeutic benefit requires metrics of state to guide titration and weaning of support. Using the transvalvular positioning of a percutaneous ventricular assist device (pVAD), device:heart interactions are leveraged to determine cardiac output (CO) and systemic vascular resistance (SVR) near-continuously without disrupting therapeutic function. An automated algorithm rapidly alternates between device support levels to dynamically modulate physiological response. Employing a two-element lumped parameter model of the vasculature, SVR and CO are quantified directly from measurements obtained by the pVAD without external calibration or invasive catheters. The approach was validated in an acute porcine model across a range of cardiac (CO = 3-10.6L/min) and vascular (SVR = 501-1897dyns/cm5) states. Cardiac output calculations closely correlated (r = 0.82) to measurements obtained by the pulmonary artery catheter-based thermodilution method with a mean bias of 0.109L/min and limits of agreement from - 1.67 to 1.89L/min. SVR was also closely correlated (r = 0.86) to traditional catheter-based measurements with a mean bias of 62.1dyns/cm5 and limits of agreement from - 260 to 384dyns/cm5. Use of diagnostics integrated into therapeutic device function enables the potential for optimizing support to improve outcomes for cardiogenic shock.

Direct Measurement of Neonatal Cardiac Output Utilizing the COstatus Monitor

Background: Knowledge of cardiac output is a valuable tool in the treatment of critically ill patients. Often, cardiac output is measured indirectly using nonspecific clinical markers. Previous methods of direct calculation of cardiac output have involved considerable risk and have not been feasible in the neonatal population. Less invasive methods exist, but are inaccurate. The COstatus monitor utilizes ultrasound dilution for direct measurement of cardiac output and is suitable for use in the neonatal population. It has been …

The effect of haemodynamic and peripheral vascular variability on cardiac output monitoring: thermodilution and non-invasive pulse contour cardiac output during cardiothoracic surgery.

While haemodynamic variability interferes with the assumption of constant flow underlying thermodilution cardiac output calculation, variability in (peripheral) arterial vascular physiology may affect pulse contour cardiac output methods. We compared non-invasive finger arterial pressure-derived continuous cardiac output measurements (Nexfin® ) with cardiac output measured using thermodilution during cardiothoracic surgery and determined the impact of cardiovascular variability on either method. We compared cardiac output derived from non-invasive finger arterial pressure with cardiac output measured by thermodilution at four grades (A-D) of cardiovascular variability. We defined Grade A data as heart rate and mean arterial pressure variability < 5% and the absence of arrhythmias (implying stable flow) and Physiocal® interval (as measure of variability in finger arterial physiology) > 30 beats. Grade B included all levels of heart rate/mean arterial pressure variability and arrhythmias (Physiocal < 30 excluded). Grade C included all Physiocal intervals (heart rate/mean arterial pressure variability > 5% and arrhythmias excluded). Grade D included all data. Comparison results were quantified as percentage errors. We analysed measurements in 27 patients undergoing coronary artery bypass surgery. Before extracorporeal circulation, the percentage error was 23% (n = 14 patients) in grade A, 28% (n = 20) in grade B, 32% (n = 22) in grade C and 37% (n = 26) in grade D, with a significant increase in variance (p = 0.035). Bias did not differ between grades. After extracorporeal circulation (n = 27), percentage errors became larger, but were not different between grades. Variability during cardiothoracic surgery affected the comparison between thermodilution and non-invasive finger arterial pressure-derived cardiac output. When the main sources of variability were included, percentage errors were large. Future cardiac output methodology comparison studies should report haemodynamic variability.

Heart Performance Determination by Visualization in Larval Fishes: Influence of Alternative Models for Heart Shape and Volume.

Understanding cardiac function in developing larval fishes is crucial for assessing their physiological condition and overall health. Cardiac output measurements in transparent fish larvae and other vertebrates have long been made by analyzing videos of the beating heart, and modeling this structure using a conventional simple prolate spheroid shape model. However, the larval fish heart changes shape during early development and subsequent maturation, but no consideration has been made of the effect of different heart geometries on cardiac output estimation. The present study assessed the validity of three different heart models (the “standard” prolate spheroid model as well as a cylinder and cone tip + cylinder model) applied to digital images of complete cardiac cycles in larval mahi-mahi and red drum. The inherent error of each model was determined to allow for more precise calculation of stroke volume and cardiac output. The conventional prolate spheroid and cone tip + cylinder models yielded significantly different stroke volume values at 56 hpf in red drum and from 56 to 104 hpf in mahi. End-diastolic and stroke volumes modeled by just a simple cylinder shape were 30–50% higher compared to the conventional prolate spheroid. However, when these values of stroke volume multiplied by heart rate to calculate cardiac output, no significant differences between models emerged because of considerable variability in heart rate. Essentially, the conventional prolate spheroid shape model provides the simplest measurement with lowest variability of stroke volume and cardiac output. However, assessment of heart function—especially if stroke volume is the focus of the study—should consider larval heart shape, with different models being applied on a species-by-species and developmental stage-by-stage basis for best estimation of cardiac output.