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Diaphragmatic hernia: an unusual cause of postpartum collapse

Sharifah H, Naidu A, Vimal K

BJOG, 2003 Jul;110(7):701-3.
PMID: 12842063
Matched MeSH terms: Cardiac Output, Low/etiology*
A randomized controlled trial of levosimendan to reduce mortality in high-risk cardiac surgery patients (CHEETAH): Rationale and design

Zangrillo A, Alvaro G, Pisano A, Guarracino F, Lobreglio R, Bradic N, et al.

Am Heart J, 2016 Jul;177:66-73.
PMID: 27297851 DOI: 10.1016/j.ahj.2016.03.021

OBJECTIVE: Patients undergoing cardiac surgery are at risk of perioperative low cardiac output syndrome due to postoperative myocardial dysfunction. Myocardial dysfunction in patients undergoing cardiac surgery is a potential indication for the use of levosimendan, a calcium sensitizer with 3 beneficial cardiovascular effects (inotropic, vasodilatory, and anti-inflammatory), which appears effective in improving clinically relevant outcomes.
DESIGN: Double-blind, placebo-controlled, multicenter randomized trial.
SETTING: Tertiary care hospitals.
INTERVENTIONS: Cardiac surgery patients (n = 1,000) with postoperative myocardial dysfunction (defined as patients with intraaortic balloon pump and/or high-dose standard inotropic support) will be randomized to receive a continuous infusion of either levosimendan (0.05-0.2 μg/[kg min]) or placebo for 24-48 hours.
MEASUREMENTS AND MAIN RESULTS: The primary end point will be 30-day mortality. Secondary end points will be mortality at 1 year, time on mechanical ventilation, acute kidney injury, decision to stop the study drug due to adverse events or to start open-label levosimendan, and length of intensive care unit and hospital stay. We will test the hypothesis that levosimendan reduces 30-day mortality in cardiac surgery patients with postoperative myocardial dysfunction.
CONCLUSIONS: This trial is planned to determine whether levosimendan could improve survival in patients with postoperative low cardiac output syndrome. The results of this double-blind, placebo-controlled randomized trial may provide important insights into the management of low cardiac output in cardiac surgery.

Matched MeSH terms: Cardiac Output, Low/mortality; Cardiac Output, Low/therapy*
Hemodynamic response to exercise and head-up tilt of patients implanted with a rotary blood pump: a computational modeling study

Lim E, Salamonsen RF, Mansouri M, Gaddum N, Mason DG, Timms DL, et al.

Artif Organs, 2015 Feb;39(2):E24-35.
PMID: 25345482 DOI: 10.1111/aor.12370

The present study investigates the response of implantable rotary blood pump (IRBP)-assisted patients to exercise and head-up tilt (HUT), as well as the effect of alterations in the model parameter values on this response, using validated numerical models. Furthermore, we comparatively evaluate the performance of a number of previously proposed physiologically responsive controllers, including constant speed, constant flow pulsatility index (PI), constant average pressure difference between the aorta and the left atrium, constant average differential pump pressure, constant ratio between mean pump flow and pump flow pulsatility (ratioP I or linear Starling-like control), as well as constant left atrial pressure ( P l a ¯ ) control, with regard to their ability to increase cardiac output during exercise while maintaining circulatory stability upon HUT. Although native cardiac output increases automatically during exercise, increasing pump speed was able to further improve total cardiac output and reduce elevated filling pressures. At the same time, reduced venous return associated with upright posture was not shown to induce left ventricular (LV) suction. Although P l a ¯ control outperformed other control modes in its ability to increase cardiac output during exercise, it caused a fall in the mean arterial pressure upon HUT, which may cause postural hypotension or patient discomfort. To the contrary, maintaining constant average pressure difference between the aorta and the left atrium demonstrated superior performance in both exercise and HUT scenarios. Due to their strong dependence on the pump operating point, PI and ratioPI control performed poorly during exercise and HUT. Our simulation results also highlighted the importance of the baroreflex mechanism in determining the response of the IRBP-assisted patients to exercise and postural changes, where desensitized reflex response attenuated the percentage increase in cardiac output during exercise and substantially reduced the arterial pressure upon HUT.

Matched MeSH terms: Cardiac Output
A method for control of an implantable rotary blood pump for heart failure patients using noninvasive measurements

Lim E, Alomari AH, Savkin AV, Dokos S, Fraser JF, Timms DL, et al.

Artif Organs, 2011 Aug;35(8):E174-80.
PMID: 21843286 DOI: 10.1111/j.1525-1594.2011.01268.x

We propose a deadbeat controller for the control of pulsatile pump flow (Q(p) ) in an implantable rotary blood pump (IRBP). Noninvasive measurements of pump speed and current are used as inputs to a dynamical model of Q(p) estimation, previously developed and verified in our laboratory. The controller was tested using a lumped parameter model of the cardiovascular system (CVS), in combination with the stable dynamical models of Q(p) and differential pressure (head) estimation for the IRBP. The control algorithm was tested with both constant and sinusoidal reference Q(p) as input to the CVS model. Results showed that the controller was able to track the reference input with minimal error in the presence of model uncertainty. Furthermore, Q(p) was shown to settle to the desired reference value within a finite number of sampling periods. Our results also indicated that counterpulsation yields the minimum left ventricular stroke work, left ventricular end diastolic volume, and aortic pulse pressure, without significantly affecting mean cardiac output and aortic pressure.

Matched MeSH terms: Cardiac Output
Fulltext Doppler echocardiography guided cardiac resynchronization therapy in heart failure

Oemar, Hamed, Abdulgani, Hafil Budianto

Medical Health Reviews, 2008;2008(1):17-28.
MyJurnal

Heart failure (HF) is a major burden in almost all countries. The prevalence of symptomatic HF is still high. Despite our best understanding of its pathophysiologic mechanisms and the recent advances in pharmacologic therapy, it remains a highmortality and morbidity disease. About 30-50% of patients with HF have concurrent electrical delay in the electrocardiogram (ECG), mainly in the form of LBBB.1 This kind of conduction delay commonly occurs in patients with idiopathic dilated cardiomyopathy and ischemic cardiomyopathy as well. The abnormality of left ventricle (LV) conduction will lead to a change in LV contraction pattern resulting dyssynchronized with right ventricle) contraction. Thus, a dyssynchronous LV contractile pattern usually manifested by late activation of the LV lateral wall which in turn impairs LV systolic function, reduces cardiac output, raises filling pressure and worsens mitral regurgitation2. Cardiac resynchronization therapy (CRT) improves cardiac function and exercise capacity leading to an improved survival in patients with advanced heart failure and ventricular conduction delay.3 The underlying mechanisms of these beneficial effects are not fully understood, but they appear to be related to a restored coordination of the left (LV) and right ventricular (RV) contraction and relaxation.4 These effects may directly lead to augmented contractility and reduction of LV filling pressures.5 Echocardiography has been widely used to identify patients who are candidates for CRT and to monitor the response in LV function at follow-up after device implantation. This review addresses the applications of CRT in patients with moderate– severe heart failure and the role of echocardiography in optimizing CRT including patient selection, risk and benefit of CRT and appropriate measures.

Matched MeSH terms: Cardiac Output
Fulltext Preload-based Starling-like control of rotary blood pumps: An in-vitro evaluation

Mansouri M, Gregory SD, Salamonsen RF, Lovell NH, Stevens MC, Pauls JP, et al.

PLoS One, 2017;12(2):e0172393.
PMID: 28212401 DOI: 10.1371/journal.pone.0172393

Due to a shortage of donor hearts, rotary left ventricular assist devices (LVADs) are used to provide mechanical circulatory support. To address the preload insensitivity of the constant speed controller (CSC) used in conventional LVADs, we developed a preload-based Starling-like controller (SLC). The SLC emulates the Starling law of the heart to maintain mean pump flow ([Formula: see text]) with respect to mean left ventricular end diastolic pressure (PLVEDm) as the feedback signal. The SLC and CSC were compared using a mock circulation loop to assess their capacity to increase cardiac output during mild exercise while avoiding ventricular suction (marked by a negative PLVEDm) and maintaining circulatory stability during blood loss and severe reductions in left ventricular contractility (LVC). The root mean squared hemodynamic deviation (RMSHD) metric was used to assess the clinical acceptability of each controller based on pre-defined hemodynamic limits. We also compared the in-silico results from our previously published paper with our in-vitro outcomes. In the exercise simulation, the SLC increased [Formula: see text] by 37%, compared to only 17% with the CSC. During blood loss, the SLC maintained a better safety margin against left ventricular suction with PLVEDm of 2.7 mmHg compared to -0.1 mmHg for CSC. A transition to reduced LVC resulted in decreased mean arterial pressure (MAP) and [Formula: see text] with CSC, whilst the SLC maintained MAP and [Formula: see text]. The results were associated with a much lower RMSHD value with SLC (70.3%) compared to CSC (225.5%), demonstrating improved capacity of the SLC to compensate for the varying cardiac demand during profound circulatory changes. In-vitro and in-silico results demonstrated similar trends to the simulated changes in patient state however the magnitude of hemodynamic changes were different, thus justifying the progression to in-vitro evaluation.

Matched MeSH terms: Cardiac Output
Population differences in cardiovascular reactivity to the cold pressor test

Duncan MT, Husain R, Chen HM, Horvath SM

Am J Hum Biol, 1995;7(3):329-337.
PMID: 28557027 DOI: 10.1002/ajhb.1310070309

The interaction of race and climatic adaptation on patterns of cardiovascular reactivity among young adult males was examined. Malay and Chinese subjects living in a tropical climate in the Orient and Caucasians living in a sub-tropical climate in North America were investigated. The cold pressor test with hand immersion in cold water was used as the stressor. Systolic and diastolic blood pressures, cardiac frequency, cardiac output, and stroke volume were measured. The results provided limited evidence for absence of differences in cardiac reactivity among racial groups and for greater vascular reactivity in the Caucasians. Cold immersion also elicited differential responses which could be partially attributed to differences in acclimatizations status. © 1995 Wiley-Liss, Inc.

Matched MeSH terms: Cardiac Output
Fulltext A cardiovascular mathematical model of graded head-up tilt

Lim E, Chan GS, Dokos S, Ng SC, Latif LA, Vandenberghe S, et al.

PLoS One, 2013;8(10):e77357.
PMID: 24204817 DOI: 10.1371/journal.pone.0077357

A lumped parameter model of the cardiovascular system has been developed and optimized using experimental data obtained from 13 healthy subjects during graded head-up tilt (HUT) from the supine position to [Formula: see text]. The model includes descriptions of the left and right heart, direct ventricular interaction through the septum and pericardium, the systemic and pulmonary circulations, nonlinear pressure volume relationship of the lower body compartment, arterial and cardiopulmonary baroreceptors, as well as autoregulatory mechanisms. A number of important features, including the separate effects of arterial and cardiopulmonary baroreflexes, and autoregulation in the lower body, as well as diastolic ventricular interaction through the pericardium have been included and tested for their significance. Furthermore, the individual effect of parameter associated with heart failure, including LV and RV contractility, baseline systemic vascular resistance, pulmonary vascular resistance, total blood volume, LV diastolic stiffness and reflex gain on HUT response have also been investigated. Our fitted model compares favorably with our experimental measurements and published literature at a range of tilt angles, in terms of both global and regional hemodynamic variables. Compared to the normal condition, a simulated congestive heart failure condition produced a blunted response to HUT with regards to the percentage changes in cardiac output, stroke volume, end diastolic volume and effector response (i.e., heart contractility, venous unstressed volume, systemic vascular resistance and heart rate) with progressive tilting.

Matched MeSH terms: Cardiac Output/physiology
Fulltext Uncomplicated hyperemesis gravidarum does not alter the course of cardiovascular changes during pregnancy

Sheila Rani Kovil George, Sivalingam Nalliah

International e-Journal of Science, Medicine & Education, 2014;8(1):34-43.
MyJurnal

The purpose of this prospective longitudinal study was to investigate the maternal cardiac haemodynamic and structural changes that occur
in pregnancies with uncomplicated hyperemesis gravidarum in a selected Malaysian population. Nine women underwent serial echocardiography beginning at 12 weeks of gestation and throughout pregnancy at monthly intervals. Their echocardiograms were repeated at 6 and 12 weeks following delivery to reflect the pre-pregnancy haemodynamic state. Cardiac output was measured by continuous wave Doppler at the aortic valve. Interventricular septum thickness was determined by M- mode echocardiography and ventricular diastolic function by assessing flow at the mitral valve with Doppler recording. Cardiac output showed an increase of 32.9% at 36 weeks and maintained till 40 weeks of gestation. Heart rate increased from 79 ± 6 to 96 ± 8 beats/min at 36 weeks. Stroke volume increased by 16.4 % at 40 weeks of gestation when compared to the baseline
value. Systolic and diastolic blood pressure did not appreciably change but showed a lower reading during the mid-trimester period. Early inflow velocity of left ventricle did not show a rise while peak atrial velocity showed an increasing trend; thus the ratio of early inflow to peak atrial transport showed a declining trend from early pregnancy to term. End diastolic dimension of left ventricle and interventricular septum thickness showed an increased value at term. Uncomplicated hyperemesis gravidarum did not alter the haemodynamic changes throughout pregnancy and concur with established data for normal pregnancy.

Matched MeSH terms: Cardiac Output