Search Results
Results 351 - 400 of 1604
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Chang K C - - 2000
Both the maximal systolic elastance (Emax) and the theoretical maximal flow (Qmax) can quantify the systolic mechanical behavior of the ventricular pump. Physically, Emax can reflect the intrinsic contractility of the myocardium as an intact heart. The quantity in (Qmax is inversely related to the internal resistance of the left ...
Cassidy SC - - 2000
The left ventricular pressure-volume relationship has been used to examine ventricular systolic and diastolic function as well as to evaluate myocardial energetics and ventricular-vascular coupling. Preload, afterload and contractility can be separately examined using indices derived from simultaneous pressure and volume measurement. Due to the development of new instrumentation and ...
Muir W W WW - - 2000
To evaluate the effects of a hemoglobin-based oxygen carrier (HBOC-301) on left ventricular preload, afterload, contractility, and ventriculo-arterial coupling in anesthetized dogs. A prospective experimental study. Seven adult male dogs weighing 2.3 to 2.7 kg. The study was performed on intact, closed-chest, chloralose-anesthetized dogs. Heart rate, left ventricular end-systolic and ...
Wronski T - - 2000
Changes in volume elasticity (VE) of the left ventricle and aorta could be important for blood flow. A procedure is presented to rapidly assess VE of the left ventricle and aorta by analyzing changes in the eigenfrequency. Six control rabbits and 11 rabbits with atheromatosis (12 wk of high-cholesterol feeding) ...
Morita S - - 2000
To evaluate the pump function of the ventricle, a parameter which (i) incorporates systolic and diastolic function and (ii) separates the heart from preload and afterload is needed. This study utilized ejection fraction (EF), calculated from the end-systolic (ES) and end-diastolic (ED) pressure-volume relationship (PVR) using an arbitrary set of ...
Petretta M - - 2000
This study evaluated the effect of angiotensin II receptor blockade on cardiac autonomic control adaptation and urine output in response to acute isotonic volume load in patients with idiopathic dilated cardiomyopathy (DCM) and asymptomatic to mildly symptomatic heart failure. Left ventricular volumes and heart rate variability measurements were assessed at ...
Mundigler G - - 2000
OBJECTIVE: We examined whether intrathoracic blood volume (ITBV) and total end-diastolic volume (TEDV), determined by the transpulmonary indicator dilution technique, adequately reflect preload changes during fluid administration in patients with reduced left ventricular function. DESIGN: A prospective, controlled, clinical study. SETTING: Medical intensive care unit in a university hospital. PATIENTS: ...
Yu Z B - - 2000
The interaction between the gravitational field, the position of the body, and the functional characteristics of the blood vessels determines the distribution of intravascular volume. In turn, this distribution determines cardiac pump function. One of the most profound circulatory changes that occurs in man during exposure to weightlessness is a ...
Royse C F - - 2000
The end-diastolic pressure-volume relation is a load-independent measurement of diastolic function. However, its clinical utility is limited because of its complexity. Instantaneous end-diastolic stiffness (IEDS) is a simple to perform, single-point, measurement of ventricular stiffness. We have validated it against the end-diastolic pressure-area relation (EDPAR) in patients undergoing cardiac surgery. ...
Hayashi K - - 2000
BACKGROUND: The ratio of ventricular end-systolic elastance (Ees) to effective arterial elastance (Ea) is known to reflect not only ventricular mechanical performance but also energetic performance. Despite these useful features, technical difficulties associated with estimating Ees make the clinical application of Ees/Ea impractical. We developed a framework to estimate Ees/Ea ...
Bastos B G - - 2000
PURPOSE: The purpose of this study was to determine the cardiac mechanisms involved in cardiovascular adjustments during postexercise circulatory occlusion (OCCL). METHOD: Heart rate (HR), mean arterial pressure (MAP), left ventricular end-diastolic (EDV) and end-systolic volumes (ESV), stroke volume (SV), cardiac output (CO), and total peripheral vascular resistance (total peripheral ...
Elvenes O P - - 2000
BACKGROUND: Warm continuous blood cardioplegia (WCBCP) has been recommended during prolonged cardiac arrest to minimize functional deterioration. Myocardial metabolism and efficiency after this cardioplegic modality are not well described. METHODS: Substrate oxidation, blood flow, and myocardial function were measured before, during, and after 3 hours of WCBCP in 7 pigs. ...
Vallejo E - - 2000
Quantitative gated SPECT (QGS) has been used for computation of left ventricular volumes and ejection fraction. This study evaluated, first, the effect of injected dose, time of imaging, and background activity on the reproducibility of QGS and, second, the accuracy of QGS, compared with cine MRI, for determining left ventricular ...
Steendijk P - - 2000
OBJECTIVE: To evaluate a new, less invasive, conductance method to measure continuous on-line left ventricular volume. End-systolic and end-diastolic volumes obtained with this transcardiac conductance method were compared with simultaneous measurements using the conventional intracardiac conductance catheter. DESIGN: Controlled animal study. SETTING: Research laboratory in a university hospital. SUBJECTS: Six ...
Kubota H - - 2000
OBJECTIVE: To evaluate cardiac function at cardiopulmonary bypass weaning, we applied a new technique clinically to determine the approximated Emax without using a conductance catheter. METHODS: Subjects were 5 patients. The left ventricular end-systolic pressure was obtained by overlaying the radial arterial pressure curve on the left ventricular pressure curve. ...
Summers R L - - 2000
PURPOSE: Traditional measures of cardiac contractility such as dp/dt and ejection fraction has been noted to be sensitive to preload and afterload conditions. The end systolic pressure-volume relationship of the left ventricle (ESPVR, Suga Index or Emax) has been found to be the best load independent measure of the cardiac ...
Zeng H - - 2000
OBJECTIVE: To understand the effect of intravenous nitroglycerin (NTG) on hemodynamics in infants and small children with congestive heart failure secondary to congenital cardiac defect of left to right shunt. METHODS: Heart rate, blood pressure and total peripheral resistance were monitored continuously. Echocardiography was used to measure ejection fraction, fractional ...
Senzaki H - - 2000
BACKGROUND: Myofilament Ca(2+) sensitizers enhance contractility but can adversely alter diastolic function through sensitization to low intracellular Ca(2+) concentration. Concomitant phosphodiesterase III inhibition (PDE3I) may offset diastolic changes but limit the mechanoenergetic benefits. We tested whether selective Ca(2+) sensitization in vivo with the use of EMD-57033 enhances both systolic and ...
Weinmann P - - 2000
BACKGROUND: Changes induced by dipyridamole infusion on left ventricular function in healthy individuals have not been investigated by gated myocardial perfusion single photon emission computed tomographic (SPECT) imaging. METHODS AND RESULTS: This study examined the amplitude and duration of changes induced by dipyridamole infusion on left ventricular function as assessed ...
Kolh P - - 2000
OBJECTIVE: The aim of this study was to investigate left ventricular contractility and energetic cost of cardiac ejection under conditions of acute increase in aortic compliance. METHODS: In six anaesthetized pigs, ascending aortic compliance was increased by adding a volume chamber in parallel to the ascending aorta. Systemic vascular parameters, ...
Tournadre J P - - 2000
BACKGROUND: Variations in systolic pressure arterial waveform (SPV) and its component have been shown to be a reasonable indicator of left ventricular preload. Creation of a pneumoperitoneum (PMOP) by insufflation of CO2 increases intrathoracic pressure, leading to overestimation of preload as assessed by pressure methods. The purpose of this study ...
Popović Z - - 2000
OBJECTIVE: To assess the effect of partial left ventriculectomy (PLV) on estimate of left ventricular end systolic elastance (Ees), arterial elastance, and ventriculoarterial coupling. PATIENTS: 11 patients with idiopathic dilated cardiomyopathy before and two weeks after PLV, and 11 controls. INTERVENTIONS: Single plane left ventricular angiography with simultaneous measurements of ...
Bengel F M - - 2000
The clearance kinetics of carbon-11 acetate, assessed by positron emission tomography (PET), can be combined with measurements of ventricular function for non-invasive estimation of myocardial oxygen consumption and efficiency. In the present study, this approach was applied to gain further insights into alterations in the failing heart by comparison with ...
Mitani H - - 2000
Effective arterial elastance (E(a)) was originally defined as the end-systolic pressure (ESP)/stroke volume (SV) ratio of the left ventricle (LV). E(a) combined with LV contractility (E(max)), E(a)/E(max), proved to be powerful in analyzing the ventriculo-arterial coupling of normal and failing hearts in regular beats. However, E(a) sensitively changes with LV ...
Karunanithi M K - - 2000
OBJECTIVES: To derive and evaluate a method of estimating the slope (Mw) of the preload recruitable stroke work (PRSW) relationship between left ventricular stroke work (SW) and end-diastolic volume (EDV) from a single beat. BACKGROUND: Mw is a load-insensitive index of contractile function, but its clinical application has been limited ...
Tyberg J V - - 2000
The Frank-Starling Law accounts for many changes in cardiac performance previously attributed to changes in contractility in that changes in contractility might have been incorrectly inferred from changing ventricular function curves (i.e. systolic performance plotted against filling pressure) if diastolic compliance also changed. To apply the Frank-Starling Law in the ...
Tielens E T - - 2000
The aim of the present study was to investigate in hypothyroid patients the reversibility of the prolongation of electromechanical delay and of the impairment of early diastolic relaxation as measured by radionuclide ventriculography after restoration of euthyroidism. We also evaluated Doppler echocardiography in relation to scintigraphic findings. Twenty-six consecutive hypothyroid ...
Strum D P - - 2000
The effect of regional wall motion abnormalities (RWMA) on regional and global left ventricular (LV) elastances has not been defined. To induce RWMA, we infused esmolol (9 mg) into the left anterior descending coronary artery in eight anesthetized open-chest canine preparations. Global and regional stroke volumes and end-systolic pressure-volume relationships ...
Ratcliffe M B - - 2000
Partial ventriculectomy (PV) has been proposed by Batista and colleagues to improve cardiac function in patients with dilated cardiomyopathy (DCM); however, results have been mixed. We tested the hypothesis that preoperative diastolic function affects the stroke volume/end-diastolic pressure (Starling) relationship after PV. A previously described finite element simulation of DCM ...
Danielsen M - - 2000
A recently developed model of the left ventricle, based on experimental data, has been shown to exhibit the main features of the heart's ability to pump. Two special cases during blood ejection, termed pressure deactivation and hyperactivation, were identified. This study proposes an 'ejection effect' correction to the model that ...
Her C - - 1999
OBJECTIVE: Whether right ventricular systolic time intervals accurately reflect right ventricular function in patients with acute respiratory failure was determined by assessing the correlation between right ventricular systolic time intervals and the right ventricular end-systolic pressure-volume relationship. DESIGN: A prospective study. SETTING: A surgical intensive care unit in a university ...
Atkins B Z - - 1999
BACKGROUND: Although cardiac transplantation is an ideal treatment for end-stage heart disease, inadequate donor availability has stimulated efforts to manage terminally injured myocardium by other innovative methods. Autologous skeletal myoblast transplantation, or cellular cardiomyoplasty, is one method to potentially mediate myocardial repair within chronically injured hearts. However, few investigators have ...
Lee D S - - 1999
BACKGROUND: Gated myocardial single photon emission computed tomography (SPECT) and radial artery applanation tonometry were used, respectively, to quantify the time-volume curve of the left ventricle and to estimate ventricular pressure wave. We developed ways of determining end-systolic elastance (Ees) with the normalized-single-beat method and tested the reproducibility of these ...
Senzaki H - - 1999
OBJECTIVES: We contrasted various methods for assessing ventricular pressure decay time constants to test whether sensitivity to slight data instability or disparities between model-assumed and real decay are systematically altered by cardiac failure. We hypothesized that such discrepancies could result in apparent increased relaxation sensitivity to load and drug stimulation. ...
Muntinga H J - - 1999
OBJECTIVE: To assess independent determinants of beat to beat variation in left ventricular performance during atrial fibrillation. DESIGN: Prospective study. SETTING: University hospital. PATIENTS: Seven patients with chronic non-valvar atrial fibrillation. INTERVENTIONS: Invasive and non-invasive haemodynamic variables were assessed using a non-imaging computerised nuclear probe, a balloon tipped flow directed ...
Yang B - - 1999
Our study compared left ventricular (LV) function between senescent and young adult mice through in situ pressure-volume loop analysis. Two groups of mice (n = 9 each), 6-mo-old and 16-mo-old (senescent) mice, were anesthetized with urethan and alpha-chloralose, and their LV were instrumented with a Millar 1.4-Fr conductance micromanometer catheter ...
Atkins B Z - - 1999
Because minimally invasive methods of preload variation are not validated for load-insensitive indexes of cardiac performance, intravenous nitroglycerin (NTG), phenylephrine, and saline solution (VOL) boluses were used in blocked and intact autonomic states to alter load and were compared with vena caval occlusion in the assessment of preload recruitable stroke ...
Lecarpentier Y - - 1999
The load dependence (LD) of relaxation was studied in the diaphragm of rabbits with congestive heart failure (CHF). CHF (n = 15) was induced by combined chronic volume and pressure overload. Aortic insufficiency was induced by forcing a catheter through the aortic sigmoid valves, followed 3 wk later by abdominal ...
Hood S - - 1999
This study assessed the use of systolic time intervals (STI) as a potential non-invasive marker of the haemodynamic effects of sumatriptan, a 5HT1 receptor agonist. Twenty-six patients undergoing diagnostic cardiac catheterization participated. STIs were derived from haemodynamic pressure tracings at baseline, following placebo injection and following either subcutaneous (n=18) or ...
Tanoue Y Y The Department of Cardiovascular Surgery, Faculty of Medicine, Kyushu University, Fukuoka, - - 1999
Nitric oxide has cardioprotective effects through several mechanisms. However, nitric oxide may have deleterious effects in the presence of superoxide because it is converted to peroxynitrite, which then initiates lipid peroxidation. Using a canine model of orthotopic heart transplantation, we examined whether adding an organic nitric oxide donor, nitroglycerin, to ...
Prabhu S D - - 1999
OBJECTIVE: This investigation sought to define the effect of heart failure (HF) on the load sensitivity of left ventricular (LV) relaxation and to correlate alterations in load sensitivity with the variables of ejection timing, systolic load profile and elastic recoil. METHODS: Nine dogs instrumented with LV micromanometers and piezoelectric crystals ...
Negroni J A - - 1999
A ventricular model based on a muscle model relating sarcomere dynamics to Ca(2+)kinetics was used to establish the relative contribution to pressure development of the two components of cross-bridge dynamics: attached cross-bridge concentration and elongation of its elastic structure. The model was tested by reproduction of experiments reflecting myofibrillar behavior ...
Summers R L - - 1999
OBJECTIVE: Differentiating systolic from diastolic congestive heart failure (CHF) is often difficult in the ED. Impedance cardiography (IC) allows for the noninvasive evaluation of systolic function and measurement of diastolic time intervals. This study was designed to assess the ability of IC to accurately measure isovolumic relaxation time (IVRT) and ...
Solomon S B - - 1999
Left ventricular relaxation is dependent on afterload conditions during systole. An abrupt increase in afterload while the ventricle is actively contracting prolongs the duration of systole. An increase in afterload during ventricular relaxation shortens the duration of systole. Therefore, we hypothesized that the point during systole when an abrupt increase ...
Kern M J - - 1999
BACKGROUND: To test whether later intra-aortic balloon pump (IABP) deflation approaching or simultaneous with left ventricular ejection would improve hemodynamics and myocardial efficiency with the use of new balloon deflation methods, 4 IABP timing techniques were evaluated in 43 patients. METHODS AND RESULTS: Later balloon deflation produced significantly greater percentage ...
Solomon S B - - 1999
Regional ischemia impairs early diastolic filling due, in part, to changes in left ventricular relaxation. This study uses open-chest pigs instrumented with high-fidelity pressure transducers to investigate the effect of regional ischemia on the active component of relaxation independent of the passive effects of filling and the effect of left ...
Furuta H - - 1999
BACKGROUND: In several experimental studies, double cardiomyoplasty using both latissimus dorsi muscles did not provide sufficient assist to the failing heart and did not clearly show improvement compared with single cardiomyoplasty. This study demonstrated the superior efficacy of our method of double cardiomyoplasty compared with single cardiomyoplasty. METHODS: In 16 ...
Ishihara S - - 1999
Cardiac contractility was studied in a clinically relevant conscious swine model simulating human hemodynamics during endotoxemia. The slope of the end-systolic pressure-volume relationship [end-systolic elastance (EES)] was used as a load-independent contractility index. Chronic instrumentation in 10 pigs included two pairs of endocardial ultrasonic crystals for measuring internal major and ...
Artrip J H - - 1999
BACKGROUND: Biventricular direct cardiac compression (DCC) can potentially support the failing heart without the complications associated with a blood/device interface. The effect of uniform DCC on left and right ventricular performance was evaluated in 7 isolated canine heart preparations. METHODS AND RESULTS: A computer-controlled afterload system either constrained the isolated ...
Korvald C - - 1999
In the "virtual work model," left ventricular total mechanical energy (TME) is linearly related to myocardial oxygen consumption (MVO2). This relationship (MVO2-TME) is supposedly independent of inotropic stimulation, vascular loading, and heart rate variations. We reexamined the effect of inotropic stimulation (dopamine) on the metabolic to mechanical energy transfer in ...
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