Search Results
Results 501 - 550 of 1606
< 6 7 8 9 10 11 12 13 14 15 16 >
Schulz S - - 1997
OBJECTIVE: The classical description of ventriculoarterial coupling by calculating the ratio between the effective arterial elastance Ea to the end-systolic elastance Ees does not give insight into the underlying dynamics of the interaction between left-ventricular pressure (LVP) and aortic pressure (AOP) and flow (AOF). The aim of this study was ...
Fahrenberg J - - 1997
Stroke volume estimates and left ventricular ejection time (1) derived from calibrated finger pulse pressure recordings (Portapres 2, TNO-BMI, Amsterdam) based on the Model Flow method and (2) derived from impedance cardiography were compared in 20 student subjects. The recordings were made for seven conditions: supine rest, standing, mental arithmetic, ...
Takaki M - - 1997
We investigated rat left ventricular (LV) mechanoenergetics in three different preparations. We obtained an upward convex curvilinear end-systolic pressure-volume relation (ESPVR) regardless of left ventricular (LV) contractility in in situ and excised cross-circulated rat hearts. We also obtained a linear myocardial O2 consumption per beat (VO2)-end-systolic pressure-volume area (PVA; a ...
Todaka K - - 1997
Myocardial mechanics and energetics were investigated in an animal model of moderate chronic heart failure (CHF) created by repeated coronary microembolizations in six dogs. The final fractional area change was 34 +/- 4%. Hearts of these animals were isolated and cross-perfused, and balloons were placed in the left ventricle (LV). ...
Ishihara H - - 1997
The aim of this study was to clarify that the depressed mechanoenergetics in patients with idiopathic dilated cardiomyopathy (DCM) resulted from compensation for the decreased contractility. The study population consisted of eight control subjects, with normal left ventricular size and ejection fraction and 31 patients with DCM. Left ventricular end-systolic ...
Swenson J D - - 1996
Ventricular preload is an important determinant of cardiac function, which is indirectly measured in the clinical setting by the pulmonary capillary wedge pressure (PCWP). Transesophageal echocardiography (TEE) is rapidly gaining acceptance as a monitor of cardiac function. Although it provides high-resolution images of cardiac structures, clinical assessment of ventricular preload ...
Hay A S - - 1996
A new method of presenting the in vivo left ventricular pressure-flow data is developed in the present study. This separates left ventricle ejection into unrestricted, progressively restricted and severely restricted cases. This method uses ejection volume and time to define a normalizing 'stroke' pressure, which is successful in collapsing the ...
Goran S F - - 1996
This article reviews the determinants of myocardial oxygen supply (MVO2) and consumption and revisits the effects of IABC on each. Measurements of MVO2, including diastolic pressure-time index (DPTI), tension-time index (TTI), and endocardial viability ratios (EVR), demonstrate the dramatic effects of balloon deflation and the resulting afterload reduction on MVO2. ...
Senzaki H - - 1996
BACKGROUND: The end-systolic pressure-volume relation (ESPVR) provides a useful measure of contractile function. However, the need to acquire multiple cardiac cycles at varying loads limits its applicability. We therefore developed and tested a novel single-beat estimation method that is based on normalized human time-varying elastance curves [EN(tN)]. METHODS AND RESULTS: ...
Redaelli A - - 1996
The dynamics of intraventricular blood flow, i.e. its rapid evolution, implies the rise of intraventricular pressure gradients (IPGs) characteristic of the inertia-driven events as experimentally observed by Pasipoularides (1987, 1990) and by Falsetti et al. (1986). The IPG time course is determined by the wall contraction which, in turn, depends ...
Meyer T E - - 1996
BACKGROUND: Nonischemic segmental performance, assessed by end-systolic measures of shortening and thickening, decreases during ischemia. These changes in performance are likely to be dependent on the size, and, possibly, the site of the ischemic zone. This study was designed to examine the effect of preload, independently from ischemic zone size, ...
ter Keurs H E - - 1996
Coronary artery disease and ischemic myocardial damage form the most common cause of failure of the heart to pump enough blood for oxygenation of the body at a healthy blood pressure and at a low pressure in the veins. This paper gives an overview of the mechanisms involved in excitation-contraction ...
Veille J C - - 1996
OBJECTIVE: Our purpose was to evaluate cardiac variables, including right and left end-diastolic and end-systolic dimensions by use of M-mode echocardiography during fetal, neonatal (transitional), and infancy periods to understand hemodynamic adaptation during these periods. STUDY DESIGN: Fifty-three fetuses were enrolled in this study. Echocardiography evaluations were started as early ...
Watkins M W - - 1996
BACKGROUND: Previous studies in cardiac muscle and isolated heart preparations generally have attributed positive effects of ejection to greater length-dependent activation. However, there have been some reports of an ejection-related increase in contractile function that is independent of end-diastolic volume (EDV) history. The present study was designed to more fully ...
Horner S M - - 1996
BACKGROUND: Mechanoelectric feedback, the process by which changes in mechanical activity change the electrophysiology of the myocardium, has been linked to the genesis of arrhythmias. We investigated possible arrhythmogenic mechanisms by measuring changes in steady-state action potential duration and, more particularly, electrical restitution on a transiently applied load change, because ...
Miyahara K - - 1996
The effect of inferior vena cava occlusion (IVCO) on end-systolic pressure-volume relations (ESPVR) of the left ventricle was studied in intact canine hearts. In 12 anesthetized open-chest dogs, left ventricular (LV) pressure and volume were measured simultaneously using a microtip catheter and a conductance catheter, respectively. ESPVR was constructed from ...
Holubarsch C - - 1996
BACKGROUND: The Frank-Starling mechanism is one of the most important physiological principles for regulation of contractile performance. We therefore studied the question of whether this mechanism may be absent or attenuated in end-stage failing human left ventricular myocardium. METHODS AND RESULTS: Different methodological approaches were used to analyze the effects ...
Hettrick D A - - 1996
BACKGROUND: The effects of desflurane, sevoflurane, and isoflurane on left ventricular-arterial coupling and mechanical efficiency were examined and compared in acutely instrumented dogs. METHODS: Twenty-four open-chest, barbiturate-anesthetized dogs were instrumented for measurement of aortic and left ventricular (LV) pressure (micromanometer-tipped catheter), dP/dtmax, and LV volume (conductance catheter). Myocardial contractility was ...
Horner S M - - 1996
AIMS: Increased sympathetic stimulation is known to be arrhythmogenic. Likewise increased loading of the myocardium can directly generate arrhythmias. The interaction between the two on the electrophysiology of the myocardium has not been investigated before. We investigated the effect of dobutamine infusion on the shortening of the monophasic action potential ...
Wieshammer S - - 1996
A series of 14 patients with heart failure due to coronary artery disease and impaired left ventricular function underwent radionuclide ventriculography with simultaneous thermodilution measurement of cardiac output by pulmonary artery catheter on two occasions (m1, m2) separated by 6 weeks in order to determine the reproducibility of haemodynamic and ...
Slinker B K - - 1996
Clinical and experimental observations in humans and animals have shown that different cardiac adaptations occur in response to different types of hemodynamic overload. However, very little is known about how different hemodynamic loads lead to these different cardiac adaptations. Accordingly, we studied the acute response of ejecting isolated rabbit hearts ...
MacGowan G A - - 1996
OBJECTIVE: To determine if left ventricular torsion, as measured by magnetic resonance tissue tagging, is afterload dependent in a canine isolated heart model in which neurohumoral responses are absent, and preload is constant. METHODS: In ten isolated, blood perfused, ejecting, canine hearts, three afterloads were studied, while keeping preload constant: ...
Gazmuri R J - - 1996
OBJECTIVE: To investigate the functional and metabolic changes in the myocardium after successful resuscitation from cardiac arrest. DESIGN: Prospective, randomized, sham-controlled study. SETTING: Animal laboratory at a university center. SUBJECTS: Domestic pigs. INTERVENTIONS: Electric induction of ventricular fibrillation by alternating current delivered to the right ventricular endocardium through a pacing ...
Herbertson M J - - 1996
OBJECTIVE: We investigated whether ibuprofen could prevent early decrease in left ventricular contractility that occurs during porcine endotoxemia. DESIGN: Prospective, randomized, controlled animal study. SETTING: University research laboratory. SUBJECTS: Adolescent crossbred pigs (n = 28). INTERVENTIONS: Anesthetized pigs were instrumented to measure hemodynamics and left ventricular pressures (using a Millar ...
Berger D S - - 1996
The objective of this study was to examine the effects of wave propagation properties (global reflection coefficient gamma IG; pulse wave velocity, c(ph); and characteristic impedance zeta(o) on the mechanical performance of the coupled left ventricle-arterial system. Specifically, we sought to quantify effects on aortic pressure (P(ao)) and flow Q(ao) ...
Silvestry S C - - 1996
Evaluating cardiac gene therapy in the intact animal requires an index of cardiac function capable of detecting regional differences in contractility in a load-independent fashion. Potentially load-insensitive measures of ventricular performance were therefore evaluated in 10 open- and closed-chested, anesthetized rabbits. LV transmural pressure and myocardial segment length were measured ...
Chew P H - - 1996
Animal data indicate that chronic, overnight pacing at normal evening heart rates impairs cardiac function. We examined the relationship of pacing rate and cardiac function in nine patients with dual-chamber pacemakers. We investigated two, 3-week pacing regimens (80 and 50 ppm: DDD mode) in a cross-over design. Doppler echocardiograms were ...
Zipprich D A - - 1996
The Frank-Starling relationship between left ventricular stroke work and end-diastolic minor-axis cross-sectional area was evaluated as a load-insensitive measure of inotropic state by two-dimensional echocardiography in 10 conscious dogs. Stroke work was calculated as the product of systolic change in cross-sectional area and either (1) beat-to-beat mean arterial pressure or ...
Lorusso R - - 1996
BACKGROUND: Correct timing of mechanical interaction between wrapped latissimus dorsi muscle (LDM) and the heart during cardiac systole has been poorly understood and remains a controversial issue. Therefore, left ventricular pressure-volume relations were analyzed in acute cardiomyoplasty while changing the synchronization delays. METHODS: Effects of different delays between the sensed ...
Weber A - - 1996
OBJECTIVE: To examine the mechanism of cardiac assist with systolic jet ventilation, specifically effects on loading conditions and left ventricular pressure-volume function. Both systolic and diastolic jet ventilation were compared in the absence and presence of heart failure. DESIGN: Prospective, two-factor, repeated-measures study. SETTING: Animal laboratory. SUBJECTS: Ten anesthetized, closed-chest ...
Seki H - - 1996
We assessed the effect of dobutamine on left ventricoarterial coupling during acute regional ischemia. Using a conductance catheter, we analyzed the end-systolic pressure-volume relation (ESPVR) in anesthetized dogs. We calculated the slope of ESPVR (Ees), the slope of the end-systolic pressure-stroke volume relation (Ea), (Ea/Ees) and the ratio (work efficiency) ...
Encke T - - 1996
According to Koepchen, stimulation of different receptors within a complex network produces typical patterns of effector responses. We investigated whether the dynamical volume elasticity of the heart chamber is an independent component of cardiovascular control. The measurement of the dynamical volume elasticity was calculated by changes of the eigenfrequency of ...
Asanoi H - - 1996
OBJECTIVES: The effects of increasing heart rate on left ventricular contraction and relaxation were examined in conscious dogs with tachycardia-induced heart failure under autonomically blocked conditions. BACKGROUND: Previous studies using isolated myocardium have shown attenuated positive inotropic responses to stimulation frequency in heart failure. However, these responses have not been ...
Gorcsan J J - - 1996
Pressure-volume relations are important means used to assess left ventricular (LV) contractility; however, on-line volume acquisition has been limited to the invasive conductance catheter. The objective was to compare simultaneous measures of LV volume by transesophageal echocardiographic automated border detection (ABD) and conductance catheter and their respective pressure-volume relations during ...
Cheung A T - - 1996
BACKGROUND: Measuring the effects of intraaortic balloon counterpulsation (IABP) in single cardiac beats may permit an improved understanding of the physiologic mechanisms by which IABP improves the circulation. The objective of the study was to use trans- esophageal echocardiography in combination with hemodynamic measurements to test the hypothesis that IABP ...
Ferrari G - - 1996
In this study an original left ventricular assist device is tested on an open loop modular physical circuit reproducing Starling's law of the heart to set an optimal control strategy for heart recovery. It is assumed that the goals of the assistance are reduction of oxygen consumption, external work and ...
Bowers P N - - 1996
OBJECTIVE: Embryonic cardiovascular function is dynamically regulated at the tissue level. Nitric oxide (NO) regulates vascular tone and influences cardiovascular function in neonatal and mature circulations. However, the role of NO in regulating embryonic cardiovascular function is undefined. We hypothesized that NO released from nitroprusside alters embryonic vascular tone with ...
Feldman M D - - 1996
BACKGROUND: OPC-18790 is a water-soluble quinolinone derivative that shares the pharmacological properties of vesnarinone and that may be useful for treating heart failure. We studied the contribution and relative dose sensitivities of the inotropic, lusitropic, and vascular effects of OPC-18790 in patients with dilated cardiomyopathy. METHODS AND RESULTS: Pressure-volume (PV) ...
Tian R - - 1996
Progressive dilatation of left ventricle has been demonstrated in hearts post-infarction. However, the relationship of performance and energy consumption in chronically infarcted heart has not been clarified. To address this problem, we measured left ventricular pressure and oxygen consumption (MVO2) during stepwise increases in left ventricular filling volume in isolated ...
Denslow S - - 1996
The pressure-volume area (PVA) has been shown to be an excellent, linear index of myocardial oxygen consumption. The thermodynamic basis for this result, however, has not been elucidated. The present study was undertaken to determine what information could be gained from analyzing the cardiac pressure-volume (P-V) cycle as an approximation ...
Zotz R J - - 1996
The aim of this study was to assess the ability of intravenous injection of Albunex to improve left ventricular volume determination in patients with various cardiac diseases. It is conceivable that the intravenous injection of microbubbles could improve echocardiographic left ventricular border delineation leading to improved interobserver variability. Echocardiograms were ...
Landesberg A - - 1996
The left ventricular (LV) pressure-volume relationship and the effect of ejection on pressure generation are predicted theoretically based on the intracellular control mechanisms. The control of contraction is described based on coupling calcium kinetics and cross-bridge cycling. The analysis of published skinned and intact cardiac muscle data suggests two feedback ...
Schipke J D - - 1996
OBJECTIVE: To amplify the description of myocardial stunning. DESIGN: Control versus 30 min after a 20 min no flow ischaemia. EXPERIMENTAL ANIMALS: 15 isolated rabbit hearts perfused with erythrocyte suspension. MAIN OUTCOME MEASURES: Left ventricular systolic function in terms of aortic flow, peak systolic pressure (LVPmax), dP/dtmax, and the end ...
Zabel M - - 1996
INTRODUCTION: It is well known that myocardial stretch can elicit ventricular arrhythmias in experimental models. However, previous reports have predominantly documented stretch-induced arrhythmias during short, pulsatile stretch. The arrhythmogenic mechanism of sustained static stretch is incompletely understood. METHODS AND RESULTS: To examine the influence of sustained load on several electrophysiologic ...
Asanoi H - - 1996
BACKGROUND: An energy-starved failing heart would benefit from more effective transfer of the mechanical energy of ventricular contraction to blood propulsion. However, the energetically optimal loading conditions for the failing heart are difficult to establish. In the present study, we analyzed the optimal left ventricular pressure to achieve maximal mechanical ...
Razzolini R - - 1996
Percutaneous balloon mitral valvuloplasty (PBMV) has been shown to induce an immediate increase in the left ventricular end-diastolic volume, which increase, in turn, has been attributed to an increase in left ventricular compliance. We studied 51 patients, 41 women and 10 men, who underwent PBMV, and were in sinus rhythm ...
Ishizaka S - - 1995
BACKGROUND: Left ventricular relaxation rate in the failing heart depends more on the systolic load than in the normal heart. To elucidate the mechanisms for the enhanced load sensitivity of left ventricular relaxation in heart failure, we examined the relative contributions of changes in end-systolic volume and loading sequence to ...
Reitan J A - - 1995
OBJECTIVE: To develop a method of measuring end-systolic elastance from information obtained outside the ventricle and thereby simplify its transduction. DESIGN: Prospective, within-animal comparative analysis. SETTING: University-based laboratory study. PARTICIPANTS: Six mixed-breed dogs. INTERVENTIONS: Instrumentation included minor axis sonomicrometry, ascending aortic flow probe, aortic and ventricular pressure transducers, and constricting ...
Chen F Y - - 1995
BACKGROUND: We introduce the use of a fluid-filled balloon, interposed between myocardium and latissimus dorsi (LD), as a new technique to measure transmural myocardial pressure in an acute goat model of dynamic cardiomyoplasty. METHODS: A half-ellipsoidal balloon, composed of polychloryl vinyl layers, was sutured to the atrioventricular groove in 5 ...
Volpe M - - 1995
BACKGROUND: Cardiac adaptations to volume overload have been poorly investigated in heart failure. The aim of this study was to assess dynamic left ventricular responses to acute volume loading by continuous radionuclide monitoring in patients with asymptomatic to mildly symptomatic left ventricular dysfunction. METHODS AND RESULTS: Left ventricular end-diastolic (EDV) ...
< 6 7 8 9 10 11 12 13 14 15 16 >