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Results 301 - 350 of 1599
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Chen C H - - 2001
OBJECTIVES: The goal of this study was to develop and validate a method to estimate left ventricular end-systolic elastance (E(es)) in humans from noninvasive single-beat parameters. BACKGROUND: Left ventricular end-systolic elastance is a major determinant of cardiac systolic function and ventricular-arterial interaction. However, its use in heart failure assessment and ...
Norton J M - - 2001
Significant differences exist among textbook definitions for the terms preload and afterload, leading to confusion and frustration among students and faculty alike. Many faculty also chose to use in their teaching simple terms such as "end-diastolic volume" or "aortic pressure" as common-usage approximations of preload and afterload, respectively, but these ...
Noguchi T - - 2001
The effect of protein kinase C (PKC) activation on cardiac mechanoenergetics is not fully understood. To address this issue, we determined the effects of the PKC activator phorbol 12-myristate 13-acetate (PMA) on isolated rat hearts. Hearts were exposed to PMA with or without pretreatment with the PKC inhibitor chelerythrine. Contractile ...
Hassapoyannes C A - - 2001
Short- and intermediate-term use of cardiac glycosides promotes inotropy and improves the ejection fraction in systolic heart failure. To determine whether chronic digitalization alters left ventricular function and performance. Eighty patients with mild-to-moderate systolic heart failure (baseline ejection fraction < or =45%) participated from our institution in a multi-center, chronic, ...
Buhre W - - 2001
BACKGROUND AND OBJECTIVE: Assessment of cardiac preload is of major importance in the management of critically ill patients. Echocardiographic determined left ventricular end-diastolic area and indicator dilution derived intrathoracic blood volume are used as surrogates for cardiac preload. However, no controlled comparison studies on the relationship between induced changes in ...
Adsumelli R S - - 2001
OBJECTIVE: To evaluate hemodynamic effects of sternal retractor removal and sternal closure after cardiopulmonary bypass and to correlate these changes with preoperative and intraoperative variables. DESIGN: Prospective. SETTING: University hospital. PARTICIPANTS: Fifty adults undergoing cardiac surgery. MEASUREMENTS AND MAIN RESULTS: Arterial, pulmonary artery, and transesophageal echocardiography measurements were obtained immediately ...
Tanoue Y - - 2001
OBJECTIVES: Phosphodiesterase III inhibitors, which have both positive inotropic and vasodilatory effects, occasionally cause hypotension due to afterload reduction and possibly due to preload reduction caused by the increase in vascular capacitance. METHODS: Six open-chest adult mongrel dogs were used to compare the effects on left ventricular contractility, afterload, and ...
Artrip J H - - 2001
BACKGROUND: Ventricular volume reduction surgery for idiopathic cardiomyopathy fails to improve cardiac output and is associated with a high incidence of recurrent heart failure. Volume reduction surgery achieved by removing akinetic or dyskinetic myocardium after myocardial infarction appears to be associated with better outcomes. The reasons for the differences in ...
Iarussi D - - 2001
BACKGROUND: In childhood, late cardiotoxicity is characterized by inappropriately thin wall and consequent increased end-systolic wall stress, but the associations of impaired left ventricular geometry and function occurring under these circumstances need further investigation. HYPOTHESIS: The purpose of this study was to assess anthracycline late effects on the relationships occurring ...
Danielsen M - - 2001
The pumping heart is described by a new mathematical approach which considers the heart as a pressure source depending on time, volume and flow. This new approach allows a separation between isovolumic (non-ejecting) and ejecting heart properties. The computed results cover most of the features of the human ventricle during ...
Bella J N - - 2001
The relation of impaired left ventricular relaxation, as measured by prolonged isovolumic relaxation time, to ventricular systolic function in hypertension remains uncertain in population-based samples. In the Hypertension Genetic Epidemiology Network (HyperGEN) Study, echocardiograms were analyzed in 1457 hypertensive participants without diabetes, >/=2+ valvular regurgitation, or coronary disease. Impaired relaxation ...
Senzaki H - - 2001
OBJECTIVES: It is particularly useful to separately quantify the ventricular contractility and loading conditions for a better understanding of the cardiovascular dynamics in congenital heart disease, where abnormalities in chamber and loading properties may coexist. Furthermore, ventricular contractility and loading conditions may alter independently or simultaneously with disease progression and ...
Du F - - 2001
1. In the present study, we investigated the effects of blood volume on postischaemic function and efficiency. In 14 anaesthetized dogs, following recovery from a period of 15 min occlusion of the left anterior descending coronary artery, the effects of hypervolaemia (HYPER; 15% increased volume produced by fast infusion of ...
Lewis M E - - 2001
1. Studies of the effect of vagus nerve stimulation on ventricular myocardial function in mammals are limited, particularly in the human. 2. The present study was designed to determine the effect of direct electrical stimulation of the left vagus nerve on left ventricular contractile state in hearts paced at 10 ...
Szabó G - - 2001
OBJECTIVE: To test the hypothesis that altered loading conditions play a key role in hemodynamic instability and cardiac dysfunction in the brain dead (BD) organ donor. METHODS: BD was induced by inflation of a subdural balloon catheter. In the first part of the study, left ventricular function was assessed in ...
Emilsson K - - 2001
The outer contour of the heart has in some studies been shown to be constant during the heart cycle and the epicardial apex almost stationary whilst the base of the ventricles moves towards apex during systole. The base of the left ventricle has been regarded as a cylinder with constant ...
Tada, Seiichi
We evaluated the ventricular mechanical effects of PhosphodiesteraseIII (PDEIII) inhibitors in the failed heart after global ischemia induced by ventricular fibrillation (VF) using the left ventricular pressure-volume relationship (PVR). In 14 anesthetized open-chest dogs, left ventricular PVR was measured using a conductance catheter. Under administration of milrinone (MIL, n=7) and ...
Rousseau M F - - 2001
This study assesses the effects of dofetilide, a new selective Ikr blocker with class III properties, on left ventricular function and hemodynamics of heart failure and compares these effects with those of placebo and amiodarone. Because available antiarrhythmic drugs may depress myocardial performance, an invasive hemodynamic study was performed to ...
Haykowsky M - - 2001
OBJECTIVE: To assess the effects of prolonged strenuous exercise in the form of a half-ironman (HI) race (2 km swim, 90 km bike ride and a 21 km run) on left ventricular systolic function. METHODS AND RESULTS: The study participants consisted of nine male triathletes (mean age +/- SD 32+/-5 ...
Hon J K - - 2001
The first stage of the two-stage arterial switch operation (ASO) for transposition of the great arteries (TGA) is associated with depressed ventricular function and an unstable immediate post-operative course. It is unclear if this is because of the acute increase in afterload of the thin-walled, low-pressure ventricle by pulmonary artery ...
Syuu Y - - 2001
Neiguan (PC-6) is a traditional acupoint in the bilateral forearms, overlying the median nerve trunk. Neiguan electroacupuncture (EA) has been believed to affect cardiovascular function and used in traditional Chinese medicine to improve or treat a wide range of health conditions and diseases, including angina pectoris, myocardial infarction, hypertension, and ...
Sakata S - - 2001
We have reported the linear relation of myocardial oxygen consumption per beat (VO(2)) and systolic pressure-volume area (PVA) in the left ventricle of the cross-circulated rat heart. The VO(2) intercept (PVA-independent VO(2)) is primarily composed of VO(2) for Ca(2+) handling in excitation-contraction coupling and basal metabolism. Recently, we proposed a ...
Lu L - - 2001
Mechanical properties of the myocardium at end diastole have been thought to be dominated by passive material properties rather than by active sarcomere cross-bridge interactions. This study tested the hypothesis that residual cross-bridges significantly contribute to end-diastolic mechanics in vivo and that changes in end-diastolic cross-bridge interaction parallel concurrent changes ...
Inoue T - - 2001
BACKGROUND: Auxiliary cardiac support using heterotopic heart transplant is of considerable interest, but the outcome is not known. To investigate technical feasibility and the possibility of using auxiliary support from heterotopic heart transplantation without cardiopulmonary bypass, we evaluated hemodynamics including the pressure-volume relationship in experimental animals. METHODS: In heterotopic heart ...
Shen I - - 2001
BACKGROUND: Perfusion of the coronary circulation with hypoxemic blood from the left ventricle has been postulated to cause myocardial dysfunction during venoarterial extracorporeal membrane oxygenation for respiratory support. METHODS: We investigated this hypothesis in 10 anesthetized open-chest piglets (7 to 9 kg) undergoing venoarterial extracorporeal membrane oxygenation after placement of ...
Baloa L A - - 2001
A new control strategy for a mock circulatory system (MCS) has been developed to mimic the Starling response of the natural heart. The control scheme is based on Suga's elastance model, which is implemented using nested elastance and pressure feedback control systems. The elastance control loop calculates the desired chamber ...
Gandhi S K - - 2001
BACKGROUND: Patients with acute pulmonary edema often have marked hypertension but, after reduction of the blood pressure, have a normal left ventricular ejection fraction (> or =0.50). However, the pulmonary edema may not have resulted from isolated diastolic dysfunction but, instead, may be due to transient systolic dysfunction, acute mitral ...
Michard F - - 2001
OBJECTIVE: To evaluate the effects of high-dose almitrine infusion on gas exchange and right ventricular function in patients with severe hypoxemia related to acute respiratory distress syndrome (ARDS). DESIGN: Prospective study. SETTING: Medicosurgical intensive care department (ten beds). PATIENTS: Nine patients with ARDS and severe hypoxemia (PaO2/FIO2 ratio, <150 torr ...
Karunanithi M K - - 2001
OBJECTIVE: To determine the effect of acute increments in left ventricular afterload on the stroke work output of the right ventricle in vivo. METHODS: After pharmacologic attenuation of autonomic reflexes, left and right ventricular pressure-volume data were obtained in 9 conscious dogs during vena caval occlusions performed before and during ...
Leite-Moreira A F - - 2001
Afterload-induced changes in myocardial relaxation are a mechanism for diastolic dysfunction when afterload is elevated beyond certain limits. The present study investigated the effects of acute afterload and preload changes on the position of the end-diastolic (ED) pressure-volume (P-V) relation. Beat-to-beat afterload elevations were induced in seven open-chest rabbits by ...
Abel F L - - 2001
Starling's law is a description relating the energy released by the contracting ventricle to the end diastolic fiber length. The peak systolic pressure during isovolumic contraction is an example of this relationship; Sunagawa and coworkers (12) termed that pressure Pmax. It may also be estimated during ejecting beats. Here we ...
Schroeder M J - - 2001
The role of physiological elastance (Ep) in maximizing external work (EW) transfer is not well understood and has not been investigated during microgravity and increased acceleration conditions. By better understanding this relationship, cardiovascular control mechanisms for meeting metabolic demands during normal gravity and altered acceleration stresses may be elucidated. Therefore, ...
Sugimachi M - - 2001
Although partial left ventriculectomy (PLV) was devised to reduce myocardial wall stress in patients with severe heart failure, whether the operation acutely improves cardiac pump function has not been determined either clinically or experimentally. Because precise control of preload, afterload, and heart rate is virtually impossible in animal experiments as ...
Firstenberg M S - - 2001
Myocardial tissue Doppler echocardiography (TDE) has been proposed as a tool for the assessment of diastolic function. Controversy exists regarding whether TDE measurements are influenced by preload. In this study, left ventricular volume and high-fidelity pressures were obtained in eight closed-chest dogs during intermittent caval occlusion. The time constant of ...
Andersson B - - 2000
OBJECTIVE: Contraction of longitudinal and subendocardial myocardial muscle fibres is reflected in descent of the atrioventricular (AV) plane. The aim was therefore to determine whether beta blocker treatment with prolongation of diastole might result in improved function as reflected by AV plane movements in patients with chronic heart failure. DESIGN: ...
Lee D S - - 2000
PURPOSE: We investigated the reproducibility of the quantification of left ventricular volumes and ejection fraction, and grading of myocardial wall motion and systolic thickening with gated myocardial single-photon emission computed tomography (SPECT) and Cedars quantification software. PATIENTS, MATERIALS AND METHODS: We performed post-stress gated myocardial SPECT in 33 consecutive patients ...
Nogaki M - - 2000
BACKGROUND: Both pulmonary and systemic circulation must be maintained by a single pump in Fontan circulation. This unique property of Fontan circulation may be related to decreased exercise tolerance or increased instantaneous postoperative mortality rate, often observed in patients with this circulation. To better understand Fontan physiology, the present study ...
Bruch C - - 2000
BACKGROUND: Congestive heart failure is related to contraction and relaxation abnormalities of the ventricle. Isolated analysis of either mechanism may not be reflective of overall cardiac dysfunction. A combined myocardial performance index (isovolumic contraction time plus isovolumic relaxation time divided by ejection time, 'Tei-Index') has been described which may be ...
Jo Y H - - 2000
Right and left filling pressures are important parameters in the automatic control of a total artificial heart (TAH) within normal physiologic ranges. Our TAH is composed of a moving actuator, right and left ventricles, and an interventricular space (IVS) enclosed by a semirigid housing. During operation of the TAH, the ...
Arthur W - - 2000
By introducing an alternating current through the ventricular cavity via a multipolar catheter the potential difference measured between adjacent electrodes can be used to assess ventricular volume. This is possible by the measurement of intracardiac impedance. The data obtained can be used to construct pressure-volume loops allowing the continuous real-time ...
Gopakumaran B - - 2000
Leakage of electric current through cardiac structures surrounding the ventricle is a primary source of error during ventricular volume measurements using a conductance catheter. This error can be represented as a leakage volume, VL. VL is generally estimated by a saline-bolus method, and is assumed constant throughout the cardiac cycle. ...
Shishido T - - 2000
BACKGROUND: Although left ventricular end-systolic elastance (E(es)) has often been used as an index of contractility, technical difficulties in measuring volume and in changing loading conditions have made its clinical application somewhat limited. By approximating the time-varying elastance curve by 2 linear functions (isovolumic contraction phase and ejection phase) and ...
Royse C F - - 2000
Afterload corrected fractional area change (FACac) is a simple measurement of contractility which can be acquired during surgery without the need to acutely alter volume. We have validated it against the load-independent measurement, stroke force / end-diastolic area relationship (SF/EDA) in patients undergoing cardiac surgery. SF/EDA regressions were analysed before ...
Leite-Moreira A F - - 2000
Left ventricular pressure (LVP) fall is the hemodynamic manifestation of myocardial relaxation. This paper reviews the most important aspects of LVP fall and its regulation by load, inactivation and nonuniformity. This regulation is explained in terms of calcium transients and cross-bridge mechanics. Specific effects of systolic pressure on LVP fall ...
Janssen P M - - 2000
Ca(2+)-sensitizers increase myocardial contractility, but may worsen diastolic dysfunction. Levosimendan, through its unique troponin-C interaction, may preserve diastolic function. We investigated the effects of levosimendan (10(-7)-10(-5) M) on diastolic and systolic function in multicellular cardiac muscle preparations from end-stage failing human hearts (1 and 2.5 Hz, 37 degrees C, 1.25 ...
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 ...
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