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Results 701 - 750 of 1599
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Sakuma M - - 1993
The aim of the present study was to examine effects of changes in afterload on regional myocardial motion in acute ischemia. Ischemic and non-ischemic segment lengths of the left ventricular free wall were measured by miniature ultrasonic gauges in eleven open chest dogs with the pericardium preserved. In a stable ...
Ishikawa K - - 1993
The effect of changes in preload on regional myocardial motion in acute ischaemia was examined by miniature ultrasonic gauges after left anterior descending coronary artery occlusion in eight open chest dogs with the pericardium preserved. Left ventricular end-diastolic pressure was varied by blood withdrawal and infusion. When preload changed, isovolumetric ...
Namba T - - 1993
We observed a few rare spontaneous cases of a suddenly widened QRS wave of left ventricular ECG associated with a simultaneous decrease in left ventricular (LV) contractility (Emax, end-systolic pressure-volume ratio) in excised cross-circulated dog heart experiments. The decreased Emax was not associated with a descent of the relation between ...
Watkins M W - - 1993
Because of the characteristics of the parietal pericardial tissue, the intact pericardial sac has a limited reserve volume, becoming relatively non-compliant when the heart volume is at the high end of the normal physiologic range. Pericardial restraint of the heart is best considered as a contact force. Measured with flattened ...
Takaoka H - - 1993
BACKGROUND: Recently, several indexes such as tension-time index (TTI), tension-time or force-time integral (FTI), rate-pressure product (RPP), pressure-work index (PWI), and systolic pressure-volume area (PVA) have been developed as predictors of myocardial oxygen consumption in experimental and clinical studies. However, it is still unclear whether these indexes are reliable predictors ...
Tanaka N - - 1993
We tested whether minimal myocardial oxygen consumption (MVO2) for a given external work would exist in the middle of a normal contractility range as previously predicted theoretically. The left ventricle of the excised cross-circulated dog heart preparation was connected to a volume servo pump. Myocardial contractility in terms of ventricular ...
Oda T - - 1993
Load-induced contractility depression, in which supernormal left ventricular ejection fraction and contractility at rest decrease by added afterload, is most often found in children with mitral valve prolapse who have symptoms. Patients have high ventricular end-diastolic pressure at rest, which is further increased by afterload challenge. The Frank-Starling mechanism may ...
Kass D A - - 1993
The influence of the two principal components of vascular loading, mean resistance and pulsatile load, on the contractile and energetic performance of the left ventricle are discussed. The data suggest that while large changes in mean resistance leading to varying ejection fraction can influence both cardiac systolic mechanics and energetic ...
Regen D M - - 1993
By fitting isovolumic phases of an ejecting beat with a model-wave function, one can predict source pressure of the ejecting beat (Sunagawa et al. Trans Biomed Eng 1980; 27:299-305), this being a major determinant of systolic performance. Prior applications of this principle have involved two assumptions: (1) that the isovolumic ...
Martin R W - - 1993
A technique is presented for three-dimensional (3-D) reconstruction of the left-ventricular endocardial surface from multiplanar transesophageal echocardiograms, using both commercial software and investigator written Fortran programs for Intel 80286 and 80386 microcomputers. The approach provides quantitative global and regional cardiac performance measures and allows viewing the endocardial surface, at end-diastole ...
Jacob R - - 1993
The relation between left-ventricular stroke volume (SV) and end-diastolic volume (EDV) was determined based on angiocardiographic measurements in 10 open-chest minipigs under varying filling conditions (blood letting or infusions). The results were compared with a theoretical relation calculated under the assumption of varying EDV but constancy of myocardial properties. In ...
Shannon R P - - 1993
The complexities of diastolic dysfunction are being recognized with increasing frequency. Prior studies of diastolic dysfunction in both clinical disease states and experimental models have overlooked the major role which altered loading conditions may play in the evolution of diastolic dysfunction. In order to determine the relative importance of the ...
Gal R A - - 1992
Most count-based radionuclide methods for calculating left ventricular volume rely on measurement of radioactivity in a peripheral blood sample and a measurement of ventricle to collimator distance. We have developed a method which requires neither a blood sample nor a distance measurement and which is applicable to first-pass radionuclide angiography. ...
Cooper D J - - 1992
To determine whether histamine alters human left ventricular contractility we measured heart rate, calibrated carotid arterial pressure, and left ventricular dimensions (echocardiogram) in nine healthy volunteers. We assessed baseline contractility using the end-systolic pressure-dimension relationship and the end-systolic meridional wall stress-rate-corrected velocity of circumferential fiber shortening relationship determined over a ...
Fortney S - - 1992
To determine whether aerobic conditioning alters the orthostatic responses of older subjects, cardiovascular performance was monitored during graded lower body negative pressure in nine highly trained male senior athletes (A) aged 59-73 yr [maximum O2 uptake (VO2 max) = 52.4 +/- 1.7 ml.kg-1 x min-1] and nine age-matched control subjects ...
Takaoka H - - 1992
Several studies have recently reported that the relationship between myocardial oxygen consumption per beat (Vo2) and left ventricular (LV) systolic pressure-volume area (PVA), which represents total mechanical energy generated by contraction, is linear and independent of loading conditions in excised, supported, and intact hearts. We assessed the Vo2-PVA relationship in ...
Amoore J N - - 1992
The maintenance of adequate blood circulation requires a sufficient ventricular contractility; in addition, to eject blood, the ventricles must first receive a sufficient volume, requiring a low diastolic stiffness. A simplified cardiovascular model was used to derive formulae for stroke volume (SV) as a function of atrial pressure and the ...
Coulshed D S - - 1992
1. Although it is known that mechanical events in the heart influence the duration of the cardiac action potential, there is no quantitative information on the effects of independent changes in ventricular end-diastolic and systolic pressures. 2. Experiments were carried out on open-chest anaesthetized dogs in which the autonomic nervous ...
Horton J W - - 1992
The effects of hemorrhagic shock on left ventricular dimensions and volume were studied in 15 splenectomized dogs. A 42 +/- 1% decrease in total blood volume caused arterial blood pressure to fall 60% (from 120 +/- 5 to 48 +/- 3 mmHg); the first derivative of left ventricular pressure at ...
Sasayama S - - 1992
The contractile function of the left ventricle has been defined within the framework of the pressure-volume relationship. We employed a conductance catheter, together with a high-fidelity micromanometer, to obtain accurate pressure and volume data continuously on a beat-to-beat basis in conscious dogs. Reproducibility of conductance volumetry was proven by repeated ...
Teitel D F - - 1992
Evaluation of ventricular performance by the end-systolic pressure-volume relationship (ESPVR) has been extensively performed in the adult heart using the conductance technique. We undertook this study to validate the conductance technique and to generate ESPVRs in the small heart. To validate the technique, we simultaneously measured left ventricular volume by ...
Baan J - - 1992
A number of fundamental mechanical properties of cardiac muscle as well as of the total ventricle are discussed. These include: Starling's law, shortening deactivation, homeometric autoregulation, and so-called hyperactivation associated with a small amount of ejection. Whenever appropriate, muscle properties are related to those of the intact ventricle. The phenomenon ...
Takeuchi M - - 1992
We compared linearity, inotropic sensitivity (using dobutamine) and afterload dependency (using captopril) of contractile indices derived from the end-systolic pressure-volume relationship (ESPVR) and preload recruitable stroke work (PRSW) in man. We investigated 60 patients, 39 with normal (EF > or = 50%, group 1) and 21 with decreased ventricular function ...
Baur L H - - 1992
As a rule, left ventricular relaxation is impaired in patients with coronary artery disease and congestive heart failure. In addition, the passive elastic properties in early and late diastole change when the ventricle dilates. Diastolic properties of the left ventricle were studied in 11 patients with congestive heart failure class ...
Ko W - - 1992
BACKGROUND: The University of Wisconsin solution (UW) has been shown to be superior to the use of traditional types of simple crystalloids in extended heart preservation. This study was designed to determine the necessity of four potentially redundant components in UW. MATERIALS AND METHODS: Forty canine hearts (n = 8 ...
Jacob R - - 1992
The functional significance of the Frank-Starling mechanism under physiological and pathophysiological conditions is discussed, based mainly on animal experiment results (in the dog, pig and rat). The dependence of individual stroke volume on end-diastolic volume can be described adequately using Frank's diagram. This can be illustrated by varying filling pressure ...
Kanstrup I L - - 1992
In 11 healthy subjects (8 males and 3 females, age 21-59 yr) left ventricular end-diastolic (LVEDV) and end-systolic (LVESV) volumes were measured in the supine position by isotope cardiography at rest and during two submaximal one-legged exercise loads before and 1 h after acute plasma expansion (PE) by use of ...
Borow K M - - 1992
OBJECTIVES: The study was designed to critically evaluate the clinical utility of ejection phase and nonejection phase indexes of contractile state in patients with severe left ventricular dysfunction. BACKGROUND: Ejection phase indexes of left ventricular systolic performance are unable to differentiate contractility changes from alterations in loading conditions. Isovolumetric and ...
Hata K - - 1992
BACKGROUND: We hypothesized that the effect of pimobendan (UD-CG 115 BS) to increase calcium sensitivity of contractile protein might result in less myocardial oxygen consumption (VO2) in comparison with dobutamine when they enhance ventricular contractility to the same extent. To examine this hypothesis, we compared the effects of pimobendan and ...
Kikura M - - 1992
The presence of an inotropic action of prostaglandin E1 (PGE1) in vivo is controversial, and there are conflicting results obtained by various indices of myocardial contractility. In this study, a direct effect of PGE1 on contractility was investigated in dogs by use of a load-independent contractile index: left ventricular end-systolic ...
Aoyagi T - - 1992
The shortening- and shortening rate-preload-afterload relations, based on the concept of the myocardial end-systolic stress-strain relation (ESSSR), are a newly developed load- and size-independent assessment of myocardial contractility. The purpose of this study was to apply this assessment to compare extent and velocity of myocardial contraction during graded infusions of ...
Burstein S - - 1992
OBJECTIVES: This study was designed to assess the direct effects of flosequinan on myocardial function. BACKGROUND: Flosequinan has been shown to improve symptoms and exercise tolerance in patients with heart failure. Although previous studies have established that flosequinan is a vasodilator, it is not known to what extent direct actions ...
Nozawa T - - 1992
We studied the effect of increased afterload on the ratios of O2 consumption (VO2) to external work (EW), VO2 to the systolic pressure-volume area (PVA), and PVA to EW at control state and with dobutamine in the left ventricles of open-chest dogs. Left ventricular volume was measured with a volumetric ...
Akagi T - - 1992
OBJECTIVES: This study was designed to evaluate changes in ventricular volume, mass and cardiac function before and after creation of an atrial to pulmonary connection in patients with a univentricular atrioventricular connection. BACKGROUND: Intact systolic and diastolic performance is critical for successful establishment of an atrial dependent circulation, and few ...
Puttick R M - - 1992
We have studied the effects of graded infusion rates of propofol (0.2-0.5 mg kg-1 min-1) on left ventricular global and regional function, in eight acutely instrumented dogs. Global function was assessed by measurement of aortic and left ventricular pressure, LV dP/dtmax, aortic blood acceleration and stroke volume. Regional function was ...
Allyn J W - - 1992
To test for oxygen wasting by norepinephrine (NE) without relying on normalization by measures of performance such as the pressure-volume area, myocardial oxygen consumption (MVO2) was determined for isovolumic beats at five different left ventricular (LV) end-diastolic volumes (EDV) in nine isolated cross-perfused canine hearts in each of three states: ...
Kelly R P - - 1992
This study tests the hypothesis that arterial vascular stiffening adversely influences in situ left ventricular contractile function and energetic efficiency. Ten reflex-blocked anesthetized dogs underwent a bypass operation in which a Dacron graft was sewn to the ascending aorta and connected to the infrarenal abdominal aorta via a plastic conduit. ...
Martich G D - - 1992
Endotoxin is a major mediator of the life-threatening cardiovascular dysfunction that characterizes Gram-negative sepsis. In animal models of endotoxemia, pretreatment with ibuprofen or pentoxifylline attenuates some of these cardiovascular changes. To evaluate the effects of these agents on the human cardiovascular response to endotoxemia, hemodynamic variables were measured serially in ...
Yaku H - - 1992
We studied the effects of cardiac hypothermia on myocardial oxygen consumption of a fibrillating ventricle and evaluated whether myocardial oxygen consumption of a fibrillating ventricle in hypothermia can be accounted for by new mechanical indexes: equivalent pressure-volume area and equivalent heart rate in the isolated cross-circulated canine heart preparation. Equivalent ...
de Tombe P P - - 1992
The agent 2,3-butanedione monoxime (BDM) has been reported to reduce the sensitivity of myofilament force development to calcium ions, without affecting the calcium transient in myocardium. One would predict, therefore, that BDM should reduce the contractile state of the heart without reducing the amount of oxygen that is consumed to ...
Hashimoto T - - 1992
The authors investigated the effects of alterations in heart rate, contractility, and loading conditions on a newly defined systolic time interval, the Q-V peak, in 46 anesthetized dogs. The Q-V peak was measured as the time from the beginning of the electrocardiographic Q wave to the moment at which the ...
Kelly R P - - 1992
BACKGROUND: This study tested whether the simple ratio of ventricular end-systolic pressure to stroke volume, known as the effective arterial elastance (Ea), provides a valid measure of arterial load in humans with normal and aged hypertensive vasculatures. METHODS AND RESULTS: Ventricular pressure-volume and invasive aortic pressure and flow were simultaneously ...
Akagi T - - 1992
Twenty children, aged 10.3 +/- 4.5 (3.3 to 17.5) years, were studied by equilibrium radionuclide angiography to establish a normal range for diastolic parameters. Ejection fraction (EF), peak ejection rate (PER) and time to peak ejection rate (TPER), peak filling rate (PFR) and time to peak filling rate (TPFR) were ...
Kameyama T - - 1992
The effects of unloading or inotropic agent in 22 patients with dilated cardiomyopathy were assessed in terms of optimal coupling between the ventricle and arterial system. In 13 patients (group A), lower body negative pressure (LBNP) was applied to reduce preload and nitroprusside was used to decrease afterload. In 9 ...
Goto Y - - 1992
Left ventricular contractility and the energetic cost of contraction were assessed in various disease models in experimental animals utilizing frameworks of Emax (left ventricular contractility index) and pressure-volume area (PVA, a measure of total left ventricular mechanical energy expenditure) derived from the pressure-volume (P-V) diagram. Under various contractile conditions, PVA ...
Beloucif S - - 1992
The effects of the pericardial constraint in control, tamponade, and absent pericardium conditions was studied in 18 anesthetized open-chest dogs. Atrial pressures and systolic and diastolic inflow volumes per beat in the superior (SVC), inferior vena cavae (IVC), and pulmonary vein (PV) were measured. With increasing tamponade, 1) the systolic-diastolic ...
Yun K L - - 1992
The effects of volume overload associated with mitral regurgitation on left ventricular systolic mechanics, energetics, mechanical to external stroke work efficiency, and ventriculoarterial coupling were examined in 11 conscious, closed-chest dogs. Miniature radiopaque tantalum markers were implanted into the myocardium to measure left ventricular volume, and biplane cinefluoroscopic images were ...
Nakagawa M - - 1992
To evaluate the left ventricular contractile state in patients with nonobstructive hypertrophic cardiomyopathy (HCM), we analyzed the maximum stress-volume index ratio (MSVR) using catheter-tip cineangiography in 11 patients with HCM and 16 normal subjects. The value of the MSVR in normal subjects was 6.48 +/- 1.25 kdyn/cm5/m2 (mean +/- SD) ...
Yokoyama Y - - 1992
Fourteen donor hearts were assessed by measurement of dopamine requirement, basic hemodynamic parameters (for example, systolic blood pressure), and the left ventricular pressure-volume relationship. The latter function was measured by a combination microtipped manometer/conductance catheter placed in the left ventricle through the ascending aorta. With an isoproterenol dose 24 hours ...
Boxt L M - - 1992
To test the utility of electrocardiographically gated spin echo nuclear magnetic resonance (NMR) imaging in quantitating right and left ventricular volumes and function in patients with primary pulmonary hypertension, right and left ventricular end-diastolic and end-systolic volumes, stroke volumes and ejection fractions were determined in 11 patients with primary pulmonary ...
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