Search Results
Results 351 - 400 of 1560
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Abe M - - 2000
BACKGROUND: Coronary blood flow occurs mainly during the diastolic phase of each cardiac cycle and is mainly dependent on diastolic driving pressure, especially in the left anterior descending coronary artery (LAD). We hypothesized that calculation of the ratio of the diastolic driving pressure of a stenotic LAD to its normal ...
Bach R - - 2000
This single-center, prospective, randomized, double-blind phase IV study with parallel-group design was performed to test whether injection of a newly designed non-ionic monomeric radiographic contrast medium in the axillary artery influences the ipsilateral cutaneous microcirculation. Twenty patients with coronary heart disease or suspected coronary heart disease were investigated. Ten patients ...
Rouleau J R - - 2000
The renin-angiotensin system plays a critical role in regulating vasoconstriction and vasodilatation that can influence myocardial blood flow and its transmural distribution. We tested the hypothesis that angiotensin inhibition can induce a leftward shift of the coronary autoregulatory pressure-flow relation and preserve distribution of myocardial blood flow at lower coronary ...
Wright C - - 2000
Previous studies which have indicated that the stimulation of ventricular mechanoreceptors induces significant reflex responses can be criticised because of the likelihood of concomitant stimulation of coronary arterial baroreceptors. We therefore undertook this investigation to examine the coronary and ventricular mechanoreflexes in a preparation in which the pressure stimuli to ...
Watanabe N - - 2000
BACKGROUND AND METHODS: In order to elucidate the underlying adjusting mechanism of human right coronary arterial (RCA) flow to increased right ventricular pressure (RVP) in children, we recorded RCA flow velocity in 24 pediatric cardiac patients at the orifice of its main trunk at the time of heart catheterization using ...
Shen Y T - - 2000
Thrombosis resulting from blood platelet aggregation via glycoprotein (GP) IIb/IIIa receptor activation triggers the local release of vasoactive substances. Therefore, inhibition of these receptors could affect coronary vasoactive function during thrombotic coronary arteriostenosis. Twenty pigs were instrumented with an aortic catheter and with hydraulic occluders and flow probes on both ...
Mathison M - - 2000
BACKGROUND: Coronary artery bypass grafting on the beating heart causes significant hemodynamic compromise during displacement of the heart. The precise mechanisms causing altered hemodynamics have not been clearly understood. The purpose of this study was to define the hemodynamic changes caused by displacing the heart in patients undergoing beating heart ...
György K - - 2000
The effects of the intracoronary administration of isosorbide-2-mononitrate (ISMN; 3 microg kg(-1) min(-1)), a major metabolite of isosorbide dinitrate, were examined in chloralose-urethane anaesthetized dogs before and during a 25 min, acute occlusion of the left anterior descending coronary artery. The only significant haemodynamic effects of ISMN administration were a ...
Lorbar M - - 2000
The aim of this study was to establish whether epicardial transudates could be used to uncover small, but physiologically important changes in interstitial NE concentrations under normal and pathological conditions. Norepinephrine (NE) concentrations measured in epicardial transudate fluid were compared to NE levels in the coronary effluent in normal and ...
Faile B A - - 2000
BACKGROUND: Compared with the conventional Thrombolysis In Myocardial Infarction (TIMI) flow grade system, the corrected TIMI frame count (CTFC) quantifies coronary blood flow in a more reproducible fashion. The purpose of this study was to determine if the CTFC is affected by sex, body size, hemodynamics, or other selected clinical ...
Kern M J - - 2000
The direct physiologic influence of a coronary stenosis, prior to an intervention for either de novo or restenotic lesions, can be easily and safely determined with sensor-tipped angioplasty guidewires, employing poststenotic absolute coronary flow velocity reserve (CVR), the relative CVR and the pressure-derived fractional flow reserve. This information supports decisions ...
Banerjee R K - - 2000
To evaluate the local hemodynamic implications of coronary artery balloon angioplasty, computational fluid dynamics (CFD) was applied in a group of patients previously reported by [Wilson et al. (1988), 77, pp. 873-885] with representative stenosis geometry post-angioplasty and with measured values of coronary flow reserve returning to a normal range ...
Hart B J - - 2000
This study was designed to determine changes in myocardial contractile function and fuel selection during moderate coronary hypoperfusion in the presence of elevated plasma free fatty acid (FFA) at normal and reduced blood glucose concentrations. Coronary perfusion pressure (CPP) was sequentially lowered from 100 to 60, 50, and 40 mmHg ...
Uchida K - - 2000
Troglitazone has direct effects on the hemodynamics of the heart. We investigated the effects of other insulin-sensitizing agents (rosiglitazone, pioglitazone and JTT-501 (4-[4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]benzyl]-3, 5-isoxazolidinedione)) on the hemodynamics of the heart using isolated perfused rat hearts. Rosiglitazone significantly decreased heart rate and coronary perfusion pressure, and increased peak isovolumic left ventricular ...
Wong L S - - 2000
An IBM PC-based real-time data acquisition, monitoring and analysis system for experimental haemodynamic studies was developed. Comprehensive haemodynamic signals, such as aortic and left ventricular pressures, aortic and coronary blood flows, two segmental lengths, two segmental thicknesses, electrocardiogram and airway pressure, were acquired and monitored to assess cardiac function. The ...
Alfonso F - - 2000
The simultaneous use of intravascular ultrasound catheters and sensor-tipped guidewires is gaining acceptance during coronary interventions as a means to gain further insights on the significance of coronary stenoses. Herein we describe four patients in whom the distal tip of the pressure wire became entrapped during an intravascular ultrasound examination. ...
Bardelli M M Institute of Medicina Clinica, University of Trieste, - - 2000
The aim was to investigate the regional and systemic haemodynamic consequences of bolus injection of fluids with different physical properties in the course of routine aortography. Iopamidol was compared with an equiosmolar solution of mannitol and with a 0.9 N saline solution. Continuous blood flow and Pulsatility Index (PI), as ...
Guiot C - - 2000
The response of the coronary vasculature to an experimental manoeuvre of step-like decrease of the perfusion pressure has been investigated with a model. The coronary vasculature was simulated using a 'windkessel' scheme. Proximal resistance and compliance were assumed to be pressure-independent. The distal resistance, on the contrary, was controlled by ...
De Bruyne B - - 2000
Background-Fractional flow reserve (FFR) is an index of stenosis severity validated for isolated stenoses. This study develops the theoretical basis and experimentally validates equations for predicting FFR of sequential stenoses separately. Methods and Results-For 2 stenoses in series, equations were derived to predict FFR (FFR(pred)) of each stenosis separately (ie, ...
Korvald C - - 2000
The myocardial oxygen consumption (MVO(2)) to left ventricular pressure-volume area (PVA) relationship is assumed unaltered by substrates, despite varying phosphate-to-oxygen ratios and possible excess MVO(2) associated with fatty acid consumption. The validity of this assumption was tested in vivo. Left ventricular volumes and pressures were assessed with a combined conductance-pressure ...
Skalidis E I - - 2000
A 52-year-old patient underwent percutaneous balloon pericardiotomy because of rapid fluid accumulation. During the procedure, we calculated the amount of blood flow to the nondiseased left anterior descending coronary artery while pericardial pressure was gradually increased by the infusion of warmed normal saline solution. Coronary vasodilator reserve was assessed by ...
Nakayama Y - - 2000
BACKGROUND: Because ascending aortic pressure has a greater effect on coronary perfusion during diastole than systole, we hypothesized that a high coronary diastolic-to-systolic pressure ratio prevents coronary lesions from restenosing after percutaneous transluminal coronary angioplasty (PTCA) and that ascending aortic pulsatility relative to mean pressure is higher in patients with ...
Sadick N - - 2000
This study explored the interaction between metabolically mediated vasodilatation (ventricular extra-activation) and pressure induced vasoconstriction (transient augmentation of aortic diastolic pressure). Eight dogs having formalin-induced heart block were chronically instrumented with aortic and left ventricular catheters and an electromagnetic flow probe on the left circumflex coronary artery. At a heart ...
Janelle G M - - 2000
OBJECTIVE: To examine the effects of calcium chloride (CaCl2) administration on blood flow through the grafted left internal mammary artery (IMA) after cardiopulmonary bypass (CPB). DESIGN: Single-arm prospective study. SETTING: University-affiliated hospital operating room. PARTICIPANTS: Twenty adult patients scheduled for coronary artery bypass graft surgery with IMA graft. INTERVENTIONS: IMA ...
Marzilli M - - 2000
OBJECTIVE: To verify the behavior of coronary microvascular tone during spontaneous ischemia in patients with unstable angina (UA). BACKGROUND: In UA, the pathogenetic role of vasoconstriction is classically confined at the stenotic coronary segment. However, microcirculatory vasoconstriction has been also suggested by previous experimental and clinical studies. METHODS: The study ...
Spaan J A - - 2000
Varying coronary volume will vary vascular resistance and thereby have an effect on coronary hemodynamics. Six ventricular septa were isolated from anesthetized dogs, dispersed in a biaxial stretch apparatus at diastolic stress, and perfused artificially with an oxygenated perfluorochemical emulsion at maximal vasodilation. Flow and thickness were measured continuously by ...
Pijls N H - - 2000
Guidewire-based coronary pressure measurement has emerged over the last years as a promising approach in the invasive assessment of coronary artery disease. It enables calculation of fractional flow reserve (FFR) which closely relates distal coronary pressure to myocardial blood flow during maximal arteriolar vasodilation. Coronary pressure measurement and FFR provide ...
Federici A - - 2000
Valsalva manoeuvre is reported to be sometimes successful for the relief of angina pectoris. The present study investigated how haemodynamic changes produced by Valsalva manoeuvre can interact to improve the relationship between cardiac work and coronary blood flow. Ten male subjects aged 53 +/- 12 years (SD) were considered. Blood ...
Boekstegers P - - 2000
There is renewed interest in the coronary venous system as an alternative access to ischemic myocardium. Selective pressure-regulated retroinfusion is a catheter-based approach which has been shown to increase the efficacy of retrograde oxygen delivery and drugs in experimental and clinical studies. Selective pressure-regulated retroinfusion may also target retrograde delivery ...
Loke K E - - 2000
We investigated the effect of bovine polymerized hemoglobin-based oxygen carrying (HBOC) solution on myocardial oxygen consumption (MVO2) and substrate use. At 15 min after the end of HBOC infusion (20% blood volume, i.v.) in nine permanently instrumented conscious dogs, mean arterial pressure and coronary blood flow were both increased by ...
Seiler C - - 1999
OBJECTIVES: The purpose of this investigation in patients with poorly and well developed coronary collaterals was to assess the influence of collateral and collateral adjacent vascular resistances and, in part, a stenotic lesion of the collateral supplying vessel on the hemodynamic collateral responses to adenosine. BACKGROUND: In humans, little is ...
Vergroesen I - - 1999
OBJECTIVE: We tested the hypothesis that the rate of adaptation of coronary metabolic vasodilatation and autoregulation is modulated by the cardiac nerves. METHODS: Anaesthetised dogs (seven innervated (control) and seven with denervated hearts) were subjected to controlled pressure perfusion of the left main coronary artery. Heart rate was controlled by ...
Rouleau J R - - 1999
The influence of left ventricle pressure and volume changes on coronary blood flow was investigated in eight anesthetized dogs. Coronary artery pressure-flow relationships were determined at two levels of left ventricular pressure and volume. The distribution of blood flow within the myocardium was also determined when these relationships varied. Reducing ...
Kaufmann P A - - 1999
PET with 15O-labeled water allows noninvasive quantification of myocardial blood flow (MBF) at baseline and during pharmacologically induced hyperemia to assess the coronary vasodilator reserve (CVR = hyperemic/baseline MBF). Despite widespread use of PET, its reproducibility during one study session has not been tested. Intravenous adenosine (Ado), a powerful coronary ...
Dankelman J - - 1999
Coronary perfusion pressure, Pp, affects coronary arterial resistance, Ra, (autoregulation) as well as myocardial oxygen consumption, MVO2 (Gregg's phenomenon). The interaction between the effects of Pp and MVO2 on coronary flow control was investigated using a coronary flow control model. Model analysis predicts that response of the pressure-flow ratio, p/q(t), ...
Kal J E - - 1999
For the assessment of metabolic coronary vasodilatation, changes in systolic rate pressure product (RPP) are frequently used to estimate the pacing- or exercise induced changes in myocardial oxygen consumption (MVO2). The present study was designed to test whether this is justified in patients with coronary artery disease. To study the ...
Karunanithi M K - - 1999
BACKGROUND: Increased left ventricular (LV) contractile force or oxygen consumption has been documented with increased coronary arterial pressure (CAP) and flow (Gregg phenomenon). We investigated whether the increase in contractile force with increased LV afterload might be mediated by the concomitant increase in CAP when coronary autoregulation is intact. METHODS ...
Niitsuma T - - 1999
It remains controversial whether basal nitric oxide (NO) production in coronary resistance vessels in heart failure is enhanced or not. A transonic Doppler flow probe was placed around the left anterior descending coronary artery, and complete atrioventricular block was produced in fifteen dogs. The coronary pressure-flow relationships during long diastole ...
Fujita H - - 1999
The angiographic assessment of coronary stenosis has many limitations, especially after coronary intervention. To determine the physiologic significance of such lesions, we measured the mean translesional pressure gradients at rest (P1), those during hyperemia induced by intracoronary administration of papaverine (12 mg in the left and 8 mg in the ...
Jin X Y - - 1999
OBJECTIVE: The acute physiological response of the coronary circulation to aortic valve replacement (AVR) has not been fully elucidated. This study aimed to characterize the changes in coronary perfusion pressure-flow velocity relationships, and to test whether this relationship is affected by cardioplegic method. METHODS: Nineteen patients (mean age 67 +/- ...
Williams M J - - 1999
The pressure-area relation of coronary arteries provides important information about the mechanical properties of these vessels. In human subjects methodological limitations have precluded measurement of instantaneous compliance and coronary stress in vivo. The purpose of this study was to assess a new method for measuring instantaneous values of coronary artery ...
Remah H A - - 1999
OBJECTIVES: The goals of this study were to elucidate the scaffolding effect of blood-filled coronary vasculature and to determine the functional role of recruited collateral flow in modulating left ventricular (LV) distensibility during balloon coronary occlusion (BCO). BACKGROUND: Although LV distensibility is an important factor affecting acute dilation after myocardial ...
Merkus D - - 1999
BACKGROUND: Because coronary blood flow is impeded during systole, the duration of diastole is an important determinant of myocardial perfusion. The aim of this study was to show that coronary flow modulates the duration of diastole at constant heart rate. METHODS AND RESULTS: In anesthetized, open-chest dogs, diastolic time fraction ...
Banerjee R K - - 1999
The coupling of computational hemodynamics to measured translesional mean pressure gradients with an angioplasty catheter in human coronary stenoses was evaluated. A narrowed flow cross section with the catheter present effectively introduced a tighter stenosis than the enlarged residual stenoses after balloon angioplasty; thus elevating the pressure gradient and reducing ...
Kawamura A - - 1999
To examine the mechanism of myocardial ischemia in hypertrophic cardiomyopathy (HCM), coronary flow velocity was measured in the left anterior descending coronary artery (LAD) using a Doppler guide wire in 11 patients with HCM and in 8 normal controls. The average peak velocity (APV), percent increase of APV (%APV), and ...
Mitsugi M - - 1999
Increased coronary sinus (CS) pressure and cardiac contraction impair coronary inflow independently. However, it has not been determined how the coronary pressure-flow relationship is strongly affected by changes in CS pressure in the beating heart compared to the non-beating heart. The purpose of this study was to evaluate the combined ...
Segers P - - 1999
Fractional flow reserve (FFR) is an index to assess the functional obstruction of an isolated coronary artery stenosis. It can be measured using only pressure measurements proximal (Pa) and distal (Pd) to the stenosis: FFR = P(d)/P(a). We studied the relation of pressure and flow-derived measurements of FFR in a ...
Swan L - - 1999
To investigate the effects of an intravenous infusion of BMS-180048, a novel 5HT1-like agonist, on the systemic, pulmonary and coronary circulations in patients undergoing diagnostic cardiac catheterisation. Ten patients (mean age 55 years (range 41-65)) were studied during diagnostic cardiac catheterisation. The haemodynamic response to an intravenous (i.v.) infusion for ...
Vacca G - - 1999
1. The present study was designed to investigate the effects of 17beta-oestradiol on the mesenteric, renal, iliac and coronary circulations and to determine the mechanisms involved. 2. In pigs anaesthetized with sodium pentobarbitone, changes in blood flow in the superior mesenteric, left renal, left external iliac and left circumflex coronary ...
Kal J E JE Department of Anesthesiology, Academic Medical Center, University of Amsterdam, The - - 1999
In the present study, we assessed the potential effect of nitroglycerin IV (NTG), a donor of exogenous nitric oxide, on metabolic coronary flow control in patients with coronary artery disease. In 12 patients scheduled for coronary artery surgery, arterial blood pressure, pulmonary capillary wedge pressure, coronary sinus blood flow (continuous ...
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