To determine the effects of dobutamine stimulation on myocardium distal to a coronary stenosis, transmural spatially localized phosphorus 31 nuclear magnetic resonance measurements of myocardial high-energy phosphate compounds (adenosine triphosphate and phosphocreatine), inorganic phosphate, and blood flow and systolic wall thickening were made in 8 open-chested dogs. Data were collected ...

Myocardial hibernation describes the clinical entity of a dysfunctional region of myocardium with reduced flow that shows improvement in function after flow is restored. It is postulated that despite the reduced flow, metabolic activity is sufficient to prevent tissue necrosis. Experimental work in animals supports this. A moderate reduction in ...

This study investigates the most appropriate protocol for measuring regional myocardial blood flow (MBF) using 15O-water in clinical applications. METHODS: Regional MBF, perfusable tissue fraction (PTF) and arterial blood volume (Va) were measured using 15O-water and dynamic PET on five healthy volunteers based on previously published models. Calculated values were ...

The actions of ITF 296 and isosorbide dinitrate (ISDN), 20, 70, and 200 g/kg/min, on myocardial transmural blood flow distribution during acute thrombotic occlusion of the left circumflex coronary artery (LCX) have been evaluated in seven and three anesthetized open-chest dogs, respectively, and compared with four animals receiving vehicle. Occlusion ...

The effect of flow steps in coronary arterial flow (Qa) on myocardial oxygen consumption (MVo2) was investigated at different heart rates (HR) to further elucidate the dependency of myocardial oxygen consumption on perfusion. In six anesthetized goats the left main coronary artery and the great cardiac vein were cannulated. The ...

The primary role of epinephrine for the treatment of ventricular fibrillation (VF) and pulseless electrical activity (PEA) is to increase blood flow to the myocardium and central nervous system and ultimately improve survival. However, despite the administration of epinephrine, survival following VF or PEA is low. In an attempt to ...

High energy phosphates [phosphocreatine (PCr) and adenosine triphosphate (ATP)] are maintained in the heart under conditions of altered myocardial contractility and under certain conditions of maintained in the heart under conditions of altered myocardial contractility and under certain conditions of myocardial ischemia (such as hibernating myocardium). However, the metabolic consequences ...

OBJECTIVES: To determine cerebral and myocardial blood flow rates during vest cardiopulmonary resuscitation (CPR) without direct cardiac compression in an infant porcine model. Also, to determine if circumferential chest compression without the chest deformity ordinarily associated with precordial compression maintains cerebral and myocardial blood flow rates during prolonged CPR. Finally, ...

The pharmacokinetics of meperidine in blood and myocardium were studied in five conscious sheep. After an intravenous (i.v.) bolus of 100, 200, or 300 mg meperidine HCl, the maximum arterial blood concentrations (mean +/- SD) were 27.8 +/- 4.6, 66.8 +/- 13.3, and 114.5 +/- 23.1 micrograms/mL, respectively, and coronary ...

Peptide mediators may play a role in the control of myocardial perfusion. We found immunohistochemical evidence of the peptide-degrading enzyme neutral endopeptidase (NEP) in cultured rat myocytes. Therefore, we examined the effect of an NEP inhibitor, phosphoramidon, on myocardial perfusion in rats after (1) stimulating sensory nerves with capsaicin and ...

To examine whether chronic high blood glucose may influence myocardial microcirculation during acute myocardial ischaemia in the dog, a noninsulin-requiring diabetes was induced by the streptozotocin-alloxan method. Seventy-five days later, myocardial ischaemia was provoked by occluding the left anterior descending coronary artery for 2 h and microcirculation regulation was assessed ...

We postulated that 99mTc-Q3, a cationic imaging agent, produces myocardial activity related to myocardial blood flow during myocardial ischemia and pharmacologic coronary artery vasodilation, and shows little or no myocardial redistribution over 4 hr after intravenous injection. METHODS: In six Group 1 dogs, the chest was opened, the left circumflex ...

Considerable progress is being made in the development of non-radioactive microsphere methods. Validation studies of the three commercially available non-radioactive microspheres are promising. In most experimental conditions the use of non-radioactive microspheres saves money. Avoiding the use of radioactivity facilitates the use of microspheres in chronic animal experiments and when ...

The effects of intracoronary administration of leukotriene D4 (LTD4) on myocardial blood flow (MBF) and myocardial energy metabolism in anesthetized open-chest dogs were examined, and compared with those of coronary ligation. Two series of experiments were conducted. In the first, LTD4 (0-3.0 micrograms/kg) was injected into the left anterior descending ...

The optimal temperature of blood cardioplegia remains controversial. Interstitial myocardial pH was monitored online with a probe that was inserted in the anterior wall of the left ventricle. Venous pH, lactate production, and creatine kinase and troponin T release were measured in coronary sinus blood obtained in 14 dogs after ...

OBJECTIVE: The aim was to determine whether modulation of intrinsic cardiac neurones influences the distribution of myocardial blood flow in canine anaesthetised open chest experimental preparations. METHODS: Intrinsic cardiac neurones were modified by locally applied nicotine (100 micrograms) or bradykinin (50 micrograms) while changes were recorded in cardiac haemodynamics and ...

The present study describes extraction fraction and uptake measurements of the [11C]methyl triphenyl phosphonium (11C-MTP), a promising positron emission tomography (PET) agent for cardiac imaging. PET imaging was performed in mongrel dogs. Under physiological flow conditions 11C-MTP uptake reached a maximum within the first 10 minutes after injection and remained ...

The haemodynamic effects of urapidil, an alpha 1-antagonist with central serotoninergic properties, were studied in an experimental canine model of chronic ischaemic heart disease. Global and regional haemodynamic recordings were made in conscious dogs with ameroid-induced single vessel coronary artery occlusion. Three intravenous bolus-infusion doses of urapidil (0.1 mg kg-1 ...

Angina, despite angiographically normal coronary arteries, is a common symptom in patients with hypertrophic cardiomyopathy (HC). Verapamil has been shown to ameliorate silent myocardial perfusion defects documented by thallium-201 in patients with HC. The aim of this study was to investigate the effects of verapamil on absolute regional myocardial blood ...

BACKGROUND: The objective of this study was to compare coronary flow reserve (CFR) as a measure of vascular integrity in asymptomatic middle-aged men with family history of coronary artery disease (CAD) and a high-risk lipid profile with men without risk factors for CAD using positron emission tomography (PET). Previous studies ...

99Tcm-methoxy-isobutyl-isonitrile (99Tcm-MIBI) is taken up by the vein through which it is injected in some individuals. We prospectively analysed technical and clinical factors that may be associated with this uptake. Imaging was performed over 1 h after injection so excluding a blood pool effect. The frequency of uptake could be ...

To study whether heterogeneous myocardial blood flow relates to the local oxidative capacity of cardiac muscle, local blood flow at resting cardiac workloads and the activity of the mitochondrial enzyme succinate dehydrogenase (SDH) were determined in small regions of the left ventricle of seven anaesthetized, mechanically ventilated, open-chest pigs (25-35 ...

Physical stress might modulate myocardial blood flow in near-maximally dilated coronary arteries by increasing coronary perfusion pressure, myocardial contractility, and heart rate. The net effect of these changes on hyperemic blood flows has not yet been defined in humans. To quantify the effect of physical exercise on pharmacologically induced hyperemia, ...

BACKGROUND: The relative intracoronary flow reserve has been found to be reduced during acute transplant rejection, but the effects of rejection on absolute flows at rest and during hyperemia have not been established previously. This has now become possible through noninvasive quantification of myocardial blood flow with positron emission tomography. ...

The aim of this study was to define the kinetics of 38K and its suitability to evaluate myocardial blood flow at rest and during pharmacological vasodilation in normal subjects. Potassium-38's kinetic characteristics were also compared to those of a 62Cu-pyruvaldehyde bis(n4-methyl-thio-semicarbazone) copper (II) (PTSM) flow tracer. METHODS: Potassium-38 and 62Cu-PTSM ...

BACKGROUND: We assessed the relation between the severity of stenosis in a coronary artery and the degree of impairment of myocardial blood flow. Studies in laboratory animals have shown that as the degree of coronary-artery stenosis increases, the maximal coronary flow measured after maximal vasodilation progressively decreases, with a concomitant ...

Myocardial contrast echocardiography (MCE) is a new technique for assessing myocardial perfusion that uses intracoronary injections of microbubbles of air. Because these microbubbles have a mean diameter of 4.3 +/- 0.3 microns and an intravascular rheology similar to that of red blood cells (RBCs), we hypothesized that their mean myocardial ...

BACKGROUND: 99mTc-labeled methoxyisobutyl isonitrile (99mTc-sestamibi) is a myocardial perfusion agent that clears slowly from the myocardium. This study evaluates the early and late myocardial distributions of 99mTc-sestamibi and 201Tl in the presence of low-flow ischemia to determine whether 99mTc-sestamibi demonstrates rest "redistribution." METHODS AND RESULTS: Low-flow ischemia was produced in ...

Accurate noninvasive assessment of coronary blood flow is dependent on the physiologic properties of the perfusion agent as well as the physical imaging properties of its radiolabel. Perfusion agents can accurately assess variable levels of flow by having a high myocardial extraction and retention. Based on extraction values, teboroxime can ...

To examine the effects of inotropic stimulation on regional myocardial blood flow (MBF), oxidative metabolism, and contractile function in stunned myocardium, nine closed-chest dogs were studied 2 hours postreperfusion after a 25 minute occlusion of the left anterior descending coronary artery (LAD). MBF was determined with microspheres, and regional myocardial ...

Numerous studies have described a progressive deterioration in resting myocardial blood flow following relief of sustained ischemia in both necrotic and salvaged myocardium (termed "no reflow" and "low reflow", respectively). We sought to determine whether release of the potent vasoconstrictor peptide endothelin-1 may play a role in these phenomena. As ...

We examined the effect of a new potassium channel opener, bimakalim, on myocardial infarct size (IS) in dogs. Barbital-anesthetized dogs were subjected to 90 min of left circumflex coronary artery (LCX) occlusion followed by 5-h reperfusion. Bimakalim (3 micrograms/kg bolus followed by 0.1 microgram/kg/min intravenously, i.v.) was initiated either 15 ...

Quantitation of myocardial blood flow has been sought by the clinician using a variety of imaging modalities and blood indicator dilution techniques. Ultrafast computed tomography has real potential for clinically useful estimations of regional myocardial blood flow. At the present time, there are limitations with this technique and early washout ...

Technetium-99m-tetrofosmin is a 99mTc-labeled perfusion tracer demonstrating promise for myocardial perfusion imaging. To determine if 99mTc-tetrofosmin tracks myocardial flow over a pathophysiologic range, the initial myocardial uptake and clearance of 99mTc-tetrofosmin relative to microsphere flow were evaluated in a canine model of ischemia during pharmacological vasodilatation. METHODS: Six open-chest dogs ...

A potentially reversible impairment of contractile function in patients with chronic coronary artery disease characteristically exhibits a regional increase in glucose utilization or, more precisely, glucose extraction, as evidenced by the presence of a blood flow-glucose metabolism mismatch. The predictive accuracy of patterns of blood flow and glucose metabolism has ...

Technetium-99m-sestamibi images reflect tracer distribution at the time of injection. This "stay put" indicator allowed us to separate the effects of segmental left ventricular dysfunction per se versus myocardial blood flow on SPECT "perfusion" images in ten dogs. METHODS: An electromagnetic flow probe and hydraulic occluder were placed on the ...

OBJECTIVES: This study tested the hypothesis that nonviable myocardium can be identified by quantitative measurements of regional myocardial blood flow obtained using positron emission tomography in conjunction with a mathematical model of nitrogen-13 (N-13) ammonia tracer kinetics. BACKGROUND: Under steady state basal conditions there is a minimal level of blood ...

The purpose of this study was to investigate atrial myocardial blood flow in the fetus under conditions of acute right ventricular pressure load and adenosine infusion. Late gestation fetal sheep were instrumented for acute right ventricular pressure loading or adenosine infusion, and regional myocardial blood flow was measured at rest ...

OBJECTIVE: To describe the relationship between hematocrit and oxygen utilization before and after the onset of a hyperdynamic septic state. DESIGN: Prospective, observational study. SETTING: Laboratory of a large university-affiliated medical school. SUBJECTS: Thirty mature sheep, each weighing 30 to 40 kg (0.9 to 1.1 m2 body surface area). INTERVENTIONS: ...

BACKGROUND: Some clinical and experimental studies suggest that propofol decreases myocardial contractility and relaxation, whereas others report preserved cardiac function. To investigate the effects of propofol on intrinsic contractility and relaxation, increasing concentrations of propofol were infused in isolated blood-perfused rabbit hearts. Equimolar concentrations of thiopental were infused as a ...

The tomographic utility of 99mTc-labeled teboroxime has been limited because of its fast washout from the heart, which requires rapid data acquisitions that have not been feasible until the recent development of multidetector SPECT systems. METHODS: Using a three-detector SPECT system to acquire dynamic tomographic data every 10.2 sec, we ...

Normothermic blood cardioplegia was developed originally to be used during cardioplegic induction and reperfusion as an adjunct for enhancing metabolic reversal of biochemical alterations occurring before, during, and after total myocardial ischemia. This adjunct was introduced clinically after extensive experimental testing. By contrast, continuous normothermic blood cardioplegia without hypothermia was ...

BACKGROUND: 99mTc-Q12 is a new Tc(III) perfusion imaging agent that permits prompt myocardial visualization in humans. We postulated that 99mTc-Q12 myocardial activity is related to actual myocardial blood flow during conditions of myocardial ischemia and pharmacological coronary artery vasodilation and that 99mTc-Q12 shows little or no myocardial redistribution as long ...

Prior studies of cold retrograde cardioplegia have demonstrated the existence of regional deficits in perfusate delivery. To address the hypothesis that these deficits persist with the use of warm perfusate, cardioplegic arrest was induced in 7 swine hearts with retrograde warm blood cardioplegia. Regional perfusion was assessed with the simultaneous ...

Myocardial and cerebral blood flow were determined with radiolabeled microspheres in 20 Sprague-Dawley rats during sinus rhythm and during stable but hemodynamically compromising ventricular tachycardias. In addition, in 10 animals the measurements were performed at hypotension induced by exsanguination. In controls (n = 10), myocardial and cerebral blood flow were ...

Positron Emission Tomography (PET) permits the non-invasive quantification of myocardial blood flow and flow reserve. This capability requires an understanding of the determinants of resting and hyperemic blood flow in order to interpret correctly quantitative findings with PET. Equally important is the knowledge of how such measurements are obtained and ...

It is not known whether myocardial energy requirements can be increased to the degree that they exceed myocardial O2 availability in the absence of abnormalities of coronary blood flow or coronary reserve. To determine whether this form of "demand ischemia" occurs, 10 swine were subjected to pressure overload induced by ...

It has been shown in previous studies that grafting a free skeletal muscle flap onto the heart of the dog produces myocardial revascularization. In order to evaluate the functional aspect of these neovessels, an Ameroid constrictor was implanted into the LADs (left anterior descending coronary artery) of five dogs. At ...

Previous studies showed that myocardial contrast echocardiography can be used to detect relative regional underperfusion in a canine model of critical coronary stenoses. The aim of this study was to determine if myocardial contrast echocardiography performed with a sterile sonicated human serum albumin preparation (Albunex, Molecular Biosystems, San Diego, Calif.) ...

Techniques which assume linear, time-invariant systems have been used to characterize indicator dilution pairs. As a basis for fully describing the relation between left ventricular (LV) and myocardial (MYC) time-density curves, produced by an intravenous contrast medium as measured by ultrafast CT, the assumption of time invariance was tested using ...