OBJECTIVE: To characterise the effect of coronary intra-arterial thrombosis upon the downstream vascular bed. BACKGROUND: The vascular response downstream from a coronary intra-arterial thrombus has not previously been characterised. We postulated that downstream vasoconstriction might result from the presence of endothelial damage with consequent growth of platelet-rich thrombus. METHODS: We ...

Changes in coronary perfusion pressure lead to alterations in intracoronary myocardial volume that may be associated with regionally altered microvascular morphology. Transmural variations in coronary capillary geometry were quantified as a function of coronary perfusion pressure in glutaraldehyde-fixed canine hearts. Capillary volume fractions, diameter, numerical density, anisotropy, and sarcomere length ...

To investigate the relationship between plasma levels and coronary vasodilation after administration of isosorbide dinitrate (ISDN), the plasma concentration and diameters of six segments of the left coronary artery were measured before and after sublingual (SL) ISDN (5 mg) and left intracoronary (IC) administration of ISDN (3 mg) in 12 ...

This study evaluated the efficacy of computer-controlled closed-loop delivery of a new synthetic catecholamine, arbutamine, when given to induce myocardial ischemia detected by electrocardiography and echocardiography with a high (10 beats/min/min) and low (6 beats/min/min) rate of increase in heart rate (heart rate slope) in 70 patients with coronary artery ...

BACKGROUND: Because the role of tonic vagus nerve activity in regulating conduit coronary artery size remains undefined, we investigated the response of epicardial coronary artery size to changes in resting vagal tone resulting from vagotomy and muscarinic receptor blockade. METHODS AND RESULTS: Using intravascular ultrasound to measure left circumflex coronary ...

BACKGROUND: The objective of this study was to investigate in patients with unstable angina and significant coronary stenosis (> 70%) whether or not the morning peak of myocardial ischemia is associated with a reduction in the ischemic threshold. The morning increased incidence of ischemic episodes in stable angina appears to ...

The aim of this investigation was to study the coronary pressure-flow relationship in 60 patients with chronic arterial hypertension of diverse aetiologies and in 14 normotensive subjects (control group). The hypertensive cohort included 6 patients with isolated systolic hypertension (ISH), 7 renovascular hypertensive patients with abnormally elevated angiotensin II plasma ...

A fibreoptic pressure sensor mounted on an 0.018 inch guidewire (Pressure Guide, RadiMedical Systems, Uppsala, Sweden) was used to measure the trans-stenotic pressure gradient in 20 patients admitted for percutaneous transluminal coronary angioplasty (PTCA) of a single, discrete stenosis. Pressure measurements were made both at rest and during maximal vasodilatation ...

Newborn piglets were subjected to 45 min of sustained norepinephrine-induced hypertension and then monitored for 4 hr at baseline conditions. They were then sacrificed and the anterior descending coronary artery was serially sectioned for study by light and electron microscopy. Other groups were sacrificed after 72 and 168 hr of ...

Isolated hearts from guinea pigs were perfused at 37 degrees C with Tyrode's solution according to the technique of Langendorff. Coronary flow, left ventricular pressure amplitude and heart rate were measured. Bolus injection of 30 ng leukotriene C4 caused a long-lasting decrease in coronary flow and left ventricular pressure amplitude ...

The functional role of ATP-dependent potassium (KATP) in hypoxic cardiac failure was investigated in isolated guinea pig hearts with glibenclamide and rimalkalim as inhibitor and activator, respectively. Monophasic action potential duration at 90% of repolarization (MAP50), left ventricular function, and cardiac energy status (31P nuclear magnetic resonance spectroscopy) were measured ...

Surgical coronary artery fistula, in which the last anastomosis is created to a low-pressure cardiac chamber, was recently introduced as an alternative method to improve graft flow and patency in a sequential graft when coronary arteries are small or diffusely diseased. To assess graft flow, effect on haemodynamics, flow distribution ...

There is a paucity of knowledge regarding right coronary pulsatile hemodynamics when the right ventricle is under hemodynamic overload as is often the case in pediatric patients with congenital cardiac anomalies. To elucidate the exact mechanisms for the right coronary artery (RCA) to cope with the overload, we studied nine ...

A total of 100 patients were studied for the diastolic blood pressure response to treadmill exercise testing. No change in the diastolic pressure or lowering of the pressure was considered normal response. Seventy four patients had normal and 26 patients had abnormal diastolic blood pressure response. Out of these, 40 ...

Coronary artery spasm is a known complication of coronary interventions, for which intracoronary nitroglycerin (ICN) is the treatment of choice. Some forms of intense spasm are resistant to ICN. Calcium channel antagonists are also known to be effective for coronary artery spasm, including nitroglycerin-resistant spasm. Here we describe a protocol ...

Left ventricular (LV) hypertrophy (LVH) secondary to chronic pressure overload is associated with increased susceptibility to myocardial hypoperfusion and ischemia during exercise. The present study was performed to determine whether exercise causes alterations in minimum coronary resistance or effective back pressure [coronary pressure at zero flow (Pzf)] that limit maximum ...

BACKGROUND: Cocaine and ethanol are often abused concomitantly, and this combination may be more lethal than either substance alone. Although previous studies showed that cocaine causes coronary arterial vasoconstriction, the combined effect of cocaine and ethanol on the coronary vasculature in humans is unknown. Thus, we assessed the effects of ...

Different conclusions have been reached with regard to the effect of endothelin (ET-1) on cardiac contractility. We examined systolic and diastolic function in response to constant known concentrations of ET-1 with or without ET-1 induced reductions in coronary flow (CF). Rat hearts (n = 21) were buffer-perfused using constant coronary ...

Nitric oxide (NO) is known to regulate basal coronary blood flow (CBF). The objective of the present study was to examine the importance of NO in CBF regulation at various coronary arterial pressures (CAPs) in vivo. Experiments were performed in 11 open-chest pentobarbitone sodium anesthetized pigs. CAP was reduced in ...

We conducted the present study to determine if pharmacologically recruitable flow reserve was present during ischemia in unanesthetized dogs studied in the absence of adrenergic activation. Microsphere measurements of regional perfusion at reduced coronary pressures in a distal circumflex region subjected to intracoronary adenosine infusion (0.265 mg/min IC) were compared ...

BACKGROUND: Studies have shown that myocardial bridging may prevent coronary atherosclerosis and that the segment proximal to the bridge is often sclerosed. The underlying mechanism is still unknown. METHODS: Intracoronary ultrasound and pressure measurements were performed in a patient with myocardial bridging in the left anterior descending coronary artery. A ...

We examined the effect of the novel nitrovasodilator ITF 296 and isosorbide dinitrate (ISDN) on myocardial blood flow (BF) distal to a coronary artery stenosis. Eleven dogs with a Doppler velocity probe, hydraulic occluder, and indwelling microcatheter in the left anterior descending coronary artery (LAD) were studied during treadmill exercise ...

The present study was designed to evaluate the potential anti-ischaemic activity of R 56865 in patients with coronary artery disease, scheduled to undergo percutaneous transluminal coronary angioplasty (PTCA). At baseline a complete haemodynamic profile, including cardiac output and coronary sinus blood flow (CSBF) was obtained. In addition, left ventricular pressure ...

Experiments were performed to characterize the role of endothelium-derived relaxing factor (EDRF) in coronary vasodilation caused by norepinephrine. The circumflex or left anterior descending coronary artery was cannulated and pump perfused with constant pressure or constant flow in closed-chest anesthetized dogs. Prostaglandin synthesis was blocked with ibuprofen. During constant-pressure perfusion, ...

The effects of equi-anaesthetic concentrations of halothane (HAL) and isoflurane (ISO) on myocardial performance, perfusion, oxygenation and lactate release were studied before, during and after a low-flow, global ischaemic insult in isolated, paced rat left heart preparations. An antegrade perfusion technique was used, where left atrial pressure (LAP) and mean ...

Reduced epicardial coronary arterial distensibility associated with early atherosclerosis may be mediated in part by reduced nitric oxide (NO) release. To directly assess the contribution of endogenous NO to coronary arterial distensibility, we examined the effect of intracoronary N omega nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase, and ...

The effects of pericardial tamponade on coronary capacitance and coronary systemic hemodynamics were calculated in two groups of animals subjected to increases in pericardial pressure (PCP) up to approximately 20 mmHg. In one group (A), flow in the left circumflex artery was measured in the intact animal under conditions of ...

This study aims to test the assumptions that: (1) coronary arterial flow is attenuated in an early activated region by ventricular pacing; (2) asynchronous mechanical activation caused by ventricular pacing under controlled perfusion pressure and intact coronary tone is associated with reduced coronary flow compared to atrial pacing; and (3) ...

BACKGROUND: The mechanism of the reversible upward shift of the left ventricular diastolic pressure-volume relation during demand ischemia is controversial. To assess the possibility that cation influx through stretch-activation channels may contribute to the upward shift, we asked whether gadolinium, a blocker of the stretch-activated channels, attenuates the upward shift ...

RATIONALE AND OBJECTIVES: The authors studied cardiac contractile responses during coronary bolus perfusion, as in coronary angiography, in three species and related the responses to the bolus content of electrolytes and to patterns of cardiac electrolyte regulation. METHODS: Isolated, paced hearts from the rat, guinea pig, and rabbit were subjected ...

PURPOSE: Our study investigated the effects of an increase in aortic pressure, induced by norepinephrine (NE) administration on coronary artery flow in a clotted artery, and rate of coronary thrombolysis induced by intravenous (i.v.) administration of recombinant tissue plasminogen activator (rtPA). METHODS: A canine model of coronary thrombosis, induced by ...

In arterial hypertension, coronary flow reserve, expressed by the difference between autoregulated and maximal coronary flow, is frequently impaired. Previous experimental and clinical investigations using acetylcholine as a stimulus for the production of endothelium-derived relaxing factor suggested that an impaired endothelium-dependent vasodilation, presumably caused by a decreased formation of nitric ...

Previous in vivo studies of the coronary vascular effects of halothane (HAL) were complicated by varying hemodynamic conditions and global cardiac work demands. Accordingly, the current study evaluated changes in coronary blood flow (CBF) and associated variables during selective intracoronary administrations of HAL in in situ canine hearts using an ...

Although quantitative coronary angiography (QCA) has been used to determine lesion severity, angiographically derived parameters of translesional physiology have not been compared with those directly measured in the same patients. Thus, the aim of this study was to correlate QCA-derived translesional pressure and flow data with directly measured data in ...

The purpose of our study was to compare the ability of dobutamine and dipyridamole infusion to induce myocardial ischemia. In a population of 16 anesthetized open-chest swine, a coronary artery stenosis sufficient to abolish the hyperemic response to a 15-second total occlusion was created. Heart rate, systolic blood pressure, and ...

Age-related arterial stiffening and widening of the pulse pressure elevates ventricular systolic wall stress while it lowers diastolic coronary perfusion pressure. These changes are thought to adversely alter the balance between myocardial work load and blood supply. To test this hypothesis, the native compliant thoracic aorta was surgically bypassed by ...

We investigated whether addition of a balanced electrolyte supplement and oxygen to the nonionic contrast medium iohexol reduces the risk of ventricular fibrillation (VF), and studied regional electrophysiology prior to the VF event. Twenty ml of each test solution were infused at a rate of 0.5 ml/s into the left ...

OBJECTIVE: The aim was to investigate the influence of the sympathetic nervous system on the native collateral circulation in the intact heart. METHODS: Experiments were performed on 10 open chest dogs anaesthetised with alpha chloralose. The left anterior descending coronary artery was cannulated and embolised with 25 microns microspheres. Collateral ...

The flow rate of phosphate buffered saline through dermis was measured as a function of applied pressure. Hyaluronan and collagen, the two principal materials which confirm resistance to flow in dermis, were not lost from the tissue during the experiments which lasted up to two days. From Darcy's Law, the ...

The hemodynamic effects of cocaine may be modulated by drugs which interact with central and peripheral adrenoceptors. This investigation examined the systemic and coronary hemodynamic effects of cocaine in conscious dogs with and without premedication with dexmedetomidine (DM). Three groups consisting of 24 experiments were performed using eight dogs chronically ...

The effects of parenteral magnesium sulphate (MS) on the regional contractile response of stunned myocardium was examined in 45 pentobarbital anaesthetized dogs. The hearts were instrumented to measure left ventricular pressure (LVP), coronary flow velocity (CFV), mean arterial blood pressure (MAP), and regional contractile function (percent segment shortening, %S; and ...

OBJECTIVES: Nonischemic contractile segmental performance was characterized by the end-systolic pressure-length and pressure-thickness relations during regional ischemia induced by proximal left anterior descending and left circumflex coronary artery occlusions. BACKGROUND: The increases in shortening and thickening of the nonischemic myocardium during acute ischemia have been attributed to alterations in the ...

Previously, we identified the presence of a circulating shock protein (CSP) in the plasma of hemorrhaged rats that depolarizes a variety of cells in vitro. In isolated perfused rat hearts, partially purified CSP produced dose-dependent decreases in contractility and heart rate associated with an increase in coronary perfusion pressure (CPP). ...

The presented hypothesis assumes, in contrast with the currently prevailing view, that blood continues to flow through the coronary vascular bed even during systole. The contraction of differently oriented myocardial layers closes the penetrating branches of the coronary arteries in the interlayer boundaries. Coronary arteries of a different caliber are ...

1. Two hypotheses relating to the influence of contraction of the heart on coronary venous pressure (Pv) were tested. The first assumes a direct transmission of left ventricular pressure (PLV). According to the alternative hypothesis the Pv is caused by cyclical changes in the elastance of the surrounding tissue. 2. ...

The principal effect of sympathetic activation on the coronary circulation is an alpha-adrenergic coronary vasoconstriction in the presence of beta-receptor blockade. Secondary effects include vasodilation due to beta-adrenoceptor stimulation and alpha 2-mediated release of endothelium-derived relaxing factor (EDRF) from the coronary vascular endothelium. We hypothesized that blockade of nitric oxide ...

The effects of administration of pressor agent phenylephrine (PE) and depressor agent, sodium nitroprusside (SNP) (10-40 micrograms/kg) on arterial blood pressure (ABP) and heart rate (HR) were investigated during acute occlusion of left anterior descending coronary artery (LAD) in anaesthetized, artificially ventilated dogs with and without the influence of selective ...

BACKGROUND: The effects of isoflurane on distribution of transmural blood flow and transmural intramyocardial tissue pressure (IMP) were studied in chronically instrumented dogs, to address following aims: (1) to evaluate the direct effects of isoflurane on transmural blood flow distribution in the absence of compounding effects of baseline anesthetics, acute ...

The usefulness of dynamic cardiomyoplasty has been demonstrated repeatedly, both experimentally and clinically. Although clinical applications of dynamic cardiomyoplasty to ischemic heart disease have been reported, its effect on the coronary blood flow has never been discussed. Therefore, we tested the hypothesis that dynamic cardiomyoplasty might adversely affect coronary arterial ...

BACKGROUND: Sevoflurane produces direct vasodilation of coronary arteries in vitro and decreases coronary vascular resistance in vivo, pharmacologic properties that may contribute to the development of "coronary steal." This investigation examined the effects of sevoflurane on the distribution of regional myocardial perfusion in chronically instrumented dogs with steal-prone coronary artery ...