Bradycardic agents could limit the consequences of myocardial ischemia via two mechanisms: by decreasing myocardial oxygen demand (MVO2) and by increasing diastolic coronary blood flow (CBF). We investigated whether the benzazepinone UL-FS 49 affects only sinus node cells or also smooth muscle and/or myocardial cells. To avoid confounding interactions with ...

Experimental models have been developed to investigate the influences of anger, fear, and sleep on coronary blood flow. Studies of anger in dogs with coronary stenosis indicate that the postarousal phase is particularly conducive to myocardial ischemia. Specifically, a delayed coronary vasoconstrictor response has been observed within 1-3 minutes after ...

We measured right ventricular coronary blood flow with radioactive microspheres during graded aortic pressure reduction in 13 normal dogs and in 13 renal hypertensive dogs with left ventricular hypertrophy. Under anaesthesia and controlled loading conditions, mean aortic pressure was lowered from control (128 mmHg in normal and 146 mmHg in ...

BACKGROUND: The hypothesis that increases in coronary perfusion increase ventricular performance independently from providing enhanced oxygen supply ("Gregg phenomenon") remains controversial. METHODS AND RESULTS: To study the physiological significance of changes in coronary perfusion on global and regional myocardial function in situ, the left anterior descending coronary artery of isoflurane-anesthetized ...

Patients in this study were assessed by coronary angiography because of classic effort angina and a positive exercise test. Of these patients, 320 had untreated primary hypertension and 320, similar in age and gender distribution, were normotensive. In all patients coronary angiography documented that at least one major epicardial branch ...

1. The left anterior descending coronary artery (LAD) was completely ligated for 90 min (i.e. myocardial ischaemia was produced) in the dog anaesthetized with pentobarbital. 2. Bevantolol, a beta 1-adrenoceptor antagonist, was injected (1 mg/kg, intravenously) 5 min before LAD occlusion. The bevantolol injection decreased heart rate without affecting blood ...

Effects of acute lethal blood loss on postresuscitation heart impairment has been studied. Experiments were performed in mongrel male rats anesthesized with sodium pentobarbital (25 mg/kg). Functional metabolic heart impairments have been evaluated in different terms after resuscitation by isolated perfused heart method (Fallen et al., J. Appl. Physiol, 22 ...

The hemodynamic, electrocardiographic, and coronary flow responses to a psychological test were studied in 13 pigs both in the absence (group 1, n = 8) and the presence (group 2, n = 5) of a transient occlusion of the left anterior descending coronary artery. The psychological test consisted of presenting ...

To determine the dynamic property of cardiac function response to alterations in coronary perfusion, we varied coronary arterial pressure (CAP) sinusoidally around one of four mean CAP levels with a constant amplitude at several frequencies in isolated, isovolumically contracting canine heart preparations. From the frequency spectrum of the peak left ...

Several studies of flow through collapsible tubing deformed by external pressures have led to a concept known as the "vascular waterfall". One hallmark of this state is a positive zero-flow pressure intercept (Pe) in flow-pressure curves. This intercept is commonly observed in the coronary circulation, but in blood-perfused beating hearts ...

Many cardiac surgical units now use a microfilter in the infusion line for delivery of crystalloid cardioplegic solution to protect against the potential hazards of particulate contamination of cardioplegic solution. The aim of this group of studies was to determine the effects of particulate contamination of cardioplegic solutions, in order ...

The effect of coronary and intraventricular pressures on the glucose uptake and its transmural distribution was studied in isolated, beating rat heart perfused using the Langendorff procedure. Left ventricular glucose uptake measured by the deoxyglucose method, and the effect of coronary (aortic) pressure was dissociated from intraventricular pressure development by ...

BACKGROUND: At any given perfusion pressure, coronary reserve is expressed by the difference between autoregulated and maximally vasodilated flow. In hypertension the raised coronary resistance reduces the steepness of the pressure-flow relationship at maximal vasodilatation. In the presence of cardiac hypertrophy the line of autoregulated flow becomes higher. For these ...

The influence of desflurane on myocardial perfusion measured by a microsphere technique during a total occlusion of the left anterior descending coronary artery and concomitant moderate or severe stenosis of the left circumflex coronary artery was evaluated in chronically instrumented dogs. Hemodynamics, regional contractile function, and myocardial blood flow were ...

Isolated observations prompted a prospective study of the possible occurrence of myocardial ischaemia following abrupt discontinuation of intravenous infusion of nitroglycerin in 46 consecutive patients with unstable angina. In 26 (55%, group 1), but not the remainder (45%, group 2), cessation of nitroglycerin produced in 10.3 +/- 5.8 (mean +/- ...

The goal of this study was to evaluate the influence of low coronary perfusion pressure on the coronary vasoconstriction induced by endothelin. For this purpose, the circumflex coronary arteries of 12 open-chest dogs were cannulated and perfused at a controlled pressure. Total coronary blood flow was measured with an electromagnetic ...

A control mechanism for the control of coronary blood flow (especially coronary autoregulation), presuming that interstitial osmotic pressure determines vascular resistance, was critically examined. A theoretical model of the control mechanism was made and the most important parameters of this theoretical model were estimated from published data. The parameters are ...

Chronic systemic hypertension has been shown to alter the distribution of vascular resistance in many microvascular beds. The purposes of this study were to assess the effects of chronic systemic hypertension on the pressure distribution in the coronary microcirculation and to determine the microvascular site where coronary vascular resistance is ...

We examined the effects of pressure overload on coronary circulation in young adult (7 months old) and old rats (18 months old). Four weeks after the ascending aorta was banded, in vivo left ventricular pressure was measured to estimate the degree of pressure load. In the two age groups, similar ...

We examined the "vascular waterfall" hypothesis, which proposes that coronary flow is unaffected by elevations in outflow pressure until the latter reaches a critical threshold level, in 29 isolated canine hearts. In fibrillating hearts vasodilated with adenosine or carbocromen, coronary flow and the coronary pressure-flow relation were not affected by ...

STUDY OBJECTIVE: The aim was to investigate the effects of regional myocardial ischaemia, calcium, and verapamil on (a) the hysteresis and (b) slope and length axis intercept of the left ventricular end systolic pressure-length relationship. DESIGN: Segment length in myocardium supplied by the left anterior descending coronary artery was measured ...

Neuropeptide Y (NPY) induces coronary vasoconstriction and an associated negative inotropic effect in the isolated rat heart, but it is unclear whether NPY produces these effects directly or through the mediation of other vasoactive substances. This question has been examined in Langendorff-perfused, paced hearts using constant pressure. In 22 dose-response ...

1. The effects of Tityus serrulatus scorpion venom and its most important toxin (toxin gamma) were investigated on isolated guinea-pig hearts, perfused with Locke solution, by the Langendorff's method. 2. The cardiac contraction, the coronary flow and the electrocardiogram (ECG) were simultaneously recorded. 3. Bolus injections of 25, 50 or ...

Intracoronary injection of papaverine is used to determine coronary flow reserve in patients. The present study was to investigate the effect of papaverine on the performance of myocardium with reduced flow reserve. In nine anaesthetized open-chest dogs a bypass from the aorta to the left circumflex coronary artery (LCX) was ...

The changes in cardiac and in total haemodynamics, occurring during the first seconds of occlusion and the subsequent desocclusion of coronary arteries were studied on 28 dogs. The most intensive changes were observed after the trunk occlusion of the left coronary artery. Simultaneously with decreasing blood inflow into the myocardium ...

The effects of acute coronary artery occlusion in anaesthetized cats has been studied with regard to changes in cardiac function and regional myocardial blood flow. Occlusion of the left anterior decending coronary artery (LAD) is followed by a rapid reduction of peak systolic blood pressure (LVSP) and contractility (dP/dt) and ...

Platelet-activating factor (PAF) has been termed an important mediator of cardiovascular shock due to immunological reactions, including anaphylaxis and endotoxic reactions. Previous studies have shown that PAF is a potent cardiodepressive agent inducing a drastic coronary constriction and a sustained impairment of myocardial contractility. In this study, an attempt was ...

An intravital fluorescence videomicroscope system was used to investigate the pharmacological effects of endothelin-1 (ET-1) on the coronary microcirculation in isolated beating hearts of rats. The heart was perfused by retrograde aortic steady flow with an oxygenated Krebs-Ringer solution containing FITC-dextran. Cumulative injections of ET-1 (1-30 pmol) elicited a dose-dependent ...

The hypertrophy of the media of coronary arteries associated with hypertension reduces cross-sectional area and limits vascular reserve. Cilazapril 10 mg/kg daily decreased cardiac hypertrophy, and decreased minimal coronary vascular resistance by 40% when administered to spontaneously hypertensive rats (SHR) at the onset of hypertension. After hypertension had developed, cilazapril ...

The effect of left-ventricular afterload on cardiac performance was investigated in normotensive Wistar rats and in spontaneously hypertensive rats (10 months old) with a left-ventricular hypertrophy of 54%. The measurements were performed on a modified heart-lung preparation in which left-ventricular afterload could be adjusted arbitrarily. In the heart in situ, ...

The acute regional hemodynamic effects of spirapril diacid, a novel nonsulfhydryl angiotensin-converting enzyme inhibitor, and enalapril diacid at an equidepressor dose were examined in anesthetized dogs by simultaneously measuring renal, coronary, vertebral arterial and aortic blood flow. Spirapril diacid (30 micrograms/kg, i.v.) lowered aortic pressure and increased aortic and renal ...

This study examined the effect of pinacidil on the transmural distribution of myocardial blood flow in the chronically pressure overloaded hypertrophied left ventricle. Studies were performed in six dogs in which banding of the ascending aorta had resulted in an 88% increase in left ventricular mass, as well as in ...

The effects of low-dose (10(-9) and 3 x 10(-9) mole/kg/min) infusions of dopexamine HCl, a new synthetic catecholamine with beta 2-adrenergic and DA1-dopaminergic agonostic actions, was tested in anesthetized dogs, with and without acute ligation of the left anterior descending coronary artery. The infusions caused diastolic arterial blood pressure to ...

The objective of this study was to determine whether exposure to high altitude (hypoxic hypoxemia) induces coronary and/or collateral growth. Fourteen mongrel dogs were maintained at a simulated altitude of 18,000 ft for 1 mo and 7 dogs maintained for 3 mo. Within 2 days after their sojourn, the following ...

There is very clear evidence that active changes in the arterial wall contribute substantially to the pathophysiology, prognosis and treatment of hypertension. Reduced aortic compliance independently affects the blood pressure through an increase in systolic pressure and a decrease in diastolic pressure at any given mean arterial pressure. With the ...

The effects of stretch on coronary pressure-flow relations are not well understood. To examine the role of wall stretch per se on coronary hemodynamics, we studied arterially perfused isolated canine interventricular septa in a noncontracting state with vasodilated vessels. We compared the hemodynamic parameters of zero-flow pressure and resistance during ...

Vasoactive intestinal peptide (VIP) is a neurotransmitter that has been identified in epicardial coronary arteries. To evaluate the direct effect of VIP on coronary hemodynamics and blood flow, graded doses of VIP (0.01, 0.03, 0.10, and 0.30 micrograms/min) were infused into the left coronary artery of 7 patients at the ...

Reactive hyperaemia, the cardiovascular response to transient occlusion of a vessel, was examined and compared in the right coronary artery (RCA) and the left anterior descending coronary artery (LAD) in the same heart of an open-chest dog. First, to study the relationship between reactive hyperaemia and occlusion time in the ...

STUDY OBJECTIVE: The aim was to determine the site of coronary vasoconstriction induced by endothelin, by investigating the response in terms of retrograde pressure and reactive hyperaemia. EXPERIMENTAL MATERIAL: Twelve anaesthetised mongrel dogs, 12-14 kg, were used for the studies. DESIGN: The left anterior descending coronary artery was cannulated and ...

To identify patients with left ventricular ejection fractions less than 20% who are likely to survive on tailored medical therapy after referral to transplantation, this study of 152 patients addressed the hypotheses that (1) severely elevated filling pressures initially measured at referral would not necessarily predict poor outcome, (2) survival ...

Using implanted pulsed Doppler microprobes sutured on saphenous bypass grafts in ten patients we studied, 6 h after cardiac surgery, the effects of 5 and 10 micrograms.kg-1.min-1 of dobutamine on mean (Qm), systolic (Qs), and diastolic (Qd) coronary bypass graft flows, as well as on coronary systolic (integral of Qs) ...

The purpose of the present study was to examine subendocardial flow and function during graded coronary pressure reduction to determine the effect of tachycardia on the lower autoregulatory pressure limit (critical coronary pressure) in unanesthetized dogs. During atrial pacing at a rate of 200 beats/min, subendocardial flow measured by radioactive ...

Calcitonin gene-related peptide (CGRP) is a potent vasodilator, but its effects on in situ ventricular function are unknown. We studied effects of intracoronary CGRP (100, 200, and 600 pmole/min, for 10 min) in 21 open-chest chloralose-anesthetized dogs. Systemic, pulmonary, left ventricular (LVP), central venous, and pulmonary capillary wedge pressures were ...

To examine the balloon inflation pressures required for successful percutaneous transluminal coronary angioplasty (PTCA), the maximal inflation pressure required for 477 coronary lesions in 200 consecutive patients was determined retrospectively. When graded balloon inflations just sufficient to achieve full expansion were used, the maximal inflation pressure used was less than ...

Adenosine is a potent vasodilator used extensively to study the coronary circulation of animals. Its use in humans, however, has been hampered by lack of knowledge about its effects on the human coronary circulation and by concern about its safety. We investigated in humans the effects of adenosine, administered by ...

Pulmonary hypertension causes right ventricular ischemia and failure as a result of increased afterload combined with reduced coronary blood flow. Increasing coronary driving pressure by raising aortic pressure with phenylephrine has been shown to reverse right ventricular ischemia from pulmonary hypertension in animals. Since vasodilators often fail to reduce afterload, ...

Endothelin, a recently described endothelial cell-derived peptide, produces pulmonary and coronary vasoconstriction in mature animals. We investigated the acute hemodynamic effects of porcine endothelin in 14 anesthetized open-chest new-born piglets during normoxia (Pao2 = 102 +/- 5 mmHg) and hypoxia (fractional inspired O2 concentration = 0.12 X 15 min, Pao2 ...

The aim of the present study was to determine if the relationship between myocardial O2 supply and O2 consumption was preserved after prolonged pressure overload due to aortic valve stenosis. This was examined in anesthetized open-chest dogs in which the aortic valve was plicated 6 months previously. We measured coronary ...

Distal intracoronary infusion of the perfluorochemical Fluosol-DA 20% has been shown to prevent systolic dysfunction during coronary artery balloon occlusion in coronary angioplasty. To assess its effect on global diastolic dysfunction, a randomized, single-blind, crossover protocol comparing intracoronary infusion of Fluosol or no infusion (control) was performed during 60 s ...

alpha-Adrenoceptor-mediated coronary vasoconstriction contributes to the initiation and aggravation of experimental and clinical myocardial ischaemia. However, the extent of alpha 1- and alpha 2-adrenoceptor-mediated constriction has not been characterized in the porcine coronary circulation despite the frequent use of this experimental model. Fifteen swine were anaesthetized with either alpha-chloralose, enflurane ...