Contractile function of human veins after long-term storage in different media.

We wished to determine the preservation of contractile function of human saphenous veins during long-term storage (36 and 96 h) at low temperatures in different solutions. Two crystalloid solutions (Krebs-Henseleit and Bretschneider's cardioplegic solution), as well as heparinized blood and albumin solution as used in cardiac surgery were compared. Contractile function of human saphenous vein ring segments was tested in a vessel myograph.

Age-related changes in vascular reactivity in genetically diabetic rats.

A long-term study to identify age-dependent alterations in vascular reactivity in obese Zucker rats, a model for non-insulin-dependent diabetes mellitus, was carried out. On aortic rings of 12-week-old obese Zucker rats, but not in older animals (36 and 52 weeks), the following different effects in comparison to the lean rat control group were observed: (i) a significantly enhanced maximal relaxation to acetylcholine and A23187, which was abolished by the nitric oxide-synthase inhibitor L-nitro-arginine methyl ester (L-NAME); relaxation of aortic rings to the endothelium-independent vasodilator nitroglycerin was similar; (ii) more pronounced maximal 5-hydroxytryptamine-induced-contractions in the presence of L-NAME, and (iii) a more pronounced reduction in phenylephrine-induced contractions by verapamil. These results are suggestive of an altered calcium metabolism in the first weeks of development in the obese rat strain, which is probably responsible for the hypotension seen in this early time period.

Frequency-dependent effects of amitriptyline and maprotiline on conduction in the guinea pig His-Purkinje-system in vivo.

In the Cardiac Arrhythmia Suppression Trial antiarrhythmic drug therapy with slow kinetic sodium channel blockers (class Ic antiarrhythmic drugs) was associated with excess mortality, presumably due to drug induced proarrhythmia. It has been suggested that the degree of rate-dependent conduction slowing produced by agents that have sodium channel blocking properties may be related to the proarrhythmic propensity of these agents. In the present study, rate-dependent conduction slowing by the antidepressants amitriptyline and maprotiline was investigated in anesthetized guinea pigs.

Prolongation of the QT interval by dofetilide modulates rate-dependent effects of mexiletine on intraventricular conduction.

Prolongation of action potential duration during treatment with agents that possess class I antiarrhythmic activity may result in a clinically relevant increase in Na+ channel block. In order to test this hypothesis in vivo, the effect of QT prolongation on intraventricular conduction was assessed during administration of mexiletine. Epicardial His bundle recordings were made in anesthetized guinea pigs.

Simultaneous assessment of cardiac output with pulsed Doppler and electromagnetic flowmeters during cardiac stimulation.

The aim of this study was to test the accuracy of cardiac output assessment by Doppler and electromagnetic flowmetry in dogs during states of (1) marked enhancement in cardiac output, which was obtained by means of either isoprenaline infusion or treadmill exercise, or (2) reduction in cardiac output obtained by administration of phenylephrine. Additionally, in vitro comparisons were undertaken between Doppler and electromagnetic flow-probes and assessment of flow by direct volumetric measurement. These in vitro experiments showed a good correlation between timed volume collections and electromagnetic flow assessment up to high flow velocities.

Kinetics of rate-dependent slowing of intraventricular conduction by the class Ib antiarrhythmic agent tocainide in vivo.

1. The effects of the class I antiarrhythmic agent, tocainide, on intraventricular conduction were assessed in guinea-pigs, anaesthetized with pentobarbitone sodium 60 mg kg-1, i.p.

Effect of ajmaline on sustained ventricular tachycardia induced by programmed electrical stimulation in conscious dogs after myocardial infarction.

As yet the antiarrhythmic efficacy of ajmaline with regard to suppressing the induction of sustained ventricular tachycardia after myocardial infarction has not been determined. Therefore, programmed electrical stimulation was performed in 8 conscious, chronically instrumented mongrel dogs 8-20 days after a 4-hour occlusion of the left anterior descending coronary artery. At baseline all animals responded with sustained ventricular tachycardia.

Distribution and metabolism of NG-nitro-L-arginine and NG-nitro-L-arginine methylester in canine blood in vitro.

The aim of the present study was to investigate the metabolism of the two NO-synthase inhibitors NG-nitro-L-arginine (L-NA) and NG-nitro-L-arginine methylester (L-NAME) in canine blood in vitro. Blood and plasma samples were incubated with L-NAME or L-NA respectively and the drug levels were determined in blood, plasma and blood cells by means of high performance liquid chromatography. Incubation of blood or plasma with L-NAME revealed that L-NAME is metabolized to L-NA in blood and plasma.

Blockade of endothelium-derived relaxing factor synthesis with NG-nitro-L-arginine methyl ester leads to enhanced venous reactivity in vivo.

This study was performed to examine whether endothelium-derived relaxing factor (EDRF) influences venous tone and reactivity in vivo. The inferior vena cava and abdominal aorta were studied simultaneously under continuous haemodynamic monitoring in anaesthetised rabbits. In addition, a 20-MHz intravascular ultrasound catheter was placed in the vena cava for on-line two-dimensional imaging of vessel cross-sectional area and calculation of wall stress (T(ension) = P(mean) * r(adius)/2).

Assessment of changes in vasomotor tone in vivo using intravascular ultrasound.

This study tested the capability of high-frequency, two-dimensional real-time intravascular ultrasound (IVUS) in the detection of dynamic changes of large vessel diameter in vivo. An IVUS-catheter (4.8 French, 20-MHz mechanical transducer) was inserted via the femoral vein, and advanced to the inferior vena cava of anesthetized rabbits (n = 7).

Oral N(G)-nitro-L-arginine in conscious dogs: 24 hour hypertensive response in relation to plasma levels.

Haemodynamic changes after oral administration of 30 mg/kg N(G)-nitro-L-arginine (L-NNA) were studied in conscious chronically instrumented mongrel dogs throughout a 24 h observation period in order to evaluate the long-term efficacy of L-NNA-induced inhibition of endothelium-dependent relaxation and its relation to plasma L-NNA level. Diastolic blood pressure remained elevated for the entire 24 h observation period, but systolic blood pressure was raised only up to the 6 h value. The hypertensive response was accompanied by bradycardia.

Catecholamine excretion and heart rate as factors of psychophysical stress in table tennis.

Table tennis, like tennis, squash and badminton, is a racket sport. All these sports have in common a rapid succession of mostly short-term maximal or submaximal efforts and short recovery phases. The goal of this paper is to investigate the psychophysical stress in table tennis by means of the stress hormones epinephrine and norepinephrine.

Mode of QT correction for heart rate: implications for the detection of inhomogeneous repolarization after myocardial infarction.

In 22 conscious, chronically instrumented dogs, the relationship between R-R interval and QT interval was better explained by linear regression than by nonlinear regression according to Bazett's formula. The correction formula QTL = QT-0.1*(RR-1000), which is based on the assumption of a linear relationship between QT and R-R interval, was then compared with Bazett's formula regarding its capability to detect inhomogeneous repolarization 5 to 7 days after temporary occlusion of the left anterior descending coronary artery.

Lidocaine has a narrow antiarrhythmic dose range against ventricular arrhythmias induced by programmed electrical stimulation in conscious postinfarction dogs.

The aim of the present study was to investigate the dose-dependent antiarrhythmic efficacy of lidocaine against electrically induced tachycardias in conscious, chronically instrumented postinfarction dogs. Programmed electrical stimulation (PES) was performed in 16 dogs 8 to 21 days after a 4 h occlusion of the left anterior descending coronary artery (LAD). Infusion of saline in 8 control animals with sustained ventricular tachycardia (SVT) inducible at baseline did not affect subsequent inducibility.

Influence of alpha 1-adrenoceptor blockade and/or 5-HT1A agonism on blood pressure and heart rate at rest and during exercise in hypertensive dogs.

1. Antihypertensive effects resulting from alpha 1-adrenoceptor blockade and stimulation of central nervous 5-HT1A receptors were compared with the effects arising from stimulation of 5-HT1A receptors alone during arterial hypertension. 2.

Epicardial His bundle recordings in the guinea pig in vivo.

In small animals, His bundle activity is commonly registered using intracavitary electrodes in Langendorff-perfused hearts. The present study evaluates the feasibility of epicardial registration of His bundle activity in 30 guinea pigs in vivo, anesthetized with 60 mg/kg sodium pentobarbital i.p.

Efficacy of verapamil against ventricular arrhythmias induced by programmed electrical stimulation in the late myocardial infarction phase in dogs.

The aim of the present study was to investigate the antiarrhythmic potential of verapamil in the late myocardial infarction period in conscious dogs. Verapamil was administered in cumulative doses (0.3 + 0.

Mechanism of antiarrhythmic efficacy of propafenone as assessed by programmed electrical stimulation in conscious dogs.

Programmed electrical stimulation (PES) was performed in 18 conscious, chronically instrumented mongrel dogs 6-21 days after a 4-h occlusion of the left anterior descending coronary artery (LAD). At baseline, 8 of 10 animals responded with sustained ventricular tachycardia (SVT) and 2 of 10 responded with ventricular fibrillation (VF). Cumulative administration of 2 and 4 mg/kg propafenone intravenously (i.

Cardiovascular and side effects of flesinoxan in conscious hypertensive dogs. Modulation by prazosin.

Previous studies on anaesthetized animals indicate that flesinoxan exerts hypotensive effects via stimulation of central 5-HT1A receptors. The purpose of the present study was to investigate the cardiovascular and side effects of flesinoxan in conscious, renal hypertensive dogs at rest and during exercise. Animals were pretreated with prazosin (2.

Ventricular arrhythmias after reperfusion: is there a correlation with infarct size?

The aim of this investigation was to examine whether any correlation exists between enzymatically estimated infarct size and arrhythmias arising in response to coronary reperfusion. Four hour occlusion of the left anterior coronary artery followed by reperfusion was carried out in conscious dogs. Serum creatine phosphokinase (CPK) analysis and planimetric determination of infarct size were performed.

Effects of beta-adrenoceptor antagonism upon delayed reperfusion arrhythmias in conscious dogs.

Whereas isolated heart preparations or anesthetized animals have been used to assess the actions of beta-adrenoceptor antagonists upon reperfusion-induced arrhythmias, this study evaluated the possible antiarrhythmic effects of beta-adrenoceptor antagonism in conscious animals. Conscious, chronically instrumented dogs were subjected to a temporary occlusion of the left anterior descending coronary artery for 4 h. After the first hour of reperfusion, flestolol (N-(1,1-dimethyl-2- ureidoethyl)-2-hydroxy-3-(O-fluorobenzoyloxy)-propylamine sulfate), an ultra short-acting beta-adrenoceptor antagonist, was administered i.

Alpha 1-adrenoceptor blockade and/or 5-HT1A agonism during treadmill exercise in dogs.

1. The hypotensive effects of alpha 1-adrenergic blockade and/or stimulation of central nervous 5-HT1A receptors were studied using drugs with different affinity for central nervous 5-HT1A and peripheral alpha 1-adrenoceptors. Urapidil, 5-methylurapidil, flesinoxan and 8-OH-DPAT were compared under states of different activation of the autonomic nervous system, i.