Assessment of myocardial postreperfusion viability by intravenous myocardial contrast echocardiography: analysis of the intensity and texture of opacification.

Background: Although defects on intracoronary myocardial contrast echocardiography (MCE) indicate loss of viability after reperfusion, opacified segments may also exhibit persistent dyssynergy. Therefore, we related the intensity and texture of opacification produced by an intravenous contrast agent to histological findings to determine the characteristics of necrotic tissue by postreperfusion MCE.

Methods And Results: MCE was performed by intravenous injection of 0.

Quantitative assessment of myocardial perfusion during graded coronary artery stenoses by intravenous myocardial contrast echocardiography.

Objectives: The purpose of this study was to examine whether coronary stenoses of variable severity could be quantitatively assessed by analysis of myocardial perfusion as determined by intravenous (IV) myocardial contrast echocardiography.

Background: Recently, new contrast agents and imaging technology have been developed that may enable improved assessment of myocardial perfusion by IV contrast injection.

Methods: Variable obstruction of the left anterior descending (LAD) coronary artery in dogs was produced by a screw occluder.

Persistence of Atrial Fibrillation After Its Induction-Importance of the Duration and Dispersion of Atrial Refractoriness and Electrical Remodeling.

BACKGROUND: The electrophysiologic mechanisms of the persistence of atrial fibrillation (AF) after its initiation are not well understood. Therefore, the electrophysiologic characteristics of the right atrium were evaluated in an acute, pacing-induced model of AF in the pig in order to identify parameters associated with persistence of AF. METHODS AND RESULTS: AF was induced by rapid atrial pacing in 30 anesthetized, open-chest, juvenile pigs.

Electrophysiological and antiarrhythmic effects of the atrial selective 5-HT(4) receptor antagonist RS-100302 in experimental atrial flutter and fibrillation.

Background: Stimulation of 5-HT(4) receptors increases atrial chronotropic and inotropic responses. Whether other electrophysiological effects are produced is unknown. In humans and swine, 5-HT(4) receptors are present only in atrium.

Atrial systolic pressure, as well as stretch, is a principal stimulus for release of ANF.

The mechanism for increased secretion of atrial natriuretic factor (ANF) during tachycardia and atrial fibrillation has remained unsettled. In seven open-chest pigs, the plasma concentration of ANF increased from 49.8 +/- 12.

Atrial contractile dysfunction after short-term atrial fibrillation is reduced by verapamil but increased by BAY K8644.

Background: Reduced atrial contractility occurs after cessation of atrial fibrillation. Its mechanism is unknown, and no pharmacological treatment exists. It has been hypothesized that this atrial contractile dysfunction results from intracellular calcium overload due to rapid depolarizations during fibrillation.

Cardiac contractile function following repetitive brief ischemia: effects of nucleoside transport inhibition.

The effects of nucleoside transport inhibition on cardiac contractile function were examined in anesthetized pigs subjected to five 6-min left anterior descending coronary artery (LAD) occlusions, separated by 20-min reperfusion, and followed by 150-min reperfusion. In group 1 (n = 8), saline was infused. In group 2 (n = 9), endogenous myocardial accumulation of adenosine was increased by intracoronary infusion of the specific nucleoside transport inhibitor R-75 231.

Significance of increased atrial pressure on stroke volume during atrial fibrillation in anaesthetized pigs.

During atrial fibrillation synchronized atrial contraction is lost and cardiac output declines. Concomitantly, atrial pressure increases. The significance of the increase in atrial pressure on stroke volume was examined before and after blood volume expansion.

Effects of atrial fibrillation on left and right atrial dimensions, pressures, and compliances.

The effects of atrial fibrillation on left and right atrial dimensions, pressures, and compliances were examined in two groups of seven barbiturate-anesthetized open-chest pigs. Atrial diameters and pressures were recorded during atrioventricular (AV) pace and thereafter during atrial fibrillation. Both rhythms were studied with constant ventricular rate after complete AV block.

Atrial contractile performance after cessation of atrial fibrillation.

Atrial fibrillation is associated with a fall in cardiac output, and cardioversion to sinus rhythm is frequently attempted. After cardioversion, atrial contractile performance might be depressed. It is, however, unclear whether or not atrial contractile performance is altered following atrial fibrillation periods lasting < 1 wk.

Right and left atrial diameters during incremental atrial pacing in pigs.

The relationship between right and left atrial diameters and heart rate was examined in 14 open-chest barbiturate-anesthetized pigs by an ultrasonic technique. The maximal atrial diameter was read at the top of the v wave, which decreased in both atria when heart rate was increased from 124 (118-130) to 159 (156-160) (median and 95% confidence interval) beats/min. Right and left atrial maximal diameter fell significantly from 25.