Search results for "Heart Atria"
showing 8 items of 78 documents
Adenosine activates a potassium conductance in guinea-pig atrial heart muscle.
1983
Adenosine shortens the action potential and diminishes the force of contraction in guinea-pig left atria. These effects may be brought about by the activation of a potassium conductance. This assumption is supported by voltage clamp and 42K release experiments.
Stimulatory effects of DB-c-AMP and adrenaline on myocardial contraction and 45Ca exchange. Experiments at reduced calcium concentration and low freq…
1973
The effects of adrenaline (2.2×10−6 M) and cyclic N6-2′-O-dibutyryl-adenosine-3′,5′-monophosphate (DB-c-AMP; 10−3 M) on mechanical performance, 45Ca uptake and total tissue calcium concentration were investigated in electrically stimulated left auricles isolated from female rats weighing 180–220 g. The experiments were performed at reduced [Ca]e of 0.45 mM and at various frequencies of stimulation (0–120 beats/min). In the first series of experiments 45Ca incubation time was 5 min. Under these conditions DB-c-AMP as well as adrenaline enhanced contractile force to 300–450% of the control values at all frequencies tested (Fig.1). This increase in contractile force was accompanied by a signif…
Effects of inhibitors of cGMP-dependent protein kinase in atrial heart and aortic smooth muscle from rats
1995
Several activators of cGMP-dependent protein kinase (protein kinase G) such as 8-Br-cGMP reduced force of contraction in rat left atria. Inhibitors of protein kinase G antagonized the negative inotropic effect of 8-Br-cGMP but not of acetylcholine in atria. However, the acetylcholine-induced relaxation in aortic rings was significantly inhibited by protein kinase G inhibition. It is concluded that the reduction by 8-Br-cGMP of force of contraction in atria is related to activation of protein kinase G. In response to acetylcholine, activation of protein kinase G is probably a major step in smooth muscle relaxation but is not involved in the reduction of force of contraction in atria.
Tetrodotoxin slightly shortens action potential duration in ventricular but not in atrial heart muscle.
1988
Tetrodotoxin (TTX), at concentrations significantly decreasing maximal upstroke velocity (dV/dtmax) of the action potential, exerted variable effects on action potential duration (APD) in different myocardial preparations. APD was virtually unchanged by tetrodotoxin in the guinea pig atrium, but slightly shortened in the guinea pig ventricle at maximally effective concentrations. In the human ventricle, both dV/dtmax and APD were reduced in the same concentration range of TTX. These results suggest that a TTX-sensitive sodium current significantly contributes to the repolarization phase of the action potential in ventricular but not in atrial heart muscle.
Giant left atrium: a condition that is rarely seen today.
2008
Today, giant left atrium is a condition that is rarely observed in clinical practice and diagnosis can be missed. It is prevalent in patients with rheumatic heart disease that has decreased considerably in industrialized countries in the last two decades. However, the immigration flow in the current era can revive its incidence.
Separation of left atrium from right pulmonary artery: a new echocardiographic sign of pericardial effusion.
1981
We report a new echocardiographic sign of pericardial effusion in patients with pericardial effusion examined by the suprasternal approach. In normal individuals the right pulmonary artery is closely connected with the superior wall of the left atrium. A separation of these structures is only to be noticed during atrial contraction. In 12 of 17 patients with a pericardial effusion observed a separation of the left atrium from the right pulmonary artery ranging from 3 to 20 mm throughout the cardial cycle. We suggest that this echo-free zone represents fluid in the transverse pericardial sinus which is located between the two structures. In five patients with a small pericardial effusion (le…
Three-dimensional transesophageal echocardiography in the guide of cardiac mass biopsy
2017
Cardiac tumors are rare. Cardiovascular imaging is more important in the differential diagnosis of cardiac masses but no current noninvasive diagnostic tool has the ability to absolutely diagnose cardiac tumors. In effect cardiac biopsy remains the gold standard in the differential diagnosis. In our case we show the advantages of three-dimensional (3D) transesophageal echocardiography as a guide for cardiac biopsy. We believe that 3D TEE is ready to be used in the guide of cardiac mass biopsy. Once interventionalists become confident with 3D imaging, this technique should be used routinely during these procedures.
Re-interpreting complex atrial tachycardia maps using global atrial vectors.
2021
Activation maps of scar-related atrial tachycardias (AT) can be challenging to interpret due to difficulty in inaccurate annotation of electrograms, and an arbitrarily predefined mapping window. A novel mapping software integrating vector data and applying an algorithmic solution taking into consideration global activation pattern has been recently described (Coherent™, Biosense Webster "Investigational").We aimed to assess the investigational algorithm to determine the mechanism of AT compared with the standard algorithm.This study included patients who underwent ablation of scar-related AT using the Carto 3 and the standard activation algorithm. The mapping data were analyzed retrospectiv…