			Home About us Contact

Atrial Myocardium (atrial + myocardium)

Distribution by Scientific Domains

Medical Sciences	71%
Life Sciences	28%

Selected Abstracts

Myocardial Connections Between Left Atrial Myocardium and Coronary Sinus Musculature in Man

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2001
ATSUNOBU KASAI M.D.
Connections Between LA Myocardium and CS Musculature.Introduction: Anatomic studies have shown that muscle morphologically identical to that of the atrial myocardium consistently surrounds the coronary sinus (CS). The CS musculature is connected to the left atrial (LA) myocardium in a variable fashion, with fewer connections in its distal portion. The aim of this study was to document the presence of connections between the LA myocardium and the CS musculature, using pacing maneuvers in man, and to study their potential association with natural atrial arrhythmia occurrence. Methods and Results: Thirty patients (19 men; mean age 50.5 years) underwent electrophysiologic study, during which a decapolar catheter with 2-mm interelectrode spacing every 10 mm was inserted into the CS, with the proximal electrode pair positioned at the ostium. Associated atrial arrhythmias were paroxysmal atrial fibrillation in 5, typical atrial flutter in 13, LA flutter in 1, and other in 11. Baseline S1 and a single extrastimulus were delivered during distal and proximal CS pacing, while recordings were obtained from the four remaining bipoles. During distal CS pacing, double potentials with increasing interpotential interval from proximal to distal CS as a function of extrastimulus prematurity were detected in nine patients, suggesting block in a discrete local pathway distally connecting the CS to the LA and leading to reversion of low LA activation. Local delay in this pathway without complete CS-LA block resulting in LA activation fusion was observed in eight patients. A single nonfractionated potential at the distal CS, even at the shortest attainable S1-S2 coupling interval, which was interpreted as no block within distal CS-LA connection(s), was observed in the other 13 patients. History of atrial fibrillation or atypical atrial flutter was found in 8 of 9 patients with block at the distal CS-LA connection but in only 3 of 13 patients with no CS-LA connection block (P = 0.004). Conclusion: The ability to dissociate the LA from the distal CS suggests the presence of discrete connections between these structures in man. This observation appears to be associated with the clinical occurrence of atrial arrhythmias. [source]

The developing embryonic cardiac outflow tract is highly sensitive to oxidant stress

DEVELOPMENTAL DYNAMICS, Issue 12 2007
Steven A. Fisher
Abstract This study tested the hypothesis that the remodeling of the cardiac outflow tract (OFT) may represent a developmental window of vulnerability to reactive oxygen species (ROS). Chick embryos were exposed in ovo or ex ovo to increasing concentrations of the stable oxidant hydrogen peroxide (H2O2). As assessed by trypan blue staining, H2O2 induced cell injury in the stage 25,30 OFT at concentrations as low as 1 nM. Higher concentrations were required to induce cell injury in the ventricular and atrial myocardium. Using DCFDA as an indicator of oxidant stress, H2O2 also induced a greater fluorescent signal in the OFT myocardium. H2O2 at these low concentrations also induced Caspase activity, indicative of activation of the pathway of PCD. Interestingly, the induction of Caspase-3 activity was predominately in the OFT cushion mesenchymal cells. Thus, the developing OFT is particularly sensitive to ROS-mediated injury, suggesting that ROS could play a role in the development of congenital defects of the cardiac OFT. Developmental Dynamics 236:3496,3502, 2007. © 2007 Wiley-Liss, Inc. [source]

High-Density Mapping of Left Atrial Endocardial Activation During Sinus Rhythm and Coronary Sinus Pacing in Patients with Paroxysmal Atrial Fibrillation

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2004
TIMOTHY R. BETTS M.D.
Introduction: This study was designed to record global high-density maps of left atrial endocardial activation during sinus rhythm and coronary sinus pacing. Method and Results: Noncontact mapping of the left atrium was performed in nine patients with paroxysmal atrial fibrillation undergoing pulmonary vein ablation procedures. High-density isopotential and isochronal activation maps were superimposed on three-dimensional reconstructions of left atrial geometry. Mapping was repeated during pacing from sites within the coronary sinus. Earliest left atrial endocardial activation occurred anterior to the right pulmonary veins in seven patients and on the anterosuperior septum in two patients. A line of conduction block was seen in the posterior wall and inferior septum in all patients. The direction of activation in the left atrial myocardium overlying the coronary sinus was different from the electrogram sequence in the coronary sinus catheter in 6 of 9 patients. During coronary sinus pacing, activation entered the left atrium a mean (SD) of 41 (13) ms after the pacing stimulus at a site 12 (10) mm from the endocardium overlying the pacing electrode. Lines of conduction block were present in the posterior wall and inferior septum. Conclusion: In patients with paroxysmal atrial fibrillation, lines of conduction block are present in the left atrium during sinus rhythm and coronary sinus pacing. Electrograms recorded in the coronary sinus infrequently correspond to the direction of activation in the overlying left atrial myocardium. [source]

Myocardial Connections Between Left Atrial Myocardium and Coronary Sinus Musculature in Man

Identification of ,- and ,-opioid receptors as potential targets to regulate parasympathetic, sympathetic, and sensory neurons within rat intracardiac ganglia

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 18 2010
Shaaban A. Mousa
Abstract Recent interest has been focused on the opioid regulation of heart performance; however, specific allocation of opioid receptors to the parasympathetic, sympathetic, and sensory innervations of the heart is scarce. Therefore, the present study aimed to characterize such specific target sites for opioids in intracardiac ganglia, which act as a complex network for the integration of the heart's neuronal in- and output. Tissue samples from rat heart atria were subjected to RT-PCR, Western blot, radioligand-binding, and double immunofluorescence confocal analysis of , (M)- and , (K)-opioid receptors (ORs) with the neuronal markers vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), and substance P (SP). Our results demonstrated MOR- and KOR-specific mRNA, receptor protein, and selective membrane ligand binding. By using immunofluorescence confocal microscopy, MOR and KOR immunoreactivity were colocalized with VAChT in large-diameter parasympathetic principal neurons, with TH-immunoreactive small intensely fluorescent (SIF) cells, and on nearby TH-IR varicose terminals. In addition, MOR and KOR immunoreactivity were identified on CGRP- and SP-IR sensory neurons throughout intracardiac ganglia and atrial myocardium. Our findings show that MOR and KOR are expressed as mRNA and translated into specific receptor proteins on cardiac parasympathetic, sympathetic, and sensory neurons as potential binding sites for opioids. Thus, they may well play a role within the complex network for the integration of the heart's neuronal in- and output. J. Comp. Neurol. 518:3836,3847, 2010. © 2010 Wiley-Liss, Inc. [source]

Evaluation of the Relationship between Atrial Septal Aneurysm and Cardiac Arrhythmias via P-Wave Dispersion and Signal-Averaged P-Wave Duration

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2010
Onur Sinan Deveci M.D.
Objective: The aim of the study was to investigate the relationship between atrial septal aneurysms (ASAs) and cardiac arrhythmias via signal-averaged P-wave duration (SAPWD) and P-wave dispersion (Pd). Methods: Sixty-six patients with ASA served as the study group (group 1; 28 men and 38 women; mean age, 34 ± 10 years) and 62 healthy volunteers served as the control group (group 2; 29 men and 33 women; mean age, 31 ± 8 years) in the current study. ASAs were diagnosed by transthoracic echocardiography based on the criteria of a minimal aneurysmal base of ,15 mm; and an excursion of ,10 mm. All subjects were evaluated by 24-hour Holter monitoring, 12 lead body surface electrocardiogram for P-wave analysis, and signal-averaged electrocardiogram for P-wave duration (PWD). Results: There was no significant difference between the study and control groups in terms of age, gender, left atrium diameter, and left ventricular ejection fraction. Supraventricular arrhythmias (SVAs) were detected in 29 patients with ASA (43.9%) and 5 controls (8.1%; P < 0.001). The mean Pd in patients with ASA was significantly longer compared to the control group (14.1 ± 8 ms vs 7.0 ± 2.9 ms; P < 0.001). Similarly, the mean SAPWD in group 1 was significantly longer compared to group 2 (127.4 ± 17.6 ms vs 99.8 ± 12.3 ms; P < 0.001). Conclusion: Prolonged SAPWD and Pd were determined to indicate electrical disturbances in the atrial myocardium, and predict the increase in the prevalence of SVA in patients with ASA. Ann Noninvasive Electrocardiol 2010;15(2):157,164 [source]

Update on Atrial Fibrillation: Part I

CLINICAL CARDIOLOGY, Issue 2 2008
Irina Savelieva M.D.
Abstract Atrial fibrillation (AF) is an epidemic, affecting 1% to 1.5% of the population in the developed world. Projected data from the population-based studies suggest that the prevalence of AF will grow at least 3-fold by 2050. The health and economic burden imposed by AF and AF-related morbidity is enormous. Atrial fibrillation has a multiplicity of causes ranging from genetic to degenerative, but hypertension and heart failure are the commonest and epidemiologically most prevalent conditions associated with AF as both have been shown to create an arrhythmogenic substrate. Several theories emerged regarding the mechanism of AF, which can be combined into two groups: the single focus hypothesis and the multiple sources hypothesis. Several lines of evidence point to the relevance of both hypotheses to the mechanism of AF, probably with a different degree of involvement depending on the variety of AF (paroxysmal or persistent). Sustained AF alters electrophysiological and structural properties of the atrial myocardium such that the atria become more susceptible to the initiation and maintenance of the arrhythmia, a process known as atrial remodeling. Angiotensin II has been recognized as a key element in atrial remodeling in association with AF opening the possibility of exploitation of "upstream" therapies to prevent or delay atrial remodeling. The clinical significance of AF lies predominantly in a 5-fold increased risk of stroke. The limitations of warfarin prompted the development of new antithrombotic drugs, which include anticoagulants, such as direct oral thrombin inhibitors (dabigatran) and factor Xa inhibitors (rivaroxaban, apixaban). Novel mechanical approaches for the prevention of cardioembolic stroke have recently been evaluated: percutaneous left atrial appendage occluders, minimally invasive surgical isolation of the left atrial appendage, and implantation of carotid filtering devices. Copyright © 2008 Wiley Periodicals, Inc. [source]