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Atrial Tissue (atrial + tissue)
Selected AbstractsGiant Right Atrial Diverticulum in an AdultJOURNAL OF CARDIAC SURGERY, Issue 1 2010Xin Chen M.D. Examination of resected atrial tissue showed extreme wall thinning, central aneurysmal formation, and focal endocardial fibrosis consistent with idiopathic dilatation of the right atrium. It is unclear what the best treatment of right atrial diverticulum are, nor are the risks of thromboembolism, arrhythmia, and rupture of the diverticulum clearly defined, either for patients as a whole or for symptomatic or asymptomatic subgroups. However, to reduce the risk of sudden death we recommend surgical resection of large diverticula.(J Card Surg 2010;25:40-42) [source] Cardiac Hemangioma of the Left Atrial Appendag: A Case Report and DiscussionJOURNAL OF CARDIAC SURGERY, Issue 5 2009Bruno Chiappini M.D., Ph.D. In contrast to myxoma, hemangioma rarely involves left atrial tissue in adults and little information about the tumor is available. We encountered a 65-year-old woman with a left atrial hemangioma arising in the appendage and growing like an extracardiac mass. The tumor was removed from the left atrium with all the left appendage under cardiopulmonary bypass. Histopathological examination revealed that it was a cavernous-type hemangioma. Among the five described cases, this case was the only one in which the tumor arose from the appendage and grew into the pericardial cavity with resultant paroxystic atrial fibrillation. [source] Apoptosis and Cardiopulmonary BypassJOURNAL OF CARDIAC SURGERY, Issue 2 2007M.S., Miljenko Kova Apoptotic index (AI) obtained with in situ terminal deoxynucleotidyl transferase-labeled dUTP nick end labeling (TUNEL) method and Bak protein expression were compared. Patients and Methods: Twenty consecutive patients who underwent coronary artery bypass surgery, myocardial samples from the right atrium were taken in three stages: before cannulation (the first sample group), after declamping (the second sample group), and 20 minutes after reperfusion (the third sample group). The percentage of apoptotic cells was determined by TUNEL method. Expression of Bak protein was immunohistochemically analyzed. Intermittent ischemia and moderate hypothermia were used as methods of myocardial management during surgery. A statistical analysis was performed by using the Friedman ANOVA analysis of variances, the Kendall coefficient of concordance and the Wilcoxon matched pair test. Results: In the first sample group mean value of Bak expression was 2.61 ± 2.18, compared with AI 5.38 ± 3.58, after declamping (the second sample group) the mean value of Bak expression was 4.31 ± 2.68 while AI was 7.63 ± 4.38 and after 20 minutes of reperfusion in the third sample group mean value of Bak expression was 8.89 ± 4.45, while AI was 15.6 ± 8.45. When compared by using Wilcoxon matched pair test two methods significantly correlated, p > 0.0001. Conclusion: The positive correlation between AI obtained by TUNEL method and expression of Bak protein may suggest that apoptosis is activated mainly through mitochondrial activation pathway in ischemic reperfusion injury. The results suggest that ischemic reperfusion injury increases the AI in the right atrial tissue. If so, immunohistochemical expression of Bak protein could be used as a marker of myocardial ischemia induced injury. [source] Esophageal Temperature During Radiofrequency-Catheter Ablation of Left Atrium: A Three-Dimensional Computer Modeling StudyJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2006FERNANDO HORNERO M.D., Ph.D. Introduction: There is current interest in finding a way to minimize thermal injury in the esophagus during radiofrequency-catheter ablation of the left atrium. Despite the fact that the esophageal temperature is now being monitored during ablation, the influence of different anatomic and technical factors on the temperature rise remains unknown. Methods and Results: We implemented a three-dimensional computational model that included atrial tissue, epicardial fat, esophagus, aorta, and lung, all linked by connective tissue. The finite-element method was used to calculate the esophageal temperature distribution during a procedure of constant-temperature ablation with an 8-mm electrode, under different tissue conditions. Results showed that the distance between electrode and esophagus was the most important anatomic factor in predicting the esophageal temperature rise, the composition of the different tissues being of lesser importance. The measurement of the esophageal temperature in different sites of the lumen offered differences up to 3.7°C, especially for a short electrode,esophagus distance (5 mm). The difference in the convective cooling by circulating blood around electrode and endocardium did not show a significant influence on the esophageal temperature rise. Conclusion: Computer results suggest that (1) the electrode,esophagus distance is the most important anatomic factor; (2) the incorrect positioning of an esophageal temperature probe could give a low reading for the maximum temperature reached in the esophagus; and (3) the different cooling effect of the circulating blood flow at different atrial sites has little impact on the esophageal temperature rise. [source] Dietary Fish Oil Protects Against Stretch-Induced Vulnerability to Atrial Fibrillation in a Rabbit ModelJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2005DANIEL M. NINIO M.B.B.S. Introduction: Dietary fish oil is thought to reduce sudden cardiac death by suppressing ventricular arrhythmias but little is known about its impact on atrial arrhythmias. We examined the effect of dietary fish oil on the rabbit model of stretch-induced vulnerability to atrial fibrillation (AF). Methods and Results: Six-week-old rabbits were fed standard rabbit pellets supplemented with 5% tuna fish oil (n = 6) or supplemented with 5% sunflower oil (n = 6) for 12 weeks. Six rabbits raised on the standard diet were used as controls. In Langendorff-perfused hearts intraatrial pressures were increased in a stepwise manner and rapid burst pacing applied to induce AF at increasing intraatrial pressures until AF was sustained (>1 minute). Atrial refractory periods were recorded at each pressure. Increased atrial pressure resulted in a reduction in atrial refractory period and a propensity for induction of sustained AF. Higher pressures were needed to induce and sustain AF in the fish oil group compared with the sunflower oil and control groups. The stretch-induced drop in refractory period was also less marked in the fish oil group. Red blood cell, atrial, and ventricular omega-3 fatty acid levels were significantly higher in the fish oil group. The ratio of atrial n-6/n-3 polyunsaturated fatty acids was 13 ± 0.9 with sunflower oil and 1.5 ± 0.01 with fish oil (P < 0.001). Conclusions: Incorporation of dietary omega-3 fatty acids into atrial tissue reduces stretch-induced susceptibility to AF. [source] Novel Imaging Techniques of the Esophagus Enhancing Safety of Left Atrial AblationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2005SCOTT J. POLLAK M.D. This report describes different imaging techniques of the esophagus in four patients during radiofrequency catheter ablation of atrial fibrillation in the left atrium. A novel use of a mixture of barium cream and gadolinium diglutamate allowed esophageal imaging during magnetic resonance angiography of the left atrium and pulmonary veins. Barium cream used during computer tomography angiographic imaging of the left atrium and pulmonary veins allowed esophageal imaging. The esophagus was also imaged with an electroanatomic mapping system. Esophageal and left atrial imaging helped to avoid catheter ablation in left atrial tissue overlapping the esophagus. [source] Characterization of Sustained Atrial Tachycardia in Dogs with Rapid Ventricular Pacing-Induced Heart FailureJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2003Bruce S. Stambler M.D. Introduction: Atrial arrhythmias often complicate congestive heart failure (CHF). We characterized inducible atrial tachyarrhythmias and electrophysiologic alterations in dogs with CHF and atrial enlargement produced by rapid ventricular pacing. Methods and Results: Endocardial pacing leads were implanted in the right ventricle, right atrium, and coronary sinus in 18 dogs. The right ventricular lead was connected to an implanted pacemaker capable of rapid ventricular pacing. The atrial leads were used to perform electrophysiologic studies in conscious animals at baseline in all dogs, during CHF induced by rapid ventricular pacing at 235 beats/min in 15 dogs, and during recovery from CHF in 6 dogs. After20 ± 7 daysof rapid ventricular pacing, inducibility of sustained atrial tachycardia (cycle length120 ± 12 msec) was enhanced in dogs with CHF. Atrial tachycardia required a critical decrease in atrial burst pacing cycle length (,130 msec) for induction and often could be terminated by overdrive pacing. Calcium antagonists (verapamil, flunarizine, ryanodine) terminated atrial tachycardia and suppressed inducibility. Effective refractory periods at 400- and 300-msec cycle lengths in the right atrium and coronary sinus were prolonged in dogs with CHF. Atrial cells from dogs with CHF had prolonged action potential durations and reduced resting potentials and delayed afterdepolarizations (DADs). Mitochondria from atrial tissue from dogs with CHF were enlarged and had internal cristae disorganization. Conclusions: CHF promotes inducibility of sustained atrial tachycardia. Based on the mode of tachycardia induction, responses to pacing and calcium antagonists, and presence of DADs, atrial tachycardia in this CHF model has a mechanism most consistent with DAD-induced triggered activity resulting from intracellular calcium overload.(J Cardiovasc Electrophysiol, Vol. 14, pp. 499-507, May 2003) [source] Adrenergic-Cholinergic Interaction that Modulates Repolarization in the Atrium is Altered with AgingJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2002EUGENE A. SOSUNOV Ph.D. Autonomic Modulation of Atrial Repolarization.Introduction: Aging is associated with involution of both limbs of the autonomic nervous system, and the prejunctional and postjunctional effects of adrenergic and cholinergic stimulation are altered with senescence. Hence, postjunctional age-related changes in adrenergic-cholinergic interaction are a likely occurrence and may contribute to an altered substrate for arrhythmias. Methods and Results: Microelectrode techniques were used to record action potentials from epicardial slices of Bachmann's bundles of dogs aged 3 to 5 years (adult) and 8 to 12 years (old) in the absence or presence of acetylcholine and isoproterenol (separately and in combination). In control, action potential duration to 90% repolarization (APD) was longer in old atria. Acetylcholine (10,8 to 10,5 mol/L) in a concentration-dependent manner hyperpolarized and shortened APD in both tissues, with more prominent effects in the old. The effects of isoproterenol (10,9 to 10,6 mol/L) to elevate the plateau and shorten APD were about the same in both adult and old tissues. In adults, low concentrations of isoproterenol (10,9 and 10,8 mol/L) significantly prolonged APD, which had been first shortened by acetylcholine. This effect of isoproterenol was decreased in old atrial tissue, resulting in shorter APD in old than adult atria in the combined presence of beta-adrenergic and muscarinic agonists. Conclusion: In adult Bachmann's bundle, beta-adrenergic stimulation effectively operates as a "brake" to decrease the extent of cholinergic-induced APD shortening. The action of beta-adrenergic stimulation to antagonize acetylcholine-induced acceleration of repolarization declines with age, which may contribute to an altered arrhythmogenic substrate. [source] Electrophysiological Remodeling in Human Atrial FibrillationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7p2 2003DAVID R. VAN WAGONER Atrial fibrillation (AF) is a progressive disease characterized by cumulative electrophysiological and structural remodeling of the atria. Cellular electrophysiological studies have revealed marked reductions in the densities of the L-type voltage-gated Ca2+ current, ICa,L, the transient outward K+ current, ITO, and the ultra-rapid delayed rectifier K+ current, IKur, in atrial myocytes from patients in persistent or permanent AF. The density of the muscarinic K+ current (IKACh) is also reduced, however the inward rectifier K+ current (IK1) density is increased. The net shortening or lengthening of the action potential is dependent on the balance between changes in inward and outward currents. The prominent reduction in ICa,L appears to be sufficient to explain the observed decreases in action potential duration and effective refractory period that are characteristic of the fibrillating atria. Earlier studies have shown that calcium overload and perturbations in calcium handling play prominent roles in AF induced atrial remodeling. More recently, we have shown that AF is associated with evidence of oxidative injury to atrial tissue, and suggested that oxidative stress may directly contribute to the pathophysiology of AF. It is anticipated that insights gleaned from mechanistic studies will facilitate the development of improved pharmacological approaches to treat AF and to prevent the progression of arrhythmia. (PACE 2003; 26[Pt. II]:1572,1575) [source] The Effect of Ablation Electrode Length and Catheter Tip to Endocardial Orientation on Radiofrequency Lesion Size in the Canine Right AtriumPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2002RODRIGO C. CHAN CHAN, R.C., et al.: The Effect of Ablation Electrode Length and Catheter Tip to Endocardial Orientation on Radiofrequency Lesion Size in the Canine Right Atrium. Although the determinants of radiofrequency lesion size have been characterized in vitro and in ventricular tissue in situ, the effects of catheter tip length and endocardial surface orientation on lesion generation in atrial tissue have not been studied. Therefore, the dimensions of radiofrequency lesions produced with 4-, 6-, 8-, 10-, and 12-mm distal electrode lengths were characterized in 26 closed-chested dogs. The impact of parallel versus perpendicular catheter tip/endocardial surface orientation, established by biplane fluoroscopy and/or intracardiac echocardiography, on lesion dimensions was also assessed. Radiofrequency voltage was titrated to maintain a steady catheter tip temperature of 75°C for 60 seconds. With a perpendicular catheter tip/tissue orientation, the lesion area increased from 29 ± 7 mm2 with a 4-mm tip to 42 ± 12 mm2 with the 10-mm tip, but decreased to 29 ± 8 mm2 with ablation via a 12-mm tip. With a parallel distal tip/endocardial surface orientation, lesion areas were significantly greater: 54 ± 22 mm2 with a 4-mm tip, 96 ± 28 mm2 with a 10- mm tip and 68 ± 24 mm2 with a 12-mm tip (all P < 0.001 vs perpendicular orientation). Lesion lengths and apparent volumes were larger with parallel, compared to perpendicular tip/tissue orientations, although lesion depth was independent of catheter tip length with both catheter tip/tissue orientations. Electrode edge effects were not observed with any tip length. Direct visualization using intracardiac ultrasound guidance was subjectively helpful in insuring an appropriate catheter tip/tissue interface needed to maximize lesion size. Although atrial lesion size is critically dependent on catheter tip length, it is more influenced by the catheter orientation to the endocardial surface. This information may also be helpful in designing electrode arrays for the creation of continuous linear lesions for the elimination of complex atrial tachyarrhythmias. [source] Calcium and polyamine regulated calcium-sensing receptors in cardiac tissuesFEBS JOURNAL, Issue 12 2003Rui Wang Activation of a calcium-sensing receptor (Ca-SR) leads to increased intracellular calcium concentration and altered cellular activities. The expression of Ca-SR has been identified in both nonexcitable and excitable cells, including neurons and smooth muscle cells. Whether Ca-SR was expressed and functioning in cardiac myocytes remained unclear. In the present study, the transcripts of Ca-SR were identified in rat heart tissues using RT-PCR that was further confirmed by sequence analysis. Ca-SR proteins were detected in rat ventricular and atrial tissues as well as in isolated cardiac myocytes. Anti-(Ca-SR) Ig did not detect any specific bands after preadsorption with standard Ca-SR antigens. An immunohistochemistry study revealed the presence of Ca-SR in rat cardiac as well as other tissues. An increase in extracellular calcium or gadolinium induced a concentration-dependent sustained increase in [Ca2+]i in isolated ventricular myocytes from adult rats. Spermine (1,10 mm) also increased [Ca2+]i. Pre-treatment of cardiac myocytes with thapsigargin or U73122 abolished the extracellular calcium, gadolinium or spermine-induced increase in [Ca2+]i. The blockade of Na+/Ca2+ exchanger or voltage-dependent calcium channels did not alter the extracellular calcium-induced increase in [Ca2+]i. Finally, extracellular calcium, gadolinium and spermine all increased intracellular inositol 1,4,5-triphosphate (IP3) levels. Our results demonstrated that Ca-SR was expressed in cardiac tissue and cardiomyocytes and its function was regulated by extracellular calcium and spermine. [source] Atrial Tachyarrhythmias Induced By Acetylcholine In Tilapia (Oreochromis SP.) Isolated AtriaCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2000Tsai-Chu Lin SUMMARY 1. Effects of the parasympathetic neuromediator acetylcholine (ACh) on atrial tissues vary greatly depending on the species, the type of atrial cells and experimental conditions. The aim of the present study was to investigate, with microelectrode techniques, the arrhythmogenic effects of ACh in tilapia (Oreochromis sp.) isolated atria at room (22,25°C) and high temperature (37°C). 2. Acetylcholine (1,10 ,mol/L) shortened action potential duration (APD), depressed action potential plateau and decreased twitch force in tilapia atria, as it did in human atrial fibres. In addition, ACh induced premature responses and re-entrant tachyarrhythmias (TA; frequency range from 7 to 25 Hz) in five of 19 and 14 of 22 tilapia atria tested at room and high temperature, respectively. The higher incidence of ACh-induced TA at 37°C compared with room temperature was statistically significant. 3. The ACh-induced TA consisted of high-frequency and uniform action potentials accompanied by tension oscillation and elevation of diastolic force (flutter). Acetylcholine-induced TA could be readily abolished by atropine (1 ,mol/L) and prevented by treatment with agents with local anaesthetic properties, such as 0.1 ,mol/L tetrodotoxin or 3 ,mol/L quinidine. The antagonistic action of quinidine occurred without significant prolongation of APD. 4. The present findings suggest that pharmacological concentrations of the cholinergic muscarinic agonist ACh readily induce TA (mainly atrial flutter) in tilapia atria, presumably via sodium channel-dependent re-entrant excitation. The poikilothermic tilapia appears to be an appropriate animal model for the study of atrial TA. [source] | ||||||||||