Expression of ion-channel subunit mRNA in different regions of canine right atrium

A trial electrophysiological heterogeneity, which plays an important role in the genesis and maintenance of atrial arrhythmia, is a major determinant of atrial reentrant arrhythmias. Recently, many studies on atrial flutter have demonstrated the anatomic architecture in the right atrium plays an important role in the genesis of atrial reentry. The crista terminalis （CT） in the right atrium, which is a unique anatomic structure of the right atrium, provides an area for conduction block and delay, leading to initiation, maintenance, and termination of atrial arrhythmias. Catheter ablation of CT can successfully eliminate these atrial arrhythmias. These literatures contrast with limited knowledge of the basic electrophysiological properties of CT and how these promote arrhythmia generation. Compared to pectinate muscles （PM） and right atrial appendage （RAA）, CT have distinct electrophysiological properties related to different densities of several ionic currents, the transient outward current （Ito） and L-type Ca^2＋ current （Ica-L） underlie the bulk of the different densities of several ionic currents. Cardiac Ito and Ica-L play a major role in action potential repolarization. Ito is particularly important in early （phase 1） repolarization and influences the participation of other currents. It is generally believed that Ica-L plays an important role in the plateau phase of repolarization. However, the mechanisms for these ionic current differences are unknown. One possible is a difference in ion channel subunit expression, but virtually no data are available regarding ion-channel subunit expression in CT, PM, and RAA. The Kv4.3 channel underlies the bulk of the α-subunit of Ito in canine and human heart.     

肺癌累及左心房或肺静脉根部的外科治疗

背景与目的 肺癌累及左心房或肺静脉根部属局部晚期肺癌（T4），单纯保守治疗效果不良，手术可能能提高其生存率。本观察旨在探讨这部分患者行手术治疗的可行性及价值。方法 回顾性分析1993年4月～2005年4月的46例肺癌累及左心房或肺静脉根部手术治疗的患者，均行左心房部分切除，其中左肺下叶切除术20例，左全肺切除术6例，右肺中下叶切除术12例，右肺下叶切除术3例，右全肺切除术5例；34例为肿瘤侵及肺静脉根部与心房交界处近心端，12例左心房明显受侵。其中2例同时侵及靠近肺动脉分叉处，常规无法处理肺动脉，因而在体外循环下切除全肺并同时切除部分左心房。应用COX模型及Kaplan Meier法（Log rank检验）分析生存及预后情况。结果 本组无手术死亡，术后发生并发症15例，其中：心律失常13例次，肺炎8例次、心功能不全1例次。患者总的中位生存期为35个月，1、3、5年生存率为84．2％、43．7％、30．5％，其中N0／N1的患者预后优于N0的患者，中位生存期分别为38、19个月（P=0．002）。COX分析发现：影响预后的因素为有无纵隔淋巴结转移（P=0．005），术前化疗与否及性别、年龄、病理类型对预后均无明显影响。结论 肺癌累及部分左心房或肺静脉根部进行手术治疗是可行的，无纵隔淋巴结转移者预后较好，应尽可能手术治疗。     

大蒜素对豚鼠心房肌电生理的作用

大蒜 (ＡｌｌｉｕｍＳａｔｉｖｕｍＬ .)作为药物 ,在中国及世界其他国家均被广泛使用[1] 。《本草纲目》云 :“捣汁饮 ,治吐血心痛。”其良好的防治心血管疾病的药理 ,已不断被现代研究所证实。大蒜素 (Ａｌｌｉｔｒｉｄｉ)是从大蒜中提取的一种稳定的有效成分 ,结构式为ＣＨ2     

Presynaptic inhibitory actions of lignocaine in canine isolated, blood-perfused atrial preparations

1. Cardiac effects of lignocaine on sinoatrial nodal pacemaker activity and atrial contractility were investigated in five canine isolated, blood-perfused right atria that were perfused with heparinized blood from support dogs. The effects of lignocaine on responses to intracardiac nerve stimulation and administered acetylcholine and noradrenaline were also examined. 2. Lignocaine was injected into the support dog intravenously or administered selectively to the sinus node artery of the isolated atrium. At doses that did not produce significant depressor action (0.3, 1.0 and 3.0 mg/kg), lignocaine produced no significant changes in heart rate. A large dose of 10 mg/kg lignocaine caused significant depressor effects and slight bradycardia. Direct administration of lignocaine (0.3, 1.0, 3.0, 10.0 and 30.0 mumol) into the sinus node artery of the isolated atrium consistently caused slight negative chronotropic and rather marked negative inotropic effects. 3. After treatment with a relatively large dose of lignocaine, electrical stimulation-induced negative chronotropic and inotropic responses were significantly inhibited in a dose-related manner, but positive chronotropic and inotropic responses were slightly depressed only at an extremely high dose of lignocaine (10.0 mumol). 4. Noradrenaline-induced positive chronotropic and inotropic effects were not modified by any doses of lignocaine used (0.3, 1.0, 3.0 and 10.0 mumol). Acetylcholine-induced negative chronotropic and inotropic effects were slightly, but significantly, depressed by 10 mumol lignocaine. 5. These results suggest that a relatively large dose of lignocaine has a dominant presynaptic inhibitory action, particularly on the parasympathetic component.     

Posterior Mediastinal Bronchogenic Cyst Compressing Left Atrium

The echocardiographic literature contains exceedingly few reports of mediastinal bronchogenic cyst; in most published cases of this entity, the cysts were imaged by computed tomography or magnetic resonance imaging. Because mediastinal bronchogenic cyst is little known as a cause of cardiorespiratory symptoms, we report such a case.     

Free-floating left atrial ball thrombus following mitral valve replacement

We report the case of a 51-year-old woman who underwent mitral valve replacement for prolapse with severe regurgitation, depressed ejection fraction, and atrial fibrillation. Two weeks post-operatively, a transesophageal echocardiogram was performed for bacteremia. The patient was found incidentally to have a large free-floating ball thrombus in the left atrium. The patient was managed with anticoagulation because of the high-risk nature of repeat surgery. One month following diagnosis, the patient still had persistent thrombus in the left atrium seen on transthoracic echocardiography despite therapeutic anticoagulation. Free-floating ball thrombus is a rare and dramatic finding seen on echocardiography in patients with mitral valve disease.     

Effects of hypochlorite and hydrogen peroxide on cardiac autonomic receptors and vascular endothelial function

1. Reactive oxygen species (ROS) are known to be involved in the progression of various cardiovascular diseases. One source of ROS is activated neutrophils, which can release superoxide anion radicals and hydrogen peroxide by membrane-bound NAD(P)H oxidases. These ROS not only destroy bacteria, but may also affect mammalian tissue. In addition, hydrogen peroxide serves as a substrate for myeloperoxidase, an enzyme that is released by activated neutrophils during inflammatory processes, as seen, for instance, in reperfusion injury and atherosclerosis. Myeloperoxidase catalyses the oxidation of chloride by hydrogen peroxide, yielding hypochlorite, an extremely potent oxidant. 2. The purpose of the present study was to evaluate the effects of hypochlorite on a variety of receptor-dependent processes in rat isolated left atria and rat thoracic aorta and to compare these results with the phenomena observed after incubation with hydrogen peroxide. 3. In the presence of hypochlorite (300 micro mol/L), the positive inotropic response of alpha1-adrenoceptor stimulation by methoxamine (300 micro mol/L) was converted into a negative inotropic response. In contrast, the positive inotropic effects of the beta1/beta2-adrenoceptor agonist isoprenaline (3 micro mol/L) and endothelin (ET)-1 (100 nmol/L) remained largely unaffected. 4. The inversion of alpha1-adrenoceptor-mediated inotropy was not obtained in the presence of hydrogen peroxide (500 micro mol/L). Hydrogen peroxide did not affect the positive inotropic response of isoprenaline, but it completely abolished the inotropic effect of ET-1. 5. The effect of cardiac M2-receptor stimulation was studied in the presence of hypochlorite and hydrogen peroxide. The negative inotropic response to acetylcholine (ACh) was significantly enhanced after hypochlorite incubation compared with control. 6. In the rat thoracic aorta, endothelial function, evaluated by means of ACh-induced vasodilation, was completely abolished in the presence of hypochlorite (100 micro mol/L), but remained unaffected by treatment with the same concentration of hydrogen peroxide. 7. From these data, we conclude that hypochlorite exerts more toxic properties than its precursor hydrogen peroxide, leading to substantial physiological alterations in cardiac and vascular tissue.     

Management of atrial arrhythmias secondary to severe congenital heart disease with the Atrioverter

An atrial defibrillator was implanted in a patient with congenitally corrected transposition of the great arteries, associated cardiac abnormalities, and persistent atrial arrhythmias. During a 15-month follow-up, 14 of 20 spontaneous episodes of his arrhythmias were successfully treated with the device. Two of these episodes were converted to sinus rhythm during ambulatory use of the device. Successful use of the device required implantation of a third defibrillation lead in the persistent left-sided superior caval vein and rigid control of congestive heart failure. An atrial defibrillator may be a valid treatment option in patients with congenital heart disease crippled by atrial fibrillation.     

Ablation of atrial fibrillation

Atrial fibrillation (AF) is a common arrhythmia, affecting an estimated 2 million people in the United States and its prevalence increases with age, reaching 10% in those > or = 80 years. AF confers a four- to fivefold increased risk of stroke compared to the general population and has been associated with a doubling of all-cause mortality. During the past decade, limited success rates of drug treatment stimulated an exploration of interventional treatment options for AF. As our knowledge on initiating triggers and perpetuating substrate of AF expanded, different potentially curative catheter ablation techniques have been developed. In this article we review the current patient selection criteria, methods, and the results of the catheter ablation of atrial fibrillation.