Left atrium

Transesophageal echocardiogram A procedure used to generate an image of the heart using sound waves, via a probe introduced into the esophagus (rather than the traditional transthoracic view) in order to obtain a better image of the left atrium. 

From the SA node, the heart beat spreads rapidly throughout both atria by way of the gap junctions. As mentioned previously, the atria are stimulated to contract simultaneously. An interatrial conduction pathway extends from the SA node to the left atrium. Its function is to facilitate conduction of the impulse through the left atrium, creating the atrial syncytium (see Figure 13.3). 

Figure 13.3 Route of excitation and conduction in the heart. The heart beat is initiated in the sinoatrial (SA) node, or the pacemaker, in the right atrium of the heart. The electrical impulse is transmitted to the left atrium through the interatrial conduction pathway and to the atrioventricular (AV) node through the intemodal pathway. From the AV node, the electrical impulse enters the ventricles and is conducted through the AV bundle, the left and right bundle branches, and, finally, the Purkinje fibers, which terminate on the true cardiac muscle cells of the ventricles.

Lees Loss Prevention in the Process Industries, 21 862-863 Left atrium, 5 79, 80 Left posterior fascicle, 5 80 Left ventricle, 5 79, 80 Legal actions, patent-related, 75 186 Legal aspects, of standardization,... 

Fig. 6.1 TandemHeart consists of an extracorporeal pump, an inlet cannula in the left atrium, and an outlet cannula in the femoral artery...

Currently available devices are able to provide left ventricular support for a short duration only. Development of percutaneously or minimally invasive long-term support devices is also underway. At least three such devices are undergoing preclinical evaluation. The Synergy device (CircuLite, Inc., Hackensack, NJ) is being developed as a pocket circulatory assist (PAC) device that would sit in a subcuatenous pocket over the chest wall and use a micro-pump with cannulas in the subclavian artery and vein to withdraw blood from the left atrium through a transseptal approach and deliver it to the subclavian artery. The device is connected to a power... 

Restoration of sinus rhythm in atrial fibrillation may dislodge thrombi that have developed as a result of stasis in the enlarged left atrium. The risk of stroke and systemic arterial embolism is decreased by anticoagulation in such patients. 

Fig. 4. Preparation of the fixed heart for visceral examination. Cut 1 Ventral view Open the right ventricle along the septum in baso-apical direction going trough the aorta and the truncus pulmonalis (cross pulmonary valve) dorsal view open right ventricle near the septum from the heart apex towards the right atrium (through tricuspidal valve). Cut2 Ventral view Open the left ventricle along the septum from the heart apex into the left atrium (through bicuspidal valve) dorsal view cut the wall of left ventricle from the heart apex towards the left atrium.

Right atrium Left atrium Adrenergic nerves Neurogenic chronotropic response Neurogenic inotropic response NA release (ES-evoked) inhibition inhibition inhibition Endou et al., 1994... 

Left atrium Afferent neurons BK-evoked inotropic response BK-evoked CGRP release inhibition inhibition Imamura et al., 1996b... 

Although heart disease commonly affects the entire myocardium, congestive heart failure is sometimes divided into left and right heart failure (Fig. 24—2). In left heart failure, the left atrium and ventricle are unable to adequately handle the blood returning from the lungs. This causes pressure to build up in the pulmonary veins, and fluid accumulates in the lungs. Consequently, left heart failure is associated with pulmonary edema (see Fig. 24—2 A). 

Kelling et al. (1987) assessed the effects of 2,3,7,8-TCDD on cardiac function tests in male Sprague-Dawley rats 7 days after single oral doses of 6.25, 25, or 100 g/kg. At 100 g/kg (near-lethal dose), an increased sensitivity to the inotropic (left atrium) and chronotropic (right atrium) effects of isoproterenol were observed. Three daily oral doses of 40 g/kg caused decreased heart rate, depressed blood pressure, and increased myocardial peroxidase activity in rats (Hermansky et al. 1988). All of these effects may have been secondary to the modulation of adenylate cyclase activity at -adrenergenic receptors as a result of hypothyroidism (Hermansky et al. 1987). 

Echocardiography is useful in risk assessment for thromboembolism. TEE is superior in the detection of reduced flow velocities and spontaneous echo contrast in the left atrium and LAA (9). Patients with AF and complex atherosclerotic plaques in the aorta have a substantially higher risk for stroke (10,1 I). 

Intracardiac echocardiogram with transseptal sheath from right atrium (upper cavity) through the oval fossa in the left atrium. Attached to the sheath is a small clot, in spite of the administration of 5000 III heparin before the puncture. 

The characteristic feature of all Amplatzer devices is the nitinol wire mesh. There are two possible methods of implantation. Either the device is placed entirely into the appendage or the distal disc is expanded in the neck and the proximal disc in the left atrium. The risk of residual shunting around the device is increased when it is totally inserted into the LAA with no part protruding into the atrium. The Amplatzer occluder series holds the widest spectrum of device sizes (4 to 40 mm), The device is attached to a delivery cable and can simply be opened or recollapsed into the delivery catheter. Release is by unscrewing the device after first testing stability with simple traction. 

Since the first steps in transluminal balloon dilation of mitral valves in 1982 (24) numerous techniques have been described. One method is to access the left atrium with a transseptal puncture from the venous side (antegrade). Another way is to advance the catheter via the aorta into the left ventricle and perform the valvulotomy from the arterial side (retrograde). The use of two dilation balloons introduced via the transseptal approach is a common technique described by Bonhoeffer using a monorail-type system over a single guidewire (25). 

Toda N. 1970. Barium-induced automaticity in relation to the calcium ions and norepinephrine in the rabbit left atrium. Circ Res 27 45-57. 

At total of 75% of cardiac emboli reach the brain. Non-valvular atrial fibrillation with thrombus formation within the left atrial appendix or the left atrium is the most common reason for cardiac emboli (Ferro 2003). Cardio-embolic infarcts within the MCA territory carry a high risk for hemorrhagic transformation after reperfusion. Hemor-... 

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