Atrial dilatation

Other uses of TEE include identification of cardiac thrombus, especially thrombi in the left atrium, and assessment of atrial dilation. After transient ischemic attacks or cerebrovascular accidents, TEE may enable identification of the site of cardiac emboli by providing excellent images of likely sources of such, namely, ventricular or atrial thrombus, valvular vegetation, cardiac shunts, cardiac tumors, or atrial and ventricular septal defects. In a study of almost 1500 patients with cerebral ischemia or nonvalvular atrial fibrillation, atrial thrombi were seen in 183 patients when evaluated by TEE versus only 2 patients using TTE. TEE can be used for intraoperative cardiac imaging to ascertain development of ischemia. 

Multisite atrial pacing techniques have been shown to prevent atrial dilatation, decrease total atrial contraction time, and decrease the conduction slowing which occurs with atrial pranature beats which can trigger atrial fibrillation (86-88). Consequently, there has been significant interest in the... 

Atrial fibrillation is commonly associated with heart failure, and the prevalence of atrial fibrillation is related to the severity of heart failure, with less than 5% affected with very mild heart failure to nearly 50% affected with advanced heart failure [66]. Heart failure and atrial fibrillation are both common cardiovascular disorders and share the same demographic risk factors, including age, history of hypertension, prior myocardial infarction, and valvular heart disease [67, 68]. Further, the incidence of heart failure increases dramatically after the diagnosis of atrial fibrillation [69]. Progression of LV dysfunction can clearly be associated with rapid ventricular rates [70-76]. Conversely, conversion to normal sinus rhythm or control of ventricular response in atrial fibrillation can improve LV function [71-74, 77]. Accordingly, rate control becomes very important in patients with heart failure and dilated cardiomyopathy, and likely even more so when ischemia from rapid rates complicate the patient s course. 

A series of pilot studies began with multisite pacing for patients with heart failure and dilated cardiomyopathy in the early 1990s [52, 105-111]. An improvement in LV function and symptoms of heart failure were demonstrated. This provided the interest in biventricular pacing for heart failure. The term cardiac resynchronization therapy was coined to refer to pacing therapies that attempt to enhance cardiac performance by using pacing to correct electrical conduction abnormalities in the heart. The most common form of this therapy is atrial-synchronous... 

Agarwal AK, Venugopalan P. Beneficial effect of carvedilol on heart rate response to exercise in digitalised patients with heart failure in atrial fibrillation due to idiopathic dilated cardiomyopathy. Eur. J. Heart Fail. 2001 3 437-40. 

Lazzari JO, Gonzalez J. Reversible high rate atrial fibrillation dilated cardiomyopathy. Heart 1997 77 486. 

Kessler G, Rosenblatt S, Friedman J, Kaphnsky E. Recurrent dilated cardiomyopathy reversed with conversion of atrial fibrillation. Am. Heart J. 1997 133 384-6. 

Kieny JR, Sacrez A, Facello A, et al. Increase in radionuclide left ventricular ejection fraction after cardioversion of chronic atrial fibrillation in idiopathic dilated cardiomyopathy. Eur. Heart J. 1992 13 1290-5. 

Grogan M, Smith HC, Gersh BJ, Wood DL. Left ventricular dysfunction due to atrial fibrillation in patients initially beheved to have idiopathic dilated cardiomyopathy. Am. J. Cardiol. 1570 69 1570-3. 

Digoxin is indicated in patients with heart failure and atrial fibrillation. It is also most helpful in patients with a dilated heart and third heart sound. It is usually given only when diuretics and ACE inhibitors have failed to control symptoms. Only about 50% of patients with normal sinus rhythm (usually those with documented systolic dysfunction) will have relief of heart failure from digitalis. Better results are obtained in patients with atrial fibrillation. If the decision is made to use a cardiac glycoside, digoxin is the one chosen in most cases (and the only one available in the USA). When symptoms are mild, slow loading (digitalization) with 0.125-0.25 mg per day is safer and just as effective as the rapid method (0.5-0.75 mg every 8 hours for three doses, followed by 0.125-0.25 mg per day). 

A 72-year-old woman with dilated cardiomyopathy was given amiodarone for fast atrial flutter and 6 months later developed abnormal thyroid function tests, with a suppressed TSH and a raised serum thyroxine. The autoantibody profile was negative and a thyroid uptake scan showed reduced uptake (44). 

Thorough cardiac examination should look for possible cardiac source of embolism, including atrial fibrillation, mitral stenosis and prosthetic heart valves. Left ventricular hypertrophy suggests hypertension or aortic stenosis, and a displaced apex from a dilated left ventricle indicates underlying cardiac or valvular pathology. 

Like all caldum channel blodcers, verapamil modulates ionic calcium influx across cell membranes of conductile and contractile myocardial cells, as well as arterial smooth muscle. The modulation of calcium influx slows atrioventricular conduction, reduces myocardial contractility and systemic vascular resistance, and results in coronary and peripheral vaso dilation. Verapamil is currently indicated for controlling angina, hypertension, paroxysmal supraventricular tachycardia, and rapid ventricular atrial flutter or fibrillation (1-5),... 

Reef V B, Relmer J M, Spencer P A 1995 Treatment of atrial fibrillation In horses new perspectives. Journal of Veterinary Internal Medicine 9 57-67 Ribner H S, Plucinski D A, Hsieh A M et al 1985 Acute effects of digoxin on total systemic vascular resistance in congestive heart failure due to dilated cardiomyopathy a hemodynamic-hormonal study. American Journal of Cardiology 56 896-904 Richardson D W, Kohn C W 1983 Uroperitoneum in the foal. Journal of the American Veterinary Medical Association 182 267-271... 

Cardioembolic stroke—An ischemic stroke thought to be caused by an embolism arising from the heart. Cardioembolic stroke can be assumed in patients with significant cardiovascular disease including atrial fibrillation, dilated cardiomyopathy, prosthetic valves, recent MI and patent foramen ovale. 

It has also been shown that atrial natriuretic factor (ANP), nitric oxide, and isosorbide dinitrite, which dilate arteries and increase intracellular cGMP levels, activate K tp channels suggesting the possibility that either elevation of cGMP or stimulation of cGMP-dependent protein kinase could activate K jp channels in smooth muscle (e.g., see Murphy and Bray den,... 

Numerous neuroendocrine biomarkers correlate with severity of cardiac dysfunction. Heart failure is associated with increase in peripheral vascular resistance due to increases in sympathetic tone, norepinephrine, renin, angiotensin II, arginine vasopressin, and endothelin-1. The increased venous pressure causes atrial distension that stimulates production and release of atrial and brain natriuretic peptides (ANP, BNP) from the atria and ventricles, respectively. ANP inhibits the renin-angiotensin-aldosterone system. In humans and mammals, BNP has been found to be an early biomarker of left ventricular hypertrophy developing with doxorubicin cardiotoxicity, congestive heart failure, or occult dilated cardiomyopathy (Erkus et al. 2006 Walker 2006 Oyama, Sisson, and Solter 2007). 

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