The sick sinus syndrome.
نویسندگان
چکیده
1. a. SSS b. SA block c. SA arrest Sick sinus syndrome is a disorder characterized by a dysfunctional sinus node. It is often idiopathic and a result of degenerative fibrosis of nodal tissue. Certain disorders such as amyloidosis, connective tissue disease, Chagas disease, and hemochromatosis are examples of intrinsic causes. Hypertensive heart disease and cardiomyopathies account for a smaller, but significant group that are also responsible for causing SSS. The extrinsic etiologies are pharmacological agents such as digitalis, calcium channel blockers, β-blockers, sympatholytic agents, and several antiarrhythmic drugs. The electrocardiographic presentations of SSS include (1) severe sinus bradycardia, (2) SA arrest or SA block, (3) SA arrest with an escape atrial or junctional rhythm, (4) SA arrest with failure of subsidiary pacemaker resulting in cardiac asystole, (5) bradycardia alternating with tachycardia, and (6) chronic AF with failure of sinus rhythm to return after cardioversion. Many patients with SSS may have more than 1 abnormality. In this case, the tracings show a markedly prolonged period of SA arrest or SA block. It is not possible to differentiate the 2 electrocardiographically. The sinus node may not fire at all (SA arrest) or may produce an impulse that cannot activate the atria because of SA block (block between the SA node and the SA fibers). The SA node may discharge, but if the impulse is blocked, the atrium will not be depolarized and consequently P waves will not be recorded. Electrophysiological studies with an electrode needle in the SA node can record SA nodal activity. The failure of a P wave recording under these circumstances is consistent with a block between the SA node and the atrial muscle, that is, SA block. The absence of an SA node impulse implies SA arrest. The history and rhythm traces are characteristic of SSS. This syndrome is accompanied by disease or CARDIOLOGY CASEBOOK
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ورودعنوان ژورنال:
- American journal of critical care : an official publication, American Association of Critical-Care Nurses
دوره 15 2 شماره
صفحات -
تاریخ انتشار 2006