ST segment alternans: Difference between revisions
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'''''Related chapter:''''' [[electrical alternans]] | '''''Related chapter:''''' [[electrical alternans]] | ||
==Overview== | ==Overview== | ||
'''Electrical alternans''' is an [[electrocardiogram|electrocardiographic]] phenomenon which describes teh beat to beat alternation in the height (ie.e amplitude), duration (the length of the interval) or the direction (up or down) of any of the EKG complexes or intervals. While electrical alernans is usually thought of as alternation in the height or direction of the QRS complex, there can also be [[P wave]], [[PR interval]], [[QRS complex]], [[R-R interval]], [[ST segment]], [[T wave]], or [[U wave]] forms of alternans (see classification below). | |||
==Historical Perspective== | |||
*1909: First described by Hearing | |||
*1910: Elaborated upon by Sir Thomas Lewis | |||
*1948: First description of electrical alternans on the surfce EKG by Kalter and Schwartz <ref>Kalter HH, Schwartz ML. Electrical alternans. NY State J Med. 1948;1:1164-66.</ref> | |||
==Pathophysiology== | ==Pathophysiology== | ||
ST segment alternans is defined as beat to beat variation in the magnitude or amplitude of [[ST segment elevation]]. It is due to abnormalities of calcium handling in the sarcoplastic reticulum as a result of [[myocardial ischemia]]. | |||
==Causes== | ==Causes== | ||
It is most often due to [[myocardial ischemia]] and includes causes such as: | |||
*[[Vasospastic angina pectoris]] | |||
*[[Acute myocardial infarction]] | |||
*[[Angina pectoris]] | |||
*[[Myocardial ischemia]] during an [[exercise tolerance test]] | |||
*[[Percutaneous transluminal coronary angioplasty]] ([[PTCA]]) | |||
*[[Subarachnoid hemorrhage]] | |||
====Natural History, Complications and Prognosis==== | |||
The presence of ST segment alternans in the setting of [[myocarial ischemia]] is associated with [[ventricular tachycardia]] and [[ventricular fibrillation]]. | |||
==Differentiating Electrical Alternans form other Disorders== | |||
The electrical form of alternans should be differentiated from the mechanical form alternans in which case there is alternation of the strength of the pulse as is observed in [[pulsus alternans]]. Electrical and [[mechanical alternans]] may coexist. | |||
==References== | ==References== | ||
Revision as of 23:01, 8 September 2012
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: ST alternans
Related chapter: electrical alternans
Overview
Electrical alternans is an electrocardiographic phenomenon which describes teh beat to beat alternation in the height (ie.e amplitude), duration (the length of the interval) or the direction (up or down) of any of the EKG complexes or intervals. While electrical alernans is usually thought of as alternation in the height or direction of the QRS complex, there can also be P wave, PR interval, QRS complex, R-R interval, ST segment, T wave, or U wave forms of alternans (see classification below).
Historical Perspective
- 1909: First described by Hearing
- 1910: Elaborated upon by Sir Thomas Lewis
- 1948: First description of electrical alternans on the surfce EKG by Kalter and Schwartz [1]
Pathophysiology
ST segment alternans is defined as beat to beat variation in the magnitude or amplitude of ST segment elevation. It is due to abnormalities of calcium handling in the sarcoplastic reticulum as a result of myocardial ischemia.
Causes
It is most often due to myocardial ischemia and includes causes such as:
- Vasospastic angina pectoris
- Acute myocardial infarction
- Angina pectoris
- Myocardial ischemia during an exercise tolerance test
- Percutaneous transluminal coronary angioplasty (PTCA)
- Subarachnoid hemorrhage
Natural History, Complications and Prognosis
The presence of ST segment alternans in the setting of myocarial ischemia is associated with ventricular tachycardia and ventricular fibrillation.
Differentiating Electrical Alternans form other Disorders
The electrical form of alternans should be differentiated from the mechanical form alternans in which case there is alternation of the strength of the pulse as is observed in pulsus alternans. Electrical and mechanical alternans may coexist.
References
- ↑ Kalter HH, Schwartz ML. Electrical alternans. NY State J Med. 1948;1:1164-66.