| Second-degree atrioventricular block: a reappraisal. | |
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MedLine Citation:
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PMID: 11155413 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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In this review, we discuss the various forms and causes of second-degree atrioventricular (AV) block and the reasons they remain poorly understood. Both type I and type II block characterize block of a single sinus P wave. Type I block describes visible, differing, and generally decremental AV conduction. Type II block describes what appears to be an all-or-none conduction without visible changes in the AV conduction time before and after the blocked impulse. Although the diagnosis of type II block is possible with an increasing sinus rate, absence of sinus slowing is an important criterion of type II block because a vagal surge (generally a benign condition) can cause simultaneous sinus slowing and AV nodal block, which can superficially resemble type II block. The diagnosis of type II block cannot be established if the first postblock P wave is followed by a shortened PR interval or is not discernible. A pattern resembling a narrow QRS type II block in association with an obvious type I structure in the same recording (e.g., Holter) effectively rules out type II block because the coexistence of both types of narrow QRS block is exceedingly rare. Concealed His bundle or ventricular extrasystoles confined to the specialized conduction system without myocardial penetration and depolarization can produce electrocardiographic patterns that mimic type I and/or type II block (pseudo-AV block). All correctly defined type II blocks are infranodal. A narrow QRS type I block is almost always AV nodal, whereas a type I block with bundle branch block barring acute myocardial infarction is infranodal in 60% to 70% of cases. A 2:1 AV block cannot be classified in terms of type I or type II block, but it can be nodal or infranodal. Infranodal blocks require pacing regardless of form or symptoms. The widespread use of numerous disparate definitions of type II block appears primarily responsible for many of the problems surrounding second-degree AV block. Adherence to the correct definitions provides a logical and simple framework for clinical evaluation. |
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Authors:
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S S Barold; D L Hayes |
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Publication Detail:
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Type: Journal Article; Review |
Journal Detail:
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Title: Mayo Clinic proceedings. Mayo Clinic Volume: 76 ISSN: 0025-6196 ISO Abbreviation: Mayo Clin. Proc. Publication Date: 2001 Jan |
Date Detail:
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Created Date: 2001-01-11 Completed Date: 2001-01-25 Revised Date: 2007-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0405543 Medline TA: Mayo Clin Proc Country: United States |
Other Details:
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Languages: eng Pagination: 44-57 Citation Subset: AIM; IM |
Affiliation:
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Electrophysiology Institute, Broward General Hospital, Ft Lauderdale, Fla., USA. ssbarold@aol.com |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adult Aged Electrocardiography* Female Heart Block / classification, diagnosis*, etiology, therapy Heart Function Tests Heart Rate Humans Male Middle Aged Myocardial Infarction / physiopathology Pacemaker, Artificial Terminology as Topic Vagus Nerve / physiology |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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