Sinoatrial block: Difference between revisions
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==Overview== | ==Overview== | ||
Sinoatrial block is an uncommon dysrhythmia of unknown mechanism, characterized by the omission of P waves in the setting of a basic regular rhythm. It is found incidentally in normal asymptomatic subjects and in some having pre syncope or syncope. It may occur as an isolated dysrhythmia or in association with sinus bradycardia, tachycardia or, sometimes, with atrioventricular conduction disorders. | Sinoatrial block is an uncommon dysrhythmia of unknown mechanism, characterized by the omission of P waves in the setting of a basic regular rhythm. It is found incidentally in normal asymptomatic subjects and in some having pre syncope or syncope. It may occur as an isolated dysrhythmia or in association with sinus bradycardia, tachycardia or, sometimes, with atrioventricular conduction disorders. | ||
<ref name="pmid13708372">{{cite journal| author=GREENWOOD RJ, FINKELSTEIN D, MONHEIT R| title=Sinoatrial heart block with Wenckebach phenomenon. | journal=Am J Cardiol | year= 1961 | volume= 8 | issue= | pages= 140-6 | pmid=13708372 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=13708372 }} </ref> | <ref name="pmid13708372">{{cite journal| author=GREENWOOD RJ, FINKELSTEIN D, MONHEIT R| title=Sinoatrial heart block with Wenckebach phenomenon. | journal=Am J Cardiol | year= 1961 | volume= 8 | issue= | pages= 140-6 | pmid=13708372 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=13708372 }} </ref><ref name="pmid1138735">{{cite journal| author=Dighton DH| title=Sinoatrial block. Autonomic influences and clinical assessment. | journal=Br Heart J | year= 1975 | volume= 37 | issue= 3 | pages= 321-5 | pmid=1138735 | doi= | pmc=PMC483972 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=1138735 }} </ref> | ||
==Classification== | ==Classification== | ||
Revision as of 21:24, 29 August 2013
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahmoud Sakr, M.D. [2]
Synonyms and keywords:; SA nodal exit block; exit block; Sino atrial exit block; Sinoatrial nodal block; sino-auricular block
block.
Overview
Sinoatrial block is an uncommon dysrhythmia of unknown mechanism, characterized by the omission of P waves in the setting of a basic regular rhythm. It is found incidentally in normal asymptomatic subjects and in some having pre syncope or syncope. It may occur as an isolated dysrhythmia or in association with sinus bradycardia, tachycardia or, sometimes, with atrioventricular conduction disorders. [1][2]
Classification
First Degree SA Exit Block
There is a conduction delay (a slowing of conduction not a block or completion cessation in electrical conduction) in the impulse traveling from the sinus node to the atrium and there are no discernible changes on the surface EKG.
Second Degree SA Exit Block
This condition refers to intermittent conduction block (not a delay or slowing of conduction but a complete cessation of conduction) between the sinus node and the atrium.
Type I (Wenckebach Phenomenon) Sinoatrial Exit Block
This is an example of group beating. The P-P cycle (time between two P waves) is progressively shortened until there is a pause. This pause is less than twice the shortest P-P interval. The cycle is then repeated. The pause is due to the dropped P wave and measures less than twice the P-P cycle. It is similar to the behavior of the RR intervals in type I second-degree AV block.
Type II Second Degree Sinoatrial Exit Block
There is an unexpected drop of the P wave. Following this drop, there is a pause in the sinus cycle which is a multiple of the basic sinus cycle. Blocked atrial premature beats sometimes mimic second-degree sinoatrial block.
Third Degree Sinoatrial Exit Block
This SA block cannot be distinguished from sinus arrest when the sinus node ceases to fire. Under such circumstances, subsidiary pacemakers in the AV junction or ventricles may take over.
Causes
Life Threatening Causes
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
- Acute coronary syndrome
- Acute renal failure
- Diabetic ketoacidosis
- Lateral medullary syndrome
- Myocardial rupture
- NSTEMI
- Organophosphate poisoning
- Parathion poisoning
- Poisonous spider bites
- Septic shock
- Severe brain injury
- STEMI
Common Causes
- Acetylcholine
- Acute coronary syndrome
- Amiodarone
- Beta blockers
- Calcium channel blockers
- Digoxin
- Dilated cardiomyopathy
- Hyperkalemia
- Hypermagnesemia
- Hypertrophic cardiomyopathy
- Myocarditis
- Pericarditis
- Sick sinus syndrome
- Sinus node fibrosis
- STEMI
Causes by Organ System
Causes in Alphabetical Order
Differentiating Sinoatrial block from other Diseases
Other types of SA nodal dysfunction are discussed in detail in other chapters on wikidoc. Follow the hyperlinks for details and those include:
Diagnosis
Treatment
Sinoatrial block principles of treatment are the same as sinus pause or sick sinus syndrome. Usually no treatment is indicated if the patient is asymptomatic. Stopping the offending drug is generally reasonable. When symptoms occur and become intolerable or life-threatening, then a permanent pacemaker would be indicated.
References
- ↑ GREENWOOD RJ, FINKELSTEIN D, MONHEIT R (1961). "Sinoatrial heart block with Wenckebach phenomenon". Am J Cardiol. 8: 140–6. PMID 13708372.
- ↑ Dighton DH (1975). "Sinoatrial block. Autonomic influences and clinical assessment". Br Heart J. 37 (3): 321–5. PMC 483972. PMID 1138735.
- ↑ Bailey PL (1990). "Sinus arrest induced by trivial nasal stimulation during alfentanil-nitrous oxide anaesthesia". Br J Anaesth. 65 (5): 718–20. PMID 2248851.
- ↑ 4.0 4.1 4.2 Mills TA, Kawji MM, Cataldo VD, Pappas ND, O'Meallie LP, Breaux DM; et al. (2004). "Profound sinus bradycardia due to diltiazem, verapamil, and/or beta-adrenergic blocking drugs". J La State Med Soc. 156 (6): 327–31. PMID 15688675.
- ↑ 5.0 5.1 Lines D, Shipton EA (1991). "Severe bradycardia and sinus arrest after administration of vecuronium, fentanyl and halothane. A case report". S Afr Med J. 80 (4): 200–1. PMID 1678901.
- ↑ Bonvini RF, Hendiri T, Anwar A (2006). "Sinus arrest and moderate hyperkalemia". Annales De Cardiologie Et D'angéiologie. 55 (3): 161–3. PMID 16792034. Unknown parameter
|month=ignored (help) - ↑ Koay S, Dewan B (2013). "An unexpected Holter monitor result: multiple sinus arrests in a patient with lateral medullary syndrome". BMJ Case Rep. 2013. doi:10.1136/bcr-2012-007783. PMID 23386489.