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− | ===2. AV Block=== | + | {{OpenPagesTop}} |
| + | == Introduction == |
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− | *The delay or failure of the atrioventricular node to conduct impulses.
| + | Atrio-ventricular block is the delay or failure of the atrioventricular node to conduct impulses. |
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| + | There are three types of AV block: |
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− | ====1st Degree (Partial AV Block)====
| + | '''1st Degree''' (Partial AV Block) - Delayed conduction through the AV node. Causes include electrolyte imbalance, drug reactions and degenerative changes in the AV node. It may be a permanent or temporary condition. |
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− | *Delayed conduction through the AV node
| + | '''2nd Degree''' (Partial AV Block) - Intermittent failure of conduction through the AV node. |
| + | :Mobitz Type I. = prolonged P-R interval |
| + | :Mobitz Type II. = no prolongation of the P-R interval. |
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| + | :There are also sub types with Type A: normal QRS length; block is above the bundle of His division (Most commonly seen with Mobitz Type I.) |
| + | :Type B: longer QRS length; block is below the bundle of His division (Most commonly seen with Mobitz Type II.). |
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− | '''Causes'''
| + | :Causes include electrolyte imbalance, drug reactions and degenerative changes in the AV node. The condition may be temporary or permanent. |
− | Electrolyte imbalance, drug reactions, degenerative changes in the AV node
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| + | '''3rd Degree''' (Total AV Block) - Total failure of AV conduction causing uncoordinated and independent atrial and ventricular depolarisations. Causes include electrolyte disturbances, drug toxicities (e.g. digitalis), acquired nodal diseases, [[:Category:Cardiomyopathy|cardiomyopathies]], [[hypothyroidism]], [[endocarditis]], [[Lyme Disease]] etc. This is a permanent life threatening condition. |
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− | '''ECG Appearance:''' Longer P-R interval
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| + | == Clinical Signs == |
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− | '''Treatment''' Treat the underlying cause
| + | Depending on which type of block and severity, clinical signs may vary. Signs may include weakness, syncope, exercise intolerance and pallor. |
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− | ====2nd Degree (Partial AV Block)====
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− | *Intermittent failure of conduction through the AV node
| + | == Diagnosis == |
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| + | Clinical signs plus auscultation of the heart will be indicative of the condition. |
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− | '''Mobitz Type I.'''= prolonged P-R interval | + | An '''ECG''' will show characteristic results which will confirm the diagnosis. In 1st degree AV block there will be a longer P-R interval on ECG. In 2nd degree AV block some P waves are not followed by QRS complexes. In 3rd degree AV block there will be independent regular and fast P waves or independent regular and slow QRS waves. |
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− | '''Mobitz Type II.'''= no prolongation of the P-R interval
| + | == Treatment and Control == |
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| + | 1st degree AV block - treat the underlying cause. |
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− | '''Type A:''' normal QRS length; block is above the bundle of His division (Most commonly seen with Mobitz Type I.)
| + | 2nd degree Av block - Mobitz Type I.: Treat underlying cause if necessary. Mobitz Type II. Treat with atropine etc. or surgical implantation of a pacemaker. |
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| + | 3rd degree AV block needs surgical intervention and the implantation of a cardiac pacemaker. |
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− | '''Type B:''' longer QRS length; block is below the bundle of His division (Most commonly seen with Mobitz Type II.)
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| + | == References == |
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− | '''Causes''' Electrolyte imbalance, drug reactions, degenerative changes in the AV node
| + | Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition) W.B. Saunders Company |
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| + | Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2)W.B. Saunders Company |
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− | '''ECG Appearance:''' Some P waves are not followed by QRS complexes
| + | Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition) Mosby Elsevier |
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− | '''Treatment'''
| + | {{review}} |
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− | Mobitz Type I.: Treat underlying cause if necessary
| + | {{OpenPages}} |
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− | Mobitz Type II. Treat with atropine etc. or surgical implantation of a pacemaker
| + | [[Category:Impulse_Conduction_Abnormalities]] [[Category:Expert_Review]] |
− | | + | [[Category:Cardiology Section]] |
− | ====3rd Degree (Total AV Block)====
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− | *Total failure of AV conduction causing uncoordinated and independent atrial and ventricular depolarisations
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− | '''Causes''' Electrolyte disturbances, drug toxicities (e.g. digitalis), acquired nodal diseases, cardiomyopathies, hypothyroidism, endocarditis, [[Lyme disease]] etc.
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− | '''ECG Appearance:''' Independent regular and fast P waves; independent regular and slow QRS waves
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− | '''Treatment''' Treat underlying disease, atropine etc., implantation of a cardiac pacemaker[[Category:Impulse_Conduction_Abnormalities]][[Category:To_Do_-_Cardiovascular]]
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