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| − | [[Sino-Atrial Block]]
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| − | | + | [[Category:Altered_Impulse_Formations]] |
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| − | ===2. AV Block===
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| − | *The delay or failure of the atrioventricular node to conduct impulses.
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| − | ====1st Degree (Partial AV Block)====
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| − | *Delayed conduction through the AV node
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| − | '''Causes'''
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| − | Electrolyte imbalance, drug reactions, degenerative changes in the AV node
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| − | '''ECG Appearance:''' Longer P-R interval
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| − | '''Treatment''' Treat the underlying cause
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| − | ====2nd Degree (Partial AV Block)====
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| − | *Intermittent failure of conduction through the AV node
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| − | '''Mobitz Type I.'''= prolonged P-R interval
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| − | '''Mobitz Type II.'''= no prolongation of the P-R interval
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| − | '''Type A:''' normal QRS length; block is above the bundle of His division (Most commonly seen with Mobitz Type I.)
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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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| − | '''Causes''' Electrolyte imbalance, drug reactions, degenerative changes in the AV node
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| − | '''ECG Appearance:''' Some P waves are not followed by QRS complexes
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| − | '''Treatment'''
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| − | Mobitz Type I.: Treat underlying cause if necessary
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| − | Mobitz Type II. Treat with atropine etc. or surgical implantation of a pacemaker
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| − | ====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, lymes 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
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| − | ===Atrial Standstill===
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| − | *Temporary or permanent lack of atrial activity resulting from a failure of atrial depolarisation. Ventricles still function normally.
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| − | ====Causes====
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| − | Electrolyte abnormalities, cardiomyopathies, muscular dystrophy, hypoadrenocorticism
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| − | '''ECG Appearance:''' Absence of P waves
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| − | ====Treatment====
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| − | Treat the underlying cause
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| − | ===Bundle Branch Block===
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| − | *Abnormal ventricular excitation as the result of blockage to the right bundle branch, the left bundle branch, or left anterior fascicular block.
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| − | ====Right Bundle Branch Block====
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| − | Characterised by the failure or delay of conduction through the right bundle branch. Left ventricle is unaffected.
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| − | =====Causes=====
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| − | Pulmonary embolism, heart worm, electrolyte disturbances, congenital diseases etc.
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| − | '''ECG Appearance:''' Wide QRS complex, Wide S wave
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| − | =====Treatment=====
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| − | Treat the underlying cause
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| − | ====Left Bundle Branch Block====
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| − | Characterised by the failure of conduction through the left bundle branch. Right ventricle is unaffected.
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| − | =====Causes=====
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| − | Congenital abnormalities, myocardial diseases etc.
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| − | =====Treatment=====
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| − | Treat the underlying cause
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| − | '''Left Anterior Fascicular Block'''=characterised by the failure of conduction through the anterior fascicle of the left bundle branch.
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| − | '''Causes:''' Electrolyte abnormalities, hypertrophic cardiomyopathy (cat), etc.
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| − | '''ECG Appearance:''' Normal QRS, tall R waves, deep S waves
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| − | '''Treatment:''' Treat the underlying cause
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| − | ===Wolff-Parkinson-White Syndrome (Ventricular Preexcitation Syndrome===
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| − | *This syndrome occurs when the conduction travels from the SA node and then completely bypasses the AV
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| − | node and travels to the bundle of His or the ventricles.
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| − | ====Causes====
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| − | Hypertrophic cardiomyopathy (cats); congenital heart disorders
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| − | '''ECG Appearance:''' Short PR interval; Prolonged QRS complex; Notch in the R wave
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| − | ====Treatment====
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| − | Treatment for tachycardia if necessary: digoxin, quinidine etc.
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| − | ===Sick Sinus Syndrome===
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| − | *This is a blanket term used to describe multiple abnormalities of the SA node involving impulse formation and conduction disturbances.
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| − | ====Causes====
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| − | Myocardial diseases, idiopathic, breed predispositions (e.g. miniature schnauzer)
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| − | '''ECG:''' Variable depending on the specific SA abnormality
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| − | ====Treatment====
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| − | Surgical implantation of a pacemaker; +/- antiarrhythmic treatments[[Category:Altered_Impulse_Formations]]
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