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Arrhythmias (Sinus Rhythm (Left Axis Deviation (Left BBB, LV hypertrophy, …
Arrhythmias
Sinus Rhythm
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SAN > Atria > AVN > Interventricular Septum > Bundle of His > Right and left bundle branches > Purkinje cells > Ventricles
Delay in the action potential between AVN and ventricles is to allow for complete emptying of the atria before the ventricles contract
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SAN is the pacemaker of the heart and it's rate of depolarisation is modulated by the autonomic nervous system
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In normal sinus rhythm, P wave is upright in leads I + II and inverted in leads AVR + V1
Atrial Fibrillation
Pathophysiology
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Increases risk of embolic stroke: when the atria spasms, blood pools and begins to clot, forming a thrombus which breaks off into an emboli
The AV node responds intermittently, causing an irregular ventricular rhythm
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Aetiology
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Hypertension (increases risk of ischaemia, which means cells are not receiving enough blood so they are faulty)
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Investigations
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Bloods: thyroid function tests, U&E
ECG: absent P waves, irregular + narrow QRS complex
Treatment
Acute AF
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If patient has adverse signs i.e. chest pain, syncope then do ABCDE + synchronized shock (cardioversion)
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Chronic AF
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Use CHA2DS2-VASc score to calculate stroke risk and need for anticoagulation. Gives points for congestive heart failure, hypertension, >75, diabetes, stroke, vascular disease, female
Rhythm control via flecainide. Rhythm control is advocated for younger, symptomatic and physically active patients
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Heart Block
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1st Degree AV Block
Caused by hypokalaemia, myocarditis, inferior MI
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Bradycardia
Intrinsic causes: acute ischaemia, infarction of SAN, sick sinus syndrome
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Extrinsic causes: digoxin, beta blockers, hypothyroidism, hypothermia, raised intercranial pressure
If symptomatic, insert pacemaker
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Sick sinus syndrome: bradycardia caused by intermittent failure of SAN depolarisation due to failure of sinus node to propagate to the atria (sinoatrial block)
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Long QT Syndrome
Acquired causes: Hypocalcaemia, bradycardia, acute MI, diabetes
Causes syncope, palpitations
Congenital causes: Jervell-Lange-Neilsen syndrome, Romano-Ward syndrome
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Tachycardia
Sinus Tachycardia
Caused by anxiety, exercise, pain
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Broad complex issues are to do with ventricular pathology. Narrow complexes are due to problems with the atria, AVN and SAN.