Arrhythmias Flashcards
What is atrial fibrillation?
Chaotic, disorganised atrial activity
Irregular atrial rhythm at 300-600 bpm
What mechanism causes atrial fibrillation?
Chaotic re-entrant impulse conduction
All meaningful atrial contraction is lost and micro-pathway compare with each other
Ectopic focus around the pulmonary veins
What causes AF?
HF/IHD Hypertension MI PE Mitral valve disease Pneumonia Hyperparathyroidism
What are associated causes of AF?
Alcohol abuse Congenital heart disease Cardiac surgery COPD Septicaemia
What is paroxysmal AF?
<48 hours, often recurrent
What is persistent AF?
> 48
Can still be cardioverted to NSR
What is permanent AF?
Can’t restore NSR
What are symptoms/signs? (AF)
May be asymptomatic Chest pain Palpitations Dyspnoea Faintness Sweatiness Irregularly irregular pulse
What are investigations? (AF)
ECG - absent P waves, irregular QRS complexes, “f”-waves
What are complications of AF?
Embolic stroke
What are the three aims of AF treatment?
Rate control
Restore NSR
Maintain NSR
Which drugs can be used for rate control? (AF)
Digoxin (if HF)
Beta-blocker
Verapamil or diltiazem
What is digoxin?
Cardiac glycoside
What is the mechanism of digoxin?
Binds (blocks) to alpha subunit of sarcolemma Na/K/ATPase in competition with K
Increase Na-Ca exchange
Increase store of Ca in SR
Increase contractility
What are indirect effects of Digoxin?
Increase vagal activity
Slow AV discharge and AV node conduction
Increase refractory period
What are direct effects of digoxin?
Shorten AP and refractory period in atrial/ventricular myocytes
Toxic concentrations of digoxin cause?
Membrane depolarisations and oscillatory after-potentials
What are side effects of dioxin?
Heart block Propensity to cause arrythmias Nausea Vomiting Diarrhoea Disturbance of colour vision
Why can digoxin cause heart block?
Excessive AV node depression
What are methods to restore NSR? (AF)
DCCV
AADs
AADs generally inhibit specific ion channels with intention of…?
Suppression of abnormal electrical activity
What is the mechanism and effect of Disopyramide?
Block/unblock sodium channels at moderate rate
Slow rate of rise of AP and prolong refractory period
What is the mechanism and effect of Flecainide?
Slow block/unblock of Na channels
Strongly depress conduction in myocardium and reduce contractility
What is the mechanism and effect of Lignocaine?
Block/unblock Na channels at rapid rate
Prevent premature beats
Lignocaine primary affects sodium channels in the area of the myocardium that?
Rapidly firs APs due to rapid unbinding (Na channels)
What is the main use of Lignocaine?
Post-MI ventricular arrhythmias
What is metoprolol?
A beta-adrenoceptor antagonist
What is the mechanism and effect of metoprolol?
Decrease rate of depolarisation in SA and AV nodes
Suppress sympathetic drive that may trigger V-tach
What is the mechanism and effect of Amiodarone?
Slow depolarisation of AP by block of K channels
Increase AP duration and effective refractory period
Suppress re-entry
Amiodarone is mainly used to treat?
SVT and VT
What are side effects of amiodarone?
Pulmonary fibrosis
Thyroid disorders
Photosensitive reactions
Peripheral europathy
What is the mechanism and effect of Veramapil?
Blocks L-type Ca channels
Slow conduction and prolong refractory period in AV node and bundle of His
Slow conduction in SA/AV nodes & decrease force of cardiac contraction
What is Veramapil used for? (AF)
Prophylaxis (adenosine for acute) of atrial fibrillation and flutter
What are methods for NSR maintenance? (AF)
AADs
Catheter ablation of ectopic focus (pulmonary veins)
Surgery (Maze procedure)
What is atrial flutter?
Rapid and regular form of atrial tachycardia (250-350 bpm)
Atrial flutter is usually _____ with espides lasting?
Paroxysmal
Seconds-years
What is the mechanism behind atrial flutter?
Macro re-entrant pathways
Circuit confined to the atrium
What are signs and symptoms of Atrial flutter?
Palpitations
Dyspnoea
Fast and steady pulse
How is Atrial flutter diagnosed?
ECG
How is Atrial flutter treated?
Termiantion (rapid atrial pacing, cardioversion or AADs) May convert spontaenously RF ablation Warfarin to prevent thromboembolism Obesity and alcohol reduction Anticoagulants to reduce stroke risk
What is sinus bradycardia?
HR <60 bpm
What can cause sinus bradycardia?
Physiological (athletes)
Drugs (beta-blockers)
Ischaemia (common in inferior STEMIs)
how do you treat sinus bradycardia?
Atropine