Arrhythmias Flashcards
What is the PR interval?
Time taken for the spread of depolarisation from the SA node to the ventricular muscle through the AV node (<0.2s)
What is interference with the conduction called during the PR interval called?
Heart block
What does a prolonged PR interval imply?
Delay in conduction of the wave of depolarisation from SA node to the ventricles
What is a supraventricular extrasystole?
Atrial ectopic beat - P wave differs in shape from the P wave in sinus rhythm
What are risk factors for AF?
Age HPT HF Obesity Chronic kidney disease Diabetes Hyperthyroidism
What is atrial fibrillation?
When the atrial muscle fibres contract independently
What are features of AF on an ECG?
No P waves
Irregular QRS complexes
Why can thrombi form during AF?
Atria produces no effective systolic contraction which means it can pool and become stagnant in the atria and form a thrombus
What are symptoms of arrhythmias?
Asymptomatic Palpitations Dyspnoea Chest pain Fatigue Embolism
What investigations should be carried out for AF?
12 lead ECG for 24hrs
Blood test: esp. TFTs
Echo
What is the treatment of AF to control rate?
Digoxin
Beta blocker
CCB
All with warfarin (or aspirin with low risk)
Describe AF ECG
Jagged line representing the many small contraction of different atrial fibres, sometime signals pass through the ventricles and cause contraction, but the QRS complexes occur at irregular intervals and usually at high rates
What is are the aim for AF treatment?
Restore sinus rhythm
Rate control
Assess coagulation needs
What are the treatments for AF to restore sinus rhythm?
Ic/III drugs +/- DC cardioversion
Pace and ablation of AV node
Substrate modification eg Pulmonary vein ostial ablation,
maze procedures
What are two types supraventricular tachycardia?
AV-nodal re-entrant tachycardia
AV re-entrant tachycardia
What are the symptoms of supraventricular tachycardia?
Palpitations
Dyspnoea
What is the treatment for SVT?
No treatment (good prognosis)
AV ablation
Drugs (B blockers)
Describe SVT on an ECG
Abnormal P wave
QRS normal and regular
What is atrial flutter?
Characterised by an atrial rate of 250-350bpm, but heart beat is regular
What are ventricular tachycardia?
Electrical signals that sent start in the SA node, but in the ventricles
How can ventricular tachycardia cause sudden death?
When chambers pump fast they dont have enough time to fill and so pump out little blood
What are the symptoms of ventricular tachycardia cardia?
Palpitations
Chest pain
Dyspnoea
Syncope
What investigations should be carried out for ventricular tachycardia?
Blood
Echo
Angiogram
ECG
Is ventricular fibrillation supportive of life?
No
What does ventricular tachycardia look like on an ECG?
No relationship with atria
Wide QRS complexes
What are indications for ICD therapy?
Cardiac arrest due to VF/VT
Sustained VT causing syncope or significant compromise
Sustained VT with poor LV function
What is First Degree heart block?
PR interval is prolonged as there is a delay in conduction from SA node through to ventricles
What is first degree heart block a sign of?
CAD
Acute rheumatic carditis
Digoxin toxicity
Electrolyte disturbances
What is second degree heart block?
Occasionally, depolarisation fails to pass through the AV node or bundle of His
What are the 3 types of second degree heart block?
Mobitz type 1
Mobitz type 2
AV block 2:1/3:1/etc
What is mobitz type 1 second degree heart block?
Progressive prolonging of PR interval over 3-6 beats until a P wave occurs, without a following QRS complex
What is mobitz type 2 second degree heart block?
PR interval is constant and then after ~8 beats, there is no preceding QRS complex
What is AV block in second degree heart block?
Alternated conduction of atrial beats (some lead to QRS complexes and some dont)
Relationship can be describe as 2:1/3:1 etc - one conducted then 2/3 non-conducted
What is third degree heart block?
Complete heart block - when atrial contraction occurs but no signals are passed through to ventricles (AV block)
What are the features of complete heart block on an ECG?
P wave is regular but has no relationship to the QRS complex or ventricular activity
What are indications for temporary pace maker?
Intermittent or sustained symptomatic bradycardia (esp syncope)
Prophylactic when patient at high risk for developing severe bradycardia (2nd or 3rd degree AV block, post anterior MI)
What are indications for permanent pace maker?
2nd/3rd degree AV block
AV block associated with neuromuscular disease (symptomatic or asymptomatic)
After AV node ablation
Alternating RBBB/LBBB
What is ventricular fibrillation?
Different parts of the myocardium depolarising independently at a fast irregular rate
What are the features of VF on an ECG?
No P wave
Extremely irregular rhythm
Fibrillation baseline
What is Wolff-Parkinson-White Syndrome?
Extra electrical conduction pathway between atria and ventricles - Bundle of Kent
Atria arrhythmia also means that the ventricles with contract are the same rapid rate
How does Wolff-Parkinson-White Syndrome cause cariogenic shock?
Atrial arrhythmia causes ventricle tachycardia so it cuts into distole and therefore heart does not pump out enough blood
What is atrioventricular reentrant tachycardia?
Seen in Wolff-Parkinson-White syndrome as the Bundle of Kent is bidirectional
What is the treatment for Wolff-Parkinson-White sydrome?
Radiofrequency catheter ablation of the Bundle of Kent
