Arrhythmias Flashcards
How do you calculate HR from the rhythm strip of an ECG?
Calculate how many big boxes are between each QRS complex, then divide 300 by this number to get the rate
e.g. 4 boxes, 300/4=75bpm
What are some symptoms and complications of arrhythmias?
Sudden death Syncope Chest pain Fatigue Dizziness Palpitations Embolisms
How do you investigate possible arrhythmias?
12 lead 24hr ambulatory ECG monitoring
Blood tests - thyroid in particular
ECHO
Describe the therapy for arrhythmias
Digoxin - AF Beta blockers - lowers HR Calcium antagonists Warfarin or aspirin Anti-arrhythmic drugs DC conversions Pace and ablation of AV node Anti-coagulation
Describe the Singh-Vaughan Williams classification of anti-arrhythmic drugs
I - interferes with Na channel II - anti-symp NS agents e.g. beta blockers III - interferes with K+ efflux IV - affects Ca channels and AV node V - other/unknown mechanism
What is supraventricular tachycardia?
Abnormally fast heart rate (150-250bpm) arising from improper electrical activity in the upper part of the heart: re-entry or increased automaticity
Normal rhythm, P waves not discernable
How do you treat supraventricular tachycardia?
Often don’t require any treatment
Radiofrequency ablation to the abnormal electrical pathways of the heart, good success rate
What are the 4 main types of supra ventricular tachycardia?
Atrial fibrillation
Wolff-Parkinson-White syndrome
Paroxysmal supraventricular tachycardia
Atrial flutter
What is atrial flutter?
Common abnormal heart rhythm starting in the atria, associated with a fast HR (100+bpm), and is classified as a type of supraventricular tachycardia
What causes atrial flutter?
CVD disease - hypertension, CAD, CM
DM
Spontaneously with no cardiac defect
What is a complication of atrial flutter?
Can degenerate into atrial fibrillation
Describe the conduction and rhythm in atrial flutter
Atrial rate is typically 300bpm, while ventricular rate is 150bpm, meaning only one flutter in 2 is conducted
Abnormal rhythm, sawtooth flutter F waves
How can you transiently impair conduction to more easily identify atrial flutter?
Drugs
Carotid sinus massage
Describe the treatment of atrial flutter
Radiofrequency catheter ablation of re-entry circuit is often curative
Can be treated like AF
What is the most common arrhythmia?
Atrial fibrillation - seen in 5-10% of >65yo and paroxysmally in younger patients
Describe atrial fibrillation
Atrial activity is chaotic and mechanically ineffective, conducting a proportion of the AV impulses to produce an irregular ventricular response
Irregularly irregular pulse, fibrillation f waves, no P waves
What are some symptoms of atrial fibrillation?
Palpitations
Fatigue
Acute heart failure
No symptoms - incidental finding
Describe ventricular fibrillation
Very rapid and irregular ventricular activation (300-600bpm) with no mechanical effect and hence no cardiac output. No p waves
Pulseless, unconscious, respiration ceases (cardiac arrest) - medical emergency
How do you treat those with ventricular fibrillation?
Immediate defibrillation (follow cardiac arrest protocol)
After revived, given ICD to reduce risk of sudden death
Describe ventricular tachycardia and its symptoms
Rapid ventricular rate (120-250bpm), broad QRS complexes, no P waves preceding QRS (unassociated)
Palpitations, chest pain, dyspnoea, dizziness and syncope
What two arrhythmias are more associated with underlying structural heart disease?
Ventricular tachycardia
Ventricular fibrillation
When is ventricular tachycardia considered ventricular flutter
bpm >250
What arrhythmias cause broad QRS complexes?
Ventricular tachycardia
Supraventricular tachycardia with BBB
Bundle branch blocks
Rule out with aid of ECG analysis
How do you treat ventricular tachycardia?
Urgent DC conversion
IV lidocaine or amiodarone
Recurrence prevented with
- beta blockers
- other anti-arrhythmias
- ICD
What investigations are used for ventricular tachycardia?
ECG - rule our SVT with BBB
Bloods - thyroid
ECHO
Angiogram
What is Torsades de Pointes?
Abnormal heart rhythm that can lead to sudden death, characterised by short-long-short RR intervals followed by TdP (looks like twirling party streamer)
Type of polymorphic ventricular tachycardia which can resolve itself or cause symptoms such as palpitations, syncope, pre-syncope and sudden cardiac death
How do you treat Torsades de Pointes?
Remove cause (e.g. drugs) if appropriate Infusion of magnesium sulfate Anti-arrhythmic drugs Electrical therapy Defibrillation
What is long QT syndrome?
Prolonged ventricular repolarisation period that cause symptoms such as palpitations and syncope, that can degenerate into TdP or VF
What causes long QT syndrome?
Congenital mutations in Na and K channels
Electrolyte disturbances
Variety of drugs
How do you treat long QT syndrome?
Treat underlying cause
Remove drugs
IV isoprenaline
When is ICD implantation indicated?
High risk of sudden cardiac death
Cardiac arrest due to transient or non-reversible cause
Sustained VT causing syncope
Sustained VT with poor lV function
What are some common causes of heart block?
CAD
Cardiomyopathy
Fibrosis of conduction tissue of heart
What is heart block?
Heart block is a disease or inherited condition that causes a fault within the heart’s natural pacemaker due to some kind of obstruction (or “block”) in the electrical conduction system of the heart, causing an abnormal rhythm where the heart beats too slowly
Where does the block have to be for AV block?
Block in AV node or His bundle
Where does the block have to be for left or right bundle branch block?
Lower conduction system e.g. Purkinje fibres
Describe 1st degree AV block
Prolonged PR interval but rate is normal
Describe 2nd degree type I AV block
Progressive PR elongation until QRS drops, then back to normal
Describe 2nd degree type II AV block
Constant prolonged PR intervals, random QRS complexes dropped
Describe 3rd degree AV block
Totally unrelated P and QRS waves
Describe RBBB on ECG
Secondary r wave in VI
Slurred S wave in V5 and V6
Describe LBBB on ECG
RSR pattern in LV leads (I, AVL, V4-6)
Slurred S in V1 and V2
What are some indications for temporary pacing?
Intermittent/sustained symptomatic bradycardia
When at high risk of severe bradycardia e.g. 2nd/3rd degree AV block, post anterior MI
What are some indications for permanent pacing?
Symptomatic 2nd/3rd degree block AV block with NMD With AV ablation RBBB/LBBB Syncope Sinus node disease Carotid sinus hypersensitivity Malignant vasovagal syncope
