Cardiology - Arrhythmias Flashcards
What are the features of left bundle branch block?
LBBB is:
- almost always pathological
- wide QRS (indicating prolonged ventricular depolarisation)
- M pattern in V5
Name some causes of LBBB?
1) IHD
2) LVH
3) Aortic valve disease
4) Cardiomyopathy
5) Myocarditis
What is the characteristic ECG abnormality in right bundle branch block?
RSR pattern in V1
MaRRoW
- majority of the QRS complex lies above the isoelectric line in lead 1 and below the line in lead 6
Name some causes of RBBB?
1) Normal variant
2) RVH/ RV strain (e.g. PE)
3) IHD
4) Congenital heard disease (e.g. ASD)
5) Myocarditis
What are the features of right ventricular hypertrophy on ECG?
1) Right axis deviation
2) Positive right wave in V1
Causes of RVH are:
- Mitral valve disease
- Pulmonary hypertension
- Pulmonary stenosis
- PE
- Fallot’s tetralogy
- Cor pulmonale
What are the causes of low voltage complexes on ECG?
1) Dextrocardia
2) Pericardial effusion
3) COPD
4) Hypothyroidism
5) Cardiomyopathy
Name some causes of a short PR interval?
1) WPW syndrome
2) Lown-Ganong-Lavine syndrome
3) P wave followed by ventricular ectopics
What conditions are associated with a long PR interval?
1) IHD
2) Digoxin toxicity
3) Hypokalaemia
4) Rheumatic fever
5) Lyme disease
6) Myotonic dystrophy
What is the prolonged QT syndrome?
The QT interval is increased and this is associated with delayed repolarisation of the ventricles. It is associated with syncope and ventricular tachycardia and death (especially from polymorphic VT).
What causes prolonged QT syndrome?
1) Familial (90%)
- Romano- Ward syndrome (autosomal dominant, no deafness)
- Jervell-Lang-Neilson syndrome (autosomal recessive; includes deafness; caused by abnormal potassium channel)
2) IHD
3) Metabolic
- HYPOcalcaemia
- HYPOkalaemia
- HYPOmagnesaemia
4) Drugs
- erythromycin
- amiodarone
- terfenadine (non sedating antihistamine)
What causes ST depression?
Myocardial ischaemia (including posterior MI)
Digoxin therapy
LVH with strain
What causes ST elevation?
MI Pericarditis Hyperkalaemia Coronary artery spasm (variant/ Prinzmetals angina) Left ventricular aneurysm
What are the causes of pulseless electrical activity (PEA)?
4Hs and 4Ts
- Hypo-or Hyperkalaemia
- Hypothermia
- Hypovolaemia
- Hypoxia
- Cardiac Tamponade
- Tension pneumothorax
- Pulmonary thromboembolus
- Drug/ Toxin overdose
Others include aortic dissection and MI.
What are the two main types of arrhythmia?
Bradycardia - the heart rate is slow (<60bpm). Slower heart rates are more likely to cause symptomatic arrhythmias
Tachycardia - the heart rate is fast (>100bpm). Tachycardias are more likely to be symptomatic if they are fast and sustained. They are divided into supraventricular (SVT), which arise from the atrium or atrioventricular junction, and ventricular tachycardias which arise from the ventricles
What are the general principles of arrhythmia management?
Patients with adverse symptoms and signs (low cardiac output with cold clammy extremities, hypotension, impaired consciousness, or severe pulmonary oedema) require urgent treatment for their arrhythmia. Oxygen is given to all patients, IV access is established and serum electrolyte abnormalities are corrected.
What are sinus rhythms?
The normal cardiac pacemaker is the sinus node, with the rate the sinus node discharges under control by the autonomic nervous system with parasympathetic predominating (causing a slower spontaneous discharge rate).
Fluctuations in autonomic tone result in phasic changes in sinus discharge rate. During inspiration parasympathetic tone falls and the heart rate quickens, and on expiration the heart rate falls. This variation is normal, particularly in children and young adults. Sinus rhythms always have a p wave preceding each QRS complex.
What are the causes of sinus bradycardia?
Athleticism Drugs - e.g. beta blockers, digoxin, verapamil MI (especially inferior) Increased vagal tone - e.g. vomiting Hypothyroidism Hypothermia Sinus node disease Raised intracranial pressure
How is symptomatic bradycardia treated?
Patients with persistent symptomatic bradycardia are treated with a permanent cardiac pacemaker. First line treatment in the acute setting with adverse signs is atropine (500 micro grams i.v. repeated to a maximum of 3mg but contra indicated in myasthenia gravis and paralytic ileus). Temporary pacing is an alternative.
What is sick sinus syndrome? What are the ECG features?
Bradycardia is caused by intermittent failure of sinus node depolarisation (sinus arrest) or failure of the sinus impulse to propagate through the perinodal tissue to the atria (sinoatrial block). The slow heart rate predisposes to ectopic pacemaker activity and tachyarrhythmias are common (tachy-brady syndrome). The ECG shows severe sinus bradycardia or intermittent long pauses between consecutive P waves (>2s, dropped p wave). Permanent pacemaker insertion is indicated in symptomatic patients. Thromboembolism is common in sinus node dysfunction and patients are anticoagulated unless there is a contraindication.
What is heart block?
The common causes of heart block are coronary artery disease, cardiomyopathy, and particularly in the elderly, fibrosis of the conduction tissue. Block in either the AV node or His bundle results in atrioventricular block, whereas block lower in the conduction system produces right or left bundle branch block.
