Medicine: ECG interpreatation Flashcards
General points to consider while looking at ECG
- What is the rate? (fast, slow or normal)
- What is the rhythm (regular or irregular)
- Are the complexes narrow (normal) or broad
- As a generalisation narrow complexes normally originate in the atria and broad ones in the ventricles
- Is there atrial activity? Are there p-waves present? What is the relation to the QRS complex?
Definition of tachycardia
A heart rate over 100 bpm
Categorisation of tachycardias
- (2) due to causes
- ( 2)due to characteristic of rythm
- (2) due to origin
- May be physiological sinus tachycardia (e.g. exercise response)
- May be pathological
–Remember: most tachycardias are a response to an insult on the body (e.g. sepsis)
•Categorised by broad vs narrow and regular vs irregular
Causes and types of narrow complex tachycardia
- Sinus tachycardia (physiological) → origin SA node
Types:
- Atrial tachycardia - aberrant atrial focus
- Atrioventricular nodal re-entry tachycardia (AVNRT) - re-entry circuit close to / in AV node
- AV macro-re-entry tachycardia (AVRT) abnormal accessory pathway
- Atrial flutter with regular AV block (e.g. 2:1, 3:1)
(2) Types of irregular broad complex tachycardia?
•Irregular
–Polymorphic VT (Torsade des pointes): sinusoidal morphology due to abnormal ventricular re-polarisation (Long QT)
–AF with BBB (Bundle branch block)
Types of regular broad complex tachycardias
–VT: single ventricular focus of origin
–SVT with rate related BBB (aberrant conduction)
–This is when the conduction rate exceeds the refractory period and the SVT conducts to the ventricle aberrantly (more common in older patients).
Causes of tachyarrhythmias
•Cardiac
–Post cardiac arrest, ischaemia, Long QT syndrome, structural: valvular heart disease / cardiomyopathy
•Non-cardiac
–Hypoxia, hypovolaemia, electrolyte abnormality, hypoglycaemia, hypo-/hyperthermia, hypo-/hyperthyroidism, sepsis
•Drug-induced
–Cocaine, amphetamines (stimulants)
–Tricyclics(generally due to QT prolongation)….and many more!
Management of tachyarrhythmia with adverse features
- ABCDE
- Monitoring
- Determine presence/absence of adverse features
–Shock, syncope, myocardial ischaemia, heart failure / fluid overload
•If pulse present → for synchronised DC cardioversion under general anaesthesia / sedation as emergency followed by I.V anti-arrhythmic (usually Amiodarone 300mg over 20 mins then 900mg over 24hrs)
Management of narrow complex tachyarrhythmia with no adverse features
*Adverse features: shock, syncope, MI, HF, fluid overload
•Narrow complex:
–Regular likely SVT
•Vagal manoeuvres
•Adenosine IV
•Verapamil / Flecanide
Management of irregularly irregular AF with no adverse features
*adverse features: syncope, shock, MI, HF, fluid overload
Irregularly Irregular AF
- Onset <48hrs → rhythm control
Flecanide / Amiodarone & anticoagulation; DC cardioversion
- Onset >48hrs → rate control
Beta-blocker (Metoprolol / Bisoprolol) or Verapamil
Digoxin may be added later
Treatment of regular broad complex tachycardia
- Treated as VT unless the patient has a documented previous ECG with Bundle Branch Block of unchanged morphology
- Definite SVT with BBB treat as narrow complex tachycardia
Rx: Amiodarone
Treatment of irregular broad complex tachycardia
–AF with Bundle Branch Block → treat as irregular narrow complex tachycardia
–Polymorphic VT → Magnesium, stop medication which prolongs QT, correct electrolyte imbalance
Further management of arrhythmias (after emergency management)
- Identify and correct underlying cause
- Cardiology referral as appropriate
- Consider DC cardioversion (may be as OP after4/52 in AF)
- Consider:
- Implantable Cardioverter Defibrillator (ICD) in malignant ventricular tachyarrhythmias- cardiologist decision only
- Long term Anti-arrhythmic drugs
What score needs to be considered for AF patients?
•Assess stroke risk (CHA2DS2VASc score) and consider anticoagulation if indicated