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
Do we use Aspirin in order to prevent stroke in a patient with AF?
Aspirin not indicated for stroke prevention in AF
When we do not consider rate-control as first-line management of AF? (5)
Rate control as first-line unless:
- New onset
- reversible cause
- heart failure due to AF
- suitable for ablation
- rhythm control clinically felt to be more suitable
What’s the method of management of AF that is not responding to drugs?
•Pulmonary Vein Isolation (PVI) ablation
–If not responding / not suitable drug treatment and
- Paroxysmal AF
- Persistent AF
Classes, MoA and names of some anti-arrhythmic drugs
Indications for Implantable Cardioverter Defibrilator (ICD)
Indications for ICD:
- Primary prevention of sudden cardiac death in patients at high risk of life-threatening VF / VT
- Secondary prevention of sudden cardiac death in patients with a history of:
- Resuscitated cardiac arrest due to VF / VT
- Previous sustained VT
Complications of ICD
Complications of ICD
- Insertion problems, e.g. infection, bleeding, displacement, lead damage
- Failure to detect arrhythmia
- Inappropriate shock delivery and driving restrictions
- Turning off defibrillator (magnet inhibition)
Indications for pacemaker in non-emergency setting
- Rapid pacing in tachyarrhythmia to terminate rhythm (in association with ICD)
- Anti-tachycardia pacing (ATP)
- Pacing indicated for symptomatic bradycardias e.g. sick sinus syndrome, AV block, HCM
- Pacing in heart failure is a different situation
Emergency management of bradycardia with adverse signs
Emergency Management of bradycardia in the presence of adverse signs:
- Atropine 0.5mg I.V repeated to a max. of 3mg
- Transcutaneous pacing
- Temporary transvenous pacing wire
- Consideration of permanent pacemaker if persistent
•If pacemaker already in put a magnet over it if bradycardic
What does ECG show? (spot diagnosis)
Supraventricular re-entry tachycardia
(QRS complexes smaller and taller alternating)
VT management in:
A. Haemodynamically stable pt
B. Not-haemodynamically stable patient
A. haemodynamically stable: Amiodarnone first (while preparing DC cardioversion equipment)
B. not-haemodynamically stable: DC cardioversion (shock)
Management (step-wise) of SVT
- Valsalva manoeuvre
- Adenosine 6mg IV → 12mg → 18mg
(full resus equipment + ECG monitoring while using adenosine; IV bolus with rapid flush)
- Anti - arrhytmics: beta blocker, Flecanide, CCB etc)
Contraindications to use of adenosine
- asthma
- sick sinus syndrome
- heart block
(as adenosine blocks the AV node)
Interactions with adenosine
- Dipyridamole → increases action of adenosine (lower doses of adenosine needed)
- chocolate, tea, coffee → decreases action of adenosine (higher doses needed)
Long- term management of re-entry tachycardia
- electrical studies and ablation
- CCB
- beta- blockers
- flecainide
*amiodarone rarely used due to its long term side effects
Draw heart axis
*this was a task at OSCE
Normal values on ECG
•1 BIG square → 0.20 seconds
(so 5 small squares → 0.20 seconds)
•1 small square → 0.04 seconds
Normal values (approximations):
- P wave → 0.10 seconds (2-3 small squares)
- QRS wave → 0.10 seconds (2-3 small squares)
- PR interval → 0.12-0.20 seconds (3-5 small squares)
- ST segment → 0.10 seconds (2-3 small squares)
Steps of ECG reading
- pt details
- ‘does a patient have a pulse’? to exclude PEA
- calibration (2 big squares) → 25 mm/sec
- HR - regular, rate
- P- wave (width, followed by complex)
- QRS - narrow or wide
- PR interval
- ST segment
- R wave progression across the leads (V1 should always be negative and V6 should always be positive)
- Axis→ possible deviation
- possible Bundle branch block
Side of infract and ECG leads corresponding to it
Mx of 3rd-degree heart block
Permanent pacing or transcutaneous pacing
How does Valsalva manoeuvre work?
Increase in thoracic pressure → Vagus nerve activated → Parasympathetic system activated → slower HR
