Making sense of the ECG

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Making sense of the ECG

• By
• Dr Saqib Mahmud
• MRCP(UK) MRCP(London) MRCGP

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Systematic approach to ECG

• Rate normal, tachycardia or bradycardia
• Rhythm sinus or irregular
• P waves present (II V1 best leads to assess)
• PR interval
• QRS complexes axis- widened QRS, Q waves,
  buddle branch block, voltage criteria for LVH
• ST segments isoelectric, depression or
  elevation
• T waves N, peaked or inverted

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Clinical correlation of ECG

• What was the indication?
• age
• Symptoms-CP, palpitations, sob, syncope,
  dizziness
• Haemodynamically stable?
• Clinical signs- HF, poor peripheral perfusion
• Pre-morbid Hx-HTN, IHD, DM, CKD
• Medications- b-blockers, diltiazem etc
• Consider repeating for interval change
• Compare with previous ECG if available

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Criteria / recap

• LVH sum of S in V1 R in V5 or V6 gt35
• RBBB tall R in V1, QRS gt0.12sec, RsR pattern
• LBBB - QS-V1,V2, QRSgt0.12
• Axis - Axis leads-IIII or IaVF, Normal axis-
  double thumbs up(IIII), RAD? I ve, III ve,
  LAD? I ve, III ve
• Inferior leads-------------?II, III, aVF
• Antero-septal leads------?V1,V2,V3V4
• Antero-lateral leads------?I,aVL,V5,V6
• Heart rate calculation-(rhythm regular) count the
  no of large squares b/w 2 consecutive QRS
  divide into 300.HR300/?
• Irregular count no QRS in 30 large squares X 10

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Normal

• RBBB

• LBBB

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axis

• Thumbs up!

• Normal axis

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• RAD

• LAD

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Bradycardia - HRlt60bpm(causes)

• Sinus bradycardia
• Sick sinus syndrome
• 2nd or 3rd degree/CHB
• Escape rhythms- form of safety net to maintain
  heart beat if impulse generation fails or blocked
  
• Negatively chronotropic drugs
  beta-blockers(dont forget eye drops!), Ca
  antagonist diltiazem, verapamil, digoxin

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Symptomatic bradycardia can present with

• Dizziness
• Syncope
• Recurrent falls in elderly
• Fatigue
• Breathlessness
• CP
• Palpitations
• O/E-look for hypotension, signs of HF poor
  perfusion
• Relevant Investigations UEs , TFTs

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Tachycardia-HRgt100bpm

• Narrow complex (lt3 small squares)
• Broad complex (gt3 small squares)
• Narrow complex tachycardias always
  supraventricular in origin
• Narrow complex tachycardias
• Sinus tachycardia
• Atrial fibrillation
• Atrial flutter
• AV nodal re-entrant tachycardia

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Broad complex tachycardia

• Occurs if normal electrical impulses are
  abnormally or aberrantly conducted to the
  ventricles causing delay in ventricular
  activation widening of QRS complex
• VT
• Torsades de pointes
• Accelerated idioventricular rhythm
• SVT with aberrant conduction

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VT
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Tosade de pointes
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SVT with aberrant conduction
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Assessment of tachycardia

• Tachycardia causing hemodynamic disturbance
  requires urgent Rx
• Evidence of hemodynamic disturbance
• Hypotension
• Cardiac failure
• Poor peripheral perfusion
• Investigations
• FBC
• UEs
• TFTs
• BNP

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Possible causes

• Hypothermia
• Hypothyroidism
• B-blockade
• Raised ICP
• Obstructive jaundice
• Uraemia
• Increased vagal tone
• Ischemia
• Structural SA node disease

• Thyrotoxicosis
• Any cause of adrenergic stimulation including
  pain
• Hypovolaemia
• Anaemia
• Pregnancy
• Fever
• Myocarditis
• drugstheophylines,salbutamol, vasodilator
  antihypertensives

• Sinus bradycardia

• Sinus tachycardia

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Heart rhythm dysrhythmias

• Is it regular or irregular?
• Regular rhythms
• Sinus rhythm- P waves precedes every QRS complex
  with consistent PR interval
• Nodal or junctional rhythm- no P wave preceding
  QRS complex but narrow regular complexes
• Atrial flutter-saw tooth appearance, rapid
  regular with a rate about 150bpm(21 block)
• SVT, AVNRT-if high rate 150-220bpm

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Junctional or nodal rhythm
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AVNRT
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Irregular rhythms

• Sinus arrhythmia-P wave precedes QRS with
  constant PR interval but irregular

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Atrial fibrillation- no P waves preceding each
QRS with an irregular rate
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2nd degree HB(Mobitz type 1/ wenckebachs)-
progressive lengthening of PR interval ending
with a dropped beat followed by short PR interval
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2nd degree HB/Mobitz type 2-P waves followed by
QRS, fixed PR interval with occasional
non-conducted or dropped beat
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3rd degree/ CHB
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ST segment elevation
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Ventricular ectopic-QRS broad bizarre,gt3 small
squares, T opposite to QRS
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Tented t waves
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VF
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The end

• Thank you