Arrhythmias & ECG Interpretation

Arrhythmias & ECG Interpretation

Normal ECG Values

• HR: 60–100 bpm; PR interval: 0.12–0.20 s; QRS: <0.12 s; QTc: <0.44 s (male), <0.46 s (female)
• Each small square = 0.04 s; each large square = 0.2 s

Atrial Fibrillation

• Irregularly irregular rhythm, absent P waves, narrow QRS (unless aberrant)
• Risk: Valvular disease, hypertension, IHD, hyperthyroidism, alcohol
• CHAÔééDSÔéé-VASc: anticoagulation if ÔëÑ2 (men) or ÔëÑ3 (women)
• Rate control: beta-blocker or rate-limiting CCB (diltiazem/verapamil)
• Rhythm control: DC cardioversion, flecainide (no structural disease), amiodarone

Heart Blocks

| Block | PR | QRS | Treatment |

|-------|-----|-----|-----------|

| 1st degree | >0.20 s fixed | Normal | None |

| 2nd degree Mobitz I | Progressive lengthening → dropped | Normal | Monitor |

| 2nd degree Mobitz II | Fixed long PR → sudden dropped | Often wide | PPM |

| 3rd degree (complete) | No relationship P–QRS | Wide escape | PPM urgent |

VT vs SVT with Aberrancy

• Favour VT: AV dissociation, capture/fusion beats, concordance in chest leads, QRS >0.14 s
• Brugada algorithm for WCT

Acute Management of Tachyarrhythmias

• Unstable (shock, syncope, chest pain, HF): synchronised DC cardioversion
• Stable narrow complex (SVT): vagal manoeuvres → IV adenosine 6 mg → 12 mg
• Stable broad complex (VT): IV amiodarone 300 mg over 20–60 min