ECG Patterns

NSVT (Non-sustained Ventricular Tachycardia)

• Definition: HR >100 bpm, ≥3 consecutive ventricular beats, lasting <30 seconds

• Clinical Approach:

  • Consider cardiology referral to evaluate for structural heart disease (e.g. echo, Holter monitoring)

  • Start beta-blocker if patient is symptomatic or if NSVT is frequent

  • Investigate and correct electrolyte abnormalities (e.g. low potassium, magnesium)

Bi/Trigeminy

• Bigeminy: PVC every second beat

• Trigeminy: PVC every third beat

• Clinical Considerations:

  • May predispose to more dangerous tachyarrhythmias (VT or SVT) in ischaemic heart disease

  • Check electrolytes and contributing factors (caffeine, alcohol, stress)

  • Treat with beta-blockers or consider catheter ablation if significantly symptomatic or in high-risk patients

Peaked T Wave

• Typically >5 mm in limb leads or >10 mm in chest leads

• Differential: Usually hyperkalaemia, but can also be early sign of transmural ischaemia

  • Urgent serum potassium check if suspicion of hyperkalaemia

  • Early ischaemia may show hyperacute T waves in leads corresponding to the affected territory

WPW (Wolff-Parkinson-White Syndrome)

• Key ECG Features:

  • Short PR interval (<0.12 sec)

  • Delta wave (slurring of the initial part of the QRS)

  • Widened QRS complex

• Risk: Propensity for AV re-entrant tachycardia, which can rapidly conduct in AF

• Referral: Electrophysiology assessment for possible ablation if symptomatic, especially if recurrent tachyarrhythmias

RBBB (Right Bundle Branch Block)

• ECG Findings:

  • QRS duration >120 ms

  • rsR′ or M-shaped R wave in V1–V3

  • Wide slurred S wave in lateral leads (I, aVL, V5–V6)

  • ST depression and T-wave inversion in V1–V3 (secondary repolarisation changes)

• Causes: Normal variant in some individuals, right ventricular overload (COPD, pulmonary embolism), or ischaemic heart disease

  
  

LBBB (Left Bundle Branch Block)

• ECG Findings:

  • QRS duration >120 ms

  • Broad monophasic R waves in I, aVL, V5–V6 (M-shaped)

  • Deep S waves in V1–V3 with secondary ST-T changes (discordance)

  • Can mask or mimic ST-elevation in leads V1–V4

• Clinical:

  • In acute presentation with chest pain, new LBBB can represent an anterior STEMI equivalent

  • Consider emergent evaluation for possible occlusion of the LAD if clinical suspicion is high

Digitalis Effect

• Classical ECG Pattern: Down-sloping ST depression (scooped or “mustache” appearance)

• May be associated with arrhythmias (e.g. AV block, junctional tachycardia) if digoxin toxicity develops

• Monitor digoxin levels, renal function, and electrolytes to avoid toxicity

Notes:

• Limb Leads: I, II, III, aVL, aVR, aVF

• Chest Leads: V1–V6

• Correlate frequent ectopics or abnormal patterns with clinical symptoms (palpitations, syncope) and risk factors

• Consider other causes of conduction abnormalities (cardiomyopathies, electrolyte imbalances, medications)

• In suspected arrhythmic events, ambulatory ECG monitoring (Holter or event recorder) can help characterise frequency and severity of episodes

• Any significant ECG changes in the context of structural heart disease or persistent symptoms warrant specialist referral for further investigation