EKG
Pre-excitation & channelopathies
EKG

Pre-excitation & channelopathies

WPW, long QT, Brugada, HCM — sudden cardiac death syndromes.

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◆WPW (Wolff–Parkinson–White)

  • •Short PR (<120 ms) + delta wave (slurred upstroke of QRS) + wide QRS
  • •Accessory pathway (bundle of Kent) bypasses AV node
  • •Risk: AFib conducting down accessory pathway → wide bizarre irregular tach → can degenerate to VFib
  • •AFib + WPW: treat with PROCAINAMIDE (or ibutilide); AVOID adenosine, β-blockers, CCBs, digoxin
  • •Definitive: catheter ablation of accessory pathway

◆Long QT syndrome

  • •QTc > 460 ms (women) or >450 ms (men) at rest
  • •Congenital: Romano–Ward (AD, isolated), Jervell–Lange-Nielsen (AR + sensorineural deafness)
  • •Acquired: hypoK, hypoMg, hypoCa, drugs (antiarrhythmics, macrolides, fluoroquinolones, antipsychotics, methadone, ondansetron)
  • •Risk: torsades → syncope → sudden death
  • •Manage: β-blockers; ICD if syncope or family history of SCD; avoid QT-prolonging drugs

◆Brugada syndrome

  • •Type 1 (diagnostic): coved ST elevation ≥2 mm + inverted T in V1–V3
  • •Autosomal dominant SCN5A mutation (sodium channel)
  • •Risk: polymorphic VT/VF, sudden death (often in sleep)
  • •ICD for symptomatic or those with family history of SCD; provocative testing with class IC antiarrhythmic to unmask

◆HCM (hypertrophic cardiomyopathy)

  • •Massive LVH on EKG often with strain pattern, dagger Q waves in lateral leads
  • •Echo: asymmetric septal hypertrophy, systolic anterior motion of mitral valve, dynamic LVOT obstruction
  • •Murmur LOUDER with Valsalva and standing (decreased preload), QUIETER with squat/hand grip
  • •Avoid digoxin, diuretics, vasodilators; β-blockers or CCBs first-line
  • •ICD for high-risk: family history SCD, syncope, septum >30 mm, NSVT on Holter

SCD syndromes — features

SyndromeHallmark
WPWDelta wave + short PR
Long QTQTc >460/450 ms
BrugadaCoved ST V1–V3
HCMLVH + dynamic LVOT murmur ↑ Valsalva
ARVCEpsilon wave V1, T inv V1–V3, RV origin VT

High-yield pearls

  • ◆AFib in a WPW patient: never give AV nodal blockers — they preferentially conduct down the accessory pathway and can precipitate VFib
  • ◆Methadone is a notorious QT prolonger — always check QTc before starting and at intervals
  • ◆Brugada often presents as nocturnal sudden death in young men (esp Southeast Asian); screen family
  • ◆HCM is the most common cause of sudden cardiac death in young athletes
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