Pre-excitation & channelopathies

◆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