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Sudden Cardiac Death in Structurally Normal Heart

Explore the causes, risk factors, genetic basis, and treatment options for sudden cardiac death in individuals with structurally normal hearts. Learn about primary electrophysiologic abnormalities and familial short QT syndrome.

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Sudden Cardiac Death in Structurally Normal Heart

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  1. Sudden Cardiac Death in Structurally Normal Heart Brian D. Le, MD Presbyterian Hospital CIVA

  2. Presentation • HPI-35 yo WM s PMH presents with exertional syncope • h/o PAF since 18 yrs of age • Holter- monomorphic isolated PVC’s • Echo- structurally normal heart • Meds- no OTC or herbal • Social- occ. Etoh, no IVDA • Family History • Sister (31) - dizziness and palpitations • Sister’s son (6) - cardiac arrest at 8 mo old after a loud noise with successful DCCV Gaita et al. Circulation. 2003; 108

  3. A- 35 yo WM c syncope • B- 31 yo sister, dizziness and palpitations • C- 6 yo son, SCD

  4. Sudden Cardiac Death • “Unexpected death from cardiac cause within a short time (~1 hour of sx) in a person without prior conditions that would appear fatal.” • 300-400,000 deaths annually (U.S.). • VT/VF account for 80%. • 20% have structurally normal hearts. Wever E, et al. JACC. Vol 43, 2004.

  5. Sudden Cardiac Death • Normal hearts, < 40 years old • < 30% successful resuscitation reaching hospital • Risk of life-threatening events in cardiac arrest survivors is 25-40% at two years Wever E, et al. JACC. Vol 43, 2004.

  6. Primary Electrophysiologic Abnormalities • WPW: anterograde BPT ERP <250ms. • Brugada: RBBB w/ST elevation V1-V3 • Catecholamine Polymorphic VT: hRyR2. • Long QT: QTc (>440ms), TdP w/long coupled PVC (600-800ms). • Short-coupled TdP: normal QTc, PVC w/short coupling (200-300ms). • Short QT syndrome • Idiopathic VF

  7. Brugada’s

  8. Catecholaminergic Polymorphic VT

  9. Idiopathic VF

  10. A- 35 yo WM c syncope • B- 31 yo sister, dizziness and palpitations • C- 6 yo son, SCD

  11. Evaluation • Physical Exam • Serial ECG’s • Holter • Heart rate variability • QT dispersion • Signal-averaged ECG • Echocardiogram • Cardiac MRI • Electrophysiological Study

  12. QT Interval • Represents ventricular repolarization. • Normal QTc upper limit: 440ms. • Bazett’s formula: QTc = QT/ RR • Rautaharju formula (14,379 pts): • QTp (ms)= 656/ (1+HR/100) • QT/QTp x 100% = % QTpredicted. • 88% of QTp = 2 SD below mean • Lower limit of nl QT int. = 88% of QTp

  13. QT Interval and SCD • Algra et al. Br.Ht.J. 1993;70:43-8. • Nested cohort 6693 consecutive pts w/24 ECG. • F/U 2.5 years in 99.5% of pts. • End point: QTc correlation w/SCD (104 pts). • Results: • QTc >= 440ms  2.3 RR of SCD. • QTc < 400ms  2.4 RR of SCD.

  14. Familial Short QT • Gussak et al. Cardiology 2000;94:99-102. • 3 members of one family; age 17-51 yo. • Palpitations, sx PAF, syncopeSCD • All w/ structurally normal hearts. • All w/ S-QT (260-280ms); QT interval <80% predicted by Rautaharju method.

  15. Factors That Shorten QT • Increase in heart rate • Hyperthermia • Hypercalcemia • Hyperkalemia • Acidosis • Changes in autonomic tone

  16. Genetic Basis of Short QT • Brugada, Antzelevitch, et al. Circ. 2004;109:30-5. • Different missense mutations in same residue codon 588 of KCNH2 (HERG [IKr]). • Mutations only seen in sQT, and not in normal relatives. • Patch clamp models

  17. Heterogeneity of Short QT • Genetic Studies- KCNQ1 gene mutation G for C, subs. valine for leucine (IKs) • Mutations negative in 200 unrelated controlled individuals • Loss of function leadsLQT1 Bellocq et al. Circulation. 109; 2004

  18. KCNJ2, encoding for inwardly rectifying K channel Kir2.1 • Rapid repolarization • SQT3 • Loss of function results in LQT7 (Anderson’s disease) Priori et al. Circ. Res. 2005; 96

  19. Loss of Function SCN5A  Brugada IKs  LQT1 IKr  LQT2 Gain of Function SCN5A  LQT3 IKs  Fam. A. Fib., Short QT IKr  Short QT 1 2 Ca > Na 3 0 Na IKr & IKs 4 Ion Channel Mutations

  20. Short QT Syndrome Rx • Gaita et al. JACC. 2004;43:1494-9. • 6 pts. from 2 different families. • Drugs: Flecainide (IV or oral), Sotalol, Ibutilide, and Hydroquinidine.

  21. Short QT Rx Results • Flecainide: slight inc. QT due to QRS prolongation. • Ibutilide & Sotalol: no change in QT • Hydroquinidine: • 5/6 pts- QTc normalized (290405ms) • EPS 5/5 pts- inc. VERP, no VF/VT • F/U 11 mos- 4/6 on hydroquinidine w/o sx or arrhythmias detected by ICD.

  22. Ventricular ERP

  23. Quinidine • VW Class: Ia (sodium channel blocker) • Blocks: INa, IKr, IKs, Ito, L-type Ca2+, IK1(in.rect.), & IKATP  QT increase. • Adverse effects: diarrhea, SLE, thrombocytopenia, hepatitis, cinchonism (tinnitus/HA), TdP, many drug interactions 2/2 block of CYP2D6.

  24. ICD • First line therapy • Risk of inappropriate shock delivery- Tw oversensing (Schimpf et al. JCE. 14: Dec 2003)

  25. - Ventricular ERP- <150ms - induction of VF - Atrial ERP- 120ms Circulation. 2003; 108

  26. Family Tree 49 yo 39 yo 39 yo 8 mo Circulation. 2003; 108

  27. Schimpf, et al. Heart Rhythm. 2004;2

  28. SummaryShort QT Syndrome • Significantly short QTc <= 300ms. • Tall & peaked T-waves. • Clinical: palpitations, syncope, SCD. • Significant FHX of SCD. • Atrial and ventricular arrhythmias. • Structurally normal hearts. • Treatment: ICD and/or Quinidine.

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