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cardio.post-arrest.long-qt-channelopathy.v1

Post-cardiac-arrest care — congenital long-QT channelopathy (KCNQ1 / KCNH2 / SCN5A) with TdP-arrest

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Phase E variant of cardio.post-arrest.core.v1 — narrowed to congenital long-QT syndrome (LQTS) channelopathy as the etiology of the index out-of-hospital VF arrest. Primary subtypes: LQT1 KCNQ1 (~30–35% — exertion/swimming triggers), LQT2 KCNH2 (~25–30% — auditory/emotional/post-partum triggers, female event predominance), LQT3 SCN5A gain-of-function (~5–10% — sleep/bradycardia triggers); rarer LQT4–17 (CALM1/2/3, CACNA1C Timothy syndrome, etc.). Per HRS 2017 PMID 28219760. Sister to cardio.cardiogenic-shock.lqt-tdp-storm.v1 — that dossier covers MID-STORM hemodynamic management (≥3 sustained TdP / 24 h with shock); THIS dossier covers POST-ROSC care after the storm has terminated in arrest, with focus on QTc reassessment after ROSC (acute electrolyte / hypoxia / hypothermia shifts mask baseline QTc), LQT subtype classification by T-wave morphology, GENETIC PANEL (KCNQ1/KCNH2/SCN5A core; expanded if family history positive), CASCADE FAMILY SCREENING (first-degree relatives ECG + genotyping at proband mutation), lifelong β-blocker (nadolol 1–1.5 mg/kg/d preferred over propranolol 2–4 mg/kg/d per recent registry data — Schwartz International LQTS Registry mortality reduction in LQT1+LQT2; less effective in LQT3), ICD per HRS 2017 Class I (sustained VT/VF survivor by definition), LCSD for refractory β-blocker failure or ICD-shock burden, and lifelong avoidance of QT-prolonging drugs. Critical post-ROSC pharmacologic AVOIDS (signature departure from generic post-arrest care): HALOPERIDOL (substitute dexmedetomidine + low-dose olanzapine); ONDANSETRON > 16 mg cumulative (FDA black-box; substitute scopolamine + low-dose olanzapine); CITALOPRAM > 20 mg + ESCITALOPRAM at high dose (FDA black-box; substitute sertraline / mirtazapine); MACROLIDES (azithromycin/erythromycin/clarithromycin — substitute doxycycline or β-lactam-only regimen); FLUOROQUINOLONES (moxifloxacin > levofloxacin > ciprofloxacin — substitute β-lactams or aztreonam); METHADONE for analgesia (substitute fentanyl + hydromorphone); CLASS IA + III ANTIARRHYTHMICS (quinidine, procainamide, disopyramide, sotalol, dofetilide, ibutilide); AMIODARONE relative-avoid (less torsadogenic than other class III but still QT-prolonging — reserve for refractory VT with no alternative); some antipsychotics (haloperidol, ziprasidone, quetiapine, pimozide). Reference: www.crediblemeds.org curated QT-prolonging drug list (gold standard). Lifestyle counseling per genotype (HRS 2017): LQT1 avoid competitive swimming + diving lifelong (water immersion is the trigger); LQT2 avoid sudden loud noises (modify alarm clock — vibrating + light-based alarms); LQT3 caution sleep alone + nocturnal cardiac monitoring (sleep is high-risk period); aggressive K repletion if hypokalemic (target K ≥4.5). Medic-alert bracelet "Long QT syndrome — AVOID QT-prolonging drugs" mandatory. Inherits manifest + design-brief pointer from parent cardio.post-arrest.core.v1; specializes the QTc reassessment + channelopathy workup + family screening + lifelong β-blocker + ICD + LCSD + drug-avoidance arcs. 5 setting playbooks (ed, icu, inpatient, transition, outpatient). 5 severity triggers: recurrent TdP storm-bridge routing, inadvertent QT-prolonging drug administered post-ROSC (common nursing handoff failure mode), bradycardia-dependent TdP recurrence, ICD eligibility evaluation, cascade family screening referral. Status INTEGRATED until terminology + RxNav-validated drug codes are reconciled. Authored 2026-05-15 by shard-06-cardio-acute Phase E wave 24.

Entry points (6)

  • symptom
    ROSC after out-of-hospital VF arrest with known long-QT syndrome (prior diagnosis, prior syncope, family history) or with sentinel post-ROSC ECG features (QTc > 500 ms, TdP runs)
    rosc_after_oohca_with_known_or_suspected_lqts
  • imaging
    Post-ROSC 12-lead ECG with QTc > 500 ms (Bazett or Fridericia) + structurally normal heart on echo — congenital LQT high concern; pivot from generic post-arrest care to channelopathy-specific avoidance protocol
    post_rosc_ecg_qtc_above_500_with_normal_structural_heart
  • history
    Witnessed arrest with classic LQT trigger pattern: exertion or swimming (LQT1), auditory startle / emotional / post-partum (LQT2), sleep / nocturnal (LQT3) — directs subtype classification
    witnessed_arrest_with_lqts_trigger_pattern
  • history
    Family history of sudden death <40 y or known LQTS in first-degree relative — congenital LQT high pretest probability; offer genetic panel + cascade screening
    family_history_sudden_death_under_40_or_known_lqts
  • history
    Prior unexplained syncope (esp exertional / auditory / nocturnal) or recent exposure to QT-prolonging drug pre-arrest — informs congenital vs acquired classification + secondary-prevention plan
    prior_unexplained_syncope_or_qt_prolonging_drug_exposure_pre_arrest
  • lab_abnormality
    Hypokalemia (K < 3.5) or hypomagnesemia (Mg < 2.0) at arrest presentation — electrolyte-driven QT prolongation may have unmasked latent LQT substrate; aggressive replacement + congenital workup mandatory
    hypokalemia_or_hypomagnesemia_at_arrest

Required inputs (24)

  • agerequired
    demographic • used at CONTEXT
    Congenital LQT typically manifests in childhood / adolescence / young adulthood; pediatric resuscitation modifications below age 8; ICD device-size considerations in pediatric / small-frame patients
  • sexrequired
    demographic • used at CONTEXT
    LQT2 has female predominance for events (especially post-partum); informs counseling + risk stratification + cascade-testing prioritization
  • witnessed_arrest_with_trigger_patternrequired
    history • used at CONTEXT
    Trigger pattern is highly informative: LQT1 = exertion/swimming; LQT2 = auditory/emotional/post-partum; LQT3 = sleep/nocturnal; predicts subtype before genetic results return
  • time_to_cpr_minrequired
    history • used at CONTEXT
    CPR within 1 min dramatically improves outcome; CAHP/OHCA score input
  • time_to_aed_defibrillation_minrequired
    history • used at CONTEXT
    AED within 3 min → 50%+ survival; venue AED program presence is dominant prognostic factor
  • initial_rhythmrequired
    history • used at CONTEXT
    VF most common in LQT (~85%); polymorphic VT degenerating to VF is the classic mechanism; informs storm-suppression bridge planning
  • family_history_sudden_death_or_known_lqtsrequired
    history • used at CONTEXT
    Family history of SCD <40 y or known LQTS in first-degree relative is a critical input — drives congenital workup priority + cascade screening of relatives
  • prior_syncope_or_qt_prolonging_drug_exposurerequired
    history • used at CONTEXT
    Prior exertional / auditory / nocturnal syncope suggests congenital LQT; recent QT-prolonging drug exposure (macrolide, fluoroquinolone, antipsychotic, methadone, ondansetron, citalopram) suggests acquired or unmasked congenital substrate
  • pre_arrest_medication_list_qt_auditrequired
    history • used at CONTEXT
    Comprehensive medication review against www.crediblemeds.org curated list — STOP all offenders + document; informs whether arrest was triggered by acquired prolongation on a congenital substrate
  • sbprequired
    vital • used at TREATMENT
    MAP ≥65 target post-ROSC; SCAI staging if shock; cautious vasopressor dosing in LQT1/2 (adrenergic surge is the trigger)
  • hrrequired
    vital • used at TREATMENT
    Bradycardia is a major TdP trigger (LQT3 + acquired); avoid β-blockers acutely if bradycardia-dependent; isoproterenol or pacing pathway may be needed
  • core_temprequired
    vital • used at TREATMENT
    TTM target 33–37.5 °C × 24 h (TTM2 PMID 34133859); hypothermia paradoxically prolongs QT — re-measure QTc after rewarm before defining baseline
  • spo2required
    vital • used at TREATMENT
    Avoid hyperoxia: SpO2 92–98% (AHA 2020 Class IIa)
  • ecg_12_lead_serial_with_qtc_bazett_and_fridericiarequired
    imaging • used at INITIAL_WORKUP
    Serial ECGs q4–6 h × 48 h with QTc Bazett + Fridericia; T-wave morphology informs subtype (LQT1 broad-based; LQT2 notched/low-amplitude; LQT3 late-onset narrow); high V1–V2 placement (2nd–3rd ICS) may unmask Brugada overlap; pause-dependence pattern; baseline for ICD planning
  • tte_high_resolutionrequired
    imaging • used at INITIAL_WORKUP
    Rule out structural disease (HCM, ARVC, anomalous coronary, infiltrative); LQT heart is structurally normal — structural finding triggers alternate or overlap pathway
  • cardiac_mri_at_4_to_6_wk
    imaging • used at FOLLOWUP
    Cardiac MRI at 4–6 wk post-arrest if echo equivocal or to rule out CPVT (catecholaminergic polymorphic VT) overlap, ARVC, or infiltrative disease; allows post-arrest stunning to resolve before assessment
  • troponinrequired
    lab • used at INITIAL_WORKUP
    Often modestly elevated from arrest + CPR; rise pattern helps differentiate from ACS-mediated arrest; LQT-TdP arrest typically negative or modest
  • lactaterequired
    lab • used at INITIAL_WORKUP
    Tissue hypoperfusion + post-arrest perfusion debt; clearance trajectory drives prognosis (SCAI 2022 PMID 35718438; CardShock PMID 26333869)
  • creatininerequired
    lab • used at CONTEXT
    AKI is major risk for drug-accumulation TdP (sotalol, dofetilide); eGFR for renal-cleared QT-prolonging drug avoidance + dose-adjust
  • potassiumrequired
    lab • used at INITIAL_WORKUP
    K target ≥4.5 mandatory in LQT — hypokalemia is major TdP precipitant; aggressive replacement
  • magnesiumrequired
    lab • used at INITIAL_WORKUP
    Mg target ≥2.0 mandatory; MgSO4 IV is also FIRST-LINE TdP suppression regardless of measured Mg level (AHA 2020 ACLS)
  • calciumrequired
    lab • used at INITIAL_WORKUP
    Hypocalcemia further prolongs QT — replace to normal range
  • genetic_panel_kcnq1_kcnh2_scn5a_expandedrequired
    lab • used at FOLLOWUP
    Targeted gene panel — KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3) core panel ≥85% yield; expanded panel for CALM1/2/3, CACNA1C, KCNJ2, ANK2 if family history positive or sentinel features; informs prognosis + cascade testing of relatives
  • cxr_post_cprrequired
    imaging • used at INITIAL_WORKUP
    Rib fractures from CPR; pneumothorax; aspiration; baseline for ICD lead placement planning

12-phase flow (12)

  1. 1FRAME
    Recognize post-ROSC + QTc > 500 ms + structurally normal heart + classic trigger pattern as congenital LQT-arrest cohort; pivot from generic post-arrest care to channelopathy-specific avoidance protocol; route to parent cardio.post-arrest.core.v1 for TTM + neuroprog while specializing on QTc reassessment + family screening + drug-avoidance + lifelong β-blocker + ICD
    inputs: ecg_12_lead_serial_with_qtc_bazett_and_fridericia, tte_high_resolution, witnessed_arrest_with_trigger_pattern
    advance: congenital LQT high pretest probability confirmed + structural disease screen initiated
  2. 2ENTRY
    Standard ACLS for index arrest; immediate scene CPR + AED deployment; transport to PCI-capable + EP-capable facility; activate EP team early; STOP all QT-prolonging drugs from pre-arrest medication list (www.crediblemeds.org)
    inputs: age, time_to_cpr_min, time_to_aed_defibrillation_min, pre_arrest_medication_list_qt_audit
    advance: ACLS + AED + transport + EP team activation + drug audit initiated
  3. 3CONTEXT
    Trigger pattern (exertion/swimming = LQT1; auditory/emotional/post-partum = LQT2; sleep/nocturnal = LQT3); time-to-CPR; time-to-AED; initial rhythm (VF most common); family history of SCD <40 y or known LQTS; prior syncope; comprehensive pre-arrest medication review
    inputs: sex, initial_rhythm, family_history_sudden_death_or_known_lqts, prior_syncope_or_qt_prolonging_drug_exposure, sbp, hr, core_temp, spo2, creatinine
    advance: context + family history + drug audit + trigger pattern documented + congenital vs acquired classification attempted
  4. 4RED_FLAGS
    Recurrent TdP / VF post-ROSC suggests storm physiology (route to sister cardio.cardiogenic-shock.lqt-tdp-storm.v1); persistent QTc > 550 ms with bradycardia → pacing or isoproterenol pathway (LQT3 + acquired phenotypes); inadvertent administration of QT-prolonging drug post-ROSC → STOP + reverse
    inputs: sbp, hr, ecg_12_lead_serial_with_qtc_bazett_and_fridericia
    actions: cardiogenic_shock, wide_complex_tach
    advance: red flags screened + storm-bridge route decided + QT-prolonging drugs cleared from active orders
  5. 5INITIAL_WORKUP
    Serial 12-lead ECG with QTc Bazett + Fridericia + T-wave morphology subtyping; STAT echo (rule out structural disease — LQT heart is normal); troponin (rule out ischemic mimic); BMP + Mg + Ca + phosphate; CBC; ABG; CXR; comprehensive medication audit against www.crediblemeds.org
    inputs: ecg_12_lead_serial_with_qtc_bazett_and_fridericia, tte_high_resolution, troponin, lactate, potassium, magnesium, calcium, cxr_post_cpr
    actions: post_arrest_care, panel.cardiac, panel.renal
    advance: workup complete + LQT pretest probability refined + structural / ischemic causes excluded + electrolytes optimized
  6. 6BRANCHING_WORKUP
    Genetic panel referral (KCNQ1/KCNH2/SCN5A core; expanded if family history positive); EP consult for ICD planning (sustained VT/VF survivor = HRS 2017 Class I); STEMI on post-ROSC ECG (rare in primary LQT) → cath; recurrent VT/VF storm → route to sister cardiogenic-shock.lqt-tdp-storm engine; CPVT overlap (exercise stress test deferred until workup complete) → consider CALM1/2/3 + RYR2 panel
    actions: acs_pathway, wide_complex_tach
    advance: branching decisions made + genetic referral placed + EP plan documented
  7. 7DIFFERENTIAL
    Congenital LQT (LQT1 KCNQ1 / LQT2 KCNH2 / LQT3 SCN5A; rarer LQT4-17) vs acquired LQT (drug-induced, electrolyte-driven, AKI-mediated drug accumulation, bradycardia-dependent) vs CPVT overlap (exertion-triggered polymorphic VT with normal QTc) vs Brugada overlap (V1-V3 coved ST) vs idiopathic VF — this differential drives long-term plan + family screening
    inputs: family_history_sudden_death_or_known_lqts, witnessed_arrest_with_trigger_pattern, prior_syncope_or_qt_prolonging_drug_exposure
    advance: congenital vs acquired classification + subtype hypothesis + overlap differential documented
  8. 8RISK_STRATIFICATION
    CAHP/OHCA scores apply (witnessed + bystander CPR + low-flow time + initial rhythm); SCAI shock stage if hemodynamic instability; HEART score not directly applicable (LQT cohort low ACS pretest); HRS 2017 ICD class — sustained VT/VF survivor = Class I (this population by definition); QTc magnitude (> 550 ms = high risk); Schwartz score for congenital LQT diagnosis
    inputs: initial_rhythm, time_to_cpr_min, time_to_aed_defibrillation_min, sbp, lactate
    actions: calc.map, calc.sofa, calc.ckd_epi_2021, calc.cha2ds2vasc, calc.heart
    advance: risk class + ICD eligibility + structural workup status documented
  9. 9TREATMENT
    Standard post-ROSC bundle (vasopressor → MAP ≥65; lung-protective vent; sedation; TTM 33–37.5 °C × 24 h); aggressive K + Mg + Ca repletion (K ≥4.5; Mg ≥2.0); MgSO4 2 g IV bolus + 2 g/h infusion if any TdP recurrence regardless of measured Mg; STOP all QT-prolonging drugs (www.crediblemeds.org); cautious vasopressor dosing in LQT1/2 (adrenergic trigger). LONG-TERM (initiate before discharge): nadolol 1–1.5 mg/kg/d (preferred) or propranolol 2–4 mg/kg/d for congenital LQT1/LQT2 once storm controlled; mexiletine for LQT3 (Na channel blocker shortens QT); ICD per HRS 2017 Class I (sustained VT/VF survivor); LCSD for ICD-shock burden or β-blocker intolerance. AVOID: haloperidol, ondansetron > 16 mg, citalopram > 20 mg, macrolides, fluoroquinolones, methadone, Class IA + III antiarrhythmics; substitute fentanyl + dexmedetomidine + low-dose olanzapine + scopolamine + sertraline + doxycycline / β-lactam
    inputs: sbp, hr, core_temp, spo2, creatinine, potassium, magnesium
    actions: protocol.cardiogenic_shock
    advance: post-ROSC bundle + electrolyte optimization + drug-avoidance protocol + long-term β-blocker initiation plan documented
  10. 10DISPOSITION
    CICU at EP-capable center for cardiac surveillance + ICD planning; transfer to inherited-arrhythmia center for refractory storm or pediatric / complex genotype; cardiology + EP own structural workup + ICD + long-term β-blocker pathway
    advance: unit + service-line ownership assigned + EP follow-up booked
  11. 11MONITORING
    Continuous telemetry × 48–72 h with QT measurement q4–6 h; multimodal neuroprog ≥72 h post-rewarm (Sandroni 2021 PMID 33745427); serial ECG q4–6 h × 24 h then q6–8 h × 48 h; BMP + Mg q4–6 h until target achieved + sustained; daily ECG until QTc < 480 ms; daily medication audit against www.crediblemeds.org
    inputs: ecg_12_lead_serial_with_qtc_bazett_and_fridericia, potassium, magnesium
    actions: panel.cardiac, panel.renal
    advance: monitoring + neuroprog + QTc trend + drug audit cadence documented
  12. 12FOLLOWUP
    Cardiology + EP / inherited-arrhythmia clinic at 2–4 wks; cardiac MRI at 4–6 wk (post-stunning resolution); GENETIC PANEL completed (KCNQ1/KCNH2/SCN5A core; expanded if needed); CASCADE FAMILY SCREENING — first-degree relatives ECG + genotyping at proband mutation; lifelong β-blocker (nadolol preferred); ICD interrogation q3–6 mo; LCSD evaluation for shock burden; lifelong drug avoidance (medic-alert bracelet "Long QT — AVOID QT-prolonging drugs"); LQT1 avoid swimming/diving; LQT2 avoid sudden loud noises (alarm clock modification); LQT3 caution sleep alone + nocturnal monitoring; aggressive K repletion if hypokalemic; PTSD / mental health screen
    inputs: cardiac_mri_at_4_to_6_wk, genetic_panel_kcnq1_kcnh2_scn5a_expanded
    advance: cardiology + EP follow-up + genetic panel + cascade family screening + ICD + lifelong β-blocker + drug avoidance + lifestyle modification + mental health all booked / documented