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cardio.cardiogenic-shock.lqt-tdp-storm.v1

Cardiogenic shock — Long-QT torsades de pointes (TdP) electrical storm

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Phase E variant of cardio.cardiogenic-shock.core.v1 — narrowed to long-QT-mediated torsades de pointes (TdP) electrical storm (≥3 sustained TdP episodes in 24 h or incessant TdP) with hemodynamic collapse / cardiogenic shock. Etiologies span CONGENITAL LQT (LQT1 KCNQ1, LQT2 KCNH2, LQT3 SCN5A gain-of-function) and ACQUIRED (Class III antiarrhythmics, macrolides, fluoroquinolones, antipsychotics, methadone, ondansetron, TCAs, citalopram; electrolyte derangement; bradycardia-dependent; AKI / dialysis-related). Per HRS 2017 PMID 28219760 + AHA 2020 ACLS. Treatment pivots: MAGNESIUM SULFATE 2 g IV bolus → 2 g/h infusion REGARDLESS of measured Mg level (AHA 2020 ACLS FIRST-LINE; mechanism stabilizes myocardial membrane independent of measured Mg); ISOPROTERENOL 0.5–2 µg/min IV for BRADYCARDIA-dependent TdP (LQT3 + acquired; CONTRAINDICATED in LQT1/2 — adrenergic trigger); OVERDRIVE TRANSCUTANEOUS / TRANSVENOUS PACING at 80–100 bpm to prevent R-on-T (shorten QT by increasing rate); aggressive K repletion to ≥4.5; Mg repletion to ≥2.0; STOP ALL QT-prolonging drugs (www.crediblemeds.org curated list — gold standard); cautious NE for MAP support. AVOID acute (paradoxical / harmful): Class IA antiarrhythmics (quinidine, procainamide, disopyramide further prolong QT); Class III antiarrhythmics (sotalol, dofetilide, ibutilide further prolong QT and may have caused storm); amiodarone (debated — long QT but suppresses VT in some; less torsadogenic than other class III; consider only if other VT mechanisms also active); β-blockers ACUTELY in bradycardia-dependent acquired TdP (slowing rate worsens TdP); ACCEPTABLE / FIRST-LINE long-term in congenital LQT1/2 (Schwartz registry mortality reduction). Long-term congenital LQT management per HRS 2017: β-blocker FIRST-LINE — propranolol 2–4 mg/kg/d OR nadolol 1–1.5 mg/kg/d (nadolol non-selective + long half-life preferred per recent registry data; mortality reduction in LQT1 + LQT2; less effective in LQT3); mexiletine for LQT3 (Na channel blocker shortens QT); ICD for high-risk (sustained TdP/VF survivor; recurrent syncope on β-blocker; QTc > 550 ms); LCSD (left cardiac sympathetic denervation) for refractory β-blocker failure. Lifestyle: avoid all QT-prolonging drugs (www.crediblemeds.org); LQT1 avoid swimming (water immersion triggers); LQT2 avoid loud noises (auditory triggers; modify alarm clock); LQT3 caution sleep alone (sleep is high-risk period); aggressive K repletion if hypokalemic. Cascade testing of first-degree relatives + KCNQ1/KCNH2/SCN5A genetic panel offered for congenital LQT; lifelong drug avoidance + medic-alert bracelet mandatory for all LQT patients (congenital or acquired). Acquired LQT typically reverses within 24–72 h of drug withdrawal + electrolyte correction. Inherits parent CS framework (vasopressor / MCS escalation, MDT activation); specialises for LQT-TdP-specific pharmacology (MgSO4 FIRST-LINE, isoproterenol or pacing for bradycardia-dependent, AVOID Class IA + III antiarrhythmics, congenital vs acquired classification pivots long-term therapy). Status INTEGRATED until terminology + RxNav-validated drug codes are reconciled. Authored 2026-05-15 by shard-06-cardio-acute as Phase E wave 16 channelopathy storm variant.

Entry points (5)

  • imaging
    ECG QTc > 500 ms (Bazett or Fridericia) with TdP runs on telemetry / 12-lead — TdP electrical storm
    ecg_qtc_above_500_with_tdp_runs
  • symptom
    Recurrent syncope or aborted SCD in patient with QTc > 480 ms — concern for congenital or acquired LQT with TdP
    recurrent_syncope_or_aborted_scd_with_long_qt
  • history
    Recent exposure to QT-prolonging drug (Class III antiarrhythmic, macrolide, fluoroquinolone, antipsychotic, methadone, ondansetron, TCA, citalopram) precipitating TdP — acquired LQT
    qt_prolonging_drug_exposure_with_tdp
  • history
    Family history of sudden death <40 y + QTc > 470 ms (M) or > 480 ms (F) — congenital LQT high concern
    family_history_sudden_death_young_with_long_qt
  • lab_abnormality
    Hypokalemia (K < 3.5) and/or hypomagnesemia (Mg < 2.0) precipitating TdP — electrolyte-driven storm; aggressive replacement
    hypokalemia_or_hypomagnesemia_with_tdp

Required inputs (14)

  • agerequired
    demographic • used at CONTEXT
    Congenital LQT often presents in childhood / adolescence; acquired LQT more common in older patients on multiple QT-prolonging drugs
  • sexrequired
    demographic • used at CONTEXT
    Female predominance in acquired TdP (longer baseline QT); LQT2 has female predominance for events; informs risk stratification
  • sbprequired
    vital • used at RED_FLAGS
    SCAI 2022 staging baseline + vasopressor titration; storm with hemodynamic collapse defines CS overlay
  • hrrequired
    vital • used at RED_FLAGS
    Bradycardia (sinus or AV block) is a major TdP trigger — pacing pathway gating; tachycardia in LQT1/2 may be adrenergic trigger (β-blocker pathway)
  • lactaterequired
    lab • used at RISK_STRATIFICATION
    SCAI 2022 staging + perfusion; CardShock prognostication (Harjola EHJ 2015 PMID 26333869)
  • creatininerequired
    lab • used at CONTEXT
    AKI is a major risk for drug-accumulation TdP (sotalol, dofetilide); eGFR for renal-cleared QT-prolonging drugs
  • potassiumrequired
    lab • used at INITIAL_WORKUP
    Hypokalemia is a major TdP precipitant; aggressive replacement to K ≥4.5 mandatory
  • magnesiumrequired
    lab • used at INITIAL_WORKUP
    Hypomagnesemia is a major TdP precipitant; replace to ≥2.0; MgSO4 IV is also FIRST-LINE TdP suppression regardless of measured level
  • calciumrequired
    lab • used at INITIAL_WORKUP
    Hypocalcemia prolongs QT; replace to normal range
  • troponinrequired
    lab • used at INITIAL_WORKUP
    Differentiate ischemic cause of polymorphic VT; usually negative or modest in primary LQT-TdP storm
  • ecgrequired
    imaging • used at INITIAL_WORKUP
    QTc measurement (Bazett or Fridericia); TdP runs identification; T-wave morphology may suggest LQT subtype (LQT1 broad-based; LQT2 notched / low-amplitude; LQT3 late-onset narrow); pause-dependence pattern
  • echorequired
    imaging • used at INITIAL_WORKUP
    STRUCTURALLY NORMAL HEART expected (LQT is channelopathy, not cardiomyopathy); rules out ischemic / structural cause of polymorphic VT
  • qt_prolonging_drug_reviewrequired
    history • used at CONTEXT
    STOP ALL QT-prolonging drugs immediately (consult www.crediblemeds.org curated list — gold standard reference)
  • family_history_sudden_death
    history • used at CONTEXT
    Family history of sudden death <40 y raises congenital LQT concern; cascade testing of first-degree relatives if congenital LQT confirmed

12-phase flow (11)

  1. 1FRAME
    Recognize LQT-TdP storm with shock — QTc > 500 ms + recurrent TdP runs + hemodynamic collapse; classify as CONGENITAL (LQT1/2/3 with family history, syncope / SCD history) vs ACQUIRED (drug / electrolyte / bradycardia / AKI); pivots therapy
    inputs: ecg, sbp
    advance: LQT-TdP storm with CS overlay confirmed + congenital vs acquired classification attempted
  2. 2ENTRY
    Activate EP team + CS team; immediate trigger reversal (STOP all QT-prolonging drugs; aggressive K + Mg + Ca repletion); START MgSO4 2 g IV bolus → 2 g/h infusion regardless of measured Mg level
    inputs: sbp, potassium, magnesium
    advance: EP team activated + MgSO4 running + drug list reviewed
  3. 3CONTEXT
    Family history of SCD < 40 y, prior syncope, prior LQT diagnosis, current medication review (every drug screened against www.crediblemeds.org), recent dose changes (sotalol, dofetilide), AKI / dialysis status, code status
    inputs: hr, creatinine, qt_prolonging_drug_review, family_history_sudden_death
    advance: Triggers identified + congenital vs acquired phenotype clarified
  4. 4RED_FLAGS
    Active TdP / VF (defibrillation per ACLS); bradycardia-dependent TdP (pacing pathway); severe hypokalemia (< 3.0); ongoing exposure to multiple QT-prolonging drugs; pre-arrest state; LQT1/2 with adrenergic trigger (β-blocker pathway long-term, not acute)
    inputs: sbp, hr, potassium, magnesium
    actions: cardiogenic_shock, wide_complex_tach
    advance: Acute arrhythmias managed + reversible triggers screened
  5. 5INITIAL_WORKUP
    ECG (QTc Bazett + Fridericia; T-wave morphology for subtype clue; pause-dependence); STAT echo (rule out structural disease — LQT heart is normal); troponin (rule out ischemic mimic); BMP + Mg + Ca + phosphate; CBC; comprehensive drug review against www.crediblemeds.org; tox screen if methadone / loperamide overdose suspected
    inputs: ecg, echo, troponin, lactate, potassium, magnesium, calcium
    actions: cardiogenic_shock, wide_complex_tach, panel.cardiac, panel.renal
    advance: LQT-TdP confirmed + structural / ischemic causes excluded + electrolytes optimized
  6. 6BRANCHING_WORKUP
    Genetic testing (KCNQ1 / KCNH2 / SCN5A panel for congenital LQT); cardiology referral for first-degree relatives screening (cascade testing); emergent angiography ONLY if troponin elevated or ECG suggests ischemia (rare in primary LQT-TdP storm)
    inputs: ecg
    actions: acs_pathway
    advance: Genetic / family screening triggered if congenital + obstructive CAD ruled out if troponin positive
  7. 7RISK_STRATIFICATION
    Storm severity (≥3 TdP episodes / 24 h vs incessant TdP); SCAI 2022 stage; HRS 2017 ICD class (Class I if sustained TdP/VF survivor or recurrent syncope on β-blocker); congenital vs acquired; QTc magnitude (> 550 ms = high risk); Schwartz score for congenital LQT diagnosis
    inputs: sbp, lactate
    advance: Risk + ICD eligibility class assigned
  8. 8TREATMENT
    STORM SUPPRESSION: MAGNESIUM SULFATE 2 g IV bolus → 2 g/h infusion REGARDLESS of measured Mg level (AHA 2020 ACLS first-line); ISOPROTERENOL 0.5–2 µg/min for BRADYCARDIA-dependent TdP (LQT3 or acquired); OVERDRIVE TRANSCUTANEOUS / TRANSVENOUS PACING at 80–100 bpm to prevent R-on-T (shorten QT by increasing rate); aggressive K repletion to ≥4.5; aggressive Mg repletion to ≥2.0; STOP ALL QT-prolonging drugs (www.crediblemeds.org); cautious NE for MAP support. AVOID: Class IA + III antiarrhythmics (further prolong QT); β-blockers ACUTELY in bradycardia-dependent acquired TdP. REFRACTORY: temporary transvenous pacing; cardiac MRI to clarify diagnosis; MCS bridge per SCAI 2022 / DanGer Shock if SCAI D-E
    inputs: sbp, lactate, potassium, magnesium, hr
    actions: cardiogenic_shock
    advance: MgSO4 + electrolyte repletion + drug withdrawal + pacing/isoproterenol if bradycardia-dependent + MCS plan all in place
  9. 9DISPOSITION
    CICU at EP-capable center; advanced HF / EP center transfer for refractory storm; congenital LQT → long-term EP / inherited-arrhythmia clinic; acquired LQT → root-cause documentation + drug-avoidance education
    advance: Disposition assigned + EP team owns long-term plan + drug review documented in chart
  10. 10MONITORING
    Continuous telemetry with QT measurement q4–6 h; A-line; central line; lactate clearance; UOP; isoproterenol or pacing titration to HR 80–100 if bradycardia-dependent; serial K + Mg q4–6 h until target achieved; daily ECG until QTc < 480 ms
    inputs: lactate, potassium, magnesium
    actions: panel.cardiac, panel.renal
    advance: Monitoring + repletion + dose titration cadence set
  11. 11FOLLOWUP
    CONGENITAL LQT — EP / inherited-arrhythmia clinic 1–4 wks; long-term β-blocker (propranolol or nadolol — Schwartz registry mortality reduction); ICD if high-risk; LCSD for refractory; lifestyle (LQT1 avoid swimming; LQT2 avoid loud noises; LQT3 caution sleep alone); cascade testing first-degree relatives. ACQUIRED LQT — drug-avoidance education + medic-alert bracelet; review home med list against www.crediblemeds.org; root-cause analysis; cardiology follow-up at 1–4 wks; baseline ECG to confirm QTc normalization (most acquired QT prolongation reverses within 24–72 h of drug withdrawal)
    advance: Long-term EP plan (congenital) or drug-avoidance + root-cause analysis (acquired) complete