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cardio.cardiogenic-shock.lqt-tdp-storm.v1PRODUCTION
cardio.cardiogenic-shock.lqt-tdp-storm.v1

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

cardiologyacuteadult
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11/12 authored

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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

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LQT-TdP storm with CS overlay confirmed + congenital vs acquired classification attempted

Patient inputs (14)

Congenital LQT often presents in childhood / adolescence; acquired LQT more common in older patients on multiple QT-prolonging drugs

Female predominance in acquired TdP (longer baseline QT); LQT2 has female predominance for events; informs risk stratification

AKI is a major risk for drug-accumulation TdP (sotalol, dofetilide); eGFR for renal-cleared QT-prolonging drugs

STOP ALL QT-prolonging drugs immediately (consult www.crediblemeds.org curated list — gold standard reference)

Hypokalemia is a major TdP precipitant; aggressive replacement to K ≥4.5 mandatory

Hypomagnesemia is a major TdP precipitant; replace to ≥2.0; MgSO4 IV is also FIRST-LINE TdP suppression regardless of measured level

Hypocalcemia prolongs QT; replace to normal range

Differentiate ischemic cause of polymorphic VT; usually negative or modest in primary LQT-TdP storm

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

STRUCTURALLY NORMAL HEART expected (LQT is channelopathy, not cardiomyopathy); rules out ischemic / structural cause of polymorphic VT

SCAI 2022 staging baseline + vasopressor titration; storm with hemodynamic collapse defines CS overlay

Bradycardia (sinus or AV block) is a major TdP trigger — pacing pathway gating; tachycardia in LQT1/2 may be adrenergic trigger (β-blocker pathway)

SCAI 2022 staging + perfusion; CardShock prognostication (Harjola EHJ 2015 PMID 26333869)

Family history of sudden death <40 y raises congenital LQT concern; cascade testing of first-degree relatives if congenital LQT confirmed

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (4)

4 need judgement
  • informationallife_threateningqt_prolonging_drug_exposure_with_active_tdp
    Active TdP storm with ongoing QT-prolonging drug exposure — STOP ALL offending drugs immediately (www.crediblemeds.org curated list); MgSO4 2 g IV bolus + 2 g/h infusion; aggressive K + Mg repletion
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningrefractory_tdp_despite_mg_and_isoproterenol
    Refractory TdP despite MgSO4 + isoproterenol + electrolyte repletion + drug withdrawal — temporary transvenous pacing at 80–100 bpm; reconsider diagnosis (myocarditis, structural disease); MCS bridge if SCAI D-E
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningbradycardia_related_tdp_needing_pacing
    Bradycardia-dependent TdP (LQT3 or acquired with high-grade AV block / sinus arrest / post-cardioversion pause) — isoproterenol 0.5–2 µg/min OR overdrive pacing at 80–100 bpm; AVOID β-blockers acutely
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverecongenital_vs_acquired_lqt_classification_critical
    Distinguish CONGENITAL LQT (family history SCD <40 y, prior syncope, T-wave morphology suggestive) vs ACQUIRED LQT (drug exposure, electrolyte, AKI, bradycardia) — pivots long-term therapy: CONGENITAL → β-blocker FIRST-LINE long-term + cascade testing of relatives + ICD if high-risk + LCSD for refractory; ACQUIRED → drug-avoidance + root-cause + typically QT normalizes within 24–72 h of drug withdrawal
    Trigger could not be auto-evaluated — needs clinician judgement.

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Recommended regimen

LQT-TdP storm with CS — MgSO4 + electrolyte repletion + drug withdrawal + pacing/isoproterenol if bradycardia-dependent; AVOID Class IA + III antiarrhythmics; congenital LQT long-term β-blocker
axis: lqt_tdp_storm_phenotype
Selected axis "LQT-TdP storm with CS — MgSO4 + electrolyte repletion + drug withdrawal + pacing/isoproterenol if bradycardia-dependent; AVOID Class IA + III antiarrhythmics; congenital LQT long-term β-blocker" by default fallback (first axis)
  • magnesium sulfate
    first line
    electrolyte_membrane_stabilizer
    2 g IV bolus over 5–15 min then 2 g/h infusion REGARDLESS of measured Mg level • IV • continuous; titrate to TdP suppression
    triggers: active_tdp_or_qtc_above_500, electrical_storm_with_tdp
    AHA 2020 ACLS — FIRST-LINE for TdP regardless of measured Mg level; mechanism stabilizes myocardial membrane independent of measured Mg; HRS 2017 PMID 28219760
    rxcui 6585
  • isoproterenol
    first line
    beta1_agonist
    0.5–2 µg/min IV titrate to HR 90–110 • IV • continuous; titrate to HR target + TdP suppression
    triggers: bradycardia_dependent_tdp_storm, lqt3_phenotype, acquired_tdp_with_bradycardia
    AHA 2020 ACLS — increases HR which shortens QT and prevents R-on-T; useful for bradycardia-dependent TdP (LQT3 + acquired); CONTRAINDICATED in LQT1/2 acute (adrenergic trigger)
    rxcui 6054
  • potassium chloride
    first line
    electrolyte
    20–40 mEq IV/PO until K ≥4.5 • IV/PO • PRN
    triggers: k_below_4.5_in_tdp_storm, recurrent_tdp_episode
    Hypokalemia is major TdP precipitant; aggressive K repletion to ≥4.5 mandatory; HRS 2017
    rxcui 8591
  • norepinephrine
    first line
    vasopressor_alpha
    0.05–0.5 µg/kg/min IV titrate • IV • continuous; titrate to MAP ≥65
    triggers: cs_overlay_on_tdp_storm, sbp_lt_90_persistent
    SOAP-II PMID 20200382 — first-line in CS; α-1 effect supports MAP; CAUTION in LQT1/2 (adrenergic trigger — minimize dose)
    rxcui 7512
  • propranolol
    comorbidity specific
    non_selective_beta_blocker
    CONGENITAL LQT long-term: propranolol 2–4 mg/kg/d divided BID-QID; do NOT initiate acutely if bradycardia-dependent acquired TdP • PO • BID-QID; lifelong in congenital LQT1/2
    triggers: congenital_lqt1_or_lqt2_long_term, post_storm_recovery_phase
    Schwartz International LQTS Registry — propranolol mortality reduction in congenital LQT1/2; FIRST-LINE long-term per HRS 2017 Class I
    rxcui 8787
  • nadolol
    comorbidity specific
    non_selective_beta_blocker_long_acting
    CONGENITAL LQT long-term: nadolol 1–1.5 mg/kg/d daily • PO • daily; lifelong in congenital LQT1/2 (preferred over propranolol per recent registry data)
    triggers: congenital_lqt1_or_lqt2_long_term, patient_compliance_concerns_with_qid_propranolol
    Long half-life + non-selective; recent registry data suggest superior to propranolol in LQT1/2; HRS 2017 Class I
    rxcui 7226

outpatient playbook — drug actions (3)

  1. 1. continue β-blocker maintenance in CONGENITAL LQT1/2
    rxcui 8787
    propranolol 2–4 mg/kg/d OR nadolol 1–1.5 mg/kg/d • PO • BID-QID or daily
    trigger: Congenital LQT1/2
    Schwartz registry mortality reduction; HRS 2017 Class I
  2. 2. consider mexiletine (sodium channel blocker) for LQT3
    150–300 mg PO TID • PO • TID
    trigger: LQT3 phenotype
    Mexiletine shortens QT in LQT3 by blocking late INa; HRS 2017 IIa
  3. 3. continue lifelong avoidance of QT-prolonging drugs
    patient education + curated list (www.crediblemeds.org) • n/a • lifelong
    trigger: LQT diagnosis
    HRS 2017

Auto-drafted A&P note

outpatient

Subjective

- Possible entry pathways: ECG QTc > 500 ms (Bazett or Fridericia) with TdP runs on telemetry / 12-lead — TdP electrical storm; Recurrent syncope or aborted SCD in patient with QTc > 480 ms — concern for congenital or acquired LQT with TdP; Recent exposure to QT-prolonging drug (Class III antiarrhythmic, macrolide, fluoroquinolone, antipsychotic, methadone, ondansetron, TCA, citalopram) precipitating TdP — acquired LQT.

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**Cardiogenic shock — Long-QT torsades de pointes (TdP) electrical storm** (cardio.cardiogenic-shock.lqt-tdp-storm.v1).
Scope: 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

No severity triggers fired against current inputs.

Plan

Regimen axis: **LQT-TdP storm with CS — MgSO4 + electrolyte repletion + drug withdrawal + pacing/isoproterenol if bradycardia-dependent; AVOID Class IA + III antiarrhythmics; congenital LQT long-term β-blocker**.
1. magnesium sulfate 2 g IV bolus over 5–15 min then 2 g/h infusion REGARDLESS of measured Mg level IV continuous; titrate to TdP suppression (electrolyte_membrane_stabilizer, first line) — AHA 2020 ACLS — FIRST-LINE for TdP regardless of measured Mg level; mechanism stabilizes myocardial membrane independent of measured Mg; HRS 2017 PMID 28219760
2. isoproterenol 0.5–2 µg/min IV titrate to HR 90–110 IV continuous; titrate to HR target + TdP suppression (beta1_agonist, first line) — AHA 2020 ACLS — increases HR which shortens QT and prevents R-on-T; useful for bradycardia-dependent TdP (LQT3 + acquired); CONTRAINDICATED in LQT1/2 acute (adrenergic trigger)
3. potassium chloride 20–40 mEq IV/PO until K ≥4.5 IV/PO PRN (electrolyte, first line) — Hypokalemia is major TdP precipitant; aggressive K repletion to ≥4.5 mandatory; HRS 2017
4. norepinephrine 0.05–0.5 µg/kg/min IV titrate IV continuous; titrate to MAP ≥65 (vasopressor_alpha, first line) — SOAP-II PMID 20200382 — first-line in CS; α-1 effect supports MAP; CAUTION in LQT1/2 (adrenergic trigger — minimize dose)
5. propranolol CONGENITAL LQT long-term: propranolol 2–4 mg/kg/d divided BID-QID; do NOT initiate acutely if bradycardia-dependent acquired TdP PO BID-QID; lifelong in congenital LQT1/2 (non_selective_beta_blocker, comorbidity specific) — Schwartz International LQTS Registry — propranolol mortality reduction in congenital LQT1/2; FIRST-LINE long-term per HRS 2017 Class I
6. nadolol CONGENITAL LQT long-term: nadolol 1–1.5 mg/kg/d daily PO daily; lifelong in congenital LQT1/2 (preferred over propranolol per recent registry data) (non_selective_beta_blocker_long_acting, comorbidity specific) — Long half-life + non-selective; recent registry data suggest superior to propranolol in LQT1/2; HRS 2017 Class I

Setting playbook (outpatient) — CONGENITAL LQT — long-term EP / inherited-arrhythmia clinic; β-blocker maintenance + dose optimization; ICD interrogation q3–6 mo if implanted; LCSD for refractory β-blocker failure; family cascade testing completion; lifelong drug-avoidance education + lifestyle modifications. ACQUIRED LQT — drug-avoidance education + medic-alert; root-cause documentation; QTc baseline established; cardiology follow-up at 3 mo then annually
7. continue β-blocker maintenance in CONGENITAL LQT1/2 propranolol 2–4 mg/kg/d OR nadolol 1–1.5 mg/kg/d PO BID-QID or daily — Congenital LQT1/2 (Schwartz registry mortality reduction; HRS 2017 Class I)
8. consider mexiletine (sodium channel blocker) for LQT3 150–300 mg PO TID PO TID — LQT3 phenotype (Mexiletine shortens QT in LQT3 by blocking late INa; HRS 2017 IIa)
9. continue lifelong avoidance of QT-prolonging drugs patient education + curated list (www.crediblemeds.org) n/a lifelong — LQT diagnosis (HRS 2017)

Non-pharmacologic actions:
- EP / inherited-arrhythmia clinic q3–6 mo for congenital LQT
- Family cascade testing — first-degree relative ECG + genetic panel
- LCSD (left cardiac sympathetic denervation) referral for refractory β-blocker failure (HRS 2017 Class IIa)
- ICD generator / lead surveillance per device clinic
- Lifestyle — LQT1 avoid competitive swimming; LQT2 avoid sudden loud noises (modify alarm clock); LQT3 caution sleep alone; aggressive K repletion if hypokalemic
- Acquired LQT — root-cause documentation in chart; drug-avoidance education; medic-alert bracelet

AVOID / contraindication checks:
- Class_ia_antiarrhythmics_AVOID_in_lqt_tdp_storm (quinidine, procainamide, disopyramide further prolong QT)
- Class_iii_antiarrhythmics_AVOID_in_lqt_tdp_storm (sotalol, dofetilide, ibutilide further prolong QT and may have caused storm)
- Amiodarone_relative_AVOID_in_lqt_tdp_storm (debated; long QT but suppresses VT in some; less torsadogenic vs other class III; consider only if other VT mechanisms also active)
- Beta_blocker_AVOID_acute_in_bradycardia_dependent_acquired_tdp (slowing rate worsens TdP); FIRST LINE long term in congenital LQT1/2 (Schwartz registry)
- Isoproterenol_AVOID_in_lqt1_or_lqt2_acute (adrenergic stress is the trigger)
- Macrolides_fluoroquinolones_antipsychotics_methadone_review_against_crediblemeds_org (curated QT prolonging drug list)
- Loperamide_overdose_can_cause_severe_qt_prolongation (high dose loperamide abuse)
- Hypokalemia_below_3.5_must_be_corrected_before_qt_prolonging_drug_use (TdP risk)

Monitoring

Regimen monitoring:
- continuous telemetry with qt measurement q4-6h (QTc Bazett + Fridericia)
- serial ECG q4-6h initially (track QT evolution + TdP suppression)
- isoproterenol titration to HR 90-110 for bradycardia dependent TdP (AHA 2020 ACLS)
- transvenous pacing at 80-100 bpm if refractory bradycardia dependent TdP (R-on-T prevention)
- arterial line continuous BP (CS support)
- lactate q1-2h (CardShock prognostication)
- UOP hourly (perfusion marker)
- electrolytes q4-6h until K above 4.5 and Mg above 2 (mandatory)
- all qt prolonging drugs documented as held (www.crediblemeds.org review)
- congenital lqt genetic panel kcnq1 kcnh2 scn5a (cascade testing of relatives)

Setting (outpatient) monitoring:
- q3–6 mo ICD interrogation if implanted
- Annual ECG
- Family cascade testing progress documentation

Follow-up plan: 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)
- Close-out criterion: Long-term EP plan (congenital) or drug-avoidance + root-cause analysis (acquired) complete

Monitoring phase: 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

Disposition

Current setting: outpatient — CONGENITAL LQT — long-term EP / inherited-arrhythmia clinic; β-blocker maintenance + dose optimization; ICD interrogation q3–6 mo if implanted; LCSD for refractory β-blocker failure; family cascade testing completion; lifelong drug-avoidance education + lifestyle modifications. ACQUIRED LQT — drug-avoidance education + medic-alert; root-cause documentation; QTc baseline established; cardiology follow-up at 3 mo then annually

Disposition criteria:
- Stable on long-term EP regimen with β-blocker ± ICD ± LCSD; lifelong follow-up for congenital; annual follow-up for acquired

Escalation triggers (move to higher acuity):
- Recurrent syncope on β-blocker → emergent EP + ICD / LCSD evaluation
- New ICD shock → emergent EP + storm investigation
- New QT-prolonging drug exposure → ED + drug withdrawal + reassessment
- Family member positive screening → cascade testing + EP referral

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Active TdP storm with ongoing QT-prolonging drug exposure — STOP ALL offending drugs immediately (www.crediblemeds.org curated list); MgSO4 2 g IV bolus + 2 g/h infusion; aggressive K + Mg repletion
- [LIFE_THREATENING] Refractory TdP despite MgSO4 + isoproterenol + electrolyte repletion + drug withdrawal — temporary transvenous pacing at 80–100 bpm; reconsider diagnosis (myocarditis, structural disease); MCS bridge if SCAI D-E
- [LIFE_THREATENING] Bradycardia-dependent TdP (LQT3 or acquired with high-grade AV block / sinus arrest / post-cardioversion pause) — isoproterenol 0.5–2 µg/min OR overdrive pacing at 80–100 bpm; AVOID β-blockers acutely

Citations

- HRS 2017 Inherited Arrhythmia Syndromes Expert Consensus (Al-Khatib PMID 28219760); AHA 2020 ACLS; Schwartz International LQTS Registry; ESC 2022 VA / SCD prevention; SCAI 2022 CS staging (Naidu PMID 35718438); CredibleMeds (www.crediblemeds.org) curated QT-prolonging drug list [PMID:28219760](https://pubmed.ncbi.nlm.nih.gov/28219760/)
- Cited evidence (PMID 33098585) [PMID:33098585](https://pubmed.ncbi.nlm.nih.gov/33098585/)
- Cited evidence (PMID 35718438) [PMID:35718438](https://pubmed.ncbi.nlm.nih.gov/35718438/)
- Cited evidence (PMID 38587234) [PMID:38587234](https://pubmed.ncbi.nlm.nih.gov/38587234/)
- Cited evidence (PMID 20200382) [PMID:20200382](https://pubmed.ncbi.nlm.nih.gov/20200382/)

Last reconciled with current guidelines: 2026-05-15.
References
  • HRS 2017 Inherited Arrhythmia Syndromes Expert Consensus (Al-Khatib PMID 28219760); AHA 2020 ACLS; Schwartz International LQTS Registry; ESC 2022 VA / SCD prevention; SCAI 2022 CS staging (Naidu PMID 35718438); CredibleMeds (www.crediblemeds.org) curated QT-prolonging drug list — PMID:28219760
  • Cited evidence (PMID 33098585) — PMID:33098585
  • Cited evidence (PMID 35718438) — PMID:35718438
  • Cited evidence (PMID 38587234) — PMID:38587234
  • Cited evidence (PMID 20200382) — PMID:20200382