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cardio.long-qt-syndrome.chronic.v1PRODUCTION
cardio.long-qt-syndrome.chronic.v1

Congenital Long QT Syndrome (chronic — genotype-driven)

cardiologychronicadult
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Encounter flow

12/12 authored

Canonical 12-phase frame with authored status for this dossier.

Current phase

Frame

Detailed

Confirm CONGENITAL LQTS (genotype/Schwartz) — distinguish acquired/drug-induced LQTS

Inputs
2
Actions
0
Advance rule
Set
Advance when

congenital LQTS framed

Patient inputs (11)

Risk varies by age/sex; pediatric school AED planning

Detect QT-prolonging drugs (crediblemeds.org)

K/Mg repletion reduces TdP risk (esp. LQT2)

LQT1/2/3 drives triggers + BB response + mexiletine eligibility

QTc magnitude (>500 ms high risk) — diagnosis + risk + therapy response

Trigger pattern supports genotype + risk

Aborted SCD = secondary-prevention ICD (Class I)

Mexiletine/BB dosing

LQT2 postpartum is highest-risk window — continue BB

Adult women higher LQT2 risk (esp. postpartum)

Events on adequate BB → LCSD/ICD escalation

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Severity triggers (9)

9 need judgement
  • informationallife_threateningaborted_scd_secondary_prevention
    Aborted SCD / documented sustained VT — secondary-prevention ICD Class I (with continued beta-blocker) — 2017 AHA/ACC/HRS VA
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverebb_breakthrough_lcsd
    Cardiac events despite adequate beta-blocker — LCSD (Class IIa) ± ICD — 2022 ESC VA
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverelqt3_mexiletine_branch
    LQT3 (SCN5A gain-of-function) — rest/sleep events, BB less effective; add mexiletine (late-Na block, QT shortening) — Mazzanti
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverelqt2_postpartum_branch
    LQT2, peripartum/postpartum window — highest event risk postpartum; continue/uptitrate beta-blocker, intensified monitoring, K repletion — 2022 ESC VA; ESC 2018 Pregnancy
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevereqt_drug_avoidance_branch
    Patient on / needs a crediblemeds.org QT-prolonging drug — substitute or, if unavoidable, intensified ECG + electrolyte monitoring — crediblemeds.org
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevereelectrolyte_branch
    Hypokalemia / hypomagnesemia (vomiting, diuretics, eating disorder) — aggressively repleted; high-risk for TdP esp. LQT2 — 2022 ESC VA
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalmoderatelqt1_exertion_branch
    LQT1 — exertion/swimming-triggered; BB highly effective; sports shared-decision + supervised-swimming caution — 2022 ESC VA
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalmoderateasymptomatic_gene_positive
    Asymptomatic gene-positive with prolonged QTc — beta-blocker indicated; with normal QTc — surveillance + trigger/drug avoidance (do not stop BB if started) — 2017 AHA/ACC/HRS VA
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalmoderateckd_special_pop
    CKD — mexiletine/BB renal dose-gating; avoid QT-prolonging renal-cleared drugs — KDIGO 2024
    Trigger could not be auto-evaluated — needs clinician judgement.

Workflow calculators

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Recommended regimen

LQTS repolarization-protection (2013 HRS/EHRA/APHRS; 2017 AHA/ACC/HRS VA; 2022 ESC VA)
axis: lqts_repolarization_protectionstep 1 - Step 1 — Non-selective beta-blocker (nadolol preferred) — ALL symptomatic + QTc-prolonged asymptomatic incl. gene-positive
Selected step "Step 1 — Non-selective beta-blocker (nadolol preferred) — ALL symptomatic + QTc-prolonged asymptomatic incl. gene-positive" — Confirmed LQTS with QTc prolongation or symptoms (and most gene-positive)
  • nadolol
    first line
    nonselective_beta_blocker
    0.5–1 mg/kg/day (typical adult 40–80 mg) • PO • once–BID (max: titrate to HR/tolerance)
    triggers: confirmed_LQTS_QTc_prolonged_or_symptomatic
    2022 ESC VA — nadolol is the evidence-preferred BB in LQTS (superior event reduction, esp. LQT1/2); long-acting non-selective
    rxcui 7226
  • propranolol
    first line
    nonselective_beta_blocker
    2–3 mg/kg/day • PO • TID
    triggers: nadolol_unavailable_or_intolerant
    Propranolol alternative non-selective BB (2017 AHA/ACC/HRS VA)
    rxcui 82084

outpatient playbook — drug actions (3)

  1. 1. nadolol (or propranolol)
    nadolol 40–80 mg (0.5–1 mg/kg/day) • PO • once–BID
    trigger: QTc-prolonged or symptomatic LQTS (2022 ESC VA)
    Preferred BB — first-line for all
  2. 2. mexiletine if LQT3
    150–200 mg TID • PO • TID
    trigger: LQT3 with persistent QT prolongation (Mazzanti)
    Late-Na block shortens QT in LQT3
  3. 3. LCSD / ICD by risk
    procedure / device • surgical/device • n/a
    trigger: BB breakthrough / aborted SCD / very long QTc (2022 ESC VA)
    Escalation; ICD adjunct to BB

Auto-drafted A&P note

outpatient

Subjective

- Possible entry pathways: QTc prolongation (≥480 ms; ≥460 ms with symptoms) on 12-lead; Syncope on exertion/swimming (LQT1), auditory/emotional/postpartum (LQT2), or at rest/sleep (LQT3); Aborted SCD / family history of LQTS or unexplained young SCD.

Objective

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

Assessment

**Congenital Long QT Syndrome (chronic — genotype-driven)** (cardio.long-qt-syndrome.chronic.v1).
Phenotype framing: Congenital LQTS vs acquired/drug-induced LQTS vs CPVT vs Brugada vs benign QT variation
Scope: Confirm CONGENITAL LQTS (genotype/Schwartz) — distinguish acquired/drug-induced LQTS

No severity triggers fired against current inputs.

Plan

Regimen axis: **LQTS repolarization-protection (2013 HRS/EHRA/APHRS; 2017 AHA/ACC/HRS VA; 2022 ESC VA)** — step "Step 1 — Non-selective beta-blocker (nadolol preferred) — ALL symptomatic + QTc-prolonged asymptomatic incl. gene-positive".
1. nadolol 0.5–1 mg/kg/day (typical adult 40–80 mg) PO once–BID (nonselective_beta_blocker, first line) — 2022 ESC VA — nadolol is the evidence-preferred BB in LQTS (superior event reduction, esp. LQT1/2); long-acting non-selective
2. propranolol 2–3 mg/kg/day PO TID (nonselective_beta_blocker, first line) — Propranolol alternative non-selective BB (2017 AHA/ACC/HRS VA)

Setting playbook (outpatient) — Lifelong nadolol (all QTc-prolonged/symptomatic incl. gene+), mexiletine LQT3, risk-stratified ICD/LCSD, QT-drug/trigger avoidance, cascade (2017 AHA/ACC/HRS VA; 2022 ESC VA)
3. nadolol (or propranolol) nadolol 40–80 mg (0.5–1 mg/kg/day) PO once–BID — QTc-prolonged or symptomatic LQTS (2022 ESC VA) (Preferred BB — first-line for all)
4. mexiletine if LQT3 150–200 mg TID PO TID — LQT3 with persistent QT prolongation (Mazzanti) (Late-Na block shortens QT in LQT3)
5. LCSD / ICD by risk procedure / device surgical/device n/a — BB breakthrough / aborted SCD / very long QTc (2022 ESC VA) (Escalation; ICD adjunct to BB)

Non-pharmacologic actions:
- Inherited-arrhythmia centre + EP referral — 2013 consensus
- Genetic counseling + first-degree family cascade screening — 2013 consensus
- Lifelong crediblemeds.org avoidance + genotype-trigger counseling — crediblemeds.org
- Sports eligibility shared-decision (more permissive if treated/controlled) — 2022 ESC VA

AVOID / contraindication checks:
- Avoid crediblemeds.org QT prolonging drugs lifelong — crediblemeds.org; 2022 ESC VA
- Nadolol preferred metoprolol less effective in LQTS — 2022 ESC VA
- Do not stop beta blocker on recovery or asymptomatic gene positive with prolonged QTc — 2017 AHA/ACC/HRS VA
- ICD is adjunct to not replacement for beta blocker — 2022 ESC VA
- Correct hypokalemia hypomagnesemia especially LQT2 — 2022 ESC VA

Monitoring

Regimen monitoring:
- serial QTc resting and exercise — 2022 ESC VA
- beta blocker dose adequacy and adherence — 2017 AHA/ACC/HRS VA
- ICD interrogation if implanted — 2017 AHA/ACC/HRS VA
- electrolytes K Mg — 2022 ESC VA
- family cascade screening and serial evaluation — 2013 consensus

Setting (outpatient) monitoring:
- Serial QTc; BB adherence/dose; electrolytes — 2022 ESC VA
- ICD interrogation if implanted — 2017 AHA/ACC/HRS VA

Follow-up plan: First-degree family cascade screening; lifelong QT-drug + trigger avoidance; sports re-evaluation
- Close-out criterion: cascade + long-term plan documented

Monitoring phase: Serial QTc, BB adherence + dose adequacy, ICD interrogation, electrolytes

Disposition

Current setting: outpatient — Lifelong nadolol (all QTc-prolonged/symptomatic incl. gene+), mexiletine LQT3, risk-stratified ICD/LCSD, QT-drug/trigger avoidance, cascade (2017 AHA/ACC/HRS VA; 2022 ESC VA)

Disposition criteria:
- QTc-prolonged/symptomatic → lifelong BB + risk-based ICD/LCSD + cascade
- LQT3 → BB + mexiletine
- Asymptomatic gene+ normal QTc → surveillance + trigger/drug avoidance + cascade

Escalation triggers (move to higher acuity):
- TdP/VF → ED + acute LQTS pathway — 2022 ESC VA
- Events on adequate BB → LCSD ± ICD — 2022 ESC VA
- New QT-prolonging drug needed → substitute / intensify monitoring — crediblemeds.org

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Aborted SCD / documented sustained VT — secondary-prevention ICD Class I (with continued beta-blocker) — 2017 AHA/ACC/HRS VA
- [SEVERE] Cardiac events despite adequate beta-blocker — LCSD (Class IIa) ± ICD — 2022 ESC VA
- [SEVERE] LQT3 (SCN5A gain-of-function) — rest/sleep events, BB less effective; add mexiletine (late-Na block, QT shortening) — Mazzanti

Citations

- 2013 HRS/EHRA/APHRS Inherited Arrhythmia Expert Consensus + 2017 AHA/ACC/HRS VA Guideline + 2022 ESC Ventricular Arrhythmia Guideline [PMID:23994779](https://pubmed.ncbi.nlm.nih.gov/23994779/)
- Cited evidence (PMID 29084731) [PMID:29084731](https://pubmed.ncbi.nlm.nih.gov/29084731/)
- Cited evidence (PMID 36017572) [PMID:36017572](https://pubmed.ncbi.nlm.nih.gov/36017572/)

Last reconciled with current guidelines: 2026-05-16.
References
  • 2013 HRS/EHRA/APHRS Inherited Arrhythmia Expert Consensus + 2017 AHA/ACC/HRS VA Guideline + 2022 ESC Ventricular Arrhythmia Guideline — PMID:23994779
  • Cited evidence (PMID 29084731) — PMID:29084731
  • Cited evidence (PMID 36017572) — PMID:36017572