This handout is for post-cardiac-arrest care — congenital long-qt channelopathy (kcnq1 / kcnh2 / scn5a) with tdp-arrest. Your care team identified this based on: 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).
Other reasons your team may use this plan: 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; witnessed arrest with classic lqt trigger pattern: exertion or swimming (lqt1), auditory startle / emotional / post-partum (lqt2), sleep / nocturnal (lqt3) — directs subtype classification; family history of sudden death <40 y or known lqts in first-degree relative — congenital lqt high pretest probability; offer genetic panel + cascade screening.
Take these medications exactly as prescribed. Do not stop or change a dose without talking to your provider.
| Medication | Starting dose | How | When | What it does |
|---|---|---|---|---|
| magnesium sulfate | 2 g IV bolus over 5–15 min then 2 g/h infusion REGARDLESS of measured Mg level; aggressive replacement to Mg ≥2.0 | IV | continuous; titrate to TdP suppression | AHA 2020 ACLS — FIRST-LINE for TdP regardless of measured Mg level; mechanism stabilizes myocardial membrane independent of measured Mg; HRS 2017 PMID 28219760 |
| potassium chloride | 20–40 mEq IV/PO until K ≥4.5 mandatory in LQT | IV/PO | PRN until target sustained | Hypokalemia is major TdP precipitant; K ≥4.5 target mandatory in LQT; HRS 2017 |
| norepinephrine | 0.05–0.5 µg/kg/min titrate MAP ≥65; CAUTION in LQT1/2 (adrenergic trigger — minimize dose to lowest effective) | IV | continuous | SOAP-II PMID 20200382; first-line post-ROSC vasoactive; in LQT1/LQT2 use lowest effective dose because adrenergic surge is the trigger for these subtypes |
| epinephrine | 1 mg IV q3–5 min during arrest | IV | standard ACLS | AHA 2020 ACLS — standard arrest pathway; in confirmed LQT post-ROSC minimize subsequent infusions because adrenergic load triggers LQT1/2 |
| propofol | 5–50 µg/kg/min; titrate RASS | IV | continuous | PADIS 2018; preferred sedative in LQT post-arrest because does NOT prolong QT (vs avoiding antipsychotics which do) |
| fentanyl | 25–200 µg/h | IV | continuous | PADIS 2018; preferred opioid (does NOT prolong QT) over methadone (QT-prolonging — AVOID) |
| dexmedetomidine | 0.2–1.4 µg/kg/h; no bolus | IV | continuous | PADIS 2018; preferred for ICU delirium in LQT cohort because does NOT prolong QT (vs haloperidol — AVOID); Class IIa AHA delirium prevention |
| nadolol | CONGENITAL LQT1/LQT2 long-term: nadolol 1–1.5 mg/kg/d daily (preferred over propranolol per recent registry data — long half-life + better adherence) | PO | daily; lifelong | HRS 2017 PMID 28219760 Class I + Schwartz International LQTS Registry — mortality reduction in LQT1/2 with long-term β-blocker; nadolol preferred over propranolol (long half-life, daily dosing improves adherence) |
| propranolol | CONGENITAL LQT1/LQT2 long-term alternate: propranolol 2–4 mg/kg/d divided BID-QID | PO | BID-QID; lifelong | HRS 2017 Class I; Schwartz registry — historical first-line; QID dosing reduces adherence vs nadolol daily |
| mexiletine | CONGENITAL LQT3 long-term: mexiletine 150–300 mg PO q8h | PO | TID | HRS 2017 IIa — mexiletine shortens QT in LQT3 by blocking late INa (the gain-of-function defect); does NOT replace ICD |
| isoproterenol | 0.5–2 µg/min IV titrate to HR 90–110 for bradycardia-dependent TdP recurrence (LQT3 + acquired); CONTRAINDICATED in LQT1/2 | IV | continuous | AHA 2020 ACLS — increases HR shortens QT prevents R-on-T; useful for bradycardia-dependent TdP (LQT3 + acquired); CONTRAINDICATED in LQT1/2 (adrenergic trigger) |
| acetaminophen | 650 mg PO/PR/IV q6h PRN | PO/PR/IV | q6h PRN | Standard analgesia / antipyresis; does NOT prolong QT |
Plan: Congenital LQT post-arrest phenotype — standard post-ROSC bundle + electrolyte optimization + drug-avoidance protocol + lifelong β-blocker initiation + ICD pathway (HRS 2017 Class I) + cascade family screening
Contact your care team if any of the following happen:
Call 911 or go to the nearest emergency room right away if you have:
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
Guideline: HRS 2017 Inherited Arrhythmia Syndromes Expert Consensus (Al-Khatib PMID 28219760) + AHA 2020 ACLS / Post-Cardiac-Arrest Care + TTM2 + Sandroni 2021 ERC-ESICM neuroprog + Schwartz International LQTS Registry + ESC 2022 VA / SCD prevention + CredibleMeds (www.crediblemeds.org) curated QT-prolonging drug list (gold standard reference)