Cardiovascular

Long QT syndrome: diagnosis, drug avoidance, and torsades management

Clinical Overview and When to Suspect Long QT Syndrome

— Congenital LQTS: inherited channelopathies. LQT1 (KCNQ1, IKs), LQT2 (KCNH2/hERG, IKr), and LQT3 (SCN5A, late INa) account for >90% of genotyped cases.

— Acquired LQTS: drug-induced, electrolyte-mediated (hypoK, hypoMg, hypoCa), bradycardia, hypothyroidism, hypothermia, anorexia, intracranial hemorrhage.

— Unexplained syncope or seizure during exertion, swimming, or auditory startle (LQT1, LQT2) — often misdiagnosed as epilepsy.

— Syncope or SCD during sleep or rest (LQT3).

— Family history of unexplained drowning, sudden infant death, or SCD <40 years old.

— Patient on QT-prolonging drugs (fluoroquinolones, macrolides, azole antifungals, ondansetron, methadone, antipsychotics, class IA/III antiarrhythmics) who develops syncope, palpitations, or polymorphic VT.

— Men: ≤450 ms

— Women: ≤460 ms

— Prolonged: ≥480 ms (or ≥460 ms with symptoms); ≥500 ms is high TdP risk.

Long QT syndrome (LQTS) is a repolarization disorder characterized by prolonged ventricular repolarization (QT interval) predisposing to torsades de pointes (TdP), syncope, and sudden cardiac death.

Two broad categories:

When to suspect on Step 3:

Cornerstone diagnostic tool: 12-lead ECG with corrected QT (QTc) using Bazett (QT/√RR) or Fridericia formula. Use Fridericia at HR <60 or >100.

Normal QTc thresholds:

Board pearl: A QTc ≥500 ms roughly doubles the risk of TdP for every additional 10 ms beyond 500. Any patient with QTc ≥500 ms warrants urgent attention — review the med list, check K+/Mg2+, and consider telemetry.

Step 3 ambulatory framing: every new prescription in a patient with known LQTS or prior drug-induced QT prolongation should be cross-checked against CredibleMeds.org categories.

Presentation Patterns and Key History

— LQT1: exertion, especially swimming/diving. Adrenergic surge with impaired IKs response.

— LQT2: auditory triggers (alarm clock, phone ringing), emotional stress, postpartum period.

— LQT3: sleep, rest, or bradycardia-dependent events.

— Palpitations → presyncope → syncope → seizure-like activity (from cerebral hypoperfusion during TdP) → aborted SCD.

— TdP often self-terminates, producing recurrent syncopal spells without postictal confusion — a clue to distinguish from epilepsy.

— Age of first event, circumstances (exercise, startle, sleep, emotion).

— Medication review: antibiotics, antifungals, antiemetics, antidepressants (citalopram >20 mg, TCAs), antipsychotics (haloperidol, ziprasidone), methadone, antiarrhythmics (sotalol, dofetilide, amiodarone, ibutilide).

— Substance use: cocaine, methamphetamine.

— GI losses (vomiting, diarrhea, laxative/diuretic misuse → hypoK, hypoMg).

— Diet: anorexia, very-low-calorie diets, liquid protein diets.

— Endocrine: hypothyroidism, pheochromocytoma.

— Family history: sudden death <40, drowning, unexplained MVA, SIDS, congenital deafness (Jervell and Lange-Nielsen — autosomal recessive LQT1 with sensorineural deafness).

Hallmark presentation: transient loss of consciousness triggered by a context-specific stimulus, often with a normal interictal exam.

Trigger-genotype correlations (high-yield):

Symptom spectrum:

Targeted history:

Key distinction: Syncope during a swim meet in a teen = think LQT1; syncope when the phone rings or postpartum = think LQT2; sudden death during sleep = think LQT3 or Brugada. Brugada is more common in males with characteristic V1–V2 ECG pattern, not QT prolongation.

Board pearl: Misdiagnosis of LQTS as seizure disorder is a classic Step 3 pitfall — any "epileptic" patient on multiple AEDs without EEG correlation and with exertional or auditory triggers needs a 12-lead ECG.

Physical Exam Findings and Hemodynamic Assessment

— Sensorineural hearing loss in a young patient with syncope → Jervell and Lange-Nielsen syndrome (homozygous KCNQ1 or KCNE1).

— Skeletal abnormalities, facial dysmorphism, periodic paralysis → Andersen-Tawil syndrome (LQT7, KCNJ2).

— Syndactyly, autism, hypoglycemia, immune dysfunction in infants → Timothy syndrome (LQT8, CACNA1C).

— Pulseless or hypotensive with polymorphic wide-complex tachycardia on monitor — classic TdP morphology with twisting QRS axis around the baseline.

— Recurrent syncope with rapid recovery (no postictal phase).

— May see bradycardia or sinus pauses preceding TdP — pause-dependent initiation is typical of acquired LQTS.

— Check pulse, BP, mental status, rhythm strip.

— Unstable polymorphic VT/TdP → immediate unsynchronized defibrillation (synchronization often fails on polymorphic VT).

— Stable but symptomatic → IV magnesium, correct electrolytes, identify trigger.

— Bradycardia (HR <50) → pause-dependent TdP risk.

— Hypothermia → Osborn waves and QT prolongation.

— Signs of hypothyroidism (bradycardia, delayed reflexes, dry skin).

— Malnutrition signs in eating disorder patients.

LQTS is fundamentally an electrical diagnosis — the resting exam is usually normal, which is itself a high-yield Step 3 teaching point.

Findings that may be present and should be sought:

During an active arrhythmia event:

Hemodynamic assessment in the unstable patient (CCS framing):

Vital sign clues to acquired triggers:

CCS pearl: On a CCS case of syncope, even when the exam is normal, order a 12-lead ECG immediately and place the patient on continuous telemetry. Failing to obtain an ECG in a syncope workup is a high-frequency CCS deduction.

Board pearl: Congenital deafness + syncope = check QTc and screen siblings — autosomal recessive Jervell and Lange-Nielsen carries the highest arrhythmic risk and warrants early ICD consideration.

Diagnostic Workup — Initial Labs, ECG, and QTc Measurement

— Bazett: QTc = QT/√RR. Valid for HR 60–100. Overcorrects at tachycardia, undercorrects at bradycardia.

— Fridericia: QTc = QT/RR^(1/3). Preferred outside HR 60–100.

— ≥480 ms on repeated ECGs in absence of secondary cause → diagnostic of congenital LQTS.

— ≥460 ms with unexplained syncope → diagnostic.

— Schwartz score ≥3.5 (combining QTc, T-wave morphology, symptoms, family history) is diagnostic.

— LQT1: broad-based, prolonged T waves.

— LQT2: low-amplitude, notched/bifid T waves.

— LQT3: long isoelectric ST segment with late-appearing peaked T wave.

— BMP (K+, Mg2+, Ca2+, creatinine), Mg level, TSH, CBC.

— Toxicology screen if substance use suspected.

— Pregnancy test in reproductive-age women (affects drug choices).

— Hypokalemia, Hypomagnesemia, Hypocalcemia

— Electrolytes / Eating disorder

— Antiarrhythmics, Antibiotics

— Drugs (methadone, antipsychotics, antiemetics)

— Myocardial ischemia

— Intracranial hemorrhage / increased ICP

— Congenital / Cardiomyopathy

12-lead ECG is the cornerstone. Measure QT in lead II or V5 (where T-wave end is clearest), from QRS onset to T-wave end (tangent method for biphasic T waves).

Correct for heart rate:

Diagnostic QTc thresholds:

T-wave morphology clues by genotype:

Initial labs in any prolonged QT:

Reversible cause checklist (mnemonic — HEAD-MIC):

Step 3 management: Before labeling LQTS as congenital, stop all QT-prolonging drugs and correct K+ to >4.0 mEq/L and Mg2+ to >2.0 mg/dL, then repeat ECG. Persistent QTc ≥480 ms after correction supports congenital LQTS.

Board pearl: Always cross-check QTc with CredibleMeds drug list; treat U waves merging with T waves cautiously — measure QT excluding the U wave to avoid overestimating QTc.

Diagnostic Workup — Advanced and Confirmatory Studies

— Failure of QTc to shorten (or paradoxical prolongation) during the 4-minute recovery phase is highly suggestive of LQT1.

— Useful when resting QTc is borderline (440–470 ms) and clinical suspicion is high.

— 24–48 hour Holter for arrhythmia burden, QTc variability across day/night.

— Event monitor or implantable loop recorder for infrequent syncope (>30 days of monitoring) — favored on Step 3 for unexplained recurrent syncope with structurally normal heart.

— Confirms structurally normal heart (rules out HCM, ARVC, cardiomyopathy).

— Required before labeling an idiopathic channelopathy.

— Recommended for patients with clinically diagnosed LQTS (QTc ≥480, Schwartz ≥3.5, or strong family history).

— Identifies pathogenic variant in ~75% of clinically definite cases.

— Enables cascade screening of first-degree relatives — major Step 3 prevention concept.

— A negative genetic test does not exclude LQTS if clinical criteria are met.

— Low-dose epinephrine infusion — paradoxical QT prolongation suggests LQT1.

— QTc ≥480 ms unexplained

— Documented TdP

— Syncope with prolonged QT

— Family history of SCD with borderline QTc

— Consideration of ICD or left cardiac sympathetic denervation

Exercise stress testing is a powerful unmasking tool:

Ambulatory monitoring:

Echocardiogram:

Genetic testing:

Epinephrine challenge test (less common; specialty setting):

Cardiology/electrophysiology referral indications:

CCS pearl: On a CCS case of "syncope with borderline QTc 465 ms," the right sequence is: echo → exercise stress test → cardiology consult → genetic testing/cascade screen. Skipping the echo or proceeding straight to EP study is a CCS misstep.

Board pearl: Provocative testing isn't done in active TdP or hemodynamic instability — first stabilize, then risk-stratify outpatient. Family cascade ECG screening of all first-degree relatives is a guaranteed Step 3 answer once a proband is identified.

Risk Stratification and First-Line Management Logic

— QTc ≥500 ms (especially ≥550 ms).

— Prior cardiac arrest or documented TdP/sustained VT.

— Syncope on beta-blocker therapy (treatment failure).

— LQT2 females, postpartum period (9-month high-risk window).

— LQT3 genotype (higher lethality per event).

— Jervell and Lange-Nielsen (recessive, deaf, very high risk).

— Onset in infancy (<1 year) with 2:1 AV block.

1. Lifestyle and trigger avoidance for all patients (universal).

2. Beta-blocker (nadolol or propranolol) — first-line for nearly all.

3. Mexiletine add-on, especially LQT3 (late sodium current blocker).

4. Left cardiac sympathetic denervation (LCSD) for breakthrough events on beta-blocker or as bridge to/adjunct with ICD.

5. ICD for: survivors of cardiac arrest, recurrent syncope despite beta-blocker, very high-risk subgroups (QTc >550, JLN syndrome).

— Avoid QT-prolonging drugs (provide written list, CredibleMeds.org).

— Maintain K+ and Mg2+ — replete during GI illness.

— LQT1: avoid competitive swimming, strenuous exertion; lifejacket near water.

— LQT2: remove sudden auditory stimuli (alarm clocks) from bedroom; awareness in postpartum period.

— Genetic counseling and first-degree relative ECG screening mandatory.

Risk stratification guides therapy intensity (beta-blocker alone vs. ICD).

High-risk features:

Intermediate risk: QTc 470–500, syncope on therapy not yet documented.

Low risk: asymptomatic, QTc <470, no high-risk family history.

Management ladder:

Universal patient counseling:

Step 3 management: A young patient with newly diagnosed LQTS, QTc 490, no symptoms, gets nadolol + lifestyle counseling + cascade family screening. ICD is not first-line in asymptomatic patients without high-risk features.

Board pearl: Never use sotalol (class III, IKr blocker) in LQTS — it prolongs QT. Beta-blocker of choice is nadolol (or propranolol); metoprolol is inferior for LQTS prevention and is a common wrong answer.

Pharmacotherapy — First-Line Drug Regimen and Drugs to Avoid

— Nadolol (preferred): non-selective, long half-life. Adult dose 40–80 mg daily, titrate to HR reduction. Most evidence for event reduction, especially LQT2.

— Propranolol LA: alternative, especially in pediatrics (2–4 mg/kg/day divided).

— Avoid metoprolol — inferior outcomes in LQTS registries.

— Adherence is critical — most breakthrough events occur with missed doses.

— Continue beta-blocker even during pregnancy (propranolol or nadolol; monitor neonate for bradycardia/hypoglycemia).

— Late sodium current blocker, shortens QT in LQT3 (and some LQT2).

— Useful adjunct when QTc remains ≥500 ms on beta-blocker.

— Test dose with QTc measurement to confirm response.

— Keep K+ ≥4.0, Mg2+ ≥2.0 chronically.

— Spironolactone may help maintain K+ in patients prone to hypokalemia.

— Antibiotics: azithromycin, clarithromycin, erythromycin, levofloxacin, moxifloxacin, ciprofloxacin (lower risk).

— Antifungals: fluconazole, voriconazole, ketoconazole.

— Antiemetics: ondansetron (especially IV), droperidol, domperidone.

— Antipsychotics: haloperidol IV, ziprasidone, thioridazine, chlorpromazine, pimozide.

— Antidepressants: citalopram (>20 mg, or >20 mg in elderly), escitalopram (high dose), TCAs.

— Antiarrhythmics: sotalol, dofetilide, ibutilide, amiodarone (lower TdP risk despite QT prolongation), quinidine, procainamide, disopyramide.

— Methadone (dose-dependent), oxaliplatin, arsenic trioxide, hydroxychloroquine + azithromycin combination.

— Nausea: metoclopramide (with caution) or prochlorperazine.

— Depression: sertraline, bupropion, mirtazapine (lower QT risk).

— UTI: nitrofurantoin, fosfomycin, TMP-SMX instead of fluoroquinolone.

— Pneumonia: doxycycline, amoxicillin instead of azithromycin/levofloxacin.

Beta-blockers — cornerstone for LQT1 and LQT2:

Mexiletine:

Magnesium and potassium repletion:

Drugs to absolutely avoid (CredibleMeds "Known Risk"):

Acceptable alternatives (Step 3 substitution game):

Step 3 management: When asked to treat a UTI or pneumonia in an LQTS patient, avoid macrolides and fluoroquinolones. Switch to a structurally unrelated agent — this is a recurrent Step 3 substitution question.

Acute Torsades de Pointes Management and Invasive Therapy

1. Assess stability. Pulseless or unstable polymorphic VT → immediate unsynchronized defibrillation (200 J biphasic). Synchronization typically fails on polymorphic VT.

2. IV magnesium sulfate 2 g IV bolus over 1–2 min, repeat in 5–15 min if needed, then infusion 2–4 mg/min. First-line drug therapy even with normal Mg level.

3. Correct electrolytes: K+ to 4.5–5.0, Mg2+ to >2.0, Ca2+ within normal range.

4. Stop all QT-prolonging drugs immediately. Document in EHR with allergy/intolerance entry.

5. Increase heart rate to shorten QT in pause-dependent (acquired) TdP:

— Isoproterenol infusion (2–10 mcg/min), titrate to HR 90–110.

— Or transvenous overdrive pacing at 90–110 bpm — definitive bridge.

— Avoid isoproterenol in congenital LQTS (adrenergic trigger).

6. Identify and treat reversible cause: bradyarrhythmia, ischemia, hypothyroidism, toxic ingestion.

— Class IA (procainamide, quinidine) and class III (amiodarone, sotalol) — they prolong QT further.

— Lidocaine is acceptable (class IB, may shorten QT) but mexiletine more commonly used long-term.

— ICD indications (secondary prevention): SCD survivor, documented sustained VT/TdP.

— ICD primary prevention: recurrent syncope on adequate beta-blocker, QTc >550 with high-risk genotype, JLN syndrome.

— Pair ICD with continued beta-blocker — never replace.

— Surgical removal of lower half of stellate ganglion + T2–T4 thoracic ganglia.

— Reduces arrhythmic events ~80% in beta-blocker-refractory LQTS.

— Useful when ICD inappropriate (very young children, frequent shocks) or as adjunct.

Acute TdP — stepwise CCS-style algorithm:

Drugs to avoid during TdP:

Invasive/device therapy for congenital LQTS:

Left cardiac sympathetic denervation (LCSD):

CCS pearl: For TdP in the ED, the order set is: defibrillate if unstable → IV magnesium 2 g → stop offending drug → replete K to >4 → isoproterenol or overdrive pacing for pause-dependent acquired TdP. Forgetting magnesium or giving amiodarone are classic CCS errors.

Special Populations — Elderly and Renal/Hepatic Impairment

— Age-related decline in repolarization reserve.

— Polypharmacy is the dominant risk — average elderly patient on QT-prolonging drugs often has 2+ contributors.

— Female sex compounds risk (women have longer QTc post-puberty).

— Common culprits in elderly: donepezil, citalopram, haloperidol, ondansetron, levofloxacin, methadone, amiodarone.

— Reduced clearance of renally excreted QT-prolonging drugs: sotalol, dofetilide, levofloxacin, fluconazole, famotidine (rare), procainamide.

— Sotalol contraindicated if CrCl <40 mL/min for AFib; reduce dose at <60.

— Dofetilide requires creatinine clearance-based dosing and inpatient initiation with 3 days of telemetry — high-yield Step 3 fact.

— Hypokalemia from diuretics in CKD is a frequent acquired LQTS trigger.

— Reduced metabolism of methadone, amiodarone, ondansetron, antifungals, macrolides.

— Cirrhosis itself prolongs QTc (cirrhotic cardiomyopathy) — baseline QTc often >440 in advanced cirrhosis.

— Reduce dose, extend interval, or switch agent in renal/hepatic dysfunction.

— Recheck ECG 48–72 hours after initiating a QT-prolonging drug in at-risk patients.

— Recheck K+ and Mg2+ at every encounter where diuretic dose changes.

— Nadolol is renally cleared — reduce dose if CrCl <50.

— Watch for bradycardia, falls, orthostasis.

Elderly patients have a baseline higher QTc and increased drug-induced TdP risk:

Citalopram dose limit: 20 mg/day max in patients >60 (FDA), due to QT prolongation; switch to sertraline if needed.

Renal impairment:

Hepatic impairment:

Dose adjustment principles:

Beta-blocker considerations in elderly LQTS:

Step 3 management: In an 80-year-old on furosemide, citalopram 40 mg, and ondansetron who develops syncope with QTc 540 — stop the ondansetron, reduce citalopram to ≤20 mg, replete K+/Mg2+, switch antiemetic to prochlorperazine or low-dose metoclopramide. Polypharmacy review is the high-value intervention.

Board pearl: Any new QTc ≥500 ms or ΔQTc ≥60 ms from baseline after a drug start mandates stopping the offending agent — this is the FDA threshold for action.

Special Populations — Pregnancy, Pediatrics, and Other Subgroups

— Pregnancy itself shortens QTc slightly due to increased HR.

— Postpartum 9-month window is highest-risk period for LQT2 women — arrhythmic events spike.

— Continue beta-blocker throughout pregnancy (propranolol preferred; nadolol acceptable). Untreated LQTS poses higher fetal risk than the drug.

— Monitor neonate for bradycardia, hypoglycemia, IUGR.

— Avoid labor-induction prostaglandins that prolong QT cautiously; oxytocin is safe.

— Anesthesia: avoid droperidol, ondansetron IV bolus, halogenated agents with QT risk; sevoflurane acceptable.

— Neonatal LQTS may present with 2:1 AV block, sinus bradycardia, prolonged QT on routine ECG — strong association with SIDS.

— School-age presentation: syncope during sports, swimming, or auditory triggers.

— Pediatric dosing: propranolol 2–4 mg/kg/day divided BID-QID; nadolol 0.5–1 mg/kg/day.

— Avoid competitive sports in symptomatic or high-risk pediatric LQTS (per AHA/ACC; some flexibility for low-risk genotyped patients).

— Mandatory school AED access and emergency action plan.

— Pre-participation ECG screening identifies many cases.

— Restrictions are individualized; LQT1 patients should avoid swimming and competitive endurance sports.

— Family members with positive genotype but normal QTc still have ~10% lifetime arrhythmic risk — counsel and reassess periodically.

— Anorexia nervosa with electrolyte derangement is a frequent acquired LQTS scenario.

— Refeeding syndrome can precipitate hypoK, hypoMg, hypoPhos and TdP.

Pregnancy and postpartum:

Pediatrics:

Athletes:

Genetic mosaics / silent carriers:

Eating disorders:

Board pearl: LQT2 postpartum mother with palpitations or syncope is a classic Step 3 stem — keep her on nadolol through breastfeeding (compatible) and counsel about adherence and sleep deprivation reducing adherence.

Step 3 management: Pediatric LQTS diagnosed during family cascade — all first-degree relatives need ECG screening; positive genotype carriers start beta-blocker even if asymptomatic with normal QTc.

Complications and Adverse Outcomes

— Untreated symptomatic LQTS has ~13% mortality at 10 years; with beta-blocker, drops to ~1–2%.

— Highest risk in LQT3, JLN, QTc >550 ms, prior aborted SCD.

— Falls, MVAs, drowning during TdP-induced LOC.

— Driving restrictions apply (see chunk 17).

— Years of unnecessary anticonvulsants, some of which prolong QT (phenytoin minimally, but loading can affect).

— Inappropriate shocks (atrial arrhythmias, T-wave oversensing — particularly problematic in LQT given large T waves).

— Lead fracture, infection, psychological impact, anxiety/PTSD.

— Programming must account for tall T waves to prevent oversensing.

— Fatigue, depression, exercise intolerance, bradycardia, bronchospasm (nadolol non-selective).

— Adherence drops to <60% over time without counseling — directly linked to breakthrough events.

— Postpartum arrhythmic events are the leading cause of LQT2 maternal cardiac death.

— Fetal bradycardia, IUGR with high-dose beta-blocker.

— Cardiac arrest, anoxic brain injury, post-arrest cardiomyopathy.

— Prolonged ICU stay, particularly in elderly on polypharmacy.

— Activity restrictions, sport disqualification in adolescents.

— Family guilt after cascade screening identifies multiple affected relatives.

— Insurance and life-insurance implications of genetic diagnosis (GINA protections apply to health insurance but not life/disability).

— Horner syndrome (ipsilateral ptosis, miosis, anhidrosis) — usually transient with modern selective denervation.

— Pneumothorax, chylothorax (rare).

Sudden cardiac death (SCD):

Recurrent syncope and injury:

Misdiagnosis as epilepsy:

ICD complications:

Beta-blocker side effects:

Pregnancy-related:

Drug-induced TdP cascade in acquired LQTS:

Psychosocial complications:

LCSD complications:

Board pearl: T-wave oversensing by an ICD in an LQTS patient causes inappropriate shocks — recognized by frequent shocks unrelated to symptoms; managed by reprogramming sensing thresholds or lead repositioning, not by removing the ICD.

Step 3 management: A patient with ICD who reports a single shock — bring in for device interrogation within 24 hours; multiple shocks in 24 hours = electrical storm, ED evaluation immediately.

When to Escalate Care — ICU, Consult, and Inpatient Triage

— Sustained or recurrent TdP.

— Polymorphic VT requiring defibrillation.

— Hemodynamic instability with QT prolongation.

— Need for isoproterenol infusion or transvenous overdrive pacing.

— Post-cardiac arrest care (targeted temperature management 32–36°C — note hypothermia itself prolongs QT, monitor closely).

— QTc ≥500 ms with symptoms but no sustained arrhythmia.

— New drug-induced QT prolongation in patient who cannot stop the drug as outpatient (e.g., methadone maintenance).

— Dofetilide or sotalol initiation (mandatory 3-day inpatient telemetry).

— Electrolyte derangement with marked QT prolongation in anorexia or refeeding.

— Confirmed or suspected congenital LQTS.

— Recurrent unexplained syncope with borderline QTc.

— ICD candidacy evaluation.

— Drug-refractory arrhythmias.

— Pre-pregnancy counseling in known LQTS.

— All clinically diagnosed LQTS patients for genotyping and family cascade.

— Survivors of unexplained SCD (consider molecular autopsy).

— Once on stable beta-blocker, QTc trends stable, no breakthrough events.

— Follow-up every 6–12 months.

— Need for LCSD, ICD implantation, or advanced EP testing.

— Refractory TdP requiring ECMO or VA support (very rare).

— Telemetry, daily ECG, daily K+/Mg2+, medication reconciliation with pharmacist, avoid QT-prolonging drugs flagged in EHR, written hand-off at every transition.

Immediate ICU admission:

Telemetry/step-down admission:

Cardiology / electrophysiology consultation:

Genetics consultation:

Outpatient management (most asymptomatic LQTS):

Transfer criteria (community hospital → tertiary):

Inpatient safety bundle for any patient with QTc ≥500:

CCS pearl: A CCS case of acute TdP must include: defibrillate if unstable → magnesium IV → ICU admission → continuous telemetry → cardiology consult → echo → medication reconciliation → patient counseling before discharge. The "consult cardiology" and "med rec" steps are frequently missed and cost points.

Step 3 management: Discharging a patient who had drug-induced TdP without documenting the offending drug as an adverse reaction in the chart and the patient's pharmacy record is a transition-of-care failure.

Key Differentials — Same-Category (Channelopathies and Arrhythmic Syndromes)

— SCN5A loss-of-function mutation; coved ST elevation V1–V2 (type 1).

— Syncope/SCD typically during sleep, fever can unmask.

— Normal or short QT, not prolonged.

— Diagnosis: spontaneous or provoked (procainamide/ajmaline challenge) type 1 pattern.

— Treatment: ICD for symptomatic; avoid fever (treat aggressively with acetaminophen), avoid Na-channel blockers, avoid heavy alcohol.

— RyR2 mutation; bidirectional VT during exertion or emotion.

— Normal resting ECG and QT.

— Stress test reproduces bidirectional or polymorphic VT.

— Treatment: nadolol + flecainide (interesting — flecainide is used here, opposite of Brugada).

— QTc <340 ms, peaked T waves; AFib and VF risk.

— Treatment: ICD, quinidine.

— Exercise-induced VT, epsilon wave in V1, fibrofatty RV replacement on MRI.

— Distinct from LQTS by structural disease.

— SCD during exertion in young athletes; systolic murmur worse with Valsalva.

— LVH on ECG, asymmetric septal hypertrophy on echo.

— Pre-excited AFib can degenerate to VF; delta wave, short PR on baseline ECG.

— Avoid AV-nodal blockers in pre-excited AFib (use procainamide or ibutilide — note ibutilide prolongs QT, separate context).

— J-point elevation in inferior/lateral leads; survivor of unexplained VF arrest with otherwise normal workup.

Brugada syndrome:

Catecholaminergic polymorphic VT (CPVT):

Short QT syndrome:

ARVC (arrhythmogenic right ventricular cardiomyopathy):

HCM (hypertrophic cardiomyopathy):

WPW with AFib:

Idiopathic VF (e.g., early repolarization syndrome):

Key distinction: LQTS vs CPVT — both have exertional syncope and normal structural heart, but LQTS has prolonged QT at rest, while CPVT has normal QT with bidirectional VT on exercise. Both treated with nadolol; flecainide is added in CPVT but avoided in LQTS.

Board pearl: A teenager with exertional syncope and a normal resting QTc but bidirectional VT on stress test = CPVT, not LQTS. Treatment: high-dose nadolol ± flecainide ± LCSD ± ICD.

Key Differentials — Other-Category Causes of Syncope and Wide-Complex Tachycardia

— Prodrome (warmth, nausea, diaphoresis), upright posture trigger, rapid recovery, normal ECG.

— Tilt-table testing if recurrent; no QT prolongation.

— Drop in SBP ≥20 or DBP ≥10 on standing; volume depletion, autonomic failure, antihypertensives.

— Aortic stenosis: exertional syncope, harsh systolic murmur, slow rising pulse.

— HCM with outflow tract obstruction: dynamic murmur.

— Pulmonary embolism with right heart strain: syncope, hypoxia, RV strain on ECG.

— AV block (Mobitz II, 3rd degree): bradycardic syncope; needs pacemaker.

— Sick sinus syndrome: tachy-brady with pauses.

— Monomorphic VT in structural heart disease (post-MI scar).

— Postictal confusion, tongue bite (lateral), incontinence, prolonged recovery — distinguishes from arrhythmic syncope (brief LOC, rapid recovery).

— But: TdP can cause convulsive syncope — get ECG before labeling seizure.

— TCA overdose: wide QRS, prolonged QT, hypotension; treat with sodium bicarbonate.

— Cocaine: ischemia-induced arrhythmias; avoid beta-blockers acutely (unopposed alpha — though this is debated, classic Step 3 answer).

— Methadone overdose: respiratory depression + QT prolongation.

— Hyperkalemia: peaked T waves, wide QRS, sine wave — distinct from LQTS.

— Hypocalcemia: prolonged QT (ST segment lengthening, not T wave).

— SAH: deeply inverted T waves, prolonged QT ("cerebral T waves"), can precipitate TdP.

Vasovagal/neurocardiogenic syncope:

Orthostatic syncope:

Cardiac structural causes:

Arrhythmic syncope without LQTS:

Seizure:

Hypoglycemia, hypotension from sepsis, hypoxia: rarely confused after basic workup.

Drug intoxication:

Electrolyte emergencies:

Intracranial events:

Key distinction: Convulsive syncope from TdP vs primary seizure — TdP has rapid full recovery, often recurrent identical events, ECG abnormalities, and family history. Always ECG first in undifferentiated LOC.

Step 3 management: For TCA overdose with wide QRS and prolonged QT, give IV sodium bicarbonate (1–2 mEq/kg bolus, then infusion) — narrows QRS, reverses Na-channel blockade. Magnesium also for TdP if it occurs.

Secondary Prevention, Discharge Medications, and Long-Term Plan

— Nadolol (preferred) or propranolol — titrated to symptom control and HR.

— Mexiletine add-on for LQT3 or persistent QTc ≥500.

— Potassium chloride supplement if on diuretic or prone to hypoK.

— Magnesium oxide as needed.

— Avoid: sotalol, dofetilide, amiodarone unless absolutely indicated under EP guidance.

— Document offending drug as adverse drug reaction in chart and pharmacy systems.

— Patient education: provide personalized QT-prolonging drug avoidance list.

— MedicAlert bracelet recommended.

— Repeat ECG 1–2 weeks post-discharge to confirm QTc normalization off offending agent.

— CredibleMeds.org — written handout, encourage patient to check every new prescription.

— Show pharmacy app/list to all providers, dentists, urgent care visits.

— Maintain hydration and electrolytes during GI illness — go to ED if vomiting/diarrhea persists >24 h.

— Aggressive treatment of fever (not LQTS-specific like Brugada, but reduces arrhythmia threshold).

— All first-degree relatives get baseline ECG.

— If proband has identified pathogenic variant, targeted genetic testing for relatives.

— Positive genotype carriers start lifestyle measures and often beta-blocker even if QTc normal.

— Most LQTS patients can do moderate recreational activity.

— LQT1: avoid competitive swimming, sprinting, endurance racing.

— LQT2: avoid sudden startles (alarm clocks).

— Shared decision-making with EP cardiologist; current AHA/ACC allows participation in many sports for low-risk well-treated patients.

— Influenza, COVID-19, pneumococcal vaccines — febrile illness raises arrhythmia risk and dehydration risk.

— Device interrogation every 3–6 months (remote monitoring preferred).

— Generator replacement every 5–10 years.

Discharge medication checklist for confirmed LQTS:

Acquired LQTS discharge plan:

Universal counseling:

Family cascade screening:

Exercise prescription:

Vaccination and infection prevention:

ICD long-term care:

Step 3 management: Every LQTS discharge summary must include: diagnosis, genotype if known, beta-blocker name/dose, list of drugs to avoid, family screening plan, and follow-up appointment. Missing the family screening recommendation is a frequent Step 3 omission.

Follow-Up, Monitoring Parameters, and Counseling

— Initial diagnosis: cardiology/EP visit within 2–4 weeks of starting beta-blocker.

— Stable, asymptomatic: every 6–12 months with ECG.

— Pregnancy: every trimester + postpartum 6-week visit (especially LQT2).

— Pediatrics: annual ECG and dose adjustment for growth (weight-based dosing).

— QTc trend — compare to baseline; flag ΔQTc ≥60 ms or absolute ≥500.

— Resting HR and BP — confirm adequate beta-blockade (resting HR typically 50–70).

— Symptom diary: palpitations, presyncope, syncope, exercise tolerance.

— Adherence assessment — most events occur off therapy.

— K+ and Mg2+ annually, more often if on diuretics.

— TSH annually (hypothyroidism can prolong QT).

— Reinforce CredibleMeds use.

— Review new medications, OTC drugs (e.g., diphenhydramine in overdose, promethazine).

— Driving restrictions after syncope (see chunk 17).

— Travel considerations: carry medication list, MedicAlert.

— Avoid recreational drugs, especially cocaine, methamphetamine, MDMA.

— Structured exercise within prescribed limits improves cardiovascular fitness and mental health.

— Avoid extreme heat/dehydration (marathons, Bikram yoga).

— Rates of anxiety and depression are elevated, especially post-ICD or after a family member's SCD.

— Avoid citalopram >20 mg, TCAs; use sertraline, bupropion, mirtazapine.

— CBT and support groups (SADS Foundation) helpful.

— Patient can recite top 5 drug classes to avoid.

— Family members trained in CPR and AED use.

— Home AED considered for high-risk patients.

Follow-up cadence:

Monitoring parameters:

Counseling at every visit:

Lifestyle and rehab:

Mental health:

Patient education endpoints:

CCS pearl: On a CCS follow-up case, advance the clock and reorder ECG and BMP at 1 month, then 6 months — demonstrating longitudinal QTc monitoring. Also include family screening orders in the plan.

Board pearl: Adherence-focused counseling at every visit reduces breakthrough events more than any drug switch — never forget to ask "do you take your nadolol every day?"

Ethical, Legal, and Patient Safety Considerations

— Probands should be counseled about implications for relatives before testing.

— Disclosure to at-risk relatives is encouraged; if patient refuses, providers have a duty to encourage disclosure but generally cannot break confidentiality (varies by state; some states allow disclosure to identified at-risk relatives).

— GINA (Genetic Information Nondiscrimination Act) protects against employment and health insurance discrimination — but not life, disability, or long-term care insurance. Patients should be informed before testing.

— Pediatric genetic testing for actionable conditions like LQTS is generally supported (treatable) — differs from adult-onset untreatable conditions.

— After syncope or sustained VT in LQTS: no private driving for 3 months; no commercial driving permanently (or until extended event-free period).

— After ICD for secondary prevention: 6 months no driving.

— After ICD for primary prevention: 1 week no driving.

— Document counseling in the chart; physician reporting requirements vary by state (mandatory in CA, some others).

— ICD implantation in adolescents: assent + parental consent; discuss psychological burden of shocks.

— LCSD: discuss Horner syndrome risk.

— Pregnancy in known LQTS: pre-conception counseling about adherence, postpartum risk.

— Medication reconciliation at every transition — ED to floor, floor to discharge, PCP handoff. Acquired LQTS often results from a new drug added during hospitalization.

— EHR allergy/intolerance entry for the offending drug — concrete Step 3 patient safety win.

— Communicate diagnosis to dentists, anesthesiologists, all prescribers — pre-op QT review prevents perioperative TdP.

— Sudden death of a young athlete may trigger family screening obligations.

— Some states require physician reporting of conditions affecting driving (impaired consciousness).

— Patients with ICDs nearing end of life should be offered ICD deactivation to prevent shocks during dying process — ethically equivalent to withholding/withdrawing other life-sustaining therapy.

— Document patient/surrogate consent; deactivation by magnet (temporary) or programmer (definitive).

Genetic testing and cascade screening — ethical landscape:

Driving restrictions (AHA/ACC 2015):

Informed consent edge cases:

Transition-of-care safety:

Mandatory reporting and public health:

End-of-life and ICD deactivation:

Step 3 management: A patient with newly diagnosed LQTS asks about returning to truck driving. The correct answer: commercial driving is restricted indefinitely (or per FMCSA case-by-case) after syncope; private driving allowed after 3 event-free months on therapy.

High-Yield Associations and Rapid-Fire Clinical Facts

— LQT1 (KCNQ1, IKs) → exertion, swimming → nadolol works best.

— LQT2 (KCNH2, IKr) → auditory, postpartum → K+ supplementation helpful.

— LQT3 (SCN5A, late INa) → sleep/rest → mexiletine adjunct.

— LQT7 = Andersen-Tawil (periodic paralysis, dysmorphism).

— LQT8 = Timothy syndrome (syndactyly, autism).

— Romano-Ward: autosomal dominant, LQT1/2/3, normal hearing.

— Jervell and Lange-Nielsen (JLN): autosomal recessive, congenital sensorineural deafness, very high risk → ICD often indicated early.

Genotype-phenotype rapid-fire:

Syndromes to know:

ECG fact: QTc >500 = high TdP risk; >550 = very high risk.

Drug fact: Methadone QT risk is dose-dependent, especially >100 mg/day.

Antibiotic fact: Among macrolides, azithromycin has lower QT risk than erythromycin/clarithromycin but is still listed; doxycycline and amoxicillin do not prolong QT.

Antiemetic fact: Ondansetron IV > PO for QT risk; max single IV dose 16 mg per FDA (originally 32 mg withdrawn).

Anesthesia fact: Succinylcholine, sevoflurane acceptable; droperidol, IV ondansetron bolus caution.

Electrolyte fact: Hypokalemia from refeeding syndrome, DKA correction, or diuretics is the most common precipitant of acquired TdP.

Magnesium fact: Works even with normal Mg level in TdP — first-line.

Pacing fact: Overdrive pacing 90–110 bpm shortens QT in pause-dependent TdP.

Cocaine + LQTS: cocaine blocks INa and IKr — massive arrhythmic risk.

Hypothermia fact: Therapeutic hypothermia (TTM) post-arrest prolongs QT — monitor and avoid QT-prolonging drugs during cooling.

Pregnancy fact: Postpartum 9 months is the LQT2 danger zone.

Pediatric fact: 2:1 AV block in a neonate = think LQTS or congenital heart block.

Diagnostic threshold: QTc ≥480 ms repeatedly without secondary cause = LQTS.

Board pearl: "Aborted SCD in a swimmer" + family history → LQT1; "syncope after the doorbell rang" → LQT2; "found dead in bed" young patient → LQT3 or Brugada (check QTc vs V1–V2 ST elevation).

Key distinction: LQTS uses nadolol; CPVT uses nadolol + flecainide; Brugada uses ICD + fever avoidance (no beta-blocker mandate).

Board Question Stem Patterns

Stem 1 — The swimmer: 16-year-old collapses during swim practice; resuscitated; QTc 510 ms; mother has unexplained syncope. Answer: nadolol, avoid competitive swimming, family ECG screening, genetic testing — likely LQT1.

Stem 2 — The doorbell: 22-year-old woman has syncope when her alarm clock rings; ECG QTc 490 with notched T waves. Answer: LQT2; nadolol; remove auditory triggers; counsel about postpartum risk.

Stem 3 — The acquired QT prolongation: Elderly woman on furosemide, citalopram 40 mg, and azithromycin develops syncope; ECG shows QTc 560 with TdP on telemetry. Answer: IV magnesium, stop azithromycin and reduce citalopram to ≤20 mg, replete K+ and Mg2+, switch antibiotic to amoxicillin/doxycycline.

Stem 4 — The postpartum collapse: 28-year-old 3 months postpartum has syncope; QTc 500 with bifid T waves; remembers brother who died in his sleep. Answer: LQT2 (sibling LQT3 differential), nadolol, family cascade.

Stem 5 — The unstable TdP: ICU patient on methadone and levofloxacin develops pulseless polymorphic VT. Answer: defibrillate, then magnesium IV, then stop offending drugs, replete K+, consider isoproterenol/overdrive pacing for pause-dependent TdP.

Stem 6 — The misdiagnosed seizure: Teen with "epilepsy" on multiple AEDs has breakthrough "seizures" only during exercise; EEG normal. Answer: 12-lead ECG → reveals long QT → reclassify as LQTS.

Stem 7 — The athlete clearance: Adolescent with QTc 470, genotype-positive LQT1, asymptomatic, wants to play soccer. Answer: shared decision-making, beta-blocker, avoid swimming/sprint events, AED at school.

Stem 8 — The substitution game: LQTS patient needs antibiotic for cystitis. Answer: nitrofurantoin or fosfomycin (avoid fluoroquinolone).

Stem 9 — The family screen: Sister of deceased SCD victim has QTc 470, asymptomatic. Answer: genotype testing (if proband variant known), beta-blocker if carrier or QTc borderline, repeat ECG.

Stem 10 — The ICD candidate: LQTS patient has syncope despite adherence to nadolol. Answer: ICD + continue beta-blocker ± LCSD ± mexiletine.

Board pearl: Recurrent Step 3 trap: choosing metoprolol or sotalol for an LQTS patient. Correct answer is almost always nadolol (or propranolol).

Step 3 management: When the stem hands you a drug list with an offender, the test point is substituting the safer agent, not just stopping the drug.

One-Line Recap

Long QT syndrome is a repolarization disorder defined by QTc ≥480 ms (or ≥460 ms with symptoms), managed with nadolol, lifestyle/trigger avoidance, electrolyte optimization (K+ >4, Mg2+ >2), strict avoidance of QT-prolonging drugs (CredibleMeds), family cascade ECG screening, and ICD for high-risk or beta-blocker-refractory patients — while acute torsades de pointes is treated with IV magnesium, defibrillation if unstable, drug withdrawal, and isoproterenol or overdrive pacing for pause-dependent acquired forms.

Diagnosis: QTc ≥480 ms repeatedly, or Schwartz score ≥3.5, after ruling out reversible causes (electrolytes, drugs, hypothyroidism, bradycardia).

Genotype-trigger map: LQT1 = exertion/swimming; LQT2 = auditory/postpartum; LQT3 = sleep/rest. Treatment cornerstone is nadolol (never metoprolol or sotalol), plus mexiletine in LQT3.

Acute TdP algorithm: defibrillate if unstable → IV magnesium 2 g → correct K+/Mg2+ → stop offending drug → isoproterenol or overdrive pacing to HR 90–110 for pause-dependent acquired TdP.

Longitudinal Step 3 pearls: cascade screen all first-degree relatives; counsel using CredibleMeds for every new prescription (especially fluoroquinolones, macrolides, ondansetron, citalopram >20 mg, methadone, antipsychotics); ICD for SCD survivors or breakthrough events on therapy; LQT2 postpartum and JLN syndrome are the highest-risk subgroups; document driving restrictions, family screening, and adverse drug reaction in every discharge plan.

Most common Step 3 traps: choosing metoprolol/sotalol, missing the family cascade, forgetting magnesium in TdP, and failing to substitute a safer antibiotic/antiemetic in an LQTS patient.