Ventricular arrhythmias VT VF clinical reference card

Cardiology — Arrhythmia / Critical

VentricularArrhythmias

VT + VF + VT storm + Torsades · treat as VT until proven otherwise if wide complex tachycardia · identify and reverse cause · ICD for secondary prevention if EF ≤35% · Super Compact

• Sx: palpitations (rapid regular) · presyncope/syncope (↓CO) · cardiac arrest (VF/pulseless VT) · chest pain (ischemia trigger or demand); wide complex tachycardia (WCT) on ECG: rate >100 bpm + QRS >120 ms; hemodynamic instability (SBP<90 + AMS + APE) → unsynchronized defibrillation immediately for VF/pulseless VT; synchronized cardioversion for pulsed VT; AV dissociation + fusion beats + capture beats = VT until proven otherwise; RBBB morphology in V1 with northwest axis = VT; concordance (all-positive or all-negative V1–V6) = VT

• Neg: denies delta wave on ECG + irregular WCT at rates >200 bpm (WPW+AF — not VT; NEVER adenosine/BB/CCB → VF; procainamide [Pronestyl] or cardioversion only) · denies regular narrow QRS tachycardia with aberrant conduction mimicking WCT (SVT with aberrancy — responds to adenosine; AV dissociation absent; fusion/capture beats absent; concordance absent; treat with adenosine 6 mg IV if uncertain and hemodynamically stable to distinguish) · denies QTc >500 ms before arrhythmia + twisting QRS morphology around isoelectric line (Torsades de Pointes — AVOID antiarrhythmics that prolong QT [amiodarone, sotalol]; MgSO4 2 g IV + overdrive pacing; isoproterenol [Isuprel] for bradycardia-dependent Torsades)

• SHx: prior MI/structural heart disease (most common substrate — scar reentry) · known EF (EF≤35%=ICD candidate) · prior ICD/ablation (last interrogation; recent shocks — appropriate vs inappropriate) · family hx SCD (channelopathy — LQTS/Brugada/CPVT) · current antiarrhythmics+QT-prolonging drugs · cocaine/stimulants · electrolyte disorders (↓K+/↓Mg2+) · medications (QT prolongers — check CredibleMeds)

• Etiology: ischemic CM (scar reentry — most common; prior MI + EF<40%); acute ischemia (ACS trigger — reperfusion VF); channelopathies: LQTS (SCN5A/KCNQ1/KCNH2 — QTc>500 ms; Torsades), Brugada (SCN5A — coved STE V1–V2; febrile VF), CPVT (RYR2/CASQ2 — exercise-induced bidirectional VT; β-blocker); nonischemic DCM (LMNA mutation — VT+AV block+SCD; early ICD); infiltrative (sarcoid — VT+AV block+LV aneurysm); HCM (septal VT — ICD if SCD risk score >4%/5yr); electrolyte (↓K+/↓Mg2+/hypercalcemia); drugs (QT prolongers + amiodarone [Pacerone] toxicity)

• RF: prior MI+scar (highest VT risk) · EF≤35% · NSVT on Holter · inducible VT on EP study · electrolyte deficiency (↓K+/↓Mg2+) · QT-prolonging drugs · family hx SCD or channelopathy · active ischemia · cocaine · hypokalemia from diuretics

• Data: ECG 12-lead (WCT: QRS>120ms+rate>100; Brugada criteria for VT: AV dissociation=VT; fusion beats=VT; capture beats=VT; RBBB morphology in V1+northwest axis=VT; all-positive concordance V1–V6=VT; RS complex nadir>100ms=VT; NW axis=VT; QTc measurement — Bazett formula: QT/√RR; LQTS=QTc>470ms men/480ms women; Brugada pattern: coved STE V1–V2) · troponin serial (ACS trigger; elevated in demand ischemia from sustained VT) · BMP STAT (K+—target≥4.0; Mg2+—target≥2.0; both must be replete before antiarrhythmic) · echo (EF; wall motion anomalies; scar; LV aneurysm; RV dilation; structural disease) · antiarrhythmic drug levels (digoxin [Lanoxin] level — toxicity: bidirectional VT; amiodarone [Pacerone] — long half-life) · drug/toxin screen · thyroid function (amiodarone [Pacerone]-induced thyrotoxicosis → VT) · EP study if unexplained syncope + structural disease

• DDx: SVT with aberrancy (responds to adenosine; no AV dissociation; rate <200 bpm; narrow if adenosine given; treat as VT until proven otherwise) · WPW+AF (irregular WCT+delta waves+rate>200 — procainamide [Pronestyl] only; NEVER AV nodal blockers→VF) · Torsades de Pointes (QTc>500+twisting morphology — MgSO4+overdrive pace; avoid QT prolongers) · Accelerated idioventricular rhythm (AIVR) (rate 60–100 bpm; benign reperfusion arrhythmia post-STEMI — no treatment needed) · Artifact/motion artifact (patient is conscious+well; check pulse; rhythm disappears on different lead)

• Home Meds: STAT review of QT-prolonging drugs (CredibleMeds.org) — stop all unnecessary QT prolongers if QTc>500 ms; hold antiarrhythmics if Torsades (sotalol [Betapace]/dofetilide [Tikosyn]/quinidine); hold digoxin (Lanoxin) if toxic (bidirectional VT); check amiodarone (Pacerone) dose+thyroid function; hold hypokalemia-promoting diuretics until K+≥4.0

Plan

• Pulseless VT/VF → ACLS immediately: unsynchronized defibrillation 200 J biphasic; high-quality CPR; epinephrine (Adrenalin) 1 mg IV q3–5 min; amiodarone (Pacerone) 300 mg IV push → 150 mg IV ×1 after 3 shocks; lidocaine (Xylocaine) 1–1.5 mg/kg IV push (alternative if amiodarone [Pacerone] unavailable or polymorphic VT on ischemic background); post-ROSC → TTM 36°C ×24h; immediate PCI if STEMI/STEMI-equivalent post-ROSC

• Unstable VT (pulse present + SBP<90 or AMS or APE) → synchronized cardioversion: 100–200 J biphasic; sedate if time permits (midazolam [Versed] 1–2 mg IV + fentanyl [Sublimaze] 25–50 mcg IV); R-wave synchronization mandatory (unsynchronized in pulsed VT risks VF)

• Stable VT (pulse present + hemodynamically stable) → antiarrhythmic termination: amiodarone (Pacerone) 150 mg IV over 10 min → 1 mg/min ×6h → 0.5 mg/min ×18h; procainamide (Pronestyl) 10 mg/kg IV over 20–60 min (max 17 mg/kg; stop if QRS widens >50% or QTc >500 ms; preferred if ischemic VT or WPW); lidocaine (Xylocaine) 1–1.5 mg/kg IV bolus → 1–4 mg/min infusion (preferred in acute MI VT; less effective for scar VT)

• K+ to ≥4.0 + Mg2+ to ≥2.0 before any antiarrhythmic — do not skip; hypokalemia ↑VT/VF risk and blunts antiarrhythmic effect | Correcting electrolytes may terminate VT without any antiarrhythmic — always replete first

• Torsades de Pointes (polymorphic VT + QTc>500 ms): MgSO4 2 g IV over 1–2 min → 1–2 g/hr infusion; stop ALL QT-prolonging drugs immediately; overdrive pacing 90–110 bpm (suppresses pause-dependent Torsades — temporary pacemaker or ICD overdrive); isoproterenol (Isuprel) 2–10 mcg/min IV (for acquired LQTS/bradycardia-dependent Torsades — ↑HR shortens QTc; CONTRAINDICATED in congenital LQTS); NEVER amiodarone (Pacerone)/sotalol (Betapace)/dofetilide (Tikosyn) in Torsades — ↑QTc → worsens

• VT storm (≥3 VT episodes in 24h or incessant VT): amiodarone (Pacerone) IV loading; deep sedation (propofol [Diprivan] 5–50 mcg/kg/min + fentanyl [Sublimaze]); general anesthesia if refractory; stellate ganglion block (left — interrupts sympathetic input to myocardium); urgent EP referral for catheter ablation; treat underlying cause (ACS → revascularization; electrolytes → replete; HF → optimize); sympathectomy if all else fails

• Identify and treat trigger: ACS → PCI/reperfusion; ↓K+/↓Mg2+ → IV repletion; drug toxicity → stop drug; HF → optimize; ischemia → revascularization; cocaine → benzodiazepine + CCB; thyrotoxicosis → PTU + propranolol (Inderal)

• Brugada syndrome VT/VF: quinidine 200–400 mg PO BID or TID (suppresses phase 2 reentry; only proven pharmacologic therapy); isoproterenol (Isuprel) IV for acute VF storm; avoid: sodium channel blockers (flecainide [Tambocor]/propafenone [Rythmol]/procainamide [Pronestyl]) — may unmask/worsen Brugada pattern; avoid fever (↑Brugada pattern; antipyretics aggressively); ICD for symptomatic Brugada

• ICD indications (secondary prevention — Class I): survived VF or hemodynamically unstable VT not from reversible cause; sustained VT + structural disease; EP-inducible VT + prior MI + EF<40%; primary prevention: EF≤35% after ≥3mo GDMT (MADIT-II: ↓mortality 31%; SCD-HeFT: ↓mortality 23%); LQTS + syncope; Brugada + syncope or aborted SCA; CPVT + sustained VT despite β-blocker; HCM + SCD risk score >4%/5yr (ESC calculator)

• PT/OT — restrict activity during acute VT; mobilize once stabilized; cardiac rehab post-ICD; driving restrictions (no driving until ICD checked + 1 shock-free month minimum; varies by state)

• Trend daily: QTc on ECG (hold antiarrhythmic if >500 ms) · K+ + Mg2+ to targets · troponin serial (ischemia trigger) · amiodarone (Pacerone) level if on chronic therapy · TFTs weekly if on amiodarone · ICD interrogation after every clinical event · fever curve (Brugada: fever unmasks — antipyretics)

• Escalate: VF/pulseless VT → defibrillation immediately · incessant VT (VT storm) → deep sedation + amiodarone (Pacerone) IV + stellate ganglion block + urgent EP for ablation · Torsades storm → MgSO4 + overdrive pacing + stop all QT prolongers + isoproterenol (Isuprel) if bradycardia-dependent · ACS as VT trigger → emergent revascularization · cardiogenic shock from VT → MCS (Impella CP [Abiomed]) before ablation

• Discharge: ICD implant if meets criteria (before discharge if secondary prevention; 40-day wait if primary prevention post-MI unless severe EF); amiodarone (Pacerone) 200 mg PO daily if recurrent VT (annual PFT/TFT/LFT/ophthalmology); mexiletine (Mexitil) 150–300 mg PO TID adjunct to amiodarone for VT storm; β-blocker (carvedilol [Coreg] or metoprolol succinate [Toprol-XL]); optimize GDMT; EP f/u 2–4 weeks post-ICD; driving restriction counseling; avoid QT prolongers (CredibleMeds list); electrolyte targets (K+ ≥4.0; Mg2+ ≥2.0); device clinic

VentricularArrhythmias

VT · VF · VT storm · Torsades · channelopathies · complete reference · all doses · Full Card

Symptoms / Associated Sx

• Palpitations (rapid, regular); presyncope; syncope (Adams-Stokes — sudden loss of consciousness without prodrome when sustained VT reduces CO below threshold for cerebral perfusion); cardiac arrest (VF or pulseless VT — requires immediate defibrillation)

• Chest pain (either ischemia trigger or demand ischemia from sustained fast VT); diaphoresis; hypotension; AMS

• Wide complex tachycardia (WCT) features: rate >100 bpm + QRS >120 ms; AV dissociation (P waves march independently of QRS — pathognomonic for VT); fusion beats (partial activation from both sinus and ventricular focus — pathognomonic); capture beats (rare normally conducted QRS during VT — pathognomonic); RBBB morphology in V1 + northwest (NW) axis = VT; all-positive or all-negative concordance V1–V6 = VT; RS nadir >100 ms in any precordial lead = VT

• AIVR (accelerated idioventricular rhythm): rate 60–100 bpm; wide complex; occurs during reperfusion post-STEMI; benign — no treatment; confused with VT but rate is non-threatening

Neg

• Pt denies delta wave (slurred QRS upstroke) on prior or current ECG with an irregular wide complex tachycardia at rates >200 bpm — argues against WPW with AF (WPW+AF: irregular wide tachycardia at very fast rates is the hallmark; NEVER give adenosine/BB/CCB/digoxin — AV nodal block → all conduction via accessory pathway → VF → cardiac arrest; procainamide [Pronestyl] 10 mg/kg IV or cardioversion only)

• Pt denies complete termination of WCT with adenosine 6 mg IV or vagal maneuvers without QRS morphology change — argues against SVT with aberrant conduction (SVT with RBBB aberrancy terminates completely with adenosine; VT slows transiently or continues; if adenosine given to stable WCT and tachycardia terminates = SVT with aberrancy; never give adenosine to hemodynamically unstable WCT)

• Pt denies QTc >500 ms before arrhythmia onset with twisting polymorphic QRS morphology rotating around isoelectric baseline — argues against Torsades de Pointes requiring entirely different management (Torsades: MgSO4 2 g IV + stop QT prolongers + overdrive pacing; do NOT give amiodarone [Pacerone] or sotalol [Betapace] — worsen QTc → more Torsades; monomorphic VT: amiodarone or procainamide [Pronestyl])

• Pt denies rate 60–100 bpm with wide complex rhythm immediately after STEMI reperfusion — argues against pathologic VT (AIVR — accelerated idioventricular rhythm at rate 60–100 = reperfusion sign; benign; no antiarrhythmic treatment needed; treating AIVR with antiarrhythmics = unnecessary drug toxicity risk)

Social History (SHx)

• Prior MI and known EF (scar reentry is most common VT mechanism; EF ≤35% = ICD candidate; date of prior MI matters — 40-day waiting period for ICD post-MI primary prevention); prior ICD (last interrogation date, recent shocks — appropriate vs inappropriate, defibrillation threshold, current battery life); prior ablation (location, success rate, recurrence)

• Family history of SCD, syncope, or arrhythmia (channelopathies — LQTS, Brugada, CPVT); medications (QT prolongers — full list at CredibleMeds.org; antiarrhythmics — dose and duration; diuretics causing electrolyte losses); cocaine/methamphetamines (coronary vasospasm + catecholamine surge → VT/VF); alcohol (holiday heart; dilated CM)

Main Etiology

• Structural heart disease — scar reentry (~70%): prior MI scar → slow conduction zone → reentrant circuit; most common mechanism of sustained monomorphic VT; EF and scar burden are primary risk determinants; catheter ablation targets the slow conduction isthmus

• Channelopathies (normal structural heart): LQTS (congenital: KCNQ1/LQT1 — exercise-triggered, swim; KCNH2/LQT2 — auditory/startle triggered, postpartum; SCN5A/LQT3 — sleep/bradycardia triggered; QTc >470 ms men / 480 ms women); Brugada syndrome (SCN5A — coved STE V1–V2; triggered by fever/Na-channel blockers; VF in sleep or rest); CPVT (catecholaminergic polymorphic VT — RYR2/CASQ2; bidirectional VT with exercise; β-blocker + flecainide [Tambocor] ± ICD)

• Acquired/reversible: drug-induced QT prolongation + Torsades (most common — check all medications on CredibleMeds.org); acute ischemia (reperfusion VF); electrolyte imbalance (↓K+, ↓Mg2+, hypercalcemia); infiltrative heart disease (cardiac sarcoidosis — VT + AV block + LV aneurysm; amyloidosis)

• Other structural: HCM (↑IVS → VT; SCD risk calculator; β-blocker + ICD if high-risk); ARVC/ARVD (fatty/fibrous replacement of RV free wall — LBBB morphology VT from RV origin; desmosomal mutations; exercise restriction); nonischemic DCM (LMNA mutation — VT + AV block + SCD; early ICD referral)

RF

• Prior MI + EF ≤35% (highest risk combination); NSVT on ambulatory monitoring; inducible VT on EP study; ↓K+ or ↓Mg2+; QT-prolonging medications; family hx SCD or channelopathy; active ischemia; cocaine; hypokalemia from diuretics; cardiac sarcoidosis

Data

• 12-lead ECG — immediately and during tachycardia if possible (WCT criteria for VT: AV dissociation [P waves march independently — pathognomonic]; fusion beats [partial activation from both foci — pathognomonic]; capture beats [occasional narrow QRS = sinus capturing ventricle during VT — pathognomonic]; RBBB morphology + NW axis = VT; all-positive concordance V1–V6 = VT [activation from LV base toward apex]; RS nadir >100 ms in any precordial lead = VT; Brugada criteria [Brugada 1991]: absence of RS in all precordial leads → VT; QTc [Bazett]: QT/√RR; LQTS ≥470 ms [M] / 480 ms [W]; coved STE V1–V2 = Brugada type 1 pattern)

• BMP — STAT (K+ target ≥4.0 mEq/L; Mg2+ target ≥2.0 mEq/L; hypokalemia is most common electrolyte cause of VT; hypomagnesemia potentiates QT prolongation; Cr — antiarrhythmic dose adjustment; glucose — hypoglycemia can trigger arrhythmia)

• Troponin serial (ACS as trigger — acute ischemia causes ~15% of sustained VT; demand ischemia from sustained fast VT can cause modest troponin elevation even without obstructive CAD; clinical context + ECG territory distinguish)

• Echo TTE (EF — primary ICD threshold ≤35%; wall motion — ischemic territory or scar; LV aneurysm [post-MI — fixed wall motion abnormality at rest]; RV size/function — ARVC; septal hypertrophy — HCM; structural disease; thrombus on LV wall)

• Drug levels + toxicology (digoxin [Lanoxin] level — bidirectional VT = classic digoxin toxicity; amiodarone [Pacerone] serum level if toxicity suspected; urine drug screen for cocaine/amphetamines; QT-prolonging drug list from CredibleMeds.org)

• Thyroid function (amiodarone [Pacerone]-induced thyrotoxicosis — can precipitate VT; TSH + free T4 in any patient on chronic amiodarone with new arrhythmia)

• Cardiac MRI (scar characterization — LGE pattern: ischemic [subendocardial/transmural] vs non-ischemic [midmyocardial/subepicardial]; ARVC [fatty infiltration RV]; sarcoidosis [patchy LGE]; identifies VT substrate for ablation planning; EF more accurate than echo)

• EP study (electrophysiology) (inducible sustained VT + prior MI + EF <40% = Class I ICD indication; Holter monitor: NSVT + EF ≤40% + prior MI = high SCD risk; loop recorder for unexplained syncope + suspected VT)

DDx

SVT with aberrancy (WCT responding to adenosine 6 mg IV; no AV dissociation; no fusion/capture beats; treat as VT until adenosine given in stable patient) · WPW + AF (irregular WCT + delta wave + rates >200 — procainamide [Pronestyl] or cardioversion ONLY; AV nodal blockers → VF → cardiac arrest) · Torsades de Pointes (polymorphic VT + QTc >500 ms + twisting morphology — MgSO4 2 g IV + stop QT prolongers; do NOT give amiodarone [Pacerone]/sotalol [Betapace]) · AIVR (rate 60–100 bpm + reperfusion post-STEMI — benign; no treatment needed) · Artifact (patient conscious and well; rhythm disappears on different lead; check pulse physically)

Home Meds

• STAT review of QT-prolonging medications (CredibleMeds.org — Risk categories: Known/Conditional/Possible QT risk; stop all Known QT-risk drugs if QTc >500 ms or Torsades present); stop antiarrhythmics that prolong QT (sotalol [Betapace]/dofetilide [Tikosyn]) if Torsades

• Hold digoxin (Lanoxin) if bidirectional VT or level >2.0 ng/mL; digoxin immune Fab (Digibind/DigiFab) if hemodynamically unstable; hold diuretics until K+ ≥4.0 and Mg2+ ≥2.0; hold amiodarone (Pacerone) if thyrotoxicosis (amiodarone-induced — endocrinology urgent)

• Continue: β-blocker (do NOT stop — rebound ischemia risk; reduce dose if bradycardia); aspirin (Bayer) if prior ACS; statins

Plan

• Step 1 — Pulseless VT/VF (ACLS):

  • Unsynchronized defibrillation 200 J biphasic immediately (do not delay for IV access or medications)

  • High-quality CPR 30:2; minimize interruptions; chest compression depth 2–2.4 inches; rate 100–120/min

  • Epinephrine (Adrenalin) 1 mg IV/IO q3–5 min (after 1st or 2nd shock)

  • Amiodarone (Pacerone) 300 mg IV push (after 3rd shock) → 150 mg IV push × 1 if needed; OR lidocaine (Xylocaine) 1–1.5 mg/kg IV push → 0.5–0.75 mg/kg q5–10 min (max 3 mg/kg); preferred if VT/VF on background of acute MI

  • Post-ROSC: targeted temperature management (TTM) 36°C ×24h (TTM2 trial 2021: 33°C vs 36°C equivalent outcomes; avoid fever); immediate 12-lead ECG; PCI for STEMI/STEMI-equivalent regardless of consciousness level; ICU

• Step 2 — Hemodynamically unstable VT (pulse present, SBP <90 or AMS or APE): synchronized cardioversion 100–200 J biphasic (R-wave synchronization mandatory — unsynchronized in pulsed VT risks delivering shock on T-wave → VF); sedate if time permits (midazolam [Versed] 1–2 mg IV + fentanyl [Sublimaze] 25–50 mcg IV); epinephrine (Adrenalin) or norepinephrine (Levophed) for hemodynamic support

• Step 3 — Stable VT (pulse + hemodynamically stable):

  • Amiodarone (Pacerone) 150 mg IV over 10 min → 1 mg/min ×6h → 0.5 mg/min ×18h (preferred for most sustained monomorphic VT; monitor QTc)

  • Procainamide (Pronestyl) 10 mg/kg IV over 20–60 min (max 17 mg/kg; preferred in WPW-associated VT; preferred if ischemic VT where amiodarone [Pacerone] may be less effective; stop if QRS widens >50% or hypotension)

  • Lidocaine (Xylocaine) 1–1.5 mg/kg IV bolus → 1–4 mg/min infusion (preferred in acute MI VT; less effective for chronic scar VT)

  • If antiarrhythmic fails → synchronized cardioversion

• Electrolyte repletion (before any antiarrhythmic): KCl IV to K+ ≥4.0 mEq/L (oral or IV — oral preferred if gut working); MgSO4 2 g IV over 15–30 min then recheck Mg level → repeat if <2.0; correcting electrolytes alone may terminate VT

• Torsades de Pointes management:

  • MgSO4 2 g IV over 1–2 min → 1–2 g/hr maintenance infusion (first-line regardless of Mg level)

  • Stop ALL QT-prolonging drugs immediately (CredibleMeds.org — remove from medication reconciliation entirely)

  • Overdrive pacing 90–110 bpm via temporary transvenous pacemaker or ICD reprogramming (suppresses pause-dependent Torsades by eliminating the long pause preceding each episode)

  • Isoproterenol (Isuprel) 2–10 mcg/min IV: for acquired (drug-induced) LQTS with bradycardia-dependent Torsades; ↑HR → shortens QTc; CONTRAINDICATED in congenital LQTS (↑catecholamines → more Torsades in LQT1/LQT2)

  • NEVER give amiodarone (Pacerone)/sotalol (Betapace)/dofetilide (Tikosyn) → ↑QTc → worsens Torsades; lidocaine (Xylocaine) and mexiletine (Mexitil) are QTc-neutral and acceptable if antiarrhythmic needed in Torsades context

• VT storm (≥3 separate VT episodes in 24h, or incessant VT):

  • IV amiodarone (Pacerone) loading: 150 mg over 10 min → 1 mg/min ×6h → 0.5 mg/min ×18h → 400 mg PO BID when stable

  • Deep sedation (propofol [Diprivan] 5–50 mcg/kg/min + fentanyl [Sublimaze] continuous infusion) — reduces sympathetic tone; may break VT storm

  • Stellate ganglion block (left-sided — most effective; fluoroscopy or US-guided injection of local anesthetic [bupivacaine] around left stellate ganglion at C6–T1; ↓sympathetic innervation to heart; used when pharmacologic treatment failing)

  • Emergent EP referral for catheter ablation (maps the reentrant circuit → ablates isthmus of slow conduction; most effective long-term strategy for scar-mediated VT storm)

  • Treat underlying trigger aggressively (ACS → emergent PCI; electrolytes → IV repletion; HF exacerbation → diuresis + inotropes)

  • Consider Impella CP (Abiomed) or VA-ECMO for hemodynamic support during ablation if EF severely reduced

• Channelopathy-specific management:

  • Congenital LQTS: β-blocker (propranolol [Inderal] 2–4 mg/kg/day PO divided TID or nadolol [Corgard] 1–2 mg/kg/day PO daily — non-selective preferred for LQT1/LQT2); avoid all QT-prolonging drugs; avoid swimming alone (LQT1 trigger); avoid auditory startle (LQT2 trigger); ICD if prior cardiac arrest or breakthrough events on β-blocker; mexiletine (Mexitil) 150–300 mg PO TID for LQT3 (SCN5A — mexiletine shortens QTc)

  • Brugada syndrome: quinidine 200–400 mg PO BID–TID (only proven pharmacologic suppression; blocks Ito current); isoproterenol (Isuprel) IV for acute VF storm; avoid sodium channel blockers (flecainide [Tambocor]/propafenone [Rythmol]/procainamide [Pronestyl]) — may unmask/worsen Brugada pattern; aggressive fever control (fever unmasks pattern → ↑VF risk); ICD for symptomatic Brugada (cardiac arrest or spontaneous sustained VT)

  • CPVT: β-blocker (nadolol [Corgard] preferred — 1–2 mg/kg/day PO daily) + flecainide (Tambocor) 100–150 mg PO BID (↓intracellular Ca2+ release; reduces exercise-induced VT); exercise restriction; ICD if breakthrough events; left cardiac sympathetic denervation (LCSD) for refractory

• ICD indications:

  • Secondary prevention (Class I): survived VF or hemodynamically unstable VT not from reversible cause; sustained VT + structural heart disease; EP-inducible VT + prior MI + EF ≤40%

  • Primary prevention (Class I): EF ≤35% after ≥3 months optimal GDMT (MADIT-II 2002: ↓all-cause mortality 31%; SCD-HeFT 2005: ↓mortality 23%); LQTS + syncope on β-blocker; Brugada + aborted SCA or spontaneous VF; CPVT + sustained VT despite β-blocker; HCM + SCD risk score >4%/5yr (ESC HCM SCD risk calculator)

  • LifeVest (ZOLL wearable defibrillator): bridge while awaiting 40-day reassessment post-MI if EF ≤35%; bridge to ICD implant; compliance is critical — if not worn, no protection

• PT/OT eval and treat — restrict all exertion during acute VT; cardiac rehab post-stabilization and post-ICD; driving restrictions (typically no driving for 1 month post-ICD shock, 6 months if VT-related syncope — state-specific; EP to advise); activity restriction for ARVC (avoid endurance exercise permanently)

• Trend daily: QTc on ECG (hold QT-prolonging drug if >500 ms; hold antiarrhythmic if QTc worsening); K+ and Mg2+ to targets; troponin if ACS trigger suspected; amiodarone (Pacerone) level if toxicity suspected; TFTs if on chronic amiodarone (weekly initially, then monthly); fever curve (Brugada — antipyretics aggressively); ICD interrogation after each clinical event (number of therapies, detection settings, battery status)

• Escalation triggers: VF/pulseless VT → defibrillation immediately · VT storm refractory to amiodarone (Pacerone) + sedation → stellate ganglion block + EP catheter ablation + MCS · Torsades storm → MgSO4 + overdrive pacing + isoproterenol (Isuprel) if bradycardia-dependent + stop all QT prolongers · ACS as VT trigger → emergent revascularization · cardiogenic shock from VT → Impella CP (Abiomed) as bridge to ablation · amiodarone thyrotoxicosis → endocrinology + methimazole (Tapazole) 20–40 mg PO daily ± prednisolone

• Discharge: ICD implant if criteria met (secondary prevention before discharge; 40-day observation for primary prevention post-MI); amiodarone (Pacerone) 200 mg PO daily if recurrent VT (annual PFT/TFT/LFT/ophthalmology monitoring); mexiletine (Mexitil) 150–300 mg PO TID adjunct for amiodarone-refractory VT; β-blocker at maximally tolerated dose (GDMT); optimize all GDMT (Entresto+Coreg+Aldactone+Farxiga); eliminate all QT-prolonging drugs (CredibleMeds); K+ ≥4.0 + Mg2+ ≥2.0 home targets; EP f/u 2–4 weeks post-ICD; device clinic for ICD checks; driving restriction per EP guidance; ARVC: permanent exercise restriction + ICD; channelopathy: family cascade screening (first-degree relatives); genetic counseling

⚠ Red Flags

• AV nodal blockers (adenosine/BB/CCB/digoxin [Lanoxin]) in WPW + AF (wide irregular tachycardia + delta wave) → AV nodal block → all conduction via accessory pathway → ventricular rates 250–300 bpm → VF → cardiac arrest; procainamide (Pronestyl) or cardioversion ONLY

• Amiodarone (Pacerone) or sotalol (Betapace) in Torsades de Pointes → ↑QTc → ↑Torsades frequency → VF; Torsades requires MgSO4 + QT-prolonger elimination + overdrive pacing; lidocaine (Xylocaine) or mexiletine (Mexitil) are the safe antiarrhythmics in this context

• Unsynchronized shock in pulsed VT → shock on T-wave → VF; always synchronize for pulsed VT (R-wave synchronization); only unsynchronize for pulseless VT/VF or rapidly deteriorating VT where synchronization delays shock

• Treating AIVR (60–100 bpm post-reperfusion) as VT → unnecessary antiarrhythmic exposure; AIVR is a benign reperfusion sign; check rate — if <100 bpm wide complex = AIVR; no treatment

• VT storm without addressing triggers (ongoing ischemia, ↓K+/↓Mg2+, thyrotoxicosis) → refractory VT despite antiarrhythmics; the trigger is the treatment in most reversible VT storm cases

• Missing LQTS in young patient with syncope → QTc measurement is mandatory in all syncope evaluations; QTc >500 ms = very high Torsades risk; eliminate all QT prolongers; β-blocker; ICD if cardiac arrest history

Senior IM Resident Pearls

• Wide complex tachycardia = VT until proven otherwise: the most dangerous assumption is SVT with aberrancy; Brugada criteria (AV dissociation + fusion/capture beats + NW axis + concordance) confirm VT but absence does not exclude; if uncertain in an unstable patient → cardiovert; in a stable patient → adenosine 6 mg IV (terminates SVT, not VT); never give verapamil (Calan) to WCT — if VT + verapamil → hypotension + cardiac arrest

• MADIT-II (2002, NEJM): prophylactic ICD vs conventional therapy in prior MI + EF ≤30% → ↓all-cause mortality 31% (NNT 18 over 20 months); SCD-HeFT (2005, NEJM): ICD vs amiodarone (Pacerone) vs placebo in EF ≤35% → ICD ↓mortality 23%; amiodarone = placebo; these two trials established EF ≤35% as the primary ICD threshold; do not withhold ICD referral from eligible patients

• Torsades vs monomorphic VT — the drug decision is opposite: Torsades: MgSO4 + overdrive pacing + remove QT prolongers; NEVER amiodarone/sotalol/dofetilide; Monomorphic VT: amiodarone (Pacerone) or procainamide (Pronestyl) or lidocaine (Xylocaine); giving amiodarone to Torsades worsens it; check QTc before every antiarrhythmic

• VT storm — stellate ganglion block: left stellate ganglion block (fluoroscopy or US-guided bupivacaine injection at C6–T1) interrupts sympathetic innervation to the heart; effective within minutes; used when pharmacologic treatment failing; bridge to catheter ablation; increasingly available at major centers; recognize this option exists and call EP early

• CredibleMeds.org — mandatory drug screen for QT risk: over 200 drugs prolong QT; check every medication list; Known QT Risk = avoid when QTc >500 ms; common culprits on ward: azithromycin (Zithromax), fluoroquinolones (ciprofloxacin, levofloxacin), haloperidol (Haldol), methadone, ondansetron (Zofran) at high doses, antifungals; check before adding any new drug in patients with baseline QTc >450 ms

• Common mistake — treating AIVR as VT: rate 60–100 bpm wide complex rhythm immediately after STEMI reperfusion = AIVR; it is a benign sign of successful reperfusion (calcium washout from reperfused myocardium); no antiarrhythmic treatment needed; treating AIVR with lidocaine or amiodarone = unnecessary drug toxicity with no benefit