Major Updates: Expanded guidance on non-ischemic cardiomyopathies, enhanced risk stratification using imaging (LGE-CMR), updated inherited syndrome algorithms, and improved exercise/sports recommendations for competitive athletes.
Strengthened role of cardiac MRI (LGE) in SCD risk stratification
New evidence-based algorithms for rare cardiomyopathies (ARVC, sarcoidosis)
Clarified long QT type-specific pharmacotherapy (LQT1 vs LQT2 vs LQT3)
Updated Brugada and CPVT management based on latest trials
Return-to-play guidelines for athletes across all arrhythmia syndromes
Special population guidance: pregnancy, CKD, congenital heart disease, elderly
Acute Management of Ventricular Arrhythmias
VT/VF Classification & Hemodynamic Assessment
Hemodynamically Stable VT: Systolic BP >90 mmHg, no signs of shock or pulmonary edema Hemodynamically Unstable VT/VF: Hypotension, altered consciousness, cardiogenic shock, signs of hypoperfusion, or cardiac arrest Monomorphic VT: Single, uniform ECG morphology; suggests reentrant mechanism Polymorphic VT: Changing QRS morphology; consider Long QT, catecholaminergic VT, Brugada, or ischemia
If Hemodynamic Deterioration: Immediate synchronized cardioversion (200J biphasic)
If Stable: Consider IV antiarrhythmics or catheter ablation depending on underlying disease and recurrence risk
Antiarrhythmic Drug Therapy
Acute IV Antiarrhythmic Therapy
Agent
Loading Dose
Maintenance
Monitoring
Cautions
Amiodarone
150 mg IV over 10 min
1 mg/min × 6 hrs; then 0.5 mg/min
ECG, BP, QT interval; hypotension common
Risk of bradycardia, hypotension; avoid in hypokalemia
Lidocaine
1–1.5 mg/kg IV
0.5–1.4 mg/min infusion
ECG, neurologic status
Caution in renal failure; tremor, confusion at high doses
Procainamide
15–20 mg/kg IV at <50 mg/min
1–4 mg/min
ECG, QRS width, BP; monitor for lupus syndrome
Hypotension risk; prolongs QRS; avoid in decompensated HF
Isoproterenol
N/A (infusion only)
1–5 μg/min; titrate by response
BP, HR, arrhythmia termination
Use only for VT with long QT or Brugada; high ischemia risk
Chronic Oral Antiarrhythmic Therapy
Agent
Target Dose
Indications
Key Monitoring
Amiodarone
200–400 mg daily
Recurrent monomorphic VT; ICD shocks
TSH, LFTs, PFTs q6–12mo; ophthalmology annually
Sotalol
80–240 mg daily (div)
Monomorphic VT; LVEF >40%
QTc, renal function; contraindicated if QTc >500 ms
Dofetilide
250–500 μg BID
Monomorphic VT in structurally normal hearts
Baseline QTc; renal dosing critical
Beta-blockers
Target dose varies
Essential background therapy; Long QT (esp. LQT1), CPVT, Brugada
HR, BP, exercise tolerance
Do: Antiarrhythmic Strategy
Use beta-blockers as first-line in all VT unless contraindicated
Add Class I/III agents only for breakthrough arrhythmias despite ICD therapy
Monitor QTc interval monthly during Class III initiation
Correct electrolytes (K+ >4.0, Mg2+ >2.0) before starting QT-prolonging drugs
Don't: Common Mistakes
Avoid Class I agents in LV dysfunction (↑ mortality in CAST trial)
Don't use QT-prolonging drugs without baseline QTc measurement
Avoid amiodarone monotherapy without ICD in structural heart disease
Do not give isoproterenol to post-MI patients without specialist guidance
ICD Indications for Primary & Secondary Prevention
Secondary Prevention (Post-Arrhythmia Event)
Indication
Class
Evidence
Notes
Survived cardiac arrest due to VF or VT (after reversible cause excluded)
I
A
Standard of care; consider within 3 days if stable
Sustained monomorphic VT with hemodynamic compromise
I
B
ICD indicated regardless of EF; assess tolerance to antiarrhythmics first
Sustained monomorphic VT with LVEF 35–40% (post-revascularization)
IIa
B
Consider after failed drug therapy or patient preference
Primary Prevention—Ischemic Cardiomyopathy
Criteria
Class
Evidence
Timing
LVEF ≤35% post-MI (≥3 days) on optimal medical therapy (ACEi/ARB, beta-blocker, MRA) × ≥40 days
I
A
≥40 days post-MI; reevaluate LVEF at 40 days; implant if still ≤35%
LVEF 36–40% post-MI with inducible VT on EPS or prior cardiac arrest
IIa
B
EPS may guide therapy; consider ICD if VT induced
LVEF ≤30% ischemic cardiomyopathy (bridge to transplant if listed)
I
B
Temporary wearable ICD option if short transplant wait
Primary Prevention—Non-Ischemic Cardiomyopathy
Diagnosis
ICD Indication
LVEF Threshold
Additional Criteria
Dilated Cardiomyopathy
Class IIa
≤35%
Sustained VT, syncope, or extensive LGE on CMR
HCM with SCD risk factors
Class I
Any
Prior CA, family hx SCD, extreme LVH, LVOT obstruction, abnormal BP response
ARVC
Class IIa
Any
Sustained VT or hemodynamic VT; primary prevention in high-risk phenotypes
Cardiac Sarcoidosis
Class I
≤35%
LVEF <35%; also consider if sustained VT irrespective of EF
LGE-CMR Impact: Extensive late gadolinium enhancement (LGE) on cardiac MRI improves SCD risk stratification in non-ischemic cardiomyopathy and may lower ICD threshold even if LVEF >35%.
Disease-Specific Management
Ischemic Cardiomyopathy
Key Points:
• ICD indicated if LVEF ≤35% post-MI (≥40 days) on optimal medical therapy
• Cardiac catheterization/revascularization may improve LVEF; reassess at 40 days post-MI
• VT ablation for recurrent shocks despite amiodarone or if ICD-independent VT control desired
• Beta-blockers, ACEi/ARB, and MRAs reduce SCD risk; ensure optimization before ICD
Hypertrophic Cardiomyopathy (HCM)
SCD Risk Factor
Management
Prior cardiac arrest or aborted CA
ICD (Class I)
Family history of SCD
Risk stratification; consider ICD if additional markers present
ARVC (Arrhythmogenic Right Ventricular Cardiomyopathy)
Diagnosis: Major criteria: epsilon waves, RV dysfunction on echo/MRI, RV apical aneurysm, fibrofatty infiltration ICD Indication: Class IIa for sustained VT or primary prevention in high-risk phenotypes (extensive RV involvement, LGE) Pharmacotherapy: Sotalol preferred for arrhythmia suppression; consider flecainide addition Activity Restriction: Competitive sports prohibition; ICD before participation in sports
Cardiac Sarcoidosis
Screening: ECG (conduction abnormalities), Holter (arrhythmias), echocardiography (regional wall motion), cardiac MRI (LGE) or PET ICD Indication: LVEF ≤35%; also consider if sustained VT irrespective of EF Steroid Therapy: Improves LV function and may reduce arrhythmia burden; consider in early stages with reversible edema on MRI Immunosuppression: Prednisone 0.5–1 mg/kg/day tapered over months if active inflammation
Inherited Arrhythmia Syndromes
Long QT Syndrome (LQTS)
Diagnosis: QTc ≥480 ms in males, ≥490 ms in females (with or without symptoms); genetic testing recommended
Genotype
Triggers
Pharmacotherapy
Other Measures
LQT1 (KCNQ1 mutation; 40% of cases)
Swimming, exertion
Beta-blockers (first-line); >90% effective
Avoid triggers; ICD if recurrent syncope on beta-blockers
LQT2 (KCNH2 mutation; 35% of cases)
Auditory stimuli, exertion
Beta-blockers + mexiletine (1.2–1.8 g/day)
Left cardiac sympathetic denervation (LCSD) if frequent syncope; ICD backup
LQT3 (SCN5A mutation; 10% of cases)
Sleep, rest, sudden arousals
Beta-blockers + mexiletine OR flecainide preferred
ICD often needed for symptomatic patients
Do: LQTS Management
Beta-blockers are first-line for all LQTS types; target heart rate <60 bpm at rest
Genetic testing and family screening essential; cascade screening in relatives
Correct electrolytes: K+ >4.0, Mg2+ >2.0, Ca2+ normal range
Diagnosis: Structurally normal heart with polymorphic VT triggered by exercise or emotion; genetic mutations in RYR2 or CASQ2
Pharmacotherapy
Dosing
Target Response
Beta-blockers (first-line)
High-dose; target resting HR <60 bpm
Suppress exercise-induced bidirectional VT
Flecainide (add-on)
100–300 mg/day (div); monitor QRS
Further suppress polymorphic VT burden
Ivabradine (alternative)
7.5 mg daily
Heart rate reduction without negative inotropes
Do: CPVT Lifestyle
Strict exercise restriction until arrhythmia controlled on therapy
ICD implantation after aborted CA or recurrent syncope despite maximal therapy
Genetic counseling and family screening (autosomal dominant in ~60%)
Avoid high catecholamine states; restrict competitive sports
Early Repolarization Syndrome (ERS)
ECG Finding: J-point elevation ≥1 mm in two adjacent inferior and/or lateral leads (II, III, aVF, V4–V6) Risk: VF in young males (median age 35 years); often during sleep/rest Management: ICD for survivors of CA; beta-blockers or quinidine for high-risk asymptomatic patients with ERS + family history of SCD
Short QT Syndrome (SQTS)
Diagnosis: QTc ≤360 ms + pathogenic mutation (KCNH2, KCNQ1, KCNJ2) or family history SCD Management: ICD for survivors of CA or symptomatic patients; sotalol or hydroquinidine for QT prolongation; genetic testing mandatory
VT Ablation Strategy
Scenario
Indication
Timing
Technique
Recurrent ICD shocks despite amiodarone
Class I
Urgent (within days of shocks)
Substrate or conventional mapping; endocardial ± epicardial
Incessant VT unresponsive to drugs
Class I
Emergency
Hemodynamic VT; urgent EP study and ablation
Frequent PVCs or non-sustained VT in structurally normal heart
Class IIa
Elective
Idiopathic VT; outflow tract or fascicular mapping
Primary prevention alternative to ICD (poor candidate)
ICD Athletes: Modern ICDs with rate-adaptive pacing and advanced detection zones allow participation in competitive sports. Counsel on device limitations, avoid direct chest trauma, and emphasize regular follow-up (every 1–3 months).
Special Populations
Pregnancy & Postpartum
LQTS & CPVT: Beta-blockers essential; continue throughout pregnancy and postpartum ICD Implantation: If indicated, perform before conception if possible; postpone elective replacement to postpartum if safe Delivery: Spontaneous vaginal delivery preferred; avoid prolonged labor; epidural anesthesia recommended Postpartum: Arrhythmia burden may increase in early postpartum; close monitoring essential
Chronic Kidney Disease (CKD)
Electrolytes: Hyperkalemia increases arrhythmia risk; maintain K+ 4.0–5.0 mmol/L with dietary/pharmacologic measures QT-Prolonging Drugs: Avoid or use with caution (amiodarone accumulation, sotalol renal elimination) ICD Decisions: Renal transplant candidacy influences timing; discuss prognosis before implantation Drug Dosing: Adjust antiarrhythmics and beta-blockers for reduced renal clearance
Congenital Heart Disease (CHD)
Repaired TOF: VT risk in 10–20% long-term; ICD if sustained VT or LVEF <40% d-TGA post-Mustard/Rastelli: Atrial arrhythmias common; VT less frequent; ICD for sustained VT Eisenmenger Physiology: Arrhythmias reflect RV dysfunction; ICD reserved for sustained VT only (high perioperative risk) Anatomic Considerations: Venous access challenges may require epicardial or subcutaneous ICD approaches
Elderly Patients (≥75 years)
ICD Benefit: Age alone not contraindication; consider functional status, comorbidities, life expectancy (>1 year benefit window) Drug Interactions: Polypharmacy increases risk; careful antiarrhythmic selection Frailty Assessment: Comprehensive geriatric evaluation advised before major interventions CRT-D vs. ICD-only: Depressed EF warrants CRT-D if QRS ≥120 ms and NYHA II–IV symptoms