Sustained Ventricular Tachycardia¶
Chapter 261 | Part 6: Disorders of the Cardiovascular System
KEY CLINICAL POINTS¶
- Sustained monomorphic VT is defined as a wide QRS tachycardia lasting ≥ 30 s or requiring intervention (e.g., cardioversion).
- Differentiation from supraventricular tachycardia (SVT) with aberrancy relies on VA dissociation, QRS morphology, and P wave analysis.
- ICD implantation is indicated for secondary prevention in patients with structural heart disease and recurrent VT.
- Catheter ablation is the preferred treatment for ischemic and nonischemic cardiomyopathy-associated VT.
- Genetic conditions like ARVC and congenital heart disease require tailored management strategies.
1. DEFINITION & OVERVIEW¶
Sustained monomorphic ventricular tachycardia (VT) is a wide-complex tachycardia with a regular rhythm, lasting ≥ 30 s or requiring intervention. It is distinct from accelerated idioventricular rhythm (AIVR) and SVT with aberrancy. VT is classified as monomorphic if all QRS complexes are morphologically identical, indicating a single reentrant circuit. Sustained VT may progress to ventricular fibrillation (VF) and is associated with significant hemodynamic compromise in patients with structural heart disease.
Table 261-1: Sustained Ventricular Arrhythmias with Aberrancy¶
| Category | Subcategory | Key Features |
|---|---|---|
| 1. Idiopathic VT | A. Outflow tract origin | (cid:127) RV outflow tract: Left bundle branch block pattern in V1 with inferior axis and late precordial transition (cid:127) LV outflow tract: Similar inferiorly directed axis with early precordial transition and prominent R wave in V2–V3 |
| 1. Idiopathic VT | B. LV fascicular VT | (cid:127) Typical right bundle branch block pattern in V1 with sharp intrinsicoid deflection and left axis deviation |
| 1. Idiopathic VT | C. Papillary muscle VT | (cid:127) Posteromedial: Atypical right bundle branch block pattern in V1 with monophasic R wave and left axis deviation (cid:127) Anterolateral: Atypical right bundle branch block pattern in V1 with positive deflection in III and negative in I |
| Category | Subcategory | Key Features |
|---|---|---|
| 2. Ischemic cardiomyopathy | (cid:127) | (cid:127) Monomorphic VT common with prior MI (cid:127) Polymorphic VT/VF suggests ischemia |
| 3. Nonischemic cardiomyopathy | (cid:127) | (cid:127) Fibrotic scars (sarcoidosis, Chagas’ disease, Lamin A/C cardiomyopathy) cause monomorphic VT (cid:127) Polymorphic VT/VF may occur independently or from degeneration of monomorphic VT |
| 4. Arrhythmogenic RV cardiomyopathy | (cid:127) | (cid:127) Monomorphic VT usually of RV origin (left bundle branch morphology in V1) (cid:127) Polymorphic VT/VF may occur independently or from degeneration of monomorphic VT |
| 5. Repaired tetralogy of Fallot | (cid:127) | (cid:127) Monomorphic VT of RV origin (left bundle branch morphology in V1) |
| 6. Hypertrophic cardiomyopathy | (cid:127) | (cid:127) Polymorphic VT or VF (cid:127) Less commonly, monomorphic VT with myocardial scars (apical aneurysms) |
| 7. Genetic arrhythmia syndromes | A. Long QT syndrome | (cid:127) Torsades des pointes VT |
| 7. Genetic arrhythmia syndromes | B. Brugada syndrome | (cid:127) Ventricular fibrillation episodes, often nocturnal |
| 7. Genetic arrhythmization syndromes | C. Catecholaminergic polymorphic VT | (cid:127) Polymorphic VT or bidirectional VT |
| 7. Genetic arrhythmia syndromes | D. Short QT/early repolarization | (cid:127) Ventricular fibrillation |
| 8. Idiopathic polymorphic VT/VF | (cid:127) | (cid:127) Usually triggered by recurrent PVCs; common origin: left posterior fascicle (right bundle branch block/left anterior fascicular block pattern) |
1.1 Clinical Context¶
VT is a life-threatening arrhythmia requiring immediate intervention. It is common in patients with myocardial infarction (MI), cardiomyopathies, and genetic disorders. Hemodynamic stability during VT does not reliably distinguish it from other wide-complex tachycardias.
2. EPIDEMIOLOGY¶
Sustained VT is common in patients with structural heart disease, particularly after myocardial infarction (MI). Incidence peaks in adults >50 years old. Risk factors include prior MI, heart failure, cardiomyopathies, and genetic disorders. Prevalence is 1–2% in patients with ischemic cardiomyopathy. Mortality risk is 1–2% per year in patients with structural heart disease and recurrent VT.
2.1 Demographics¶
Most common in males >50 years old with ischemic heart disease. Patients with nonischemic cardiomyopathy (NICM) may present at younger ages. Congenital heart disease (ACHD) patients have a 3–14% risk of VT after TOF repair.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
VT arises from reentry circuits in scarred myocardium or Purkinje system. Key mechanisms include: 1. Scar-related reentry in infarcted myocardium (most common in ischemic cardiomyopathy) 2. Purkinje system reentry (e.g., bundle branch reentry, fascicular VT) 3. Genetic disorders (ARVC, Brugada syndrome, Lamin A/C cardiomyopathy) 4. Inflammatory cardiomyopathies (sarcoidosis, Chagas’ disease) 5. Congenital heart disease (TOF repair, septal defects)
3.1 Molecular Basis¶
Inflammatory processes and genetic mutations (desmosomal proteins, Lamin A/C) disrupt myocardial integrity, creating reentrant substrates. Early identification of these processes is critical for targeted treatment.
4. CLINICAL FEATURES¶
Symptoms vary from syncope to palpitations. Rapid VT may cause hypotension and syncope in patients with severe LV dysfunction. Patients with preserved LV function may tolerate sustained VT with minimal symptoms. Complications include progression to VF, hemodynamic instability, and sudden cardiac death.
4.1 Presentation¶
- Syncope (common in patients with severe LV dysfunction)
- Palpitations (common in patients with preserved LV function)
- Chest discomfort or dyspnea (in patients with ischemia)
- Hemodynamic instability (hypotension, shock)
5. DIFFERENTIAL DIAGNOSIS¶
Differentiate from SVT with aberrancy using ECG criteria: 1. VA dissociation (P waves not associated with QRS complexes) 2. QRS morphology (monophasic R wave in V1/V2 for VT vs. biphasic in SVT) 3. P wave presence (P waves may follow QRS in VT with slow atrial rate) 4. Fusion beats (evidence of VA dissociation) 5. QRS duration >180 ms in sinus rhythm suggests VT origin
5.1 Key Differentiators¶
- Presence of VA dissociation (most reliable)
- QRS morphology (monophasic R wave in V1/V2 for VT vs. biphasic in SVT)
- P wave presence (may follow Q, but not in 1:1 conduction)
- Fusion beats (evidence of VA dissociation)
6. INVESTIGATIONS & DIAGNOSIS¶
ECG criteria for VT include VA dissociation, QRS morphology, and P wave analysis. Cardiac imaging (MRI, echocardiography) identifies scarred myocardium. Cardiac biomarkers (troponin, CK-MB) help differentiate acute MI from VT. Cardiac MRI detects delayed gadolinium enhancement in scarred regions.
Table 261-2: Summary of Randomized Controlled Studies Assessing Catheter Ablation of VT¶
| Study | Year | Sample Size | Inclusio n Criteria | Control Arm | Age (years) | Male (%) | ICM (%) | Baselin e LVEF (%) | Follow- up (mon ths) |
|---|---|---|---|---|---|---|---|---|---|
| SMASH- VT | 2000–20 06 | 64 | Prior MI, ICD for VF or unstable VT | Medical therapy | 67 ± 10 | 87 | 100 | 32 ± 9 | 22.5 ± 5.5 |
| VTACH | 2010 | 52 | Prior MI, LVEF £50%, ICD indicated for stable VT | ICD + medical therapy | 66 ± 8 | 93 | 100 | 34 ± 9 | 22.5 ± 9 |
| CALYPS O | 2012–20 14 | 13 | IHD, ‡1 ICD shock or ‡3 ATP t herapies for mono morphic VT in last 6 months | AAD therapy | 63 ± NR | 93 | 100 | 30 ± NR | 6 |
| VANISH | 2016 | 132 | Prior MI, ICD in situ, ‡1 episode of VT while on class I/III AAD | Escalati on of AAD therapy | 69 ± 8 | 93 | 100 | 31 ± 11 | 27.9 ± 17.1 |
| SMS | 2017 | 54 | IHD, LVEF £40%, unstable VT | ICD + medical therapy | 67 ± 8 | 84 | 100 | 31 ± 7 | 27.0 ± 13.2 |
| BERLIN- VT | 2020 | 76 | Prior MI, LVEF 30–50%, ICD in situ for lif e-threate ning VT | Medical therapy until third ICD shock (then VT ablation) | 66 ± 10 | 87 | 100 | 41 ± 6 | 13.2 ± 9.5 |
| PARTIT A | 2022 | 23 | Cardiom yopathy, had first ICD shock | Medical therapy | 68 ± 9 | 85 | 81 | 32 ± 9 | 24.2 |
| SURVIV E-VT | 2022 | 71 | Prior MI, sustaine d VT causing ICD shock or syncope | AAD therapy | 70 ± 9 | 96 | 100 | 33 ± 11 | 23 |
| Study | Year | Sample Size | Inclusio n Criteria | Control Arm | Age (years) | Male (%) | ICM (%) | Baselin e LVEF (%) | Follow- up (mon ths) |
|---|---|---|---|---|---|---|---|---|---|
| PAUSE- SCD | 2022 | 60 | LVEF <50%, ICD indicated for seco ndary pr evention or inducible monomo rphic VT on EPS | ICD + medical therapy | 55 (46–64) | 81 | 35 | 40 (30–49) | 31.3 (20. 1–40) |
6.1 Diagnostic Algorithm¶
- Assess for VA dissociation (P waves not associated with QRS)
- Evaluate QRS morphology (monophasic R wave in V1/V2 for VT)
- Check for P wave presence (may follow QRS in VT)
- Use cardiac MRI to identify scarred myocardium
- Rule out acute MI with cardiac biomarkers
7. MANAGEMENT & TREATMENT¶
Initial management follows ACLS guidelines. Synchronized cardioversion is used for hemodynamically unstable VT. Antiarrhythmics (amiodarone, sotalol) are used for stable VT. ICD implantation is indicated for secondary prevention in patients with structural heart disease. Catheter ablation is the preferred treatment for ischemic and nonischemic cardiomyopathy-associated VT.
7.1 Pharmacologic Therapy¶
- Amiodarone (drug of choice for heart disease)
- Sotalol, flecainide (for ARVC)
- Beta-blockers (for exercise-induced VT in ARVC)
- Antiarrhythmic drugs may not improve survival without ICD
7.2 Interventional Therapy¶
- Catheter ablation (70% success rate in ARVC)
- ICD implantation for secondary prevention (reduces mortality by 50%)
- Substrate mapping and ablation for NICM
8. PROGNOSIS & COMPLICATIONS¶
ICD reduces annual mortality from 12.3% to 8.8% in patients with structural heart disease. Recurrent VT episodes in ICD patients have a 5-year mortality >30%. Complications include heart failure, recurrent ischemic events, and arrhythmic death. Patients with idiopathic VT have a low risk of sudden death unless associated with structural disease.
8.1 Long-Term Outcomes¶
- ICD reduces arrhythmic deaths by 50% in patients with hemodynamically significant VT
- 70% of patients with infarct scars have VT recurrence within 2 years
- NICM patients have lower ablation success rates compared to ischemic VT
9. SPECIAL CONSIDERATIONS¶
Pregnancy: ICDs are safe but require careful monitoring. Pediatric patients: VT in congenital heart disease requires tailored management. Elderly: Consider comorbidities and frailty. Genetic disorders (ARVC, Brugada syndrome) require ICD implantation and genetic counseling.
9.1 Congenital Heart Disease¶
- 3–14% risk of VT after TOF repair
- 1% annual risk of sudden cardiac death in adults >40 years
- Repeated bursts of monomorphic VT may cause tachycardia-induced cardiomyopathy
10. KEY POINTS & CLINICAL PEARLS¶
- Use ECG criteria (VA dissociation, QRS morphology) to differentiate VT from SVT.
- ICD implantation is indicated for secondary prevention in structural heart disease.
- Catheter ablation is the preferred treatment for ischemic and nonischemic VT.
- Genetic testing is critical for patients with idiopathic VT or family history.
- Monitor for recurrent VT in ICD patients and consider ablation for incessant episodes.