Premature Ventricular Contractions, Nonsustained Ventricular Tachycardia, and Accelerated Idioventricular Rhythm¶
Chapter 260 | Part 6: Disorders of the Cardiovascular System
KEY CLINICAL POINTS¶
- PVCs and NSVT are common in structurally normal hearts but may indicate underlying heart disease or genetic syndromes (e.g., ARVC, Brugada syndrome).
- QRS morphology and axis help localize arrhythmia origin (e.g., left bundle branch block pattern suggests right ventricular origin).
- ICDs are indicated for high-risk patients with ejection fraction <35% or NYHA class II/III heart failure.
- Antiarrhythmic drugs (e.g., β -blockers, amiodarone) may be used for symptomatic arrhythmias, but long-term use requires careful risk-benefit assessment.
- Frequent PVCs (>10/hour) or NSVT correlate with increased mortality in heart failure and may require ICD implantation.
1. DEFINITION & OVERVIEW¶
Premature ventricular contractions (PVCs), nonsustained ventricular tachycardia (NSVT), and accelerated idioventricular rhythm (AIVR) are ventricular arrhythmias. PVCs are early depolarizations originating in the ventricles, while NSVT consists of 3-30 consecutive ventricular beats at >100 bpm. AIVR is 3 or more ventricular beats at <100 bpm. These arrhythmias may be benign or indicate underlying heart disease.
ECG Features of Ventricular Arrhythmias¶
| Arrhythmia Type | QRS Duration | Rate | Axis | Clinical Implication |
|---|---|---|---|---|
| PVC | >0.12 sec | Variable | Depends on origin | Benign or indicates structural disease |
| NSVT | 0.12-0.16 sec | 100-250 bpm | Depends on origin | May indicate underlying disease |
| AIVR | 0.12-0.16 sec | <100 bpm | Depends on origin | Usually benign, may indicate heart failure |
1.1 ECG Characteristics¶
PVCs show wide QRS complexes (>0.12 sec) with abnormal morphology. NSVT has 3-30 consecutive ventricular beats. AIVR has 3 or more ventricular beats at <100 bpm. QRS axis and morphology help localize origin (e.g., inferior axis suggests inferior wall origin).
1.2 Clinical Significance¶
Asymptomatic PVCs in structurally normal hearts are generally benign. However, frequent PVCs (>10/hour) or NSVT may indicate structural heart disease, myocardial ischemia, or genetic syndromes (e.g., Brugada syndrome, ARVC).
2. EPIDEMIOLOGY¶
PVCs are common in healthy individuals (up to 10% of ECGs). NSVT occurs in 1-2% of patients with structural heart disease. Risk factors include myocardial ischemia, electrolyte abnormalities (e.g., hypokalemia), and sympathetic stimulation. Prevalence increases with age and in patients with heart failure.
2.1 Demographics¶
Common in adults, especially those with hypertension, coronary artery disease, or heart failure. More frequent in males. Asymptomatic in 70-80% of cases.
2.2 Risk Factors¶
Myocardial ischemia, electrolyte imbalances (hypokalemia, hypomagnesemia), sympathetic overactivity, and structural heart disease (e.g., cardiomyopathy, valvular disease).
3. ETIOLOGY & PATHOPHYSIOLOGY¶
PVCs arise from enhanced automaticity, triggered activity, or reentry. NSVT is often due to reentry circuits in diseased myocardium. AIVR is typically due to automaticity in the ventricles. Structural heart disease, electrolyte disturbances, and ischemia predispose to these arrhythmias.
Genetic Syndromes Associated with Ventricular Arrhythmias¶
| Syndrome | ECG Features | Management |
|---|---|---|
| Long QT Syndrome | Prolonged QT interval, T-wave abnormalities | Beta-blockers, implantable defibrillator |
| Brugada Syndrome | ST elevation in V1-V3, T-wave abnormalities | Implantable defibrillator, sodium channel blockers |
| ARVC | T-wave inversion, epsilon waves | ICD, avoid strenuous exercise |
| HCM | Left ventricular hypertrophy, septal abnormalities | ICD in high-risk patients |
3.1 Mechanisms¶
Enhanced automaticity (e.g., in ischemic myocardium), triggered activity (afterdepolarizations), and reentry (e.g., in scarred myocardium). Left bundle branch block morphology suggests right ventricular origin.
3.2 Genetic Syndromes¶
Long QT syndrome, Brugada syndrome, arrhythmogenic right ventricular cardiomyopathy (ARVC), and hypertrophic cardiomyopathy (HCM) are associated with ventricular arrhythmias.
4. CLINICAL FEATURES¶
Asymptomatic in most cases. Symptoms include palpitations, chest discomfort, and dyspnea. Complications include ventricular dysfunction, heart failure, and sudden cardiac death. Frequent PVCs (>10/hour) or NSVT correlate with increased mortality.
4.1 Symptoms¶
Palpitations, chest discomfort, dyspnea, and syncope. Asymptomatic in 70-80% of cases.
4.2 Complications¶
Ventricular dysfunction, heart failure, sudden cardiac death, and ventricular dyssynchrony. Frequent PVCs may induce chronic tachycardia or reduce ejection fraction.
5. DIFFERENTIAL DIAGNOSIS¶
Structural heart disease (e.g., coronary artery disease, cardiomyopathy), electrolyte abnormalities, myocardial ischemia, and genetic syndromes (e.g., Brugada syndrome, ARVC). A family history of sudden death suggests genetic evaluation.
5.1 Structural Heart Disease¶
Coronary artery disease, cardiomyopathy, valvular disease, and myocardial infarction. Echocardiography and cardiac MRI are essential for diagnosis.
5.2 Genetic Syndromes¶
Long QT syndrome, Brugada syndrome, ARVC, and HCM. Genetic testing and ECG analysis are required for confirmation.
6. INVESTIGATIONS & DIAGNOSIS¶
12-lead ECG, Holter monitoring, echocardiography, cardiac MRI, and electrophysiologic studies. ECG morphology and axis help localize origin. Cardiac MRI detects scar tissue and ventricular dysfunction.
Diagnostic Criteria for Ventricular Arrhythmias¶
| Arrhythmia | ECG Findings | Key Features |
|---|---|---|
| PVC | Wide QRS complex (>0.12 sec), abnormal morphology | Single or multiple beats |
| NSVT | 3-30 consecutive ventricular beats at >100 bpm | May be monomorphic or polymorphic |
| AIVR | 3 or more ventricular beats at <100 bpm | Usually benign, may indicate heart failure |
6.1 Diagnostic Criteria¶
PVCs: Wide QRS complexes (>0.12 sec) with abnormal morphology. NSVT: 3-30 consecutive ventricular beats at >100 bpm. AIVR: 3 or more ventricular beats at <100 bpm.
6.2 Imaging¶
Echocardiography for ventricular function and valvular disease. Cardiac MRI for scar detection and assessment of myocardial viability.
7. MANAGEMENT & TREATMENT¶
Asymptomatic patients require no treatment. Symptomatic patients may benefit from β -blockers, calcium channel blockers, or antiarrhythmics (e.g., amiodarone). ICDs are indicated for high-risk patients. Catheter ablation is effective in ~90% of cases.
Pharmacologic Treatment Options¶
| Drug Class | Examples | Indications | Contraindications |
|---|---|---|---|
| b-Blockers | Metoprolol, Carvedilol | Symptomatic PVCs, NSVT | Severe heart failure |
| Calcium Channel Blockers | Verapamil, Diltiazem | Symptomatic PVCs | Structural heart disease |
| Antiarrhythmics | Flecainide, Propafenone | Idiopathic arrhythmias | Structural heart disease |
| Amiodarone | Amiodarone | Severe arrhythmias | Severe heart failure |
7.1 Pharmacologic Therapy¶
β -Blockers (e.g., metoprolol), nondihydropyridine calcium channel blockers (verapamil, diltiazem), and antiarrhythmics (flecainide, propafenone, amiodarone). Avoid sodium channel blockers in structural heart disease.
7.2 Non-Pharmacologic Therapy¶
Catheter ablation for focal PVCs. ICD implantation for high-risk patients (ejection fraction <35%, NYHA class II/III). Lifestyle modifications (avoid caffeine/alcohol).
8. PROGNOSIS & COMPLICATIONS¶
Asymptomatic PVCs in structurally normal hearts have excellent prognosis. Frequent PVCs (>10/hour) or NSVT in heart failure correlate with increased mortality. Complications include ventricular dysfunction, heart failure, and sudden cardiac death.
8.1 Prognostic Factors¶
PVC burden (>10-20% of total beats), ejection fraction, NYHA class, and presence of structural heart disease. ICDs reduce mortality in high-risk patients.
8.2 Complications¶
Ventricular dysfunction, heart failure, ventricular dyssynchrony, and sudden cardiac death. Frequent PVCs may induce chronic tachycardia.
9. SPECIAL CONSIDERATIONS¶
Pregnancy: Monitor for arrhythmias and avoid certain drugs. Pediatrics: PVCs are common but may indicate congenital heart disease. Elderly: Higher risk of complications from arrhythmias. Genetic testing is critical in families with sudden death history.
9.1 Pregnancy¶
Monitor for arrhythmias and avoid drugs with negative inotropic effects. ICDs may be required in high-risk patients.
9.2 Pediatrics¶
PVCs are common but may indicate congenital heart disease or genetic syndromes (e.g., ARVC). Echocardiography is essential.
10. KEY POINTS & CLINICAL PEARLS¶
- Asymptomatic PVCs in structurally normal hearts are generally benign. 2. Frequent PVCs (>10/hour) or NSVT correlate with increased mortality. 3. ICDs are indicated for ejection fraction <35% or NYHA class II/III heart failure. 4. Avoid sodium channel blockers in structural heart disease. 5. Catheter ablation is effective in ~90% of cases.