Ventricular Tachycardia

Key points

• Ventricular tachycardia, defined as a series of three or more ventricular complexes occurring at a rate of 100 to 250 beats/min, is the most frequently encountered life-threatening arrhythmia and the most common etiology of a wide-complex tachycardia in a patient with a previous myocardial infarction
• Ventricular tachycardia should not be ruled out in a patient with stable blood pressure
• Electrocardiography (ECG) should be done as soon as is practical in order to confirm the diagnosis; the absence of an RS complex in all precordial leads or the presence of an RS interval >100 ms in any precordial lead is specific for ventricular tachycardia
• Patients with ventricular tachycardia should be transferred to the hospital immediately
• In patients with hemodynamically stable ventricular tachycardia, pharmacologic cardioversion with intravenous amiodarone or lidocaine may be attempted during close cardiac monitoring
• In patients with sustained ventricular tachycardia (lasting longer than 30 seconds) and hemodynamic compromise, severe heart failure, or ongoing ischemia or infarction, immediate treatment with synchronized direct-current cardioversion and initiation of Advanced Cardiac Life Support (ACLS) are required
• Once the patient is stabilized, blood samples should be obtained for assessment of electrolyte, cardiac enzyme, and therapeutic drug (eg, digoxin) levels

Background

Description

• Coronary artery disease with myocardial infarction is the most common structural heart disease predisposing patients to ventricular tachycardia
• Typical symptoms of ventricular tachycardia include palpitations, breathlessness, lightheadedness, angina, and syncope; however, patients also may be asymptomatic
• ECG shows wide QRS complexes (usually >120 ms) with T-wave polarity opposite that of the major QRS deflection; atrioventricular dissociation is usually seen
• Ventricular tachycardia can be classified according to ECG appearance into two subgroups:
  • Monomorphic ventricular tachycardia, which is defined as having nearly identical QRS morphology in all of the component beats
  • Polymorphic ventricular tachycardia, which is characterized by QRS morphology that varies from beat to beat
• Idiopathic ventricular tachycardia is defined as monomorphic ventricular tachycardia in the absence of structural heart disease. More frequently, however, patients with idiopathic ventricular tachycardia present with symptomatic premature ventricular contractions typically arising from the outflow tracts. Frequent ventricular ectopy with a 15% to 20% daily premature ventricular contraction burden may lead to the development of tachycardia-induced cardiomyopathy
• Torsade de pointes is a variation of ventricular tachycardia with a distinctive ECG pattern of shifting axis and voltage QRS complexes; the heart is usually structurally normal
• Underlying structural heart disease is commonly found in patients with nonsustained or sustained ventricular tachycardia
• Untreated ventricular tachycardia may degenerate to ventricular fibrillation, resulting in cardiac arrest, hemodynamic collapse, and death

Epidemiology

Incidence and prevalence:

• Out-of-hospital ventricular tachycardia is reported to show a circadian pattern, with a primary peak during the morning hours and a second, smaller peak during the afternoon
• Occurrence is reported more often during the winter months
• Ventricular tachycardia is most common within 72 hours of myocardial infarction
• The prevalence of nonsustained ventricular tachycardia detected by 24-hour ambulatory ECG in older, disease-free patients without cardiovascular disease is 2% to 4%; prevalence in older patients with preexisting cardiovascular disease is 4% to 16%

Demographics:

• Prevalence increases with age
• Genetic abnormalities of cardiac ion channels are implicated in some long QT syndromes
• Persons living in homes with insufficient ventilation and furnaces in poor condition are at increased risk for carbon monoxide poisoning, which may cause ventricular tachycardia

Causes and risk factors

Causes

Common causes:

• Coronary artery disease with myocardial infarction
• Nonischemic cardiomyopathy
• Infiltrative disease (eg, sarcoidosis, amyloidosis)
• Infectious disease (eg, viral myocarditis, Chagas disease, Lyme disease)
• Inflammatory diseases that affect the myocardium (eg, systemic lupus erythematosus, rheumatoid arthritis, giant cell myocarditis)
• Digitalis toxicity (bidirectional ventricular tachycardia)
• Mitral valve prolapse
• Electrolyte (notably potassium and magnesium) abnormalities
• Structural, toxic, or metabolic derangement affecting the homogeneity of ventricular repolarization (eg, prolonged QT syndromes, Brugada syndrome), most often associated with torsade de pointes, polymorphic ventricular tachycardia, or ventricular fibrillation
• Arrhythmogenic right ventricular dysplasia
• Blunt chest trauma

Rare causes:

• Congenital myocardial defects (eg, tetralogy of Fallot, pulmonary stenosis, previous corrective surgery for congenital heart defect)
• Marfan syndrome with aortic dissection
• Torsade de pointes is caused by certain drugs (eg, haloperidol, erythromycin, quinidine, and methadone, among others) or by inherited defects in cardiac ion channels (eg, cardiac channelopathy)
• Carbon monoxide poisoning

Risk factors

• Ischemia
• Cardiomyopathy
• Heart failure
• Cocaine use
• Use of certain medications, such as quinidine, phenothiazines, and tricyclic antidepressants
• Congenital heart disease
• Surgical repair of congenital heart defects
• Primary and metastatic malignancies involving the heart muscle
• QT prolongation and Marfan syndrome in neonates
• Trauma
• Pericardial inflammation

Screening

• Patients potentially at risk for ventricular tachycardia due to family history or other medical conditions (eg, hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, long QT syndrome, Brugada syndrome, sarcoidosis) should undergo ECG evaluation at their annual physical examination
• According to guidelines, patients with previous myocardial infarction and reduced left ventricular ejection fraction (LVEF) are at risk for life-threatening ventricular arrhythmias and should undergo screening echocardiography
• Holter monitoring, echocardiography, and stress testing are costly but can identify patients with early signs of ventricular tachycardia

Primary prevention

Summary approach

• Lifestyle changes, such as smoking cessation, avoidance of excessive alcohol consumption and recreational drug use, dietary modification, and exercise, are essential in preventing ventricular tachycardia in patients at risk for cardiovascular disease
  • Tobacco use is a major risk factor for developing heart disease, which is a major cause of ventricular tachycardia and ventricular fibrillation
  • Heavy alcohol consumption can cause cardiomyopathy, which is a risk factor for ventricular tachycardia
• A medication history should be obtained to ensure that any over-the-counter, prescription, or alternative medicines the patient is taking do not interfere with antiarrhythmic medications and are not contraindicated for the underlying cardiovascular condition
• Placement of an implantable cardioverter-defibrillator (ICD) should be considered in selected patients at high risk of developing ventricular tachycardia

Population at risk

• Patients with conditions that contribute to heart disease, such as hyperlipidemia, hypertension, and diabetes
• Patients with a family history of sudden cardiac death and coronary artery disease
• Smokers
• Alcoholics
• Patients with previous heart disease, including atherosclerosis, moderate to severe heart failure, and specific arrhythmias

Preventive measures

• Patients at risk for coronary artery disease should take the following preventive lifestyle measures:
  • Discontinue use of tobacco products, including cigarettes, cigars, pipes, and chewing tobacco
  • Maintain a regular physical activity program with an emphasis on cardiovascular exercise
• Patients at risk for sudden cardiac death should take the following preventive lifestyle measures:
  • Avoid recreational drug use and excessive alcohol consumption; however, drinking one glass of wine (especially red wine) every day may reduce the risk of coronary artery disease
  • Modify their diet to reduce intake of fat and red meat and increase intake of fruit, vegetables, and fish
• Medications that can interfere with antiarrhythmic medications should be substituted with those that do not have interactions
• Data from the first Multicenter Automatic Defibrillator Implantation Trial (MADIT I) show that ICD placement successfully prevents sudden death (but not necessarily ventricular tachycardia) in patients with an ejection fraction less than 35%, previous myocardial infarction, nonsustained ventricular tachycardia, and inducible ventricular tachycardia at the time of electrophysiologic testing