Ventricular Tachycardia

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Monomorphic ventricular tachycardia (VT)

• Nonsustained: 3 or more consecutive QRS complexes of uniform configuration and of ventricular origin at a rate of more than 100 bpm

• Sustained: lasts more than 30 seconds, requires intervention for termination, or is hemodynamically significant

• Polymorphic: beat-to-beat variation in QRS configuration

GENERAL CONSIDERATIONS

• VT along with ventricular fibrillation causes 400,000 sudden cardiac deaths (SCDs) per year in the United States

• Most common with ischemic substrate and depressed left ventricular function

• Idiopathic dilated cardiomyopathy is also a frequent cause

• Bundle branch reentry occurs most often with idiopathic dilated cardiomyopathy

• VT can occur in a structurally normal heart, albeit this is rare

• Myocardial infarction (MI)–induced scar plays an integral role in reentry that facilitates monomorphic VT

• Acute ischemia facilitates polymorphic VT

• Wide QRS tachycardia is mostly secondary to VT

• Aberrant conduction as a cause of wide QRS tachycardia is rare

• In patients with a history of MI, wide QRS tachycardia is almost always VT

• Hemodynamic stability does not exclude VT

• Sustained versus nonsustained VT does not imply clinical significance

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Resuscitated sudden cardiac death

• Syncope

• Near syncope

• Palpitations

• Lightheadedness

• Can be asymptomatic

PHYSICAL EXAM FINDINGS

• Cannon a waves

• Hypotension if there is hemodynamic disturbance

DIFFERENTIAL DIAGNOSIS

• Supraventricular tachycardia with aberrancy

• Wolff-Parkinson-White syndrome with antidromic tachycardia

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• CBC, basic metabolic panel

• Serum magnesium

• Cardiac biomarkers

• Arterial blood gases if patient is hypoxic

ELECTROCARDIOGRAPHY

• ECG with rhythm strip to confirm VT and identify location of VT

  • – Atrioventricular dissociation, presence of fusion beats, and duration of R wave to nadir of S wave > 110 ms in chest leads help to differentiate VT from supraventricular tachycardia with aberrancy

• Outpatient cardiac monitoring to identify frequency, duration, and burden of VT

IMAGING STUDIES

• Echocardiogram to evaluate left ventricular function and hypertrophic cardiomyopathy (apical variety may be associated with monomorphic VT)

DIAGNOSTIC PROCEDURES

• Coronary arteriography to identify and quantify coronary artery disease along with ventriculogram and hemodynamic assessment

• Electrophysiology study to establish diagnosis and determine suitability for ablation

TREATMENT

CARDIOLOGY REFERRAL

• All patients should be seen by a consulting cardiologist and possibly a cardiac electrophysiologist

HOSPITALIZATION CRITERIA

• All symptomatic patients must be hospitalized initially in an intensive care unit

MEDICATIONS

• Medication for stable patients:

  • – Amiodarone (150 mg IV over 10 minutes, then 1 mg/min ...