Emergent Care / Stabilization:

• Place patient on cardiac monitor.
• Obtain large bore intravenous (IV) access.
• Connect patient to defibrillator device.

Diagnosis Overview:
Ventricular tachycardia (VT) is a cardiac arrhythmia originating from the ventricles that is characterized by a wide QRS complex (duration > 120 milliseconds) and a heart rate over 100 beats per minute (bpm). This is caused by enhancement of automaticity activity triggered by reentry or early and late afterdepolarizations. Transient ischemia caused by myocardial infarction can create injury currents between the healthy and infarcted tissue due to the increased extracellular potassium changing the resting membrane potential, thus triggering arrhythmias.

VT may be classified as:

• Sustained or nonsustained – Sustained VT is defined as persistence for more than 30 seconds (or duration of less than 30 seconds with hemodynamic instability). Nonsustained VT is defined as duration of more than 3 consecutive ventricular beats but spontaneous termination within 30 seconds and no hemodynamic instability or collapse.
• Monomorphic or polymorphic – Morphology of all QRS complexes is the same in monomorphic VT, whereas beat-to-beat variation in QRS morphology is seen in polymorphic VT. Polymorphic VT associated with prolonged QT is known as torsades de pointes.
• Stable or unstable – VT can present with minimal symptoms and hemodynamic stability. However, it can also present with hemodynamic collapse or pulseless cardiac arrest. Hemodynamic stability of the patient is the key factor in management decisions.
• VT electrical storm – Three or more discrete episodes of VT within 24 hours, or incessant VT for more than 12 hours.

VT is more common in men and in individuals older than 65 years. The most common risk factors include coronary artery disease, myocardial infarction, structural heart disease (ie, congenital heart conditions, cardiomyopathies, sarcoidosis), and ion channel mutations (ie, Brugada syndrome, long QT syndrome, catecholaminergic polymorphic VT). Idiopathic VT occurs in a structurally normal heart and is very rare.

Presentation varies from asymptomatic to pulseless cardiac arrest. Common presenting symptoms are weakness, dizziness, palpitations, chest pain, shortness of breath, syncope, sudden collapse, and cardiac arrest.

Treatment varies depending on the presenting symptoms and the patient's hemodynamic stability. For pulseless VT, cardiopulmonary resuscitation needs to be started immediately. Other treatments include electrical cardioversion and the use of antiarrhythmic drugs (eg, amiodarone or lidocaine). Patients with a history of life-threatening or recurrent VT will often undergo radiofrequency catheter ablation and/or placement of a cardioverter defibrillator (implantable or external).