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Ventricular Tachycardia

Practice Essentials

Ventricular tachycardia (VT) or ventricular fibrillation (VF) is responsible for most of the sudden cardiac deaths in the United States,
at an estimated rate of approximately 300,000 deaths per year.
VT refers to any rhythm faster than 100 (or 120) beats/min, with three or more irregular beats in a row, arising distal to the bundle of His. The rhythm may arise from the working ventricular myocardium, the distal conduction system, or both. See the image below.

This electrocardiogram (ECG) shows rapid monomorph

This electrocardiogram (ECG) shows rapid monomorphic ventricular tachycardia (VT), 280 beats/min, associated with hemodynamic collapse. The tracing was obtained from a patient with severe ischemic cardiomyopathy during an electrophysiologic study. A single external shock subsequently converted VT to sinus rhythm. The patient had an atrial rate of 72 beats/min (measured with intracardiac electrodes; not shown). Although ventriculoatrial dissociation (faster V rate than A rate) is diagnostic of VT, surface ECG findings (dissociated P waves, fusion or capture beats) are present in only about 20% of cases. In this tracing, the ventricular rate is simply too fast for P waves to be observed. VT at 240-300 beats/min is often termed ventricular flutter.

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Signs and symptoms

History

Symptoms of VT are often a function of the associated heart rate, or the causal process, such as an acute myocardial infarction (MI). They may include the following bulleted items. VT may also be asymptomatic, or the symptoms may be those of the associated triggered therapy (eg, an implantable cardioverter-defibrillator [ICD] shock).

Palpitations

Light-headedness

Syncope

Chest pain

Anxiety

Physical examination

During VT, the following may be observed:

Hypotension

Tachypnea

Signs of diminished perfusion, including a diminished level of consciousness, pallor, and diaphoresis

High jugular venous pressure

Cannon A waves (if the atria are in sinus rhythm)

Variation in intensity of first heart sound (S1), caused by loss of atrioventricular (AV) synchrony

After cardioversion, physical findings during normal sinus rhythm are related to any underlying structural heart disease.

VT can also result in sudden death, especially after degeneration to VF. Patients in whom this occurs may first present with syncope.

See Presentation for more detail.

Diagnosis

Electrocardiography (ECG) is the criterion standard for the diagnosis of VT. If the clinical situation permits, a 12-lead ECG should be obtained before conversion of the rhythm. In a patient who is hemodynamically unstable or unconscious, however, the diagnosis of VT is made from the physical findings and ECG rhythm strip only. Advanced cardiovascular life support (ACLS) protocols should be quickly followed. Typically, laboratory tests should be deferred until electrical cardioversion has restored sinus rhythm and the patient is stabilized.

Assess levels of serum electrolytes, including the following, in all patients with VT:

Calcium (ionized calcium levels are preferred to total serum calcium levels)

Magnesium

Phosphate

Hypokalemia, hypomagnesemia, and hypocalcemia may predispose patients to either monomorphic VT or torsade de pointes.

Laboratory studies can also include the following:

Levels of therapeutic drugs (eg, digoxin)

Toxicology screens (potentially helpful in cases related to recreational or therapeutic drug use, such as cocaine or methadone)

Serum cardiac troponin I or T levels or other cardiac markers (to evaluate for myocardial ischemia or MI)

Postconversion VT 

In patients with VT after conversion, the diagnostic workup proceeds as follows:

Repeat the ECG after termination of VT

Include electrolyte levels in an acute evaluation; the hyperadrenergic state or hemodynamic compromise often associated with VT may affect the subsequently obtained laboratory values

Perform toxicology screens for cocaine metabolites and tricyclic antidepressants, in accordance with the patient’s clinical history

Check cardiac enzyme levels if clinical symptoms or signs of ischemia are present

Perform echocardiography and coronary angiography after conversion to sinus rhythm to assess for structural and ischemic heart disease

Electrophysiologic study

Diagnostic electrophysiologic study (EPS) requires placement of electrode catheters in the ventricle, followed by programmed ventricular stimulation using progressive pacing protocols. EPS is particularly relevant in patients considered to be at high risk for sudden death as a result of significant underlying structural heart disease.

See Workup for more detail.

Management

Unstable patients with monomorphic VT should be immediately treated with synchronized direct current (DC) cardioversion, usually at a starting energy dose of 100 J (monophasic). Unstable polymorphic VT is treated with immediate defibrillation. Please refer to the most current ACLS guidelines, which are subject to periodic revision.

Medications

In stable patients with monomorphic VT and normal left ventricular function, restoration of sinus rhythm is typically achieved with intravenous (IV) procainamide, amiodarone, sotalol, or lidocaine

IV lidocaine is effective at suppressing peri-infarction VT but may have common and limiting side effects and, consequently, increase the overall mortality risk

In torsade de pointes, magnesium sulfate may be effective if a long QT interval is present at baseline

For long-term treatment of most patients with left ventricular dysfunction, current clinical practice favors class III antiarrhythmics (eg, amiodarone, sotalol)

In patients with heart failure, the best proven antiarrhythmic drug strategies include the use of beta receptor–blocking drugs (eg, carvedilol, metoprolol, bisoprolol); angiotensin-converting enzyme (ACE) inhibitors; and aldosterone antagonists

Implantable cardioverter-defibrillators

Multisociety guidelines recommend ICD therapy to augment medical management for the following
:

Most patients with hemodynamically unstable VT

Most patients with prior MI and hemodynamically stable sustained VT

Most cardiomyopathy patients with unexplained syncope (an arrhythmia is presumed)

Most patients with genetic sudden death syndromes when unexplained syncope is noted

Ablation

Radiofrequency ablation (RFA) via endocardial or epicardial catheter placement can be used to treat VT in patients who have the conditions noted in the following bulleted list. For patients with structural heart disease, it is currently uncertain whether VT ablation obviates other therapies, such as an ICD.

Left ventricular dysfunction from prior MI

Cardiomyopathy

Bundle-branch reentry

Various forms of idiopathic VT

See Treatment and Medication for more detail.

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