Sandbox/WCT
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# Overview
Wide complex tachycardia is characterized by a heart rate more than 100 beats per minute associated with a QRS interval of more than 120 ms.  When wide complex tachycardia is present, it is important to determine whether the tachycardia is of a supraventricular or a ventricular origin.  The diagnosis of wide complex tachycardia is very challenging as there is no fixed criteria to accurately determine the cause and type of the WCT. Hemodynamically unstable patients should receive urgent synchronized cardioversion.  If the QRS complex and the T wave can't be distinguished in unstable patients, then we proceed with unsynchronized cardioversion.

# Causes

## Life Threatening Causes
Wide complex tachycardia may be a life-threatening condition and must be treated as such irrespective of the causes.

## Common Causes
- Atrial fibrillation with aberrancy
- Atrial fibrillation with pre-excitation
- Supraventricular tachycardia (SVT) with aberrancy
- Ventricular tachycardia

# FIRE: Focused Initial Rapid Evaluation
A Focused Initial Rapid Evaluation (FIRE) as shown below should be performed to identify patients in need of immediate intervention.
Boxes in salmon signify that an urgent management is needed.

# Complete Diagnostic Approach
A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.
Abbreviations: ECG: electrocardiogram; VT: ventricular tachycardia; VF: ventricular fibrillation; ICD: implantable cardioverter-defibrillator; BPM: beat per minute
The above algorithm is adapted from the 2003 American College of Cardiology.

# Treatment
A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.
ABC: Air, breathing and circulation; Afib: Atrial fibrillation; BBB: Bundle branch block; LV: Left ventricle; SVT: Supraventricular tachycardia; VT: Ventricular tachycardia; WPW: Wold Parkinson White

## Differentiating SVT from VT
Shown below is a table summarizing some clues that help differentiate SVT from VT.
For more details about differentiating VT from SVT, click here

## Antiarrhythmics
Shown below is a table summarizing the choices of the antiarrhythmic drugs for the different types of tachycardia according to the 2003 ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias.
BBB: Bundle branch block; LV: Left ventricle; SVT: Supraventricular tachycardia

# Do's
- Refer the patient to an arrhythmia specialist when the tachycardia causes syncope or dyspnea as well as when the wide complex tachycardia is of unknown cause.
- Place an ambulatory 24 hour Holter when the tachycardia is frequent and transient.
- Treat the patient as having a ventricular tachycardia when the diagnosis of supraventricular tachycardia can not be made.
- Suspect ventricular tachycardia in a patient with wide complex tachycardia and previous myocardial infarction or a history of structural heart disease.
- Use beta blockers with caution in pulmonary diseases or congestive heart failure.

# Dont's
- Don't rely on the hemodynamic status of the patient and the heart rate to differenciate SVT from VT.