Narrow complex tachycardia resident survival guide

# Overview
Narrow complex tachycardia is characterized by a heart rate > 100 beats per minute and a QRS complex of a duration < 120 milliseconds.  Narrow complex tachycardia may originate in the sinus node, atria, AV node, bundle of His, or a combination of these tissues.  The diagnosis of narrow complex tachycardia is based on the ECG findings.  Hemodynamically unstable patients should receive urgent synchronized cardioversion.

# Causes

## Life Threatening Causes
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
- Wolff-Parkinson-White syndrome (orthodromic atrioventricular reentrant tachycardia)
- Idiopathic fascicular ventricular tachycardia

## Common Causes
- Atrial fibrillation
- Atrial flutter
- Atrial tachycardia
- Atrioventricular reentrant tachycardia (AVRT)
- AV nodal reentrant tachycardia (AVNRT)

# FIRE: Focused Initial Rapid Evaluation
A Focused Initial Rapid Evaluation (FIRE) should be performed to identify patients in need of immediate intervention.
Boxes in the red color 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; SVT: Supraventricular tachycardia; ms: milliseconds; AV:  atrioventricular; AVNRT: atrioventricular nodal reciprocating tachycardia; MAT: multifocal atrial tachycardia; ms: milliseconds; PJRT: permanent form of junctional reciprocating tachycardia; RP interval: is the time between anterograde ventricular activation (R wave) and retrograde atrial activation (P wave)

## ECG Examples
Shown below is a table depicting the ECG findings of the different types of narrow complex tachycardia.
 ECG strips are courtesy of ECGpedia.

# Treatment

## Initial Treatment
Shown below is an algorithm summarizing the management of narrow complex tachycardia according to the 2003 ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias. 
Abbreviations: AF:  atrial fibrillation; AV: atrioventricular; AVNRT: atrioventricular nodal reciprocating tachycardia; AVRT: atrioventricular reciprocating tachycardia; BBB: bundle-branch block; ECG: electrocardiography;  IV: intravenous; LV: left ventricle; SVT: supraventricular tachycardia; VT: ventricular tachycardia

## Treatment of Specific Supraventricular Arrhythmia

### Focal Atrial Tachycardia

### Focal and Nonparoxysmal Junctional Tachycardia

### AVNRT

### Inappropriate Sinus Tachycardia

# Do's
- Consider the arrhythmia to be paroxysmal if it is recurrent and abruptly begins and terminates.
- Identify possible triggers and educate the patient to avoid them.
- Refer patients with narrow complex tachycardia with any of the following to a cardiac arrhythmia specialist:
- Drug resistance
- Intolerance to drugs
- Refusal of drug therapy
- Severe symptoms such as syncope and dyspnea
- Wolff-Parkinson-White syndrome
- Consider trying different types of anti-arrhythmic agents in case the SVT is refractory; however, closely monitor the blood pressure and heart rate.
- Consider invasive electrophysiological investigation in the presence of pre-excitation and severe disabling symptoms.
- Monitor the 12 lead ECG during the administration ofadenosine or carotid massage.
- Make sure the equipment for resuscitation is available during the administration of adenosine in case of the occurrence of any complication, such as ventricular fibrillation or bronchospasm.
- Administer higher doses of adenosine in patients taking theophylline.
- Perform the following tests when indicated:
- Echocardiography in case of sustained SVT to rule out structural heart disease
- 24 hour holter monitor in case of frequent but transient tachycardia
- Loop recorder in patients with less frequent arrhythmia
- Trans-esophageal atrial recordings if other investigations have failed to document an arrhythmia

# Don'ts
- Do not perform esophageal stimulation if an invasive electrophysiological investigation is planned.
- Do not initiate treatment with anti-arrhythmic agents in a patient with undocumented arrhythmia.
- Do not administer adenosine in patients with severe bronchial asthma or heart transplant recipients.