Tachycardia - Differential Diagnosis

Differential Diagnosis

An electrocardiogram (ECG) is used to classify the type of tachycardia. They may be classified into narrow and wide complex based on the QRS complex. Presented in the order of most to least common they are:

Narrow complex

• Sinus tachycardia, which originates from the sino-atrial (SA) node, near the base of the superior vena cava.
• Atrial fibrillation
• Atrial flutter
• AV nodal reentrant tachycardia
• Accessory pathway mediated tachycardia
• Atrial tachycardia
• Multifocal atrial tachycardia
• Junctional tachycardia

Wide complex

• Ventricular tachycardia, any tachycardia which originates in the ventricles.
• Any narrow complex tachycardia combined with a problem with the conduction system of the heart, often termed "supraventricular tachycardia with aberrancy."
• A narrow complex tachycardia with an accessory conduction pathway, often termed "supraventricular tachycardia with pre-excitation" (e.g. Wolff-Parkinson-White syndrome).
• Pacemaker-tracked or pacemaker-mediated tachycardia.

Tachycardias may be classified as either narrow complex tachycardias (supraventricular tachycardias) or wide complex tachycardias. Narrow and wide refer to the width of the QRS complex on the ECG. Narrow complex tachycardias tend to originate in the atria, while wide complex tachycardias tend to originate in the ventricles. Tachycardias can be further classified as either regular or irregular.