Determine hemodynamic stability. If instability regardless of the tachycardia mechanism the strategy is the same. There is no need to define the tachycardia's mechanism. Sinus rhythm has to be restore by electrical cardioversion.
In patients with stable hemodynamic parameters, the mechanism of the tachycardia must be known to start the appropriate treatment.
Distinction between tachycardias is based on QRS complex duration.
We separate tachycardia in 2 sections narrow QRS complexes and wide QRS complexes.
When diagnosis is made treatment has to be started. .
Pharmaceuticals and useful drugs are presented in the section [pharmaceuticals](# 125).
To decide for eventual anticoagulation in atrial fibrillation click on scores.
Differential diagnosis of wide QRS complex tachycardia
One must seek the following:
[AV Dissociation] (# 189). If there is an AV dissociation it is a VT.
[Fusion or capture] (# 190). If there is fusion or capture it is a VT.
[If there is no fusion complexes no capture no AV dissociation] (# 193) we must analyzed the QRS complex to determine if it is a VT or SVT with conduction aberrancy.
Fusion complexes and capture complexes
The fusion complexes are complex originated from both supraventricular and ventricular.
Captures are normal sinus complex emerging during tachycardia.
If these complexes are present it is a ventricular tachycardia.