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 narrow QRS complexes tachycardias.