Tachycardia

Diagnosis and treatment

Differential diagnosis of tachycardia

1. 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.
2. 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.
3. When diagnosis is made treatment has to be started. .
4. Pharmaceuticals and useful drugs are presented in the section [pharmaceuticals](# 125).
5. To decide for eventual anticoagulation in atrial fibrillation click on scores.

Differential diagnosis of narrow QRS complexes tachycardias.

1. Define if tachycarida is regular or irregular.
2. Search P wave and define their position with respect to the QRS complex.

Regular tachycardia

1. Look for QRS complex alternance. If present in diagnosis is in > 90 % AV reentry tachycardia using an accessory pathaway AVRT
2. Look for P waves. P waves can be visibles or non visibles.
3. Determine P waves position and number of P waves related to the QRS complexes.

Absence of P waves

If P waves are absent it is probably an AV nodal reentry tachycardia (AVNRT) . Often the waves P' are seen at the end of QRS complex in V1.