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.

QRS complexes duration < 120ms
  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.

Present and visibles P waves

Present and visibles P waves

When P waves are visible must specify their number and position.

There are 3 possibilities:

Number of P waves = number of QRS complexes

Look for electrical QRS complexes alternance (variation of the amplitude of the QRS complex between beats). Electrical QRS complexes alternance is in > 90 % AVRT.

If no electrical alternans is present look for P' waves and measures RP' et P'R intervals.

No QRS complexes alternans

No QRS complexes alternans

RP' interval and P'R interval

If no alternance measure RP' and P'r interval.

Three options:

RP' interval < P'R interval

RP' interval < P'R interval

If RP' interval < 100 ms diagnosis is AVNRT. If RP' interval > 100 ms diagnosis is AVRT.

Typical AV nodal reentry tachycardia (AVNRT), RP’ < 120 ms