ECG Library


All ECG 90

  1. Sinus tachycardia
  2. 3rd degree AV block
  3. Poor R wave progression

This ECG shows P waves that are not always associated with a QRS complex. This is called "AV dissociation" and occurs in complete heart block (a.k.a. 3rd degree heart block). In this situation, the P waves have their own rate (tachycardic here) and the QRS complex have their own rate. In pure complete heart block, no P waves are conducted from the atrium to the ventricles through the AV node (which is dysfunctional).

"High grade AV nodal block" or "Advanced heart block" (a type of 3rd degree heart block) occurs when there is AV dissociation similar to complete heart block, but occassional P waves DO conduct through the AV node to produce a QRS complex. This example makes you suspect that some P waves are conducting through to the ventricles due to their relationship with the QRS complex, however it may be coincidental (no way to know for sure). Usually, if some P waves are indeed conducting successfully, the R-R interval would be irregular which is not present in this example making us suspect complete heart block and not high grade AV block. Treatment includes implantation of a permanent pacemaker.

Sinus tachycardia can occur in the setting of other ventricular rhythms such as in this case. Sinus tachycardia can be seen with AV dissociation during ventricular tachycardia as well.

Related Topic Reviews: Sinus Tachycardia, 3rd Degree AV Block, Poor R Wave Progression