Question #1

Based on this ECG, pick the uncertain statement:

1. A case of CRT.
2. One of the pacing leads is in the outflow tract.
3. Intermittent ventricular fusion complexes.
4. Intermittent loss of LV capture.

Question #2

Para-Hisian pacing: (pick the wrong statement):

1. The accessory pathway is not demonstrated.   
2. The accessory pathway cannot be ruled out. 
3. The pure His-bundle capture not seen.
4. None of the above.

Answer to Question #1

The uncertain statement is – Intermittent loss of LV capture.

The very narrow (40-60ms) QRS complexes are the result of biventricular pacing (CRT). 

The paced QRS complexes, which are intermittently wide with inferior axis, suggest one of the pacing leads is in the outflow tract. 

The width of the biventricular paced complexes vary intermittently (due to ventricular fusion complexes).

The periodic widening of the paced QRS complexes can be a result of loss of capture of any one of the ventricles. What can be inferred with certainty is that the loss of capture is by the lead, which is placed in the apical region.

Answer to Question #2

None of the above. 

Pacing stimulus to ‘A’ interval is changing, which is not supportive of accessory pathway. 

However, para-Hisian pacing at a given cycle length may not unmask a free wall accessory pathway.

The para-Hisian pacing has resulted in QRS complexes of varying width always wider than the native QRS. A pure His-bundle capture should have resulted in complexes similar to the native QRS.