@narrowQRS PVC concealing into accessory pathway, thereby allowing initiation of orthodromic AVRT with next sinus beat? But I don’t know if I can completely exclude PVC concealing into slow pathway, leading to initiation of atypical AVNRT.
@jeffrey_vinocur@syamkumarmd The fact that VA is unchanged at prox CS with loss of His capture suggests a septal pathway. In the first two beats with His capture, the HRA signal seems pretty early (coincides with septal activation). Perhaps 2 accessory pathways?
@ECG_Emily@syamkumarmd Tough to see the P waves in all leads but I think you’re right - that long of a VA would also be pretty uncommon. So just an atrial bigeminy after a paced beat?
@jeffrey_vinocur Retrograde conduction over left sided pathway with both. Loss of His capture leads to a longer VA time due to extra time needed for transseptal conduction. For this to manifest, my guess is that patient doesn’t have good retrograde conduction over AV node.
@syamkumarmd AVNRT with LBBB (likely due to concealed retrograde penetrance of left bundle). His-PVC “peels back” refractoriness of left bundle and normalizes QRS.