EP 101

EP Quiz

Ulhas M. Pandurangi, MD, DM
Chief - Cardiac Electrophysiology & Pacing, The Madras Medical Mission
Mogappair, Chennai, India

Ulhas M. Pandurangi, MD, DM
Chief - Cardiac Electrophysiology & Pacing, The Madras Medical Mission
Mogappair, Chennai, India

Question #1:

Based on this ECG, pick the correct statement:

VVIRV mode.
Intrinsic AV conduction affecting QRS morphology.
Atrial timing affecting QRS morphology.
All of the above.

(Answer on page 40)

Question #2:

Simultaneous premature atrial contraction (PAC) and premature ventricular contraction (PVC) during a short RP tachycardia. The maneuver rules out:

Atrial tachycardia (AT). 
Atrioventricular nodal re-entry tachycardia (AVNRT).
Junctional ectopic tachycardia (JET).
None of the above.

(Answer on page 40)

Answer Key

Answer to Question #1: 

All of the above.

The QRS complexes are preceded by pacing artifacts.
The narrowness and the axis of QRS suggest biventricular pacing.
The AV dissociation suggests effective VVIOV/VVIRV mode.
The morphology and timing of the ‘P’ waves are changing. The interval between the onset of the ‘P’ and pacing artifact determines the QRS morphology by way of intrinsic AV conduction and ventricular activation (fusion).  

Answer to Question #2: 

The maneuver (PAC delivered from CS 7-8 at the same time of RV apical PVC) rules out AT. 

Post-maneuver, the tachycardia initiation should have been with ‘A’ in case of atrial tachycardia. 
A PAC can initiate/reset AVNRT with prolonged AH. Similarly, a PAC or PVC can terminate JET and the tachycardia restarts with ‘H’.