Question # 1
- There is a loss of LV capture.
- Both the ventricular leads are placed apically.
- The ECG demonstrates an abnormal magnet response.
- There is no intrinsic AV conduction.
Question # 2
- Atrial tachycardia.
- Atrioventricular nodal re-entrant tachycardia.
- Atrioventricular re-entrant tachycardia.
- None of the above.
Answer to Question # 1
Both the leads are placed apically.
The paced QRS complexes (on magnet) in V1 are positive (R), suggestive of LV capture.
The paced QRS complexes in the inferior lead (LII) are negative, suggesting apical placement of both the ventricular leads.
On magnet, the device has appropriately converted into DOO mode at magnet rate and AV delay, causing physiological change in P and QRS morphology. In the absence of change in the V-V delay, changing morphology of QRS suggests contribution from intrinsic AV conduction to ventricular activation.
Answer to Question # 2
None of the above.
There are two extrastimuli that are delivered at the RV apex at a time when the His bundle was refractory during a regular narrow QRS tachycardia with HV interval of 65ms.
The third and seventh QRS complexes are the result of fusion by tachycardia and extrastimuli. The advancement or delay of atrial activation following these extrastimuli would have been suggestive of AVRT. However, the atrial activation is unperturbed in this case. This phenomenon does not rule out AT, AVNRT, or AVRT (using free wall pathways).