Which is the least likely diagnosis?
- Inducible ischemia.
- Atrial tachycardia.
- AVNRT and AVRT.
- Junctional ectopic tachycardia.
The correct diagnosis is:
- AVRT using left free wall accessory pathway.
- AVRT using right free wall accessory pathway.
- AT with and without preexcitation.
- AT with and without LBBB.
Abrupt onset of ST segment depression is against inducible ischemia. The intracardiac electrograms as shown explain the differential diagnosis of AT, AVNRT, AVRT and also junctional ectopic tachycardia. Indeed, the patient had typical AVNRT and AVRT using left free wall accessory pathway. The tachycardia used to spontaneously convert from AVNRT to AVRT and also AVRT to AVNRT.
AVRT using left free wall accessory pathway.
Note the following:
- The wide QRS tachycardia of LBBB morphology has changed into narrow QRS tachycardia after the PVC.
- The tachycardia is faster during narrow QRS.
- Perceptible HV interval during wide QRS.
- PVC was delivered during His refractory and subsequent ‘A’ was advanced.
- VAV response.
These features rule out AT and confirm the diagnosis of AVRT using left free wall accessory pathway.