Case:
A 74-year-old female was admitted due an episode of loss of
consciousness with a 3-year history of recurrent syncope and previous
loop recorder implant (Medtronic Reveal Linq®). There was no history of
coronary artery disease, structural heart disease, or other
cardiovascular implantable electronic devices (CIED). Resting
echocardiogram and stress testing were normal. Electrocardiogram (ECG)
at baseline showed left bundle branch block (LBBB) (Figure 1), with no
history of pre-excitation. She was not on antiarrhythmic medications.
Interrogation of the device showed multiple episodes of wide complex
tachycardia temporally unrelated to the loss of consciousness, with a
changing QRS morphology (Figure 2). What are the differential diagnoses
for the arrhythmia?