ECG: HR variable; AV dissociation due to third degree AV block with an AV nodal escape rhythm most of the time with occasional conducted beats. Occasionally she goes into sinus rhythm with Mobitz type II second degree AV block.
ECHO: Trivial to mild mitral and aortic regurgitation; moderate basilar septal thickening.
Conclusion: The cat most likely has the fainting episodes due to the AV block. To prove this, an event recorder was placed to see what the heart is doing, when the cat faints. If the cat has a bradycardia cause of the syncope, a pacemaker implantation may be indicated.
Please have the Cardiology Service technician paged, when the cat faints and the owner has recorded an event (during work hours) for instruction how to transmit the recorded event over the phone.