I didn't answer earlier because of the "P", I just stumbled on it today and realized you meant TEE.
Anyway, some cardios will knock you out and some won't. My cardio said he would knock me out and then some idiot in his office sched. me with his partner who wasn't qualified enough or confident enough to knock me out. Fortunately, I was really upset and unwilling to just swallow the transducer/tube and the mgr. of the endoscope lab got wind of my story and found out I was indeed supposed to be sched. with my cardio and knocked out. So they resched me for the following morning with him.
He knocked me out and I only had one moment of pain in my chest and it didn't bother me, because I went right out again. No problems whatsoever during or after the procedure.