In the several weeks before my second surgery, I had my first heart cath so was nervous but it was truly painless and I had no residual discomfort. They gave me versed and (I think) demerol and I felt nothing and remember little. It took less than an hour and I went home after resting about 3 hours to be sure the wound had sealed. I would never dread a cath again as it went so easily for me. I was permitted to drive and go about my regular routine next day.
TEE was a snap and something I was anxious about, as well. It, too, went easily, took about 15 minutes, gave them excellent info about the condition of my valve. Again, I rested a short while after (maybe 30 minutes), went home and went about my usual routine next day with no limitations.
Day before my surgery, I had blood test (NOT a blood gas test), chest x-ray, urine, EKG, physical exam and meeting with anesthesiologist.
None of this was anything more, for me, that pain free and easily done.