6 years ago I had something called a reverse "P" wave. Are you sure you heard him right? The doc noticed. It was a hobby of his to predict what the CAA might notice before he sent the ECG up to the CAA. He asked if I had taken exercise recently before the ECG. "Yes" I said, "I've just come from the Gym" (and shower).
He said come back tommorrow before the gym and we will throw this ECG away. I suggest you stay away from CAA medical centres if you can. Some CAA docs are a bit harsh.
Next day no reverse "P" wave = CAA medical renewal.
Take it easy during the stress test, and best of luck.
The moral of my story is: Take it easy the night before your urine test. 