I Am 81 And Had Quad Bypass A Year And

I am 81 and had quad bypass a year and a half ago.
I am very active in riding my bike and doing tree work all winter and just had a stress test.
I have not had such hard workout in over 8 years since my last stress test.
My hart rate and blood pressure dropped during the procedure when I was really getting winded
when they stopped the test. Now I have to go for the die test and so forth.
Is it necessary? seeing I have been very active and sleeping well and feeling well.