What was the reason for a Chemical Stress Test, not the usual work on a treadmill to get up to the desired heart rate?
In my experience a nuclear stress test, done with a treadmill exercise to elevate my heart rate, is not accurate. I don't recall ever being told one side of my heart was "weak" but that may be a stress test indicator of a blockage in the heart blood supply. But the catheter "said" no blockage and that test is very accurate in my understanding.
The fact that you had a heart catherization that found no blockages should give you a lot of comfort, as Jerry stated, it is the gold standard used by Cardiologists. That said, I disagree with Jerry, my experiences with nuclear stress tests has been quite accurate, and in fact, life-saving.
I'd suggest to you and anyone having a heart procedure to request the procedure reports. You are entitled to them, they are usually available from the institution where they were done. It could be, and this is just a guess, that what is called your Ejection Fraction (EF) was a little low, or you have a mild valve issue. There are people on this board that can help you understand the results. Keep us informed.