I've been monitoring this board and helping answer questions since about 2009. I've not run across a question or concern about it here. Bad news travels fast, if negative side effects were common I'd expect to have seen them here by now.
There is a risk to everything, the risk with lexiscan is less than if they put you on the treadmill. The risk goes up if your heart has any issues, but it's still less risk then walking up a hill.
Better to find out now, in a controlled environment. Your other option is an avoidance strategy and I won't lecture you on where that will land you.
I had to have a chemical stress test a couple of years ago after an episode of afib. I tried the treadmill but because of all the medication I couldn't get my heart rate up high enough. I will not lie to you, it was unpleasant..the medication they gave me to accelerate by heart made me very short of breath...they told me in advance it would do that and it definitely did. When they give you the meds to slow your heart back down..it "resets" your heart. You may feel a little dizzy for just a second but then you are fine. There was a cardiologist present and 2 technicians, plus I was hooked up to all kind of monitors. Don't worry, you will be fine. They do those tests many times every day.
Had the chemical stress test followed by pics.. It wasn't as bad as I thought it would be.. Tomorrow is part 2.. just pics.. I left there about 5 hrs ago.. Worried about the results. Hope all is good.. my friend had the test done a few years back and was told to go right to the hospital.. So I guess I was able to leave without that piece of news.