3 stents with heart muscle damage here as well. My cardiologist loves that I exercise regularly on my bike.
Heat really affects me now. I always ride wearing a HRM and can tell when it's time to back down, find a shady spot, and rest. My HR normally goes up on efforts/climbs (and there are plenty of those around here) but drops back to normal quickly. When it gets really hot, I notice the recovery time starts to increase. Once I finished a particularly hard climb that maxed out my BPM. I was enjoying the long downhill coast, but my HR stayed up there, only coming down a small amount. At the bottom of the descent I stopped, rested under a shady tree, and drank a whole bunch of Gatorade. When my HR finally came down, I got back on the bike but took it really easy. It was 94 degrees and humid that day.