Almost all 12 of my gym's LifeCyclers are precisely accurate on heart rate and time (on calories another story
I DO wish there was a way to get a good BP reading on it though...all I get is ERR with my home tester. All that jostling makes the poor meter think my diastolic is ZERO!
Best I can do is get off the machine and wait a minute or two and test (lying on floor...EVERYBODY looks, they think I'm having a Heart Attack.)
It doesn't matter how tired your other muscles get; if you're heart rate stays low you're not getting much of a cardio workout.
Best way to find the effect of your ACEI is to stop it for a week and see what kind of a heart rate you get without it. There's no substitute for personal experience.