
Not Easy but possible
Heart Attacks are normally fairly easy to observe when you get a decent EKG recording, basically just monitor the electrical heart muscle contractions, they are quite complex but looking at the baseline level changes with the "p", "QRS" and T-waves will give you a good diagnosis of a potential heart attack or other issues. So all you need to do is look at their heartbeats for a few minutes once you have some EKG interpretation experience (mine's about 40 years now, because that's how I started electronics).