Not only did you do the right thing, you did what you had been trained to do. Ultimately it comes down to doing your job and letting the fates decide. We're not allowed to 'call' codes in this country as EMT-Intermediates or Basics, so we'll perform CPR for long periods of time on essentially dead people en route to the closest hospital (sometimes a transport time of 30-40 minutes where I live). Despite the fact that we know that unless we'd arrived as the patient hit the floor we have no chance of resuscitation, we still go through the motions. I know if my loved one had an AMI, I'd want the responding personnel to put some effort in, no matter how much they may think the pt. is unsalvagable. As an EMT, I need to come away from every job feeling that I did everything I possibly could for the patient - otherwise I'd be haunted by doubt at every turn.