Studies show four in ten people experience prodromal symptoms—that's medical speak for the body's way of saying 'pay attention'—days or weeks before the actual cardiac event happens. 1 Extreme Fatigue That Won't Quit or Dizziness 2 Disrupted Sleep and Restlessness or Anxiety: Persistent insomnia or waking with palpitations warrants urgent medical evaluation 3 Chest Discomfort Beyond Pain 4Shortness of Breath Unprovoked 5 Cold Sweats and 6 Unexplained Nausea Pain radiating to arms, jaw, or shoulder blades compounds concern. Act fast; visit your doctor immediately.