Diagnostic apparatus for testing heart rate variability, high blood pressure, heart rate, ventricular tachycardia, likelihood of onset of heart attack and cardiac arrest, for medical purposes; heart pacemakers; defibrillators; pulse meters; heart rate monitoring apparatus; cardiac arrest monitors in the nature of heart monitors, heart rate monitors, heart rate variability monitors, blood pressure monitors, ventricular tachycardia monitors, ventricular fibrillation monitors, heart attack monit...