After a heart attack or onset of cardiomyopathy, many people are left with a heart that pumps poorly. This is heart failure (HF), a condition primarily affecting people ages 65 to 85. HF increases the risk of dying suddenly from rapid, irregular, disorganized heart rhythms known as ventricular tachycardia (VT) and ventricular fibrillation (VF). About half of all HF patients die from cardiac arrest. But help is often available from implantable cardioverter-defibrillators (ICDs). These small devices act like internal shock paddles to save the lives of many patients with failing hearts.