A combination of several factors may put people at risk for a life-threatening arrhythmia. This includes prior heart attacks, reduced heart function, advanced heart failure and spontaneous VT or VF that is not due to a transient or reversible cause. If you’re at risk for Sudden Cardiac Arrest (SCA), an ICD is the best treatment option available. 98% of people survive a lethal arrhythmia when treated with defibrillation. Only 3% survive without. People who have a combination of risk factors may be referred for an electrophysiology study to determine if an ICD is necessary.