Some patients with heart conditions, particularly severe heart failure, are at risk of fatal heart rhythm problems. These patients are typically offered an ICD. An ICD has the same functionality as a pacemaker, and is implanted in a similar way. However, should they diagnose a potentially fatal heart rhythm, they can either deliver a short series of very fast heart beats to terminate the problem, or in the worst case scenario are able to deliver an electric shock to the heart to re-start it. If I felt you would be a candidate for an ICD I would go through this with you in some detail before any procedure was considered.