First of all we are sorry to hear about your friend, unfortunately it is a relatively common problem. An implantable defibrillator is used when the heart muscle weakens, such as after a heart attack. The right side of the heart is normally smaller than the left side and is more prone to damage after a heart attack. Everyone responds differently to treatments and medications. It's very important to try and control other risk factors that can cause further damage such as blood pressure, cholesterol, blood sugar, and weight. People can live many years with only have of the heart muscle functioning but again each case is individual.