After you’ve started on medications for heart failure, typically after six months or so, your doctor will want to look at the function of your heart. This is called the ejection fraction or EF for short. Usually in an average person, the EF is about 65%. If your EF is staying low and typically lower than 35%, you may need to get what’s called an ICD or an implantable cardiac defibrillator or implantable cardioverter defibrillator. This is a device that’s implanted in your chest and can deliver shocks. If you go into a abnormal heart rhythm, it’s indicated for people with a persistent EF of less than 35%.