Patient alerts are rare and your ICD is usually silent, so a beep or vibration means the device wants to draw your attention to something.
The common reasons are a low battery, a fault with the device or a lead, a therapeutic shock having been delivered, a magnetic field interfering with the device, or the device being unable to reach your home monitor for a prolonged period.
You do not need to attend A&E for an alert unless you feel unwell. Contact your ICD clinic as soon as you can so they can check what triggered it. If you have also received a shock or feel unwell, treat it as urgent and seek help straight away.
Our ICD sounds and alerts page explains each alert type in more detail.