Will exercise set off my ICD?
No, not in normal circumstances. Your ICD is programmed to deliver therapy only above a specific heart rate threshold, set well beyond what ordinary vigorous exercise produces. Raising your heart rate through exercise will not trigger an inappropriate shock.
Your device clinic takes your activity levels into account when programming the device, so tell them if you are returning to running, cycling or other demanding exercise. If you are ever shocked during or after exercise, stop, rest, and contact your device clinic or cardiology team the same day so they can review what the device recorded.
Most people with ICDs exercise regularly and without issue. The bigger barrier is usually confidence rather than the device itself, and that improves with gradual, consistent activity.
Category: Implantable DevicesHow do I know if my CRT-D is working?
Your device clinic monitors CRT-D function at regular check-ups, just as with a standard ICD. They use a programmer to review pacing data, check battery levels, assess how much of the time the device is delivering biventricular pacing (the percentage pacing figure), and adjust settings if needed. Remote monitoring between appointments allows the clinic to track this data without a visit.
From your perspective, CRT often produces noticeable improvements over weeks and months after implant: reduced breathlessness, better exercise tolerance, and less fatigue. These changes can be gradual rather than immediate. Response to CRT is not universal — roughly one in three patients does not experience the expected benefit, sometimes because the lead positioning is not optimal or because of underlying heart anatomy. If this appears to be the case, your clinic may adjust settings or consider lead repositioning.
If your symptoms worsen after a CRT-D implant rather than improving, or if you receive a shock, contact your device clinic or attend A&E. As with any ICD, any shock should always be reviewed.
Category: Living With an ICDCan my ICD shock me during everyday activities?
It is rare. Your ICD is programmed to allow your heart to normally rise without treatment shocks being delivered. Your device should only deliver a shock when your heart rate meets the specific criteria programmed by your heart doctor. If you receive a shock during intimacy or other activities, contact your cardiologist or device nurse. Your doctor will then determine the cause of the shock and may also make adjustments in the programming of your heart device.
Category: Living With an ICDHow much energy is in a shock?
ICDs are programmed to meet a person’s needs. Typically, an ICD will be set to deliver 20-35 joules per shock. Talk to your doctor to discuss how your ICD is programmed.
Category: ShockHow often does an ICD fail to work?
ICDs are highly effective. When the device detects a dangerous heart rhythm, it delivers a shock in the vast majority of cases. Clinical evidence consistently shows appropriate shock delivery rates above 95%, though the exact figure varies depending on the device, the condition being treated, and how the device is programmed.
ICDs do not fail often, but they are not infallible. Lead fractures, sensing errors, and inappropriate shocks (where the device fires when it does not need to) are all recognised but relatively uncommon complications. Your device clinic monitors for signs of these at every check-up, and remote monitoring can flag concerns between appointments.
If your ICD delivers a shock, contact your device clinic or go to A&E. Whether the shock was appropriate or not, it should always be reviewed. Our page on living with an ICD covers what to do if your device activates.
Category: Implantable DevicesWhat if I had external defibrillation, like with an AED (Automatic External Defibrillator)?
If you go into cardiac arrest and an AED or external defibrillator is available, it should always be used. Do not hesitate because of your ICD. Saving your life takes priority.
An external shock can occasionally alter your ICD’s programmed settings or, in rare cases, cause minor damage to the device. For this reason, your ICD should be checked by your device clinic as soon as possible after any external defibrillation, even if you feel well. The clinic will test the device and confirm it is functioning and correctly programmed.
If you carry an ICD identification card, it can help emergency responders understand your situation, though it should never delay the delivery of a shock if one is needed.
Category: Implantable Devices