Where irregular or life-threatening heart rhythms occur, the device delivers a ‘shock’ to reset the heart rhythm, preventing the patient going into cardiac arrest. Patients are unaware of the ICD for the most part. However, if the device needs to deliver a shock, patients sometimes describe the feeling of this as a ‘kick to the chest’.
The ICD also stores and records information about your heart rhythm for your Consultant to review. An ICD can also be programmed to act as a pacemaker if required.
It can act like a pacemaker when the heart is beating too fast or too slow, delivering a series of electrical impulses. If your heart beat is too fast it can deliver a burst of even faster beats to try to restore normal rhythm. This is known as “anti-tachycardia pacing” or ATP. When your heart is beating too slowly the device works like a regular pacemaker giving your heart the extra beats. This is known as “bradycardia pacing”. It may deliver one or more electrical shocks to remedy more serious abnormalities or if ATP does not bring the heart beat back to normal. This is known as defibrillation.
ICDs are generally implanted in people who have had a life threatening heart rhythm problem (arrhythmia) or possibly even have had a cardiac arrest or are considered at risk of developing a serious heart rhythm problem and may have the device inserted as a precaution.
You are usually asked to fast (have nothing to eat or drink) for about 6 hours before having the ICD implanted. Check with your cardiac team about taking your usual medications. If you are taking any blood thinners e.g.Warfarin/Xarelto/Pradaxa/Apixaban, you may need to stop taking these 3-5 days beforehand, so make sure you follow your doctor’s instructions.
ICDs are usually implanted under the skin in the upper left side of the chest near to the shoulder. The leads are threaded through a large vein into the chambers of the heart. The procedure is carried out in the cath lab and is often done using local anesthetic so you will be awake but should not feel anything. The procedure can take a few hours to complete particularly if 3 leads are inserted.
When the ICD is in place your doctor will test it and programme it to treat your specific heart rhythm problem. This may involve giving you some extra sedation/anaesthetic, as it may require speeding up your heart into a disorganised rhythm and ensuring the ICD delivers a shock to correct it back to a normal rhythm.
When the ICD delivers therapy you may experience a number of different sensations. You may feel an abnormal heart rhythm before the ICD treats the rhythm disturbance.
When the ICD is pacing the heart, treating a fast rhythm, you may experience a painless fluttering feeling.
If the ICD has to deliver a low-level electric shock it can feel like a thump on the chest and be mildly uncomfortable.
In the case of more serious rhythm disturbances, you may feel dizzy or faint shortly before the shock is delivered and then experience a stronger sensation of being hit really hard on the chest as the rhythm is corrected.
You will receive an identification card from the cardiac physiologist which you must carry at all times as this contains all the relevant information regarding your device and will be required if travelling through airport security.