ICD Implantation

An ICD has two main parts: a pulse generator, a sealed metal case slightly larger than a pacemaker that holds a battery, capacitors and a small computer, and one or more leads that connect it to the heart. The device reads every heartbeat. If it detects ventricular tachycardia, a fast rhythm from the lower chambers, it can first try anti-tachycardia pacing, a short burst of rapid beats that often ends the rhythm without you noticing. If that fails, or if the rhythm is ventricular fibrillation, a chaotic quivering that stops the heart from pumping, it delivers a shock to reset the rhythm. A transvenous ICD has its leads inside the heart and can also pace a slow heartbeat. A subcutaneous ICD has a lead placed under the skin beside the breastbone, with no wire inside the heart or veins, but it cannot provide ongoing pacing. Some ICDs also coordinate both ventricles in heart failure, a combination known as CRT-D.

ICDs are used in two broad situations. Secondary prevention means the device is fitted after you have survived a cardiac arrest or a sustained dangerous fast rhythm, when there was no temporary, fully reversible cause, such as an acute heart attack that has been treated. Primary prevention means the device is fitted before any such event, because your heart condition places you at high risk. The most common example is a weak heart pump, measured as a reduced ejection fraction on imaging, after a previous heart attack or from cardiomyopathy, which persists despite several months of full heart failure treatment. Other examples include hypertrophic cardiomyopathy with risk features, inherited rhythm conditions such as long QT syndrome or Brugada syndrome in selected people, and arrhythmogenic cardiomyopathy. The decision weighs your individual risk, overall health and wishes, and is usually made by an electrophysiologist after an echocardiogram, often a cardiac MRI, rhythm monitoring and sometimes genetic testing.

A transvenous ICD is implanted much like a pacemaker. In a heart rhythm laboratory, usually under local anaesthesia with sedation, the cardiologist makes a cut of about 5 to 7 centimetres below the left collarbone, passes one or more leads through a vein into the heart under live X-ray, fixes their tips to the heart wall and tests them. The generator is connected and placed in a pocket under the skin or the chest muscle. For a subcutaneous ICD, the generator sits on the left side of the chest below the armpit and the lead is tunnelled under the skin beside the breastbone, often under general anaesthesia or deep sedation, because creating the tunnel is more uncomfortable. Some teams test the device by briefly inducing a fast rhythm under deep sedation to confirm that it detects and corrects it, although this is now done less routinely. An antibiotic is given beforehand, and the procedure usually takes about one to two hours.

An ICD is offered when the expected benefit of preventing sudden death is meaningful for you. It is generally not recommended when life expectancy is short because of another illness, in the first weeks after a heart attack or bypass operation, when the risk often falls as the heart recovers, or when a dangerous rhythm had a clear reversible cause. Some people at temporary risk wear an external defibrillator vest while the picture becomes clear. Before implantation you will have an ECG, an echocardiogram, blood tests and a review of your medicines, particularly blood thinners, which may be adjusted, and you fast for about six hours. It helps to discuss practical questions in advance: what a shock feels like, what to do after one, driving, work and how the device will be followed up near home. For international patients, ECGs, scans, monitor recordings and genetic results can usually be reviewed remotely before travel.

Most people go home the day after implantation, once a chest X-ray, a wound review and a device check are complete. For about four to six weeks you avoid raising the arm on the device side above shoulder height, heavy lifting and vigorous arm movements while the leads settle. Walking and light activity can resume within days, and many people benefit from a cardiac rehabilitation programme. Driving restrictions after an ICD, and again after any shock, differ considerably between countries and between private and professional licences, so check the rules where you live before driving. Plan to stay abroad for about 3 to 7 days. Carry your device card: airport security arches are generally safe, but ask staff not to hold a hand-held detector over the device for long. Most modern ICDs support remote monitoring from home, and your team should arrange a device clinic near you that can read and adjust your model.

Implanting an ICD carries the same procedural risks as a pacemaker: bruising and blood collections, a lead moving out of place, a punctured lung, device infection that may mean removing the whole system and, rarely, injury to the heart wall. The device also brings its own considerations. Appropriate shocks treat a real dangerous rhythm and are the device doing its job. Inappropriate shocks happen when the device misreads a fast normal rhythm, atrial fibrillation or a lead fault as dangerous; careful programming, medicines and sometimes catheter ablation reduce them. Shocks can be frightening, and anxiety or low mood afterwards is understandable and treatable, so ask for support. Lead problems may appear years later. An ICD does not cure the underlying heart condition and does not usually make you feel better day to day unless it also provides resynchronisation; its purpose is protection against sudden cardiac death. The battery commonly lasts several years before a shorter replacement procedure.