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Implantable defibrillators (ICDs)

By Dr Maite Tome, Consultant Cardiologist, Heart Hospital, London

What is an ICD?

An ICD (implantable cardioverter defibrillator) is a device able to detect life threatening cardiac rhythms and discharge or deliver energy—what we call a shock— to restore normal rhythm. An ICD has different parts, the generator (box) and the leads (wires). The generator has a circuit that works as the detector and processor of the cardiac cycles and a battery. The leads connect the heart to the generator. They have two different ends - the heart end and the generator end. The lead tip in contact with the heart muscle has different shapes. All of them aim to provide stability and good contact with the heart. You will often hear your doctor say that an ICD is a special pacemaker. That is true; the ICD also has additional pacemaker functions.

The first ICD was approved for human use in 1985. Enormous progress has followed this landmark in the history of modern cardiology.
The early devices were large, requiring cardiac surgery for their implantation and at least a week in hospital for recovery. They had very simple diagnostic capacities and the battery life was short.  Today’s devices are smaller, their batteries last longer and cardiac surgery is not required for their implantation. Only minor surgery is required.

 
The device pictured is a Medtronic Maximo model, which is just 68mms x 51mms x15mms.

 In 2000 the annual rate of implantation in the UK was about 15 to 20 per million population per year, compared with 30 per million in Western Europe and 200 per million in the USA.
The National Institute for Health and Clinical Excellence (NICE: www.nice.org.uk) guidelines of 2000 anticipated that the rate would rise to approximately 50 per million per year. Although the average implantation rate is now closer to 50 per million per year, there are still numerous regions where this target hasn’t been achieved. These variations cannot be explained by the difference on ICD indications in the population.
ICD costs have fallen considerably since 2000 from about £22,000 to today when they range from slightly below £10,000 to about £15,000. 

Some ICDs also include biventricular pacing.

Who needs an ICD?

ICDs are also known as lifesavers - they can change a fatal heart rhythm into a normal one. They cannot, however, treat a disease or change an underlying cardiac disease. ICD indications include primary and secondary prophylaxis.  Secondary prophylaxis is when a person has experienced a cardiac arrest and survived, or suffers from malignant arrhythmias that are refractory to medical treatment.  Primary prophylaxis is when a device is implanted to prevent sudden cardiac death, which is given to those identified as high risk patients Cardiomyopathies are a known cause of sudden cardiac death, but it is clear that the vast majority of the patients with cardiomyopathy are not high risk and will not need an ICD.


Implantation

Implantation is generally done under local anaesthetic and sedation. Some special cases may require general anaesthesia too. Although the abdominal implantation has been used widely in the past, nowadays the device is implanted under the collarbone with a small incision. The wires are passed through a main vein onto the right heart and positioned there.  The medical team then tests that the signal received from the heart muscle is good and will also test the device functions.

To test the device a malignant rhythm is induced and successfully treated with a shock from the device.  This will ensure that the device is safe and will work when required.
The risk of implantation includes the risk related to any minor surgery, that is infection, adverse reaction to the medication and bleeding. At the time of the implantation, while trying to pass the wire to the heart, there is also a small risk of damaging adjacent structures like the lungs, the vessels or the heart at the place of contact with the wire. The risk of serious complications is small.

Follow-up

Like any device, the ICD requires technical checks. Your pacing clinic will check that the battery life is adequate and will also download all the possible events and analyse them. The medical team will ensure that the wires are still functioning and there are no problems, for example resistance or failure in detection. All the ICD settings can be assessed and adjusted through monitoring. The communication between the generator and the computer is based on their magnetic properties. It is important for you to know that strong magnetic fields need to be avoided. It is particularly important that equipment generating strong magnetic fields should not be placed in direct contact with the box. The boxes are, however, very well built so everyday tools like microwaves and computers do not interfere with their normal functioning.

Can I have a normal life?

Your doctor will restrict your activities during the first few weeks to allow healing. Once that period is over you will be able to return to your normal activities. If you have doubts about special activities, please ask your medical team or pacing clinic. But it can take time to adjust psychologically to having an ICD. To read more about this click here

ICD and driving

The main question to consider is always the underlying disease and the reason why the ICD was implanted in the first place. It’s important to remember that it’s not your ICD that restricts your driving. The restrictions are those dictated by your underlying condition and risk profile. Regulations are published by the DVLA. They need to be taken as a guide and you should check the position in relation to your case. The regulations are constantly being updated. If you have had a cardiac arrest and a defibrillator fitted, you must tell the DVLA. You can start driving after six months as long as the device has not been activated in that period and you are not prone to fainting. You will have to stop driving for one month each time the setting on your ICD is adjusted or if your anti-arrhythmic medication is altered.  One week off driving is required after reinsertion of a defibrillator box, provided that the settings remain unchanged. If you have not had a cardiac arrest and your ICD is being fitted as a precaution, you need not tell the DVLA but you should not drive again for a month. However, having an ICD does bar you from driving lorries or public vehicles such as buses, even if it is only fitted as a precaution. For further details call the DVLA on 0870 600 0301 or see the website www.dvla.gov.uk/welcome.htm

Accepting and coping with an ICD

 If can take time to adjust to having an ICD. Read more about this in our ICD page in our living with cardiomyopathy section. The CMA has a network of affected volunteers who talk to others by telephone and email.  Many of those volunteers have an ICD. If you would like to talk to one of the volunteers, email the CMA's Sarah Dennis

Future of ICDs

Modern devices are smaller, lighter and last longer, and new functions have been developed. They include better filters to decrease the rate of inappropriate shocks and new therapies to decrease the number of appropriate shocks. Developments have also been made to improve accessibility of the generator. At present the follow-up needs to be done by a pacing clinic and the patient has to attend. The new devices will allow accessibility from home through the internet. Initially this will only have diagnostic capabilities, ie checking the ICD memory to see what rhythm disturbances have occurred and what action the ICD took. But in the near future it may be possible to have control from home (ie changing settings remotely). 

A large magnet or a large magnetic field can affect the normal functioning of the device. A large magnet should not be positioned on the top of the generator (box). Once a ICD has been implanted, imaging techniques like MRI cannot be performed. An ICD is a committed device, as its main function is to treat life threatening arrhythmias. The settings are therefore adjusted to so. In a small number of occasion there are other rhythm disturbances that can be identified by the ICD as a threat. The ICD then will treat them with a shock. We call this an inappropriate shock. ICD research has also showed that in some cases the life threatening arrhythmias can be treated by the ICD with fast pacing, this development reduce the number of shocks and therefore is pain-free therapy.

A patient talks about the devastation of being told that she needed an internal defibrillator, the anger she felt and how later fell in love with it:

I have worked for several years as a nurse and midwife for an aid organisation mainly in Africa. 

It was during this time I noticed my first palpitations, which I attributed to the stress and challenge of the work. As the palpitations increased, I eventually underwent investigations, which led to me being diagnosed with arrhythmogenic right ventricular cardiomyopathy (ARVC).

Initially, like many people with cardiomyopathy, I adopted a tactic of denial, which I embraced eagerly. I would run mother and baby clinics overseas while having many episodes of ventricular tachycardia. I became an expert at disguising my numerous near fainting events, cheerfully explaining that it was “just the heat of the African sun”. I never confessed either scenario to my doctors. 

On returning to the UK and following an ablation, I was told that I needed an internal defibrillator  (ICD). I felt devastated and was resentful of the suggestion. I was confused by my own reaction. I had always prided myself on being stoical. I was, after all, the person who worked in war zones and so why did I find this so difficult to cope with?

Many health care professionals feel perplexed at the myriad of reactions witnessed when proposing an ICD. They are offering something that “saves a life” and the seeming reluctance and lack of gratitude that many patients exhibit is confusing. My experience is that there is a gap in perception at least initially. The approach from the health care professional is an intellectual one; they see a list of symptoms, from which the obvious conclusion is ICD implantation. For the patient it is not an intellectual decision but almost entirely an emotional one. Patients must come to terms with admitting, perhaps for the first time, that they have a problem with their heart.

The prospect of an ICD marks the end of any denial that the person has comfortably harboured. With its passing, there arrives an intense sense of  anger and loss of control. It is not perceived as this wondrous life saving device but as something that potentially affects your employment status, insurance prospects and family relationships. And then there’s coping with the prospect of your first shock. It took me seven days to finally see the reasoning behind the intellectual standpoint of the suggestion. I agreed, reluctantly, that it was the obvious solution.

My ICD implantation was turbulent due to unforeseen complications that I should point out are rare. However, even if the path runs smoothly, the aftermath can be daunting and isolating. I obsessed about my ICD all the time. I was miserable and felt that the essence of who I was prior to its insertion had gone and I didn’t like what I saw in its place. I spent a frantic three months waiting for a decision from my employers as to whether I could ever work overseas again. It wasn’t just a job but my way of life and now my whole future was uncertain. The question was “how much of a liability was I?” According to most insurance companies I had contacted trying to take a holiday in Europe, I was “too much of a liability” to insure.

My family found it difficult and I realised that they had taken refuge in my original denial. Now they too had to acknowledge  “something” but were confused as to what. Even now they remain unable to talk about it.  I finally understood that, while I had rebuked myself for clingint to denial, for them it is a coping mechanism best left alone.For those going through “the post insertion blues”, believe me there will be a turning point. Mine came when I was told I could resume my work overseas and a subsequent short mission to Sri Lanka was planned. I visited a mother and baby clinic I had helped to set up some six years earlier during the war. I was humbled at the realisation that I was now in possession of some £20,000 worth of technology in my body while remembering that with less than £600 we set up a whole clinic and trained the midwives.

Today the clinic thrives and I was reminded that the person who I am had not gone but that she had just temporarily lost her perspective. I had already started to tentatively like my ICD but the trip confirmed that I was now “in love” with it. It was no longer the invasion that I so resented; it would enable me to continue my work and I no longer lay in bed at night fearing the sound of my palpitations. More importantly, I ceased deceiving myself or expecting others to be complicit with that deception. For anyone who is about to receive an ICD my advice is to take your time when making the decision and do not be surprised by any emotion you may experience.

If you feel anger it is normal. Remember you do not have to feel grateful that you being offered something that saves your life. That feeling will come, but allow yourself to react in the way that is most appropriate for you. What is important is that you talk to someone. 

I talked to my family in the United States where ICDs are commonplace and found the cultural difference refreshing. My cousin said “over here you get older, you have your boobs fixed, you get your liposuction and then have your ICD!” She told me to imagine that I was “just getting mine done the other way around!”

I will be returning to my work overseas, blessed with “my gift” and leaving the liposuction until later!




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