What is it about ?
The heart is made up of a left atrium, a right atrium, a left ventricle, and a right ventricle. These cavities are separated by partitions. Blood enters the heart through the atria. The ventricles eject blood into the body.
The heart works autonomously, that is, it beats without intervention on our part. The heart muscle (myocardium) contracts under the effect of an electrical stimulation (stimulus). This stimulus is created in a node of nerves called the sinus node, located in the heart wall of the right atrium. This sinus node is the natural pacemaker. From the sinus node, current travels to the heart muscle through a special electrical conduction system. Thus, the electrical impulses pass through the entire myocardium. These impulses stimulate this muscle, which contracts.
Normally, this is done on a regular basis, at a rate of between 60 and 100 beats per minute (rhythm or heart rate) while resting.
It can happen that this system does not work very well, causing irregular stimuli, too slow, too fast, or not at all. The problem may be trivial, but it can also be life threatening. Some abnormalities can be corrected by putting on what is called an “automatic implantable defibrillator (ICD)”. This is a device (device) that is implanted that can send an electrical current through the heart to restore a normal heart rhythm. This device can also bypass the activity of the electrical system when it detects a natural rhythm that could be fatal. The system is literally “reset” and can then resume normal activity.
How does it work?
An ICD is actually a small computer equipped with a battery, which is implanted under local anesthesia under the skin of the chest, just below the left collarbone. An electrode connects the small computer to the heart through a vein. Electric current is sent from the battery to the heart muscle through the electrode. The device continuously monitors the heart rate and intervenes in the event of excessive abnormalities. If the heartbeat becomes too slow, it works like a normal pacemaker. If the heartbeat is too fast and / or irregular, the device will trigger a series of light electrical impulses. These are painless and are usually not perceived by the wearer of the ICD. If the increased heart rate does not normalize, the device produces an electric shock (a strong electrical pulse) called “defibrillation”. This is what makes the difference between a pacemaker and an ICD, the ICD can give an electric shock to interrupt a severe arrhythmia.
The big advantage of an implantable device is that it is always there when you need it. It is therefore no longer necessary to wait for emergency services. The device works on its own and does not need to be adjusted manually. It is the ideal device for people who need unexpected and repeated interventions.
When is it used?
The device is implanted to prevent cardiac arrhythmias which can be fatal and sudden cardiac death: it therefore has a preventive function. This prevention can be primary, in order to avoid the occurrence of (new) complications, or secondary, to prevent the recurrence of previous complications.
An ICD is indicated in the following cases:
- To prevent rhythm disturbances which can be fatal and sudden death after a heart attack (myocardial infarction) in people with disease of the heart muscle (myocardium) or an inherited heart defect which may be associated with such complications.
- As a preventive measure in people who have previously had cardiac arrest, for which no treatable cause has been found.
Implantation of an ICD is therefore not indicated if a reversible or treatable cause of the heart disease has been identified, such as inflammation of the heart muscle, and if the person’s life expectancy is is less than 12 months. An exception can be made if the person is waiting for a heart transplant.
Follow-up after implantation of the device
A first check will be carried out 1 to 3 months after the implantation. Then the checks will take place every 6 months. The technical operation of the device, the condition of the electrodes and the battery, etc. are systematically checked. In addition, each DAI intervention is analyzed. All of this data is stored in the device’s memory. It is estimated that 10-30% of interventions are unnecessary. This is why the programming of the device is adjusted on the occasion of the checks. It may also be necessary to adjust the drug treatment slightly. Indeed, drugs against arrhythmias and anticoagulants are continued after implantation.
Additional intermediate checks may be necessary, for example whenever the device has administered an electric shock. In this case, you must contact the clinic responsible for monitoring your pacemaker the next day. If the device triggers several successive shocks or if your general condition deteriorates rapidly, you must go to the emergency department.
Can the operation of the DAI be affected by external influences?
The devices are generally very resistant to external influences exerted by electrical devices. Household appliances, computers and mobile phones have no influence on the operation of an ICD. Chainsaws, welding equipment and strong magnets, on the other hand, can have some impact. So stay away from these devices. The electronic control gates found in shops and airports only have an influence if you stay underneath without moving. You risk nothing by crossing them normally. The authorized official will carry out a manual check on presentation of a medical certificate.
Ordinary activities, whether professional or domestic, and leisure are generally not a problem. You can also have a normal sex life. It is advisable to avoid intense physical efforts, as they can trigger arrhythmias. You cannot practice swimming, diving or martial arts without being accompanied. Professional driving of a vehicle (taxi, truck, bus, …) is not allowed, but you can drive your personal vehicle. After an episode of unconsciousness, you will be prohibited from driving for 6 months. After this period, you will be allowed to get back behind the wheel provided you can present a certificate from your attending physician. If you are not sure whether you can perform certain activities, seek medical advice first.
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