Pacemaker: heart pacemaker
The first pacemaker was implanted in humans in 1958. Endocavitary probes appeared in the course of the 1960s, that is to say, implanted in the cardiac cavities via the veins and without the need for thoracic surgery. to position them on the surface of the heart. In 1972, the first atomic fuel stimulator was implanted, this energy having been abandoned in the early 80s.
The box
The case, whose average diameter is about 4 cm, consists of a titanium shell containing a battery and a microcircuit with software, and a connector. Its size has been considerably reduced in recent years, and remains mainly limited by that of the battery. This is made of lithium with a lifespan of 5 to more than 10 years. It is not rechargeable and the stimulator is therefore replaced before its battery runs out in a generally very simple operation.
Different functions are present or not depending on the pacemaker model, such as:
– Physical activity sensor for detecting efforts and accelerating the heart in response (effort control), either by measuring movements (piezoelectric sensor) or by measuring the respiratory rate (thoracic impedance measurements ), or by measuring cardiac contractility
– Remote transmitter/receiver to establish a connection with an external box, at the patient's home (telemonitoring, teleconsultation)
– Now systematically present, heart rate tracing memories recording any anomaly such as arrhythmias occurring between two consultations
– Various adjustment options depending on the type of pathology to be treated.
Respondents
The box is connected to the heart via one or more flexible and fine probes. These probes are electrical conductors.
The internal conductor is made of an alloy comprising titanium, iridium, carbon; the insulation is made of silicone, polyurethane or a mixture of the two (see fig.1). These are fixed to the endocardium by a screw, more rarely by a system of barbels surrounding the distal end of the probe. The number of probes depends on the nature and the disorders motivating the implantation. A probe is almost always implanted at the apex or on the septum of the right ventricle, a 2nd is frequently connected to the right atrium (except if the patient is in arrhythmia), a 3rd is more rarely introduced into the coronary venous network to control the left ventricle by synchronizing it with the right ventricle. All these probes are placed by percutaneous endocavitary route via the superior vena cava, except in the case of an epicardial surgical approach.
Why is a pacemaker inserted?
The pacemaker is used to trigger, control the heartbeat. It therefore fights against bradycardia, that is to say the excessive slowing of the heart rate. It is prescribed in the failures of the natural electrical conduction pathways of the heart, in particular when these no longer allow contractions at normal frequency to be obtained.
Conventional pacemakers have one or two leads, which are used to pace and/or sense right atrium and/or right ventricle activity. Thus, when the beat control, which is in the atrium (sinus node) is involved, it is the atrium that the pacemaker will stimulate. On the other hand, as often, if it is the connection between atria and ventricles (atrioventricular node and bundle of His) that is lacking, it will serve as a relay between the command from the atrium that will be detected, and the ventricle that 'it will stimulate.
In heart failure, there has existed for about 15 years a technique adapted to certain cases, to improve the efficiency of the left ventricle by resynchronization. Bringing spectacular results when the indication is well established, this type of pacemaker comprises 3 probes: one for the right atrium and 2 for the right and left ventricles, so as to make the simultaneous contraction of the walls of the heart which are asynchronous. Note that this technique is also possible with a defibrillator (see this chapter).
When to do the intervention?
Heart slowdowns, sometimes permanent and sometimes sporadic, can lead to symptoms such as syncope (with the risk of a traumatic fall), shortness of breath or simple fatigue. Some electrical conduction disorders can even lead to cardiac arrest with the risk of sudden death.
A pacemaker is prescribed when heart slowdowns are already or may become symptomatic. In some cases there has not yet been bradycardia, but electrocardiographic signs raise fears of this development and suggest a pacemaker.
The intervention in practice
Hospitalization
The stayHospital stay for the procedure usually lasts between 2 and 4 days.
Some teams perform the operation during an outpatient hospitalization.
anesthesia, pain
The pain is usually mild enough for the operation to be performed under local anesthesia and light sedation. General anesthesia may be considered depending on the context of each patient.
The vascular approach, access to the heart
To implant the probes, access to the venous network is therefore necessary, allowing the arrival in the right atrium, which is the cardiac vestibule, of venous blood before it is directed, by the right ventricle, to the lungs for its reoxygenation. .
An incision of about 4 cm is made under the collarbone, at the shoulder (right or left indifferently, and therefore according to the preferences of the operator and the patient), where two veins can be used:
– the cephalic vein that can be stripped and incised between the shoulder muscles (pectoral and deltoid)
– the subclavian vein, which is punctured behind the collarbone
The probes are positioned under radioscopic vision thanks to a suitable X-ray device. Once fixed in the heart at the expected location, their proper electrical functioning, indicating good contact, is checked in the theater using an analyzer fitted with a sterile cable.
They are then connected to the stimulator, and the latter is introduced into a subcutaneous or submuscular pocket (box) depending on the patient, in the subclavicular region.
Duration of the procedure
Variable between patients depending on anatomical data, the intervention can be rapid, around 30 minutes, but also more rarely reach 1 to 2 hours.
In the case of triple stimulators for resynchronization, this duration can be 30 to 45 minutes in simple cases, but can also sometimes reach 3 hours.
Postoperative consequences
Surveillance
Discharge from the hospital can usually take place the day after the procedure, after an electrocardiogram, check of the scar and a chest X-ray showing the position of the probes. Correct operation is also checked, this time by telemetric communication with the pacemaker, at the patient's bedside.
Complication risks
The complication rate is low, less than 5%. These complications are all the more rare as they are serious. The most common are simple to manage, such as:
– pneumothorax: detachment of the lung during the subclavian puncture, which sometimes requires an evacuation of air until the lung returns to the chest wall
– the compartment hematoma: pocket of blood by internal bleeding, often very limited and simply monitored until resorption
– the displacement of one of the probes in the first days, requiring a resumption for repositioning
– an early infection of the surgical site, which requires the removal of all the material for reimplantation after a few days of antibiotics
Very exceptionally, serious vascular complications such as thoracic hematoma (pleural or mediastinal) or tamponade may occur.
What results?
The operation of a pacemaker is extremely reliable and accurate, with rare hardware anomalies. Its effectiveness in avoiding the symptoms that one wishes to treat is therefore practically systematic. Cases where the result would be disappointing, such as persistent shortness of breath or fatigue, or malaise, are generally a sign that these symptoms were not related to bradycardia but to other phenomena.
After implantation
The first days
Immediately after implantation of the pacemaker, it is important to monitor the scar and inform your doctor in case of redness, swelling or oozing.
During the first 24 hours, any sudden movement of the shoulder is to be avoided, but it is preferable not to stiffen the shoulder either in order to avoid ankylosis. Gentle movements to regain mobility are therefore recommended.
During the first month, avoid carrying heavy objects and intense physical activity.
Apart from that, it is quite possible to quickly resume a normal life.
The follow-up
After the installation, a pacemaker wearer's notebook is given, indicating information on the implanted device. It should be kept on you at all times as much as possible.
A specialized follow-up is established to check the proper functioning of the device, collect its memories and monitor the wear of the battery. This follow-up includes regular telemetric checks (by the computer dedicated to the pacemaker) generally in the center where the device was implanted. A first check is carried out 4 to 8 weeks after installation. Thereafter, consultations are scheduled every 6 to 12 months.
The day of change
The progress of theBattery wear is closely monitored during regular checks. Before the battery runs out, signs of wear are observed and the change is scheduled as much as possible without urgency. It is therefore important not to neglect the follow-up.
The intervention generally consists of an incision next to the box, which is removed and replaced by a new one. Sometimes, gestures on the probes are necessary if they posed operating problems.
Life with the stimulator
The presence of the pacemaker should be forgotten as much as possible, as it has few consequences in everyday life.
What precautions should be taken ?
At home
– The telephone: whether wired or wireless, it poses no problem. For cellular portables, possible wave interference is taken into account and it is recommended to use the ear opposite the side of the stimulator; nor should the phone be carried in a pocket close to the device.
– In the kitchen: the microwave oven, electric hotplates or food processors are no problem. Only induction hobs generate a weak magnetic field, for which it is recommended to keep a certain distance; their use, to start them for example, remains possible.
– For DIY: drills or other electric saws are safe; arc welding creates an electromagnetic field, it is in theory contraindicated, but can be considered subject to certain precautions.
shopping, travel
– The anti-theft gates of shops or libraries can be crossed without any problem. However, it is recommended not to stop there.
– Travel is obviously not contraindicated. For aircraft, airport gates could theoretically be crossed, but are prohibited for reasons of liability and the precautionary principle. On the other hand, more powerful manual detectors are to be avoided, which justifies having your pacemaker card with you.
– The pacemaker does not contraindicate driving or wearing a seat belt.
The sport
– The pacemaker does not limit sports activities apart from avoiding the intensive practice of golf; for racquet sports, if possible, an implantation on the side opposite to the hand holding the racquet is preferred.
– You should avoid hanging (for example from a bar) with your arms extended, as this can stretch the probes.
– Rifle hunting requires an installation on the opposite side to the cocking shoulder, in order to avoid the recoil force of the rifle on the case.
At work
– Certain substations close to electromagnet motors, for example, must be subject to magnetic field measurements by specialized companies.
– Wearing a pacemaker is also compatible with most professions.
To the hospital
It is also necessary to have your pace maker card with you and show it to healthcare professionals.
– Surgery: the use of an electric scalpel in most operations requires certain precautions such as preoperative settings of the stimulator and a limitation in the intensity of this scalpel; postoperative monitoring is also recommended.
– Medical imaging: conventional x-rays, scanner (computed tomography) pose no problem; on the other hand, MRI (magnetic resonance imaging) generating a very powerful magnetic field, should only be carried out in specialized centers in agreement between cardiologists and radiologists, with very specific precautions.
– Radiotherapy: it is potentially harmful for the device, but with a low accident rate; regular checks and specific adjustments are carried out during treatment periods.
