Cardiac pacemaker

History

It is in 1780 that Luigi Galvani shows that the electric stimulation of a nerve causes the contraction of the muscle connected. In 1791, it successfully repeats the same experiment on the Cœur.
In 1872, Duchenne of Boulogne tries ressusciter one drowned with rythmées electric impulses.
Of other attempts at electric stimulations of the heart by external way was tried in 1926 with Sydney.
In 1931, Albert Hyman deposits a delivering patent for a machine of the electric impulses in the middle via a needle inserted in this last and described the first success of its method.
In 1950, a new model is developed, always external, containing vacuum tubes and making nearly 30 cm height. There was to remain connected with the sector.
In 1957 appears the first model on battery.
the first completely plantable cardiac pacemaker is posed in October 1958.
the Sixties will see the appearance of the probes endocavitaires which are used nowadays: the electrode is introduced into the cardiac cavities by a puncture of a Veine and thus does not require any more one surgeon to position this one on the surface of the heart. The first apparatuses with function of listening appear during the same period.
the middle of the Seventies sees appearing two major progress: first stimulative programmable by an external case, using radio frequencies, and first stimulative double-room in 1963 (a probe in the auricle and one in the ventricle, which makes it possible to preserve the natural sequence of the auriculo-ventricular contraction).
In 1972 is established the first stimulative one with atomic fuel. This model was abandoned at the end of the Eighties.
the Eighties are marked by the stimulative ones controlled (increasing the frequency of stimulation with the effort of the patient).
the first plantable defibrillator is created in 1985. Thanks to a reduction in its volume and its cost, this material starts to have a true clinical development.
end of the year 90 sees appearing the stimulative multisite ones making it possible to stimulate the two ventricles (or auricles) in a synchronous way allowing an improvement in the event of Cardiac failure.

The cardiac pacemaker

It is composed of a case and one or more probes.

The case

It is composed:

of an energy source (a battery functioning with the Lithium-Ion). It is not refillable (the case at the end of the lifetime must be replaced at the time of a Surgical operation).
of an electronics allowing to deliver electric impulses gauged in frequency, amplitude and width of amplitude.
of a system of detection of the spontaneous electric activity of the heart, allowing to function only in the event of failure of this one (sentinel mode).
of a system of measurement allowing to know the resistance of the probes (impedance), the load of the pile, the statistics of operation.
an antenna radio frequency allowing the data communication through the skin towards an external device.

According to the models, the case also comprises:

one (or several) sensor (S) of activity of the patient allowing to accelerate the heart rate according to this last. The pile at the time known as “is brought under control to the effort”. The simplest sensor is a detector of inertial movement which postulates that the intensity of this last is proportional to the effort of the patient. However, of the sensors known as physiological were developed, as the measurement of ventilation or the segment ST
of the algorithms allowing the swing of one mode the other in the event of Troubles of the cardiac rhythm, to control the output voltage according to the situations, which makes it possible to lengthen the lifespan of the pile.

The size of stimulative also was considerably reduced and remains mainly limited by the size of the battery/integrated pile (up to 10 cubic centimeter).

Probes

Flexible, they connect the case in the middle. They consist of a conducting heart and a insulating sleeve. They can be unipolar (only one distal electrode), or bipolar (two distal electrodes). In order to ensure a better contact with the cardiac muscle, they can be equipped with a head salting out a drug fighting against the local ignition. The fixing of the probes at the cardiac level it muscle can be made in a passive way (“with barb” in the form of asperities) or activates (“with screw”)

A case can be connected to only one probe (pile monochambre or monofocale) or to two probes (pile doubles room or bifocal). In this last case, the end of the first probe is positioned in the right auricle, that of the second in the ventricle right.

In certain cases, there exists a third probe whose end is located in the coronary Sinus in contact of the left ventricle. It is then about stimulative triple room (or Bi-ventricular), employed in the treatment of certain types of Cardiac failure. Systems quadri-rooms also were developed and established. They remain however of rare use.

The probes of defibrillator are, in rule, bipolar, and covered in their distality with a long metal spring allowing the delivery with the electric shock.

Types of cardiac pacemakers

Stimulative can be simple or monochambre, double room, even triple room (and even quadri-room). It can increase or not its frequency of stimulation at the time of an effort ( control ). It can comprise a ventricular function of Défibrillation via an electric shock delivered by the ventricular probe: it is then about a plantable automatic Défibrillateur ( DAI ).

The type of stimulation is symbolized by the association of three capital letters, sometimes supplemented by a fourth.

the first letter symbolizes the stimulated cardiac cavity (has as an auricle, V for ventricle)
the second letter symbolizes the detected cardiac cavity
the third letter symbolizes the mode of release: I for inhibited , T for started (English trigger), D for both.
the fourth letter symbolizes the complementary functions: R is most frequent and means controlled with the effort .

Thus a pile VVI stimulates only the ventricle, has a function of detection of the spontaneous activity of this last, the presence of this one inhibiting the release of the pile.

A fourth letter can be added to mark mainly the function of control (R).

Manufacturers

In 2006, seven marks (5 industry groups) divide the market:

Medtronic;
Vitatron which belongs to Medtronic;
Saint-Jude;
Guiding which belongs to Boston Scientific;
Sorin Group fruit of association Sorin Biomedica and Medical ELA;
Biotronik;

Indications

A cardiac pacemaker must be posed if the heart is too slow (Bradycardie). The latter is defined by a heart rate too slow compared to the needs for the organization and likely to cause:

a tiredness,
a Malayan,
a loss of consciousness,
even, a Cardiac failure.

This slow rate/rhythm can be:

permanent,
paroxystic (i.e. transitory)
spontaneous,
or secondary with the catch of certain drugs. In this case the installation of a cardiac pacemaker remains justified if the doctor estimates that the latter are essential.

See detailed article: Turbid of cardiac conduction.

This bradycardia is found in:

the disease of the auricular sine (" sick sine syndrom") ;
disorders of conduction;
the over-sensitiveness of the sine carotidien;

In certain cases, one can have to pose a cardiac pacemaker, not because of a too slow heart, but when there exists a certain degree of synchronization of the contraction of the various walls of the cardiac muscle, as one sees it in certain forms of Cardiac failure. In this case, one positions another probe in the coronary Sinus, whose end is found in contact with the left ventricle, in addition to the probe in the point of the ventricle right, the whole is connected to same stimulative. One then speaks about cardiac resynchronisation .

Technique of installation of a cardiac pacemaker

The patient must be in practice hospitalized.

The installation is generally made by a doctor cardiologist specialized, called sometimes stimulist or electrophysiologist (not to be confused with the rythmologist which deals with the Troubles cardiac rhythm).

The patient must be with jeûn and to have had a recent blood assessment including/understanding in the month a NFS and an analysis of sound Hémostase.

Generally, a premedication by Antibiotique S is made in order to avoid an operational infection.

An incision is made in lower part of one of the two clavicles after a Local anesthesia. The probes are introduced either after denudation of a cephalic vein or after puncture of the vein subclavian. They are pushed in the venous network and the progression of their end is followed by an apparatus of radioscopy. They are placed in their respective cardiac cavity. Good positioning is checked by the radioscopy and the measurement of the threshold of stimulation (minimal electrical energy transmitted to the probe and causing a contraction of the muscle of the cavity) and threshold of detection (measurement by a Voltmètre of the electric activity of the heart via this probe).

The probes are then connected to the case which is introduced into a pocket under the skin in the area under-claviculaire. The skin is then recousue.

The intervention lasts approximately an hour but can be prolonged in an important way if the doctor does not manage to find a place satisfactory to position the end of one or more probes. It is the case in particular if it is about stimulative triple room, the coronary sine being sometimes very difficult to find.

The exit of the patient is done between 24 and 48 H after the intervention. The wire must be withdrawn about the tenth day.

If it is about a simple replacement of a case, the gesture is easier, the probes being, generally, left places from there and being reconnectées at the new case.

Medical supervision of a cardiac pacemaker

It must be made in a regular way either by the doctor cardiologist of the patient, or by the doctor stimulist (that which posed the pile).

This monitoring allows:

to see whether the pile works well;
to see whether the level of load of the battery is correct to be able to program the replacement of the cardiac pacemaker in time;
to check the integrity of the probes;
to detect some Troubles cardiac rhythm for the models having a function of monitoring (holter), which is the case if the pile is recent.

It is carried out:

by a test with the magnet: the positioning of this last on the case, through the skin, starts a particular behavior of the pile which constitutes the " signature" of the latter. If the latter diverges so much that is to say little of what is noted on the model, that can mean dysfonction.
By the interrogation of the case by a system of radio frequency connected to a computer. One can obtain multiple information thus: level of load, degree of operation, frequency, control of the Electrical resistance of the probes… Each mark of pile has its own material system of interrogation. It is thus essential to know the latter to be able to charge the data and to make the adequate tests.

The patient must be carrying in all the circumstances a document attesting the presence of the cardiac pacemaker, the mark of this last and the probes, the address of the center which made the establishment and the main features of the last adjustment. It is about the notebook of pile .

The current lifespan of a battery of cardiac pacemaker is from five to ten years. The regular monitoring of the pile makes it possible to detect the end-of-life of the latter before it takes place and to be able, thus, to program well in all peace, its replacement.

Precautions to be taken at a carrier of stimulative

The port of a pacemaker requires some precautions to avoid the electromagnetic interferences:

To avoid plates of heatings to induction, arc cutting, storage of the cellphone in the pocket close it pacemaker, to station close to the anti-theft arches of the stores.
Against indication of the use of apparatuses of electrotherapy or electrostimulation…
To inform in the event of passage under detecting metal gantries (airports…) : risk release of alarm
At the medical level: against theoretical indication of IRM even if examinations could be made without main issue, precautions for use in the event of use of lancet electric, in the event of radiotherapy.
To avoid the direct solar exposure (risk of burn increased because of presence of a metal mass which can store heat under cutaneous)

In fact, these situations are rather rare in the everyday life and do not have to worry. In case of doubt or of question, to speak to the doctor about it.

In the case of the death of the carrier, the cardiac pacemaker must obligatorily be withdrawn either by a doctor or Thanatopracteur. Indeed the lithium contained in the stimulative one can explode starting from 180 degrees (point melting of lithium) by knowing that the temperature of a furnace of cremation varies from 600 degrees to 1100 degrees that constitutes a main risk, and even if there should be burial (burial) the withdrawal is obligatory owing to the fact that it may be that the family requests later on a exumation from the ends of cremation.

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