Disorders of cardiac conduction

Physiopathology and classification

Anatomical recall

The synchronization of the contractions auricle-ventricles is under electric drive. The electric phenomenon is secondary with a depolarization of the cells (inversion of the electric polarity between the interior and the outside of the cell by migration of ions through the wall). The macroscopic translation of this phenomenon constitutes ECG. This depolarization is led gradually to the whole of the heart but can take preferential ways which are the ways of conduction. The principal structures in causes are:

the sinusal node (also called node of Keith and Flack): located in the right auricle. It is where begins the rhythmic electric activation from the heart which is transmitted gradually until the
ventricular node auriculo (also called node of Aschoff-Tawara), located at the auriculo-ventricular junction. It is about a specialized fabric allowing the transmission and the filtering of the auricular electric activity (of the auricle) the ventricles. Thanks to him, a too fast auricular stimulation only is partially transmitted, thus avoiding the racing of the ventricular frequency.
It is connected to the beam of His (with the high part of the septum inter ventricularie) which is divided into two branches, going towards the ventricles right and left.

The attack of these structures appears either by a normal frequency or by a bradycardia

Classification

These three structures can be injured completely or partially:

auricular Block sino or sinusal dysfonction: conductive disorder at the auricular level. If it is associated with disorders of the rate/rhythm supraventriculaire, it is then about a rhythmic disease of the auricle.
ventricular Block auriculo: conductive between the auricles and the ventricles
Block of branch, right or left, complete or incomplete disorder: conductive disorder on the level of the ventricle, which does not appear regulates some by a bradycardia.

The conductive disorder can be paroxystic and transitory, or permanent.

Causes

Generally degenerative, secondary with a fibrosis of fabrics concerned, and becoming increasingly frequent with the age. Should of course be eliminated a medicamentous cause: antiarythmic primarily, of which beat-blockings. There exist other rarer causes: auriculo-ventricular block with the waning of a acute infarction, certain infectious pathologies, or congenital (of birth).

Diagnosis

Private clinic

In the event of too important deceleration of the heart rate or prolonged pause, one can have faintnesses, or a syncope (loss of consciousness, typically brutal).
If the deceleration of the heart rate is moderate, the patient can complain only about one simple asthenia (tiredness) or about one intolerance to the effort.

Complementary examinations

ECG: key examination for the diagnosis on the condition of being able to surprise the conductive disorder if it is only paroxystic.
the Holter: It is about an electrocardiographic recording on 24:00 using a portable device. It makes it possible to detect a paroxystic conductive disorder if it took place during the recording.
electrophysiological exploration is an examination being done during a hospitalization, under local anesthesia and under conditions of surgical cleanliness. One or more probes are assembled after venous puncture, directly in the cardiac cavities under x-ray inspection. This examination makes it possible to locate the level of the attack.

Treatment

In urgency

It is initially necessary to try to stop the drugs bradycardisants (which slow down the heart rate). In the urgency and if the cardiac rhythm is too slow and the symptomatic patient:

To call the services of urgent Medical assistance for a medicalized assumption of responsibility.
If the patient presents himself in a table of cardiac arrest, to begin the operations of reanimation.
the drugs employed by the doctor to accelerate the heart are primarily the Atropine and the Isoprénaline.
At in-patient, with a badly tolerated bradycardia, one can have to pose électroentraînement systolic temporary ( provisional pacemaker ): under radioscopy and local anesthesia, one mounts a probe by venous way (generally femoral) to the point of the ventricle right. A case is connected there, delivering short electric impulses at a given frequency allowing the maintenance of the cardiac rhythm.
In urgency, one now has électroentraînement systolic external: two gelled pallets are laid out, one former face of the thorax, the other posterior face, and are connected to a scope defibrillator making it possible to deliver small electric shocks rythmiquement what makes it possible to involve the heart.

The pacemaker

The curative treatment remains final cardiac stimulation (“ pacemaker ” or “Cardiac pacemaker”): under conditions of surgical asepsis and under local anesthesia, a pocket is made in the area under claviculaire in order to put a metal case at it (current size of a few millimetres thickness and less 5 cm diameter) containing an electronics of control as well as the battery. To this case one or more probes are connected whose distal end is positioned in the auricle and/or the ventricle right. The monitoring is done thanks to a direct question of the case by an external computer and a simpler way by a ECG.

The current lifespan of a pacemaker is from 5 to 10 years. In the event of exhaustion of the pile, it is then necessary simply to change the case into connecting it to the old probes.

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 indication of the IRM, precautions for use in the event of use of lancet electric, 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. Each patient carrying a pile must be provided permanently with a “notebook of pile” on which are mentioned the mark of the case and the probes, the date of installation and the address of the center of establishment, the adjustments and controls made on this pile.

See too

the detailed article: Cardiac pacemaker

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