Auricular Fibrillation

The auricular fibrillation (F) is most frequent of the Troubles cardiac rhythm. It belongs to the supra-ventricular disorders of the rate/rhythm. It corresponds to a myocardic action not coordinated of the cells S auricular S, which will involve a fast and irregular contraction Ventricule S.

It is sometimes called arrhythmia although this term corresponds, in any rigor, with the whole of the disorders of the rate/rhythm and not with the only fibrillation. Other abbreviations are of everyday usage: AC/FA (cardiac arrhythmia by auricular fibrillation), TAC/FA (cardiac tachy-arrhythmia by auricular fibrillation).

Epidemiology

It is the disorder of the most frequent cardiac rhythm, in particular in the old adult. Its Prévalence increases with the age. One speaks about auricular fibrillation:

paroxystic: duration < 7 days,
persistent: duration of 1 week with 1 month,
permanent: > 1 chronic month
: > 3 to 6 months.

Physiopathology

The normal cardiac contraction comes from a Dépolarisation (inversion of the electric polarity of the cellular membrane) cyclic of a group of cells located on the high part of the right auricle, the sinusal Nœud. This depolarization is propagated from top to bottom and gradually, in direction of the auriculo-ventricular Nœud.

In the case of auricular fibrillation, it creates for itself an anarchistic depolarization of the auricular muscle fibers (either on the level of centers of Hyperexcitabilité or on the level of circuits of reentry which maintain the multiple and fast hearths of depolarization).

This absence of synchronization of auricular muscle fibers has several consequences:

of the hemodynamic consequences: the auricles will become mechanically ineffective: they do not contract any more (loss of the physiological Systole); there is thus disappearance of the fast ventricular filling, from where reduction in the cardiac Débit. The passive filling of the ventricles also will be as for him disturbed by the speed of the heart rate.
of the embolic consequences: risk formation of a Thrombus in the left auricle.

Occurred of auricular fibrillation is favoured:

when the left auricle is dilated (diameter > 5 cm with echography),
when the auricular fibers are subjected to a rise in the rate of Thyroxine, or of Catécholamine S.

At the time of an auricular fibrillation, the auricular frequency exceeds the 300/mn. Because of presence of the auriculo-ventricular Node, the entirety of the auricular electrical signal is filtered: the ventricle beats then at a frequency quite less than the auricles even if there remains fast, thus ensuring, most of the time, a correct tolerance, at least at rest.

Diagnosis

Functional signs

The patient can be completely asymptomatic (does not complain about nothing) and the fibrillation discovered during a electrocardiogram makes for very an other reason.

the Palpitations, if they exist, are described classically with a progressive beginning and an end.
palpitations are sometimes felt like irregular.
the patient can complain about a tiredness (Asthénie), faintnesses (Lipothymie S), of breathlessness (Dyspnée).
It can complain about a thoracic Douleur (functional Angor).

Clinical examination

the cardiac rhythm is irregular, more or less fast (the heart rate owes, in this case, being estimated with the cardiac Auscultation and not with the Pouls, the figure under being very often estimated in this last case).
One systematic search for manner of the signs of Cardiac failure.
the presence of a transitory neurological deficit (transitory ischemic Accident) or present (Cerebral vascular accident made up) mark a complication of the arrhythmia.
One seeks signs in favor of a particular cause: HTA, Heart murmur, signs of Hyperthyroïdie, pulmonary Embolism, péricardite (pericardial friction)…

Complementary examinations

ECG

cardiac Echography

This examination visualizes the heart thanks to the Ultrason S. It makes it possible to seek the cause of an arrhythmia and to evaluate the repercussion of it on the cardiac muscle:

cardiac study of the valves S, in particular, search for anomalies of the mitral Valve being able to cause the arrhythmia;
study of the cardiac cavities: seek of a left ventricular hypertrophy (HVG), of a Thrombus in the left auricle, of an auricular dilation, the latter being able to be the cause of the arrhythmia, but also the consequence of the latter if it is old;
characters of a Cardiac failure (systolic or diastolic) if it exists.

Other examinations

At least:

standard biological assessment, comprising an assessment of the coagulation, an anticoagulant treatment being likely to be prescribed;
proportioning of the TSH in the search of a Hyperthyroïdie (proportioning is ploughed up in this case).

According to the cases:

pulmonary Radiography for the evaluation of the size of the heart and the search for a vascular overload testifying to a Cardiac failure;
cardiac Holter (recording of the ECG on 24:00) if the arrhythmia is paroxystic;

Etiology

Cardiac causes

arterial Hypertension;
mitral valvulopathies primarily ;
ischemic cardiopathies: Myocardial infarction, chronic coronaropathy;
Cardiomyopathie S (hypertrophic form dilated or );
Cardiopathie congenital: inter-auricular Communication;
Péricardite S acute or chronic;
pulmonary Embolism;
cardiac Surgery postoperative;
Syndrome of Wolf-Parkinson-White.
Syndrome tachycardia-bradycardia

Extra-cardiac causes

Hyperthyroïdie ;
Phéochromocytome ;
thoracic pathologies: Cancer, Infection, épanchement pleural;
Infection S acute;
acute ethyl intoxication;
intracranial hemorrhages, cerebral tumor.

Forms Idiopathique S

No cause is then found. They are current, especially at the old subject.

Evolution and complications

Auricular fibrillation is generally controlled with an adapted treatment. However, its tendency " naturelle" is with the chronicisation. Moreover, it can be the source of multiple complications:

increase in cardiovascular mortality (risk multiplied by 2) and in the total Mortality;
accidents thrombo-embolic: in particular, risk of Cerebral vascular accident;
Cardiac failure;
repetitions;
rhythmic disease of the auricle: association of a hyperexcitability and a Bradycardia (sinusal or sino-auricular Block);
complications Iatrogenic S (i.e., secondary with the treatment);
in the particular case of the Syndrome of Wolf-Parkinson-White: auricular fibrillation exposes to the ventricular risk of Fibrillation and thus of Sudden death.

Treatment

It rests on:

The reduction of fibrillation

I.e. the return at normal intervals said " sinusal".

it can be obtained by the administration of Médicament S or by external electric shock.
it must always be tried after setting under effective treatment Anticoagulant during at least 3 weeks, or after echocardiography trans-oesophagienne to check the absence of thrombus in the auricles.
it is all the more easy as fibrillation is recent.

medicamentous reduction: use of Antiarythmique S of the type Amiodarone per bone or IV;
electric reduction (Défibrillation) under general anesthesia short; the drugs Digitalique S having to be stopped since more than 48 hours.

a reduction should not be tried in the event of old auricular fibrillation tolerated well, because of the very high percentage of early repetition of the arrhythmia.

The maintenance in sinusal rate/rhythm

After reduction, it is carried out by the regulation of drugs antiarythmic per oral way (examples of molecules usable: Amiodarone, Propafenone, Disopyramide, Sotalol, Flécaïnide and Quinidine). The rate of repetitions remains however high.

The regulation of a medicamentous treatment antiarythmic is not obligatory if it is about a first crisis, of fast resolution, with a correct tolerance and the absence of subjacent cardiac disease.

Control of the heart rate

When the attempts at reduction showed a failure, or that there is a counter-indication with the reduction, one will be satisfied to slow down the cardiac rhythm in order to avoid the appearance of invalidating symptoms and a bad cardiac tolerance.

Drugs such as the Béta-blocking S, the calcic inhibiting bradycardisants (Diltiazem and Vérapamil), as well as the Digoxine (to a lesser extent the Amiodarone, because of its multiple long-term side effects) can be used.

The objective is to maintain the heart rate of rest to less than 80 beats per minute.

In the event of failure, it is possible to carry out a " déconnexion" between the auricle S and the Ventricle S by a technique of radio frequency which will destroy the Faisceau of His. This method requires the installation of a final Cardiac pacemaker.

Prevention of the formation of a Thrombus in the auricle

At the beginning, a treatment Anticoagulant by Héparine (standard Heparin into intravenous or subcutaneous or Heparins of low molecular weight into subcutaneous) is founded. This treatment is relayed by a anticoagulation by oral way using the Antivitamines K (AVK).

In general, the anticoagulant treatment is continued at least 1 month after the reduction then stopped if the arrhythmia is regarded as stabilized (not of repetition).

If the arrhythmia persists, the maintenance of the anticoagulation must be discussed the more so as the patient is old, that it is complicated of an accident embolic and that there exists a cardiac disease. The accident risk embolic is decreased of almost 60% in this case. In certain cases, the risk of an anticoagulant treatment is higher than the awaited benefit; one then prefers to use the plate antiagrégants: primarily the aspirine. This last showed a certain effectiveness in the prevention of the accidents embolic but with a degree definitely less than for the anticoagulant treatment

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