Tachycardia

Physiology

The normal Cardiac rhythm oscillates normally around 60 beats per minute for a Adulte and depends on multiple factors, generally without relationship with a cardiac disease: physical effort, anxiety, fever, catch of alcoholic drinks…

The normal goal of a tachycardia is to increase the cardiac Débit. This last equal to the heart rate is multiplied by the systolic volume of ejection . This last corresponds to the difference between diastolic volume (" ventricle plein") and stroke volume (" ventricle vide").

The normal cardiac rhythm is controlled by the sinusal Nœud, together of cells located in the right auricle, being depolarized rythmiquement. This node is stimulated by the Adrénaline (system hormonal sympathetic nerve) and slowed down by the Vagus.

A too important acceleration of the heart rate can involve, paradoxically, a fall of the flow, the ventricle not having more time to fill.

An acceleration of the heart rate will increase the requirements in Oxygène cardiac muscle. If its contribution is insufficient (because of an attack of the coronary arteries for example), that can involve a myocardic ischaemia being able to be responsible for a Cardiac failure or a thoracic Douleur with type of Angina pectoris.

An excessive and prolonged tachycardia, from its acceleration, can be a dangerous phenomenon. Indeed the acceleration of the cardiac muscle involves a demand additional for resources. However the perfusion of the cardiac muscle is done during the diastole. By increasing the rate/rhythm, one decreases the time of diastole and thus of perfusion whereas the muscle, on the contrary requires more resources.

Tachycardia can be felt as of the Palpitations where the subject feels its cardiac beats like unpleasant. It is very often, on the contrary, completely asymptomatic (the subject does not feel anything and the diagnosis is made by another person by the catch of the Pouls for example). The asymptomatic character or not prejudges neither gravity, nor of the cause.

Causes

Noncardiac causes

It is about a sinusal tachycardia , corresponding to a normal response of the heart to certain stimulations.
Elle generally asymptomatic and is relatively well tolerated, except in the event of Cardiopathie subjacent advanced.
L' ECG watch:

an accelerated cardiac rhythm (in general > 100 per minute),
a tachycardia regular, permanent,
" sinusale" means that each complex QRS is preceded by a wave P (aspect ECG is that of a normal ECG with an accelerated rate/rhythm),
complexes QRS have a normal aspect (except in the event of preexistent Bloc of branch).

The causes can be multiple:

at the time of an physical effort,
a Stress (whatever is the cause), which will involve an increase in secretion of Adrénaline and thus an increase in the heart rate, the Anxiété,
a Fièvre,
in the event of Déshydratation,
in the event of fall of the oxygenation of blood: Anemia (by deficit in Hemoglobin), in the event of pulmonary Embolism,
the catch of some exciting (Cafeine, Amphetamine S for example) can increase the heart rate directly,
a Sécrétion inappropriate of Adrénaline (in the case of a Phéochromocytome for example), in the event of Hyperthyroïdie, or of disordered state of the secretion of the Cortisol.
an excessive consumption and specific of alcohol (example of the Binge-drinking),
there exist also cases of constitutional sinusal tachycardia (without found cause).

Cardiac causes (except disorders of rate/rhythm)

Any fall of the cardiac flow involves an acceleration of the rate/rhythm by secretion of Adrénaline in order to try to restore a satisfactory flow.
C' is the case:

lowers blood Pressure (Hypotension), in the cardiac Collapsus of origin,
in the event of pulmonary Embolie,
of the Cardiac failure by an adaptation mechanism,

Tachycardia by disorders of the cardiac rhythm

Treatment

For the noncardiac causes, it is initially necessary to treat the cause and not obligatorily to slow down the cardiac rhythm by drugs.
In the event of tachycardia badly tolerated or invalidating, possibility of having recourse to certain drugs Antiarythmique S, Beat-blocking S.
Pour the cardiac causes, the treatment is function of the Cardiopathie or the disorder of the responsible rate/rhythm.

Another direction of the term

The Takicardie is the name of the imaginary Pays directed by the struck king of strabism of the King and the bird.

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