Hypertrophic Cardiomyopathy

A hypertrophic cardiomyopathy is a form of Cardiomyopathie (literally, disease of the cardiac muscle ) in which it exists a hypertrophy of a more or less great part of the cardiac muscle.

In this pathology, the normal structure of the muscular fabric cardiac is disturbed and will also be able, in addition to the disturbances related to myocardic hypertrophy, to involve disturbances of the electric functions of the heart.

There exist four great types of cardiomyopathies: the Cardiomyopathie dilated, the restrictive Cardiomyopathie, the ventricular cardimyopathy right arythmogene and hypertrophic cardiomyopathy.

The hypertrophic cardiomyopathy is recognized like origin Génétique, secondary with change S on some Gène S coding of the muscular Protéine S .

According to the degree of obstruction to the flow of blood flow coming from the left ventricle, the hypertrophic cardiomyopathy will be defined with or without obstruction.

This pathology is also known under the name of sténose under-aortic or of obstructive cardiomyopathy .

Epidemiology

The hypertrophic cardiomyopathy is met at all the ethnic groups.
La sporadic form more often reaches the men than the women, towards the age of 30-40 years. The family form more frequently reaches as for it the women and occurs more precociously.

The Risk factors of Sudden death are: a young age at the time of the diagnosis (less than 30 years), a family history of hypertrophic cardiomyopathy with sudden death, the specific change S on the Gene S coding the Troponine T and the Myosine, a tachycardia to supra-ventriculair E or ventricular supported, Syncope S with repetition, a inter-ventricular septum thickened beyond three centimetres, a loss of adaptability with the effort.

Physiopathology

Physiological mechanisms and anatomopathology

In microscopy, one assists with a disorganization of the myocardic fibers, which are not any more laid out in parallels but in an anarchistic way, with muscular cells very hypertrophied. The amorphous fabric located between the muscle fibers proliferates, which increases the rigidity of the cardiac muscle gradually.

Anatomically, the subjects reaches of a hypertrophic cardiomyopathy present, to differing degree, a hypertrophy of the left ventricle. Generally, it is about an asymmetrical hypertrophy, interesting the inter-ventricular septum (one speaks about asymmetrical septal hypertrophy ); but it can be total. This asymmetrical hypertrophy contrasts with the concentric hypertrophy which one meets in the aortic sténose or the arterial Hypertension. The septum is thickened generally more on the level of its upper part, creating a pad making covered in the left ventricle.

The hypertrophied muscle contracts normally. However, the pad will be responsible for one obstruction to the ejection of blood starting from the left ventricle. The degree of obstruction is variable east depends on the quantity of blood present in the left ventricle right before the contraction (Systole) ventricular. The systolic function thus will be reached by the systolic obstruction ventricular left (mainly in the obstructive form).

Moreover, difficulties join it the filling of the ventricle because the Myocarde is more rigid and is slackened badly after the Systole. The consequences of this phenomenon appear at the time of significant efforts, since the heart cannot increase the quantity of Sang necessary to the muscular activity.
Si this defect of filling is too important, blood stagnates in the pulmonary vessels and makes increase the pressure in the fabrics. If the pressure is too high, water invades the Poumon S, it is the pulmonary edema.

Causes

It is presented in two forms: a sporadic form and a family form.

It is transmitted on the autosomic mode dominating and is related to Mutation S of a certain number of Gène S coding of the Protéine S muscular such, for examples, the heavy chain of beta Myosine (approximately 45% of the changes), the cardiac Actine, the troponine T cardiac, alpha Tropomyosine, the troponine I cardiac.

At the subjects not having family history of hypertrophic cardiomyopathy, the most current cause of this disease occurred of a Mutation of novo of gene coding the heavy chain of beta-myosine.

Diagnosis

Clinical symptomatology is variable. Many subjects remain a long time asymptomatic (or not very symptomatic).

Functional signs

The functional signs include Dyspnée effort (breathlessness), thoracic pains (typical or atypical), Palpitation S, Asthénie, Lipothymie S, Syncope S and Sudden death. They are not specific of this disease.

Clinical examination

With the Sounding, in the obstructive form, there exists a systolic breath similar to that heard in the aortic sténose. However, this noise increases intensity with any operation tending to decrease the volume of Sang in the left ventricle (example at the time of the Manœuvre of Valsalva). A breath of mitral Insuffisance is frequent.

Complementary examinations

The electrocardiogram is generally abnormal. One can find signs of left ventricular Hypertrophie, waves Q (aspect of pseudo-necroses), of the turbid of conduction and the repolarization. These anomalies are however not specific.
Un Holter-ECG (recording ECG over 12 midnight) could be carried out in case of doubt about a paroxystic arrhythmia.

On the pulmonary Radiography , the Cardiomégalie (increase in size of the cardiac silhouette) is generally moderate.

The cardic echography is the best examination for the diagnosis. Trans-thoracic echography could be coupled to a trans-œsophagienne echography, which will allow images plus précices because the probe is then closer to the heart.
Elle allows of visualier the cardiac muscle, to study its movement at the time of the cardiac cycle, as well as the valves and allows the measurement thickness of the walls and the size of the cardiac cavities.
Elle watch a hypertrophy of the asymmetrical inter-ventricular septum with a posterior report/ratio thickness septum/wall superior with 1,3 and will seek an obstruction with the ejection of blood.
Avec the Doppler, it will be possible to measure the speed of blood flow through the cardiac valves and to evaluate the pressures in the cardiac cavities. The sealing of the cardiac valves also could be studied. It could thus be highlighted a premature closing partial of the aortic valves.

The realization of a cardiac Cathétérisme is proposed. At the healthy individuals, during the ventricular Systole, the pressures in the Aorta and the left ventricle are equalized, and the aortic valves will open. To the subjects reached of cardiomyopathy hypertrophic (or sténose aortic, the phenomenon being the same one), it will create a gradient (a difference) of pressure between the left ventricle and the Aorte, the pressures on the level of the ventricle being higher than the aortic pressures. This gradient represents the degree of obstruction which must be surmounted so that the ventricle ejects the blood which it contains towards the aorta.

Clinical forms

The obstructive form is characterized by a systolic breath of ejection, a left ventricular cavity very deformed, an asymmetrical septal hypertrophy and the presence of a intra-ventricular gradient of pressure.
Dans the nonobstructive form , it does not have there a breath éjectionnel and it hypertrophy is more diffuse.

Assumption of responsibility

The purpose of the treatment is to decrease the gradient of pressure between the left ventricle and the aorta, and the symptoms such as dyspnea, the thoracic pains and syncopes.

The medical care is effective at the majority of the patients. Are used the Bêta-bloquant S, the Vérapamil (a calcic Inhibiteur), the Diurétique S, Antiarythmique S, even a treatment Anticoagulant in the event of cardiac arrhythmia.

At the subjects carrying a severe form obstructive and which remain symptomatic and very constrained in spite of a maximum medical care, two techniques can be proposed:

the septal myotomie-myectomy . It is about a surgical intervention only palliative. It consists in trenching in the hypertrophied wall of the septum to reduce the muscular mass.
the septal alcoholization , introduced by Sigwart in 1994 in alternative to the surgery. It corresponds to the chemical destruction of part of the septum by the local alcohol injection to 95 degrees in a perforating branch of a coronary artery by catheterization, the goal being to cause a infarction myocardic localized within the septum. It is also about a palliative treatment.

Certain patients profits from the establishment of a Cardiac pacemaker, even of a automatic Défibrillateur.

For the refractory patients with the medical care, a heart Transplant is to be discussed.

Evolution and complications

The evolution of the hypertrophic cardiomyopathy is slow and progressive, with installation of a Cardiac failure. It is variable because it can remain during long years tolerated well.

The complications are the Embolie S systemic, the bacterial Endocardite (primarily of the mitral valve), the turbid of the rate/rhythm (auricular Fibrillation and others supra-ventricular tachycardias, ventricular Tachycardie even ventricular Fibrillation).

The Sudden death remains the main risk of this pathology that it is for the obstructive form or the nonobstructive form. This risk is independent of the degree of obstruction.

In the animals

The hypertrophic Cardiomyopathie cat-like is the most frequent Cardiomyopathie at the Chat. The progression of the disease and its origin Génétique seem to be similar to human pathology.

Notes and references of the article

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