Hypertrophic cardiomyopathy: the thickness of the left ventricular walls is increased in some areas or in a pervasive manner.

Hypertrophic cardiomyopathy

La Hypertrophic cardiomyopathy (HCM) is a disease of the heart muscle characterized by the presence of increased thickness of the walls of the left ventricle (VS) (left ventricular hypertrophy) not secondary to arterial hypertension, heart valve disease or other causes that can generate an increase in wall thickness.

The diagnosis of HCM in the adult is given when the thickness of even one wall of the LV is equal to or greater than XNUMX mm, measured by echocardiography or MRI. Hypertrophy can only be present in the interventricular septum, i.e. the portion of muscle that separates the two ventricles (asymmetric septal hypertrophy), but it can also extend to all walls (concentric hypertrophy). In about 10% of patients it is localized in the midventricular level (midventricular HCM), while localization at the tip of the heart (apical HCM) is common in Asians (25%) and rare in Europeans (7%).

In the presence of mild hypertrophy (13--14mm); the diagnosis of Hypertrophic cardiomyopathy may be given if there are also major ECG abnormalities and / or genetic mutations considered responsible for hypertrophy and / or at least a family member who has or has had HCM.

Its prevalence in the general population is about XNUMX per thousand. But given that the majority of HCM develop slowly and progressively after adolescence, the prevalence is lower in childhood and much higher, up to XNUMX per thousand, namely XNUMX%, in adults, particularly between the ages of 30 and 60. Consequently it is not considered a rare disease.

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In females, hypertrophy development occurs later, even in the sixth or seventh decade of life. The course of Hypertrophic cardiomyopathy may be worse in these cases, as well as in those of patients who have HCM since the pediatric age. The extent of hypertrophy is variable, from mild (15-20 mm) to extreme forms, with diffuse thicknesses up to 4 cm.

In the majority of patients, Hypertrophic cardiomyopathy is caused by one or more genetic mutations that can be identified, with current techniques, in about XNUMX% of family cases, in the genes that produce contractile proteins of the sarcomere ( Myosin-binding protein C, Myosin, Troponin). In these cases, HCM is defined as "sarcomeric". In about 5% of family cases, two mutations can be identified in the same gene or in two different genes which can be carried, for example, by both the father (one mutation) and the mother (a second mutation).

Initially,  HCM is often asymptomatic, i.e. the symptoms may be absent or not perceived by the patient and the diagnosis in these cases is made by random checks such as during a sports doctor visit. The most common symptoms, when present, are: palpitations, difficulty making efforts such as climbing stairs due to shortness of breath ("dyspnea"), chest pain at rest or from exertion, sudden loss of consciousness ("syncope").

To make the diagnosis, it is necessary to perform non-invasive clinical and instrumental examinations (medical examination, basic electrocardiogram and echocardiogram). Other investigations are then carried out, which include blood chemistry tests, dynamic ECG for 48 hours, stress or cardiorespiratory tests, magnetic resonance with contrast. These allow the doctor to assess the severity of heart disease and any risk of complications. The results of these tests, together with those of the genetic examination, carried out with the patient's consent after carrying out a genetic consultation, can establish with sufficient accuracy, the specific genetic cause of HCM and the most appropriate therapy, with the aim of mitigating or eliminating symptoms and reducing the risk of complications.

Therapy can be different, based on the specific genetic mutation that causes hypertrophic cardiomyopathy.

Once the diagnosis has been made, it is therefore necessary to try to identify the cause of hypertrophy and distinguish Sarcomeric HCM from other Cardiomyopathies such as syndromic and metabolic forms at birth, mitochondrial or glycogen accumulation forms, and in the adult, Fabry disease, and cardiac amyloidosis.

HCM can change over time: wall thicknesses tend to decrease, while the diameters of the left atrial chamber and left ventricle increase by one or more centimeters over time ("remodeling"). Inside the walls of the LV, scarred areas composed of fibrotic tissue may appear, which can be highlighted and then observed over time by MRI with contrast.

Hypertrophic Cardiomyopathy (different locations and entities seen in MRI)