A normal, healthy heart is about the size of a closed fist. However, if the heart muscle is thickened, it is enlarged, as this is a disease characterized by a thickening of the walls of the ventricles. Medically, it is also known as hypertrophic cardiomyopathy.
In most cases, the heart is not evenly affected by the thickening, as the left ventricle is the preferred site for thickening. This can have different causes and, depending on its severity, can have different consequences. Basically, a distinction must be made between physiological – i.e. natural – thickening of the heart muscle in people who are very active in sports and pathological – i.e. abnormal – thickening of the heart muscle due to continuous stress on the heart.
The causes of heart muscle thickening are manifold. In people who are very active in sports, the heart thickens because they are used to pumping a lot and strongly. Not only the athlete’s skeletal muscles, but also the heart becomes stronger under physical stress.
This makes sense because the athlete’s heart is able to transport more blood volume with fewer beats and therefore works more efficiently under stress. However, the heart can also enlarge pathologically. The most common cause of this is permanent high blood pressure.
A narrowing of the aortic valve, i.e. the valve between the left ventricle and the aorta, (aortic valve stenosis) also causes a sharp increase in pressure on the walls of the heart muscle. These thicken compensatorily. Usually only the left ventricle is affected.
If the right ventricle thickens, the most common causes are an increase in pressure in the pulmonary circulation, for example due to various pulmonary diseases, or a narrowing of the pulmonary valve, the valve between the right ventricle and the pulmonary artery. From a medical point of view, two different forms of heart muscle thickening can be distinguished: the concentric form and the eccentric form. Concentric heart muscle thickening is caused by pure pressure load, for example high blood pressure.
This causes the walls of the heart muscle to thicken, so that the interior of the heart chambers is reduced. The walls of the heart become stiffer as a result of the thickening and can no longer relax as well during the filling phase of the heart. As a result, less blood flows into the heart.
As a result, it can also no longer discharge as much blood – the pumping action becomes inefficient. Eccentric heart muscle thickening is a combination of pressure and volume loading. This occurs, for example, when the aortic valve becomes leaky (aortic valve insufficiency).
As a result, a certain amount of the blood ejected from the heart flows back into the heart during the relaxation phase (diastole). This results in an unnaturally high blood volume in the ventricle, which causes the walls of the ventricle to be stretched. These thicken compensatorily. At the same time, the ventricle virtually becomes empty, i.e. the ventricular volume increases.