Aortic stenosis represents the damage of the aortic valve due to the obstruction of blood flow from the left ventricle into the aorta.
This pathology is the most frequent type of obstruction and is also the most common, having the third place in the frequency of cardiovascular disease in Europe and North America.
Ischemic heart disease and hypertension occupy the other two places.
The prevalence of aortic stenosis tends to be growing, and this is mainly due to the general context of aging in the population.
For a better understanding of the manifestations and signs of valvular pathologies, we must understand how they work and their role in the circulation of the blood.
It is known that the heart consists of four chambers: two atria and two ventricles. The separation between the four rooms is through two valves, which act in unidirectional flow of blood – from the atria to the ventricles. So between the left atrium and left ventricle we can find the mitral valve and between the right atrium and right ventricle there is the tricuspid valve.
From the heart, from each of the ventricles, two major vessels leave; they are the pulmonary artery with origin in the right ventricle, and the aorta starting in the left ventricle.
To ensure the unidirectional flow of blood from the ventricle into the arteries, there are two valves: the aortic valve between the left ventricle and the aorta and the pulmonary valve between the right ventricle and the pulmonary artery.
Summarizing these findings, the blood has a unidirectional flow from the atria to the ventricles and from there on throughout the body through large calibre vessels, the pulmonary artery and aorta. Any retrograde flow of blood denotes the existence of valvular pathology.
Causes of aortic stenosis
Largely, aortic stenosis can be classified into congenital aortic stenosis, meaning that the valves are damaged at birth, and acquired aortic stenosis, which can be of several causes. The most common forms of acquired aortic stenosis are the degenerative form and the rheumatic form.
Congenital form – is an abnormality of the valve that is present at birth
The aortic valve normally consists of three wafers, known in the literature as the leaflets. In the form of congenital aortic stenosis, the valve can be unicuspidal (shows one cusp), bicuspid (shows two cusps), tricuspid (has three leaflets, but the shape and size are affected) and more rarely we can meet a cvadricuspid valve (shows four cusps).
Unicuspidal aortic valve is the cause to blame for most situations of stenosis in young children and is the most responsible valvular malformation of death in children under 1 year.
Of all the forms of congenital aortic stenosis, the bicuspidal is the most common in adults and has an “affinity” for males. During childhood, bicuspidal aortic stenosis accompanies no valve dysfunction, but all patients will require surgery to correct the abnormalities in the course of life.
The rheumatic form comes following an acute episode of rheumatic fever, pathology that occurs after an infection with Group A beta haemolytic streptococcus. In time, it leads to valvular calcification and the opening of the valve is limited. This way, there is an obstacle while emptying the left ventricle into the aorta and it causes decreased cardiac output.
The degenerative form is known as aortic stenosis with calcification of the valves. This form of aortic stenosis is the most common in adults.
Degeneration (calcification) of a valve can occur both in a normal valve and in one with congenital defects. Initially, it was believed that the process of calcification occurs passively, following the mechanical stress during which the valve was put during the blood flow; eventually, some studies reached a new concept known as calcified aortic valve with aortic disease. The study concluded this process is biologically active, very much resembling the process that occurs in vascular atherosclerosis (plaque formation).
The effects of aortic stenosis on the heart
The first effect aortic stenosis has on the heart is left ventricular hypertrophy.
The heart consists of four chambers that are designed to direct the oxygenated blood from the lungs throughout the body and deoxygenated blood received from the body to the lungs to be oxygenated; the responsible chambers for redirecting oxygenated blood from the lungs to the entire body are the left atrium and the left ventricle, the latter bringing its greatest contribution to this function.
In a person with normal aortic valve the blood flow has one direction only, from the left ventricle to the aorta, due to the presence of this valve.
In aortic stenosis, the aortic valve is not opened normally and produces an obstacle in draining the blood, thus forcing the ventricle to develop a greater force to overcome this obstacle. The higher the degree of stenosis, the greater the force the left ventricle has to develop.
The degree of stenosis in the aortic valve is determined by measuring the orifice in the affected valve. In case of larger than 1.5 square cm wide we call it large aortic stenosis, if the size is between 1 -1.5 cm square we call it average aortic stenosis and if it is smaller than 1 cm square, it is called critical aortic stenosis.
Considering the efforts of the left ventricle in order to eject the necessary amount of blood in the circulation to maintain the metabolic processes, it suffers hypertrophy and muscle growth. In other words, the heart’s response to the obstacle created by the aortic stenosis is to increase the muscle mass in the left ventricle.
This increase in the muscle mass will also lead to other effects that aortic stenosis has on the heart, such as myocardial ischemia, impaired diastolic function and impaired ventricular systolic function of the left ventricle.
The diagnosis of aortic stenosis
The clinical picture of the disease associated with laboratory investigations (ECG, imaging, cardiac catheterization, biological samples, etc.) ultimately lead to the diagnosis of this pathology.
A long period of time, aortic stenosis remains asymptomatic and is discovered in routine investigations or during investigations of other pathologies.
The occurrence of symptoms in aortic stenosis highlights an important moment in the disease because without surgery, the patient’s survival rate decreases dramatically. A careful history is a key element in evaluating these patients.
The most common symptoms of aortic stenosis which also warn the doctor about the seriousness of the disease are: dyspnea (shortness of breath), angina (chest pain) and syncope (fainting with loss of consciousness).
Investigations in patients with aortic stenosis can be divided into primary and secondary investigations.
Primary investigations include: ECG – shows the hypertrophy of the left ventricle in more than three quarters of the patients; cardiopulmonary radiography; echocardiography – is the key investigation in the diagnosis of aortic stenosis.
The clinical diagnosis is confirmed using echocardiography, the severity of stenosis and the prognosis are estimated and lesions associated with this condition can be highlighted. It is a non-invasive technique, easy to repeat and provides the necessary information to evaluate the need of surgery.
Secondary investigations carried out in patients with aortic stenosis are: cardiac catheterization and angiography – the method through which you can view the anatomy and permeability of the coronary vessels (the vessels supplying the heart).
If the patients experiences chest pain or shows cardiovascular risk factors, they should benefit from surgery or undergo an interventional process: coronarography (a form of angiography) to view the anatomy and function of the coronary vessels, effort ECG, blood tests. Other tests that may be performed are: computed tomography, magnetic resonance imaging (MRI / NMR), etc.
Treatment of the aortic stenosis
The treatment can be divided into: a) non-pharmacological treatment; b) pharmacological treatment; c) Interventional treatment and d) surgery.
- a) Non-Pharmacologic Treatment – represents all the hygienic-dietary measures (physical activity, diet, stopping vices) that the patient must take into account to improve the symptoms and the disease.
- b) Pharmacological treatment – represents the correction of cardiovascular risk factors that could lead to a more rapid installation of the symptoms. It is recommended the use of statins in patients with high cholesterol, oral agents or insulin in patients with diabetes, antihypertensive medication in patients with hypertension, etc.
- c) Interventional Treatment – is a modern technique, minimally-invasive, through which the stenotic aortic valve is corrected.
- d) Surgery – indicated for patients who failed interventional therapy or patients with contraindications for performing interventional techniques.