diease

Aortic Stenosis


Aortic Stenosis overview and Definition

Aortic stenosis is termed as the narrowing of the aortic valve.The aortic valve helps to transfer the blood from left ventricle to the aorta which in tuen supplies the blood to the vital organs and other tissues


Epidemiology

Epidemiology:it occus in 2% of people of 65 years.It is more common among men than women.A study says people on bisphosphonates has less progression to aortic stenosis.20-30% of the population tends to have aortic scelerosis.


Structure of Aortic Stenosis

The normal aortic valve is a trileaflet structure located at the junction between the left ventricular outflow tract and the aortic root. The leaflets are composed of three distinct layers, which from the aortic to ventricular surface are the fibrosa, spongiosa, and ventricularis. This leaflet structure is covered on both the ventricular and aortic surfaces by endothelium in continuity with both the ventricular endocardium and the aortic endothelium. Each layer of the aortic valve has a distinct structure and function: the fibrosa contains circumferentially oriented collagen fibers, which provide most of the strength of the leaflets; the spongiosa is found at the bases of the leaflets, contains mucopolysaccharides, and functions to resist compressive forces and facilitate movements between the fibrosa and ventricularis during leaflet motion; and the ventricularis contains radially oriented elastin and contributes to the flexibility of the leaflet


Pathophysiology

The human aortic valve consists of three cusps or leaflets and has an small opening. When the left ventricle contracts, it forces blood through the valve into the aorta and subsequently to the rest of the body. When the left ventricle expands again, the aortic valve closes and prevents the blood in the aorta from flowing backward -regurgitationinto the left ventricle. In aortic stenosis, the opening of the aortic valve becomes narrowed or constricted -stenotic (e.g., due to calcification). Degenerative (the most common variety), and bicuspid aortic stenosis both begin with damage to endothelialm cellsfrom increased mechanical stress.Inflammation is thought to be involved in the earlier stages of the pathogenesis of AS and its associated risk factors are known to promote the deposition of LDL cholesterol and lipoprotei  A, a highly damaging substance, into the aortic valve, causing significant damage and stenosis over time.

As a consequence of this stenosis, the left ventricle must generate a higher pressure with each contraction to effectively move blood forward into the aorta. Initially, the LV generates this increased pressure by thickening its muscular walls (myocardial hypertrophy). The type of hypertrophy most commonly seen in AS is known as concentric hypertrophy, in which the walls of the LV are (approximately) equally thickened.

In the later stages, the left ventricle dilates, the wall thins, and the systolic function deteriorates (resulting in impaired ability to pump blood forward. Research was in progress to see if different coronary anatomy might lead to turbulent flow at the level of valves leading to inflammation and degeneration


Clinical signs & symptoms

Mild or moderate stenosis

Exertional dyspnoea

Angina

Exertional syncope due to minimal supply of blood to brain

Episodes of acute pulmonary oedema


Differential Diagnosis

Electrocardiogram:

Left ventricular hypertrophy is seen

Left bundle branch is also seen

Chest xray:

It shows enlarged left ventricle

Dilatation of the ascending aorta

Calcification is also shown by xray on lateral view

Doppler:

Measurement of severity of stenosis

Detection of associated aortic regurgitation

Cardiac catheterisation:

May be used to measure the gradient between left ventricle and aorta.it measures pressure on both the sides of the aortic valve.

Echocardiogram:

 Echocardiogram (heart ultrasound) is the best non-invasive way to evaluate the aortic valve anatomy and function


Prevention

Eat a healthy diet

Keep blood pressure under check

Avoid food containing high amounts of cholesterol

Quit smoking

Keep your teeth and guma healthy:Reseachers beleive that there is a connection between the infection in the heart and oral cavity

Get your heart murmur checked.


Reference

http://cdc.in

Davidson principle of general medincine -22nd edition

http://medicinenews.in

http://clevelandclinic.com