diease

Aortic Stenosis


OVERVIEW OF Aortic Stenosis :

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


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


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.


CAUSES :

Congenital heart defect: Some children are born with an aortic valve that has only two cusps (bicuspid aortic valve) instead of three (tricuspid aortic valve). Rarely, an aortic valve may have one (unicuspid) or four (quadricuspid) cusps.

Calcium buildup on the valve:

Calcium is the mineral found in the boody.as blood steadily flows through the tissues the calcium is collected from the tissue and it might get deposited in the aortic valve.

Rheumatic fever:

The complication of strep throat is the formation of scar tissue in the aortic valve and this results in narrowing of the valve.

Senile degenerative aortic stenosis

Congenital subvalvular aortic stenosis

Congenital supravalvular aortic stenosis


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


COMMON CLINICAL SIGNS AND SYMPTOMS :

Mild or moderate stenosis

Exertional dyspnoea

Angina

Exertional syncope due to minimal supply of blood to brain

Episodes of acute pulmonary oedema


DIAGNOSTIC :

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


TREATMENT AND PROGNOSIS :

Medications:

Statin therapy:

They prevent the deposition of cholesterol and reduces the osteoblastic activity.

Betablockers and calcium channel blocker.Nitrates are contraindicated in the aortic stenosis patients as it might cause hypotension in them.

Anticoagulants are indicated in patients who has atrial fibrillation or those who had a valve replacement with mechanical prosthesis.

 Aortic valve repair:

Aortic valve repair or aortic valve reconstruction describes the reconstruction of both form and function of the native and dysfunctioning aortic valve. Most frequently it is applied for the treatment of aortic regurgitation. It can also become necessary for the treatment of an aortic aneurysm, less frequently for congenital aortic stenosis.

Aortic valve replacement:

It is done in complicated cases.it is done by using open heart surgeries or minimally invasive cardiac operations.

Surgical and catheter therapy:

The treatment of aortic stenosis is balloon aortic valvulotomy.The balloon is carefully placed in the stenotic aortic valve and expansion of the valve is done using the monitor.

Manual Prosthetic valves are available for the expansion of the stenotic aorta.they are coated with anticoagulants such as warfarin.

Biprosthetic valve made od 3 bovine tissue orifice does not require any anticoagulant coating.

Biprosthetic valve is less durable than manual valve and the durability is 15-20 years after the implantation.

Biological valves are man made.they are produced from pig,cow and human heart tissues.They have less risk for blood clots

 


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.


Recovery Period :

The time it takes to fully recover varies depending on factors like age and overall health.During aortic valve replacement with  surgeries usually requires 8-9 weeks.


REFERENCE :

http://cdc.in

Davidson principle of general medincine -22nd edition

http://medicinenews.in

http://clevelandclinic.com