AORTIC STENOSIS

AORTIC STENOSIS

WHAT IS IT

Aortic stenosis is the obstruction of blood flow across the aortic valve. The results in a decrease of total blood sent to the body.

SYMPTOMS

For Aortic Stenosis, symptoms usually take 10-20 years to develop. The classic triad of symptoms in patients with aortic stenosis is as follows:

• Chest pain that is made worse with exertion and resolves with rest.
• Heart failure: Symptoms include paroxysmal nocturnal dyspnea, orthopnea, dyspnea on exertion, and shortness of breath
• Fainting due to lack of blood flow to the brain

WHAT CAUSES IT

Aortic stenosis can be caused by various conditions.

Congenital Heart Defect:  The aortic valve normally consists of 3 triangular-shaped leaflets.  However, some people are born with an aortic valve that only has one (unicuspid), two (bicuspid), or four (quadricuspid) leaflets.  Bicuspid valves are prone to calcification and scarring, which significantly narrows the aortic valve. This congenital defect occurs in about 2% of the population and is the most common cause of aortic stenosis in patients under 70 years old.  Although patients may be asymptomatic when they’re young, the 2-leaflet valve does not open as widely as a 3-leaflet valve.  Thus, the blood flow through the valve is more turbulent.  The increased wear and tear on the leaflets eventually leads to calcification and scarring.

Degenerative Calcific Aortic Stenosis: Calcium is a mineral found in your blood and can deposit on your heart valves.  As blood is continuously pumped through your aortic valve to the rest of your body, calcium deposits tends to accumulate as you get older. This is the most common cause of aortic stenosis in patients > 70 years old.  The valves become thickened and eventually less mobile.  It should be noted that these calcium deposits are not linked to taking calcium tablets or drinking calcium-fortified drinks.  Risk factors for this condition includes hypertension, hypercholesterolemia, diabetes mellitus, and smoking.

Rheumatic Fever: Rheumatic fever is a complication that results from untreated strep throat infections by Group A streptococcal bacteria.  Scar tissue forms on the aortic valve and also creates a rough surface for more calcium to accumulate on.  Fibrosis of the valves can also cause the leaflets to fuse together, narrowing the aortic valve.  Although rheumatic fever is uncommon in the United States, it is the most common cause of aortic stenosis in all age groups in developing countries.

WHY DO WE CARE

When the aortic valve becomes stenotic, blood flow to the body encounters high resistance, decreasing the amount of blood flow through the valve. This increased resistance causes the left ventricle pressure to increase as well, putting unnecessary amount of strain on the heart. Overall, there is a decrease in cardiac output of blood flow to the rest of the body eventually causing heart failure. Furthermore, the increased strain on the heart leads to a decrease in the amount of blood supplying the heart itself, which can lead to a heart attack.

HOW DO WE TREAT IT

If you are not experiencing any symptoms, medical therapy is not necessary and only close observation until symptoms develop.  You should be seen by your cardiologist and evaulated with echocardiography to monitor disease progression.  If you have moderate aortic stenosis (valve area 1.5-1.0 cm²), it is recommended that you avoid strenuous activities such as weight lifting.

Medications may help treat symptoms temporarily but they cannot reverse aortic stenosis. Lowering blood pressure may slow the progression of this condition. Balloon Valvuloplasty is another option that is mainly used as a palliative measure for patients who are not surgical candidates or used as a bridge to aortic valve replacement in patients with a poorly functioning heart.  This procedure provides only temporary relief because the valves eventually narrow again within 6-18 months.

The only definitive treatment for aortic stenosis is aortic valve replacement. The development of symptoms due to aortic stenosis provides a clear indication for replacement.

Bioprosthesis involves replacing aortic valves from those processed from pigs (porcine) or cows (bovine).  Bioprosthetic valves are less durable than mechanical valves and typically last 10-15 years.  However, they have the advantage of not requiring life-long blood thinning medication to prevent clots from forming on the valves.  These are good choices in older patients or in anyone who cannot take blood thinners.

Mechanical valves are much more durable and last 20-40 years.  They require life-long blood thinning medication such as Warfarin (Coumadin) to prevent clots from forming on the valves.

http://www.webmd.com/heart-disease/video/aortic-valve-replacement

REFERENCES:

http://www.uptodate.com/contents/clinical-features-and-evaluation-of-aortic-stenosis-in-adults?source=search_result&search=aortic+stenosis&selectedTitle=1%7E150#H5

http://www.mayoclinic.org/diseases-conditions/aortic-stenosis/basics/causes/con-20026329

http://www.merckmanuals.com/professional/cardiovascular_disorders/valvular_disorders/aortic_stenosis.htm

http://www.medicinenet.com/aortic_stenosis/page2.htm#what_causes_aortic_stenosis

http://emedicine.medscape.com/article/150638-overview#aw2aab6b2b4aa

http://emedicine.medscape.com/article/150638-overview