Treatment and Management for Aortic Stenosis

Treatment should be done based on symptoms; often the severity is a good indication.

SURGICAL
Harden valves by calcification and deformities should undergo surgery.
Note: Valve replacement is necessary for all symptomatic patients.
This is because prognosis of patients with onset syncope, angina or heart failure due to aortic stenosis is poor, about 50% 3-year mortality rate.
Aortic Valve Replacement
3 types
1. Mechanical
Pros
-Most durable
- Recommended for 60 y.o and below
- anticoagulation can be accomplished at lower risk
Cons
-Need of anticoagulants-- Thromboembolic complications possible in the absence of anticoagulation include stroke and fixation of the valve in either the open or closed position.
Type of valve:
Caged-ball and tilting-disk valves were popular in the twentieth century, the bileaflet valves are most commonly used today.


2. Pulmonic valve transplantation (Ross Procedure)
- patient's native pulmonic valve (autograft) is removed and sewn into the aortic position.
-prosthetic valve or a pulmonic homograft is then sewn into the pulmonic position.
Pros:
- Own biological valves has excellent hemodynamic characteristics, plus durability esp during high pressure, high stress and when left sided circuit where prostheses can fail.
- Low stress on pulmonary valves as it is low pressure and low stress, it is better to place the bioprosthesis here rather than the aortic valve position.
Cons:
-Amount of surgery is very demanding and tedious procedures.


3. Bioprostheses
2 types:
Heterographs
- From porcine aortic valve leaflets or bovine pericardium (both preserved with glutaraldehyde).
- Advantage: low thromboembolic potential. In the absence of atrial fibrillation, the risk of thromboembolism following aortic valve bioprosthetic implantation is less than 1 event per 100 patient years, and anticoagulation is not required.
- Also if the patient is of normal sinus rhythm, anticoagulants are not needed.
- Disadvantage: If AS is accompanied with AF, risk of thromboembolism
: Durability low (approximately 50% of valves have failed within 15
Years.
: Calcification and degeneration of the valves leads to tears in the cusps or stenosis of the valve or flail leaflets.
: modest obstruction to outflow and a residual pressure gradient in patients requiring implantation of small valves.
Ideal Patients for heterographs: elderly patient whose life expectancy is less than the durability span of the valve or the patient for whom anticoagulation poses a significant risk.( above 65 y.o)





Homographs
- harvested from human donors.
- Pros: excellent hemodynamic profile
o relatively resistant to bacterial endocarditis
o more durable than heterograft valves
- Cons: use of homograft valves is limited by availability-- many potential donors for homograft valves are also whole-heart donors, the number of available homografts is small.
-Ideal for: patients with a small aortic root where other types of prostheses might cause a transvalvular gradient.
Alternative for surgery is
1. Balloon Dilatation ( Valvuloplasty)
Procedure: a thin tube (catheter) with a small deflated balloon at its tip (balloon-tipped catheter) is inserted through the skin in the groin area into a blood vessel, and then is threaded up to the opening of the narrowed heart valve. The balloon is inflated to stretch the valve open and relieve the valve obstruction.

4 hour procedure
Patient placed supine on the x-ray table
Upper leg is washed and treated with iodine to prepare for insertion of catheter.
Under local anesthesia, the cardiologist inserts the catheter to the blood vessel, which passes the smaller balloon tipped catheter through the first catheter.
Guided with an x-ray monitor, visualization of the catheter in the blood vessel can be monitored as it progressively enters the coronary artery in the heart.
The deflated blood vessel is placed at the opening of the valve and then inflated repeatedly to allow the pressure to dilate the valve.
This is done by splitting the valve leaflets apart.
Once widened, the balloon tipped catheter is removed.
The other catheter must remain in place for 6 to 12 hours because the procedure must be repeated.
2x ballon valvuloplasty is performed in high risk patients (elderly) as this is more efficient in restoring blood flow.

PHARMACOLOGICAL
Antibiotic prophylaxis
- infective Endocarditis
High risk infection in mitral valve prolapsed
High risk infection in valve replacement (accompaniment with aortic valve replacement)
High risk in thickened valve leaflets
Moderate risk in acquired valvular heart disease
Moderate risk in structural cardiac abnormalities
Drug Regimen (Note: For adults!)
Amoxicillin (beta lactam antibiotic, moderate spectrum, target cell wall for both gram negative and gram positive bacteria)= 3g oral 1 hour preprocedure or 2g IV <30>70
Weight < 50kg
Liver Failure
Recent history of bleeding
Recent surgery
International normalized ratio (INR): the ratio of the time taken for a patient's blood to clot compared with a normal person not taking warfarin. Thus a normal person will have an INR of 1.
INR should be maintained between 2.0 and 2.5
At the induction phase, monitoring of 1-3 days should be observed, until the INR target value is consecutive for 2 measurements.
After that, monitoring every 2-3 times a week is needed.
Note: Warfarin also can be used as a means of prevention of recurrent transient ischemic attacks
Contraindications of warfarin related to heart:
If the patient has subacute endocarditis, warfarin will cause hemorrhaging.
Also, pericarditis and pericardium effusion also is a contraindication of using warfarin

http://www.ohsu.edu/academic/medicine/residency//handouts/pharmpearls/General%20Care/WarfarinProtocol.pdf.

http://www.accessmedicine.com.ezproxy.lib.monash.edu.au/content.aspx?aID=3250101&searchStr=aortic+valve+stenosis

http://www.surgeryencyclopedia.com/A-Ce/Balloon-Valvuloplasty.html

http://www.accessmedicine.com.ezproxy.lib.monash.edu.au/content.aspx?aID=3646902&searchStr=aortic+valve+replacement#3646902

K. Parven & C. Michael (eds.) 2009, Kumar & Clark's Clinical Medicine Seventh Edition.