The following observations can be made in valve replacement surgery
Mitral valve function is closely linked to LV function while Aortic valve is not .
AVR patients always do well than MVR in the immediate post operative period
Aortic stenosis patients do well than aortic regurgitation .
Mitral stenosis patient do well than mitral regurgitation
In DVR the excess mortality is due to the addition of MV , not by AVR .
Aortic valve replacement has better post operative outcome when compared to mitral valve replacement ,Why ?
Aortic valve has only two components namely a annulus and leaflets. The prosthetic aortic valve replaces both these natural components . Mitral valve has 6 components , prosthetic mitral valve has only two components . Hence , any prosthetic mitral valve is far inferior to natural mitral valve . The pap muscle, chordae, and LV muscle fail to assist the artificial mitral valve. So , between AVR and MVR AVR is far perfect prosthetic surgery and the hemodynamics mimic as closely to the natural valve.
Why aortic stenosis patients do better than aortic regurgitation ?
Aortic stenosis results in severe LV outflow obstruction .The LV struggles to pump across the obstruction.So , once it is relieved by a prosthetic valve , there is great relief for LV .We know the the aortic valve orifice becomes <1cm2 in critical AS . (Like a pin hole !) .Prosthetic aortic valve at least doubles or triples this orifice and the LV enjoys this sudden relief and becomes active or even hyperactive in immediate post operative phase , later it settles to a near normal LV function. It has been observed even very severe LV dysfunction associated with aortic stenosis recovers well .
What happens in AVR done for dominant or isolated aortic regurgitation ?
Here the situation is dramatically opposite.The purpose of prosthetic aortic valve is reduce the aortic valve orifice .
In AR , the left ventricle is used to eject blood merrily across LVOT without much resistance , only to find part of the blood returning back into the chamber again . In the next beat it does the same and the cycle continues for ever .This in due course , dilates the LV and increases wall stress and afterload. LV dysfunction follows .This takes long time to set in.That’s why chronic asymptomatic AR patients do so well and they do not require surgery until after the onset of LV dysfunction .(End systolic LV >55mm)
After the aortic valve replacement , the LV suddenly finds the newly introduced prosthetic valve a hindrance !. As all artificial valves have less than the natural orifice. LV takes some time to adapt to the new environment . The EF initially may slightly fall and recovers later.
If pre- operative LV dysfunction was significant the immediate post operative period can be critical.As even a slight fall in EF can result in prolonged hypotension.Many of these pateint may require prolonged inotropic support.
What are the differences between MVR done for mitral stenosis and MVR done for mitral regurgitation ?
Here again , the same principles apply.The Mitral stenosis patients do well following MVR than MR patients.This is because of two reasons . MR patients have dilated LV and may also have associated impaired LV function .A chronic MR is some what a stress reliever for the LV , as with every contraction it can decompress a little bit . It is an important hemodynamic fact ie , presence of even a trivial MR helps the LV to tackle the it,s afterload easily by increasing the dp/dt and also the EF.
So when we introduce a a fully competent prosthetic mitral valve all of a sudden the LV again struggles for some time.
MVR patients has less favorable clinical outcome than AVR .
How different is the anticoagulation protocol difference between AVR and MVR ?
Patients with a biological valve may need of 10-15 years. Mechanical valves may also fail, so patients should inform their doctor if they have symptoms of valve insufficiency. Patients with mechanical valves must take blood-thinning medication at the end of their lives. Because these medicines increase the risk of bleeding in the body, you should always be used in medical notification bracelet and the doctor or dentist that you are taking anticoagulant medicine. Even if you take anticoagulant medication, you should always inform your doctor and dentist to have had valve surgery. If you have any surgery or dentistry, you should take antibiotics before the procedure. The bacteria can enter the bloodstream during these procedures. If bacteria enter the repair or artificial heart valves, can lead to a serious condition called bacterial endocarditis. Antibiotics can prevent bacterial endocarditis.