The most commonly affected valve in rheumatic heart disease is the mitral valve. But why? is there any specific pathomechanism. I haven't found the evidence based answers yet.
Dear Joshua,
The exact explanation I don't think is available. Greater mechanical stress on the left sided valves is believed to be the reason why they are far more commonly involved than right sided valves.. Mitral valve is more often involved than aortic valve because the pressures across the mitral valve in systole is much higher - LV pressures are much higher than the pressure in LA in systole. The warty non infective vegetations form on the atrial side of the mitral valve along the line of closure of the leaflets. Similar degree of pressure differences do not exist across aortic valve.
Moreover the entire connective tissue and mitral valve apparatus get involved in acute rheumatic fever. A combination of valvulitis, annulitis and chorditis contribute to mitral regurgitation in acute rheumatic fever. Clinically significant myocarditis does not occur.
But similar issues (chordal lengthening, prolapse, rupture and the sphincter mechanism of the annulus) do not exist for the aortic valve. This may partly explain why MR is commoner than AR.
Untreated strep throat or other infections with strep bacteria that progress to rheumatic fever can cause heart valve disease. When the body tries to fight the strep infection, one or more heart valves may be damaged or scarred in the process. The aortic and mitral valves most often are affected.
Dearly respected sir
A plausible explanation for the mitral valve being commonly affected by rheumatic disease could be the mitral valve is located on the left side of the heart, furthermore the stress on a valve is maximum during the valve closure. When the left ventricle contract to pump the blood to the body the valve is more stressed compared to the aortic and right side valves.
Because the high content of n-acetil glucosamine on tfe mitral valve, correspondent the also very content of this ac d in the medium layer of the Strepoccocus betahemolitycus. And the high pressure in the mitral valve by the dinamic in left ventricule during the left ventricular systolic events
Lurildo Saraiva,MD RECIFE< BRASIL
These data are from an outpatient clinic specializing in Valvular Diseases of Incor- USP, São Paulo / Brazil. In 30 days I attended a little more than 400 patients with valve disease, and 60% had rheumatic disease.
Aortic stenosis 17%
Aortic Insuf 9%
Mitral Stenosis 13,5%
Mitral Insuf 15,5%
Double ds Mitral 13,9%
Double ds Aortic 6%
The shear stress on the large mitral leaflets is more than the shear stress on the small aortic cusps and much more on the right sided cusps. The mitral cusps are exposed to pressure of the LV during contraction (Say 120 mmHg) in systole but the aortic cusps are exposed to the aortic diastolic pressure during closure (say 80 mmHg). Years ago we had a study in Egypt, if we diminish heart rate and BP during acute rheumatic fever; we can diminish the mitral injury, explained by diminishing shear stress.
Hi Joshua,, very interesting question. Thanks Dr koshy for nice and elaborative answar. Dr koshy almost everything like mechanical stress and complicated structure of mitral valve apparatus. Slight deformation of mitral valve apparatus can cause significant mitral regurgitation. Wheather molecular composition of mitral valve have any role in interacting with the antibodies that part need to be studied.. Thanks
The Mitral valve is exposed to a higher shear stress than any other valve as explained by Dr Samir
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