Let ventricle is an elliptical or ovoid chamber .The pattern of LV enlargement can vary considerably in different pathologies. We know a dilated , globular heart is the typical feature of terminal congestive heart failure. But in the early stages of cadiac enlargement there are some distinct differences in the contour. (Aortic stenotic lesions retain the ellipitical shape till late in the course )
LV enlargement due to mitral regurgitation is somewhat different from aortic regurgitation. A globular configuration occurs more often in severe MR than AR. This is due to the fact, the long axis and short axis ratio of LV is maintained till late in the course of aortic valve disease . Cardiac long axis enlargement is more pronounced in aortic valve disease than in MR. The AR jet reaches LV at a higher pressure gradient (Diastolic pressure of aorta) than mitral inflow velocity . (Often mimic physiological flow with an S3)
For a given degree of regurgitant volume AR will cause more cardiac enlargement than MR. In the same note , one should realise the LA becomes huge in MR which receives high pressure regurgitant jet . Further ,mitral valve disease is more likely to result in early PAH and that results in right sided chamber enlargement giving the cardiac contour a more globular configuration
Is the cardiac contour different in rheumatic and degenerative(Myxamatous) mitral regurgitation ?
Yes , rheumatic MR results in less enlargement of the base of the heart as the fibrotic process restricts and restrains LV and prevents uncontrolled LV dilatation . In fact , giant LV are often reported in mitral regurgitation due to mitral valve prolapse than rheumatic MR.
Why the configuration of LV important in the management of cadiac failure ?
The globular configuration of LV implies , the papillary muscles are attached in a disadvantaged angle and keep the free wall stress high. Specialized procedures are required to restore the LV shape especially in secondary to mitral annular dilatation. Isolated aortic valve disease rarely require LV remodeling surgeries , even if AVR is done late stages.
What is the maximum dimension of LV reported in cardiac failure ?
The upper limit of normal for LV diastolic dimension is 5.6cms. In MR it often reaches 6-7 cms . The maximum of 10cm has been reported with AR. An LV beyond this level looses it’s elasticity and likely to be incompatible with survival unless LV reduction surgeries like Batista are performed.
Is secondary valvular cardiomyopathy an accepted entity ?
The term cardiomyopathy when originally defined decades ago , required exclusion of all known cases of cardiac enlargement. But now we have a more liberal working concept , if the LV enlarges disproportionate to the loading conditions of the valvular lesions , secondary cardiomyopathy is said to be present. If cadiomyopathy sets in, the cardiac shape invariably takes in a globular configuration irrespective of the valvular lesions. So, the simple parameter of shape of LV in X ray chest can give us a clue regarding the outcome in valvular heart disease.
Also read sphericity index by echocardiography A spherical LV can be easily quantified by echocardiography