Human heart is a compact elastic organ . We know elasticity is lost when it is stretched beyond a point.This is what happens in dilated cardiomyopathy .When the heart muscle fibers stretch too long from the baseline it loses its ability to contract and relax efficiently.In fact , after a cut of point even if it comes the original length the elastic fibers are fractured and suffer from irreversible damage.
Among the systolic vs diastolic dimension it is the diastolic dimension that becomes important in defining dilatation.
When do you say a ventricle is dilated?
- When the EDD (End diastolic dimension) > 60mm
- EDD > 56mm
- EDD > 10 % from baseline
- EDD > 25 % from baseline
Any of the above can be right.
The normal human ventricle measures between 35 to 55mm in diastole .
Currently accepted definition for enlargement of heart is EDD of 56 mm and above. Some believe in a more strict criteria of 60mm.
Consider the following situation
A man with 35mm EDD can increase 20mm ( ie 60 % ) from of his baseline and still be labeled as normal LV dimension ! . If the above patient is destined to develop dilated cardiomyopathy his heart would begin its final journey slowly but surely ( from 35 mm ! ) . So , according to current criteria we can diagnose DCM only after it travels the half way towards hell . What a way to define DCM ! Be cautious LV dimensions can fool you . . .
If the EF is low and symptoms develop early , one may recognise the above entity ( at least erroneously !) as non dilated cardiomyopathy or RCM.
If the patient is relatively asymptomatic and if we overlook the baseline LV parameters , we are likely to miss most of the early DCMs
Final message
We need to stress the importance of baseline LV dimension in defining DCM . It is proposed from this site , an increase of 25 % and above from baseline can be included as an additional criteria for LV dilatation . This could help us understand the early muscle dynamics in DCM.
Un-Answered questions
- How to diagnose early DCM ?
- When does the EF begins to decline in DCM ?
- What is the relation between EDD and EF %?
- Is HF with preserved LV function ( previously called diastolic dysfunction ) is the earliest point in the natural history of DCM
- Is there a overlap between non dilated cardiomyopathy , RCM and early phase of DCM ?
Dr.S.Venkatesan MD 