yA classical restrictive cardiomyopathy . Both atria balloon out as they face stiff resistance from the ventricles
Restrictive cardiomyopathy(RCM) is a common form of myocardial disease which was difficult to recognise in the past.It was also commonly confused with constrictive pericarditis. Today , one can easily recognise this entity.A simple clue is bi- atrial enlargement with relatively normal ventricle size.The above case is a classical form of RCM.
In late stages of RCM ,both LV, RV begins to dilate and can mimic a dilated cardiomyopathy. Doppler filling pattern , and tissue Doppler motion of mitral annulus are recently validated methods to identify RCM. Still , 2D features are very useful .This implies , the anatomical changes in the chamber size are as important as physiological AV filling profiles. It is generally believed , physiological impairment precedes anatomical defects.( But not proven concept yet ! )
Note: The ventricles are not dilated and retain good systolic function
In the above patient , etiology could not be confirmed and was labeled as idiopathic RCM as tests for amyloid and eosinophilic infiltrations were negative.
M -Mode of the same patient confirms good systolic function
One would call for doppler mitral filling profile here , to confirm restrictive physiology ( A short DT , Short IVRT . A reversal in pulmonary veins , E/E’ ratio etc etc ) But all these are redundant here.
How is RCM different from non dilated cardiomyopathy ?
A new entity is being recognised in the cardiac muscle disease.This is often referred to as NDCM (Non dilated cardiomyopathy) .Global systolic LV dysfunction with normal LV dimension.This a similar to the terminology MDCM (Minimally dilated cardiomyopathy where LV dimension increases not more than 15 % of basal size ) .
This is seen in CKD and diabetic individuals.Atria may be enlarged .Diastolic dysfunction may co exist. It is no surprise, this entity closely mimics RCM. But in RCM LV systolic function is not greatly compromised till late stages , while NDCM it begins with systolic dysfunction. This is the only difference .There can be overlaps .
Many strongly believe , both RCM and NDCM are one and the same entities , that present in different time frames in their natural history.
Final message
Diagnosing RCM is no longer difficult in established cases* . The message from this article is , 2 D echo can strongly suggest the possibility of RCM (or even clinch it) . Never ever diagnose RCM with normal 2 D echo. Doppler filling profiles are useful additional tools . We can not diagnose RCM with doppler features alone , but we can be fairly certain about RCM when we encounter typical bi-atrial enlargement and a normal LV by 2 D echo.
Caution : Patients with longstanding atrial fibrillation of any cause , can dilate their atria and could mimic RCM .They can be some compromise in LV function due to chronic tachycardia .
* Recognizing RCM , very early in the course is still a problem . Here the newer modalities like Phase MRI, tissue doppler, speckle tracking, and velocity vector imaging may be useful.
