The Diagnosis of Primary Endocardial Fibroelastosis
Authors: SELLERS FRANK J. , KEITH JOHN D. , MANNING JAMES A. 
Published: June 2012

A comparison has been made of the clinical features of a group of autopsy-proved cases of endocardial fibroelastosis and a clinically diagnosed group with similar findings. It has been possible to make a diagnosis of endocardial fibroelastosis before death in all cases showing a characteristic clinical and electrocardiographic pattern. The characteristic features are (a) appearance of congestive heart failure; (b) absence of organic heart murmurs; (c) onset of signs or symptoms in the first 8 months of life (85 per cent) and rarely after 1½ years; (d) a period of observation under therapy during which is ruled out the conditions that simulate endocardial fibroelastosis, such as an anomalous coronary artery arising from the pulmonary artery, glycogen-storage disease, coronary artery necrosis, or myocarditis; (e) an abnormal increase in voltage of R in V
6
, S in V
1
, or both together; (f) a flat or inverted T wave in V
6
(85 per cent have a T wave 1 mm. or deeper); (g) a Q wave in V
6
(present in 60 per cent).

All the cases proved at autopsy that fulfilled these criteria during life were correctly diagnosed before death. Approximately 85 per cent of the total group were thus recognized. Fifteen per cent were not identified because electrocardiographic tracings showed an atypical right loading pattern. An occasional case with right loading may be suspected by history of a previous sibling with endocardial fibroelastosis.

Since the differential diagnosis between endocardial fibroelastosis and acute myocarditis has been considered difficult in the past, a group of infants and children with myocarditis were reviewed. The majority were proved at autopsy. Such children were also correctly diagnosed during life in most instances. The patients who were diagnosed clinically as having endocardial fibroelastosis and who survived had electrocardiographic patterns that were similar to those in the autopsy-proved group and unlike those in the myocarditis group. The chief differences were in voltages of R and S waves in precordial leads V
6
or V
1
, T waves in V
6
, and Q waves in V
6
.

Cases of endocardial fibroelastosis associated with mitral or aortic valvular disease usually had a similar age of onset or a little earlier. The electrocardiographic pattern was similar. The presence of an aortic or mitral systolic murmur made it difficult to be certain about the underlying pathology. The left loading pattern, however, with increased voltage in the pertinent precordial leads accompanied by a flat or inverted T wave in V
6
in a baby with a large heart or with congestive heart failure, provides suggestive evidence of endocardial fibroelastosis.

The contracted type of endocardial fibroelastosis reported by Edwards is a relatively rare finding. When it does occur, it may or may not be associated with a right loading pattern in the electrocardiogram. The right loading pattern in endocardial fibroelastosis is more likely to be due to heart failure with pulmonary congestion and overloading of the right ventricle, which in an infant may then overshadow the left. This pattern may revert to the more characteristic one of left loading after digitalization has been completed.
The mumps antigen skin test is proving to be a useful diagnostic tool, since it is found to be positive in primary endocardial fibroelastosis in the first 2 years of life. In our experience this occurs without a positive serum antibody reaction to mumps virus. Normal children, or those with congenital heart disease in the same age group, rarely have a positive skin reaction unless they have a recent history of mumps. Further work is needed to clarify this relationship, but on the evidence to date its diagnostic value in primary endocardial fibroelastosis shows considerable promise.