Echocardiographic and pathoanatomical characteristics of isolated left ventricular non-compaction: a step towards classification as a distinct cardiomyopathy

Abstract

Aim: To determine clear cut echocardiographic criteria for isolated ventricular non-compaction (IVNC), a cardiomyopathy as yet "unclassified" by the World Health Organization. The disease is not widely known and its diagnosis mostly missed.

Methods and results: In seven out of a series of 34 patients with IVNC the in vivo echocardiographic characteristics were validated against the anatomical examination of the heart removed after death in four and due to heart transplantation in three patients. Four morphological criteria diagnostic for IVNC were found. (1) Coexisting cardiac abnormalities were absent (by definition). (2) A two layer structure was seen, with a compacted thin epicardial band and a much thicker non-compacted endocardial layer of trabecular meshwork with deep endomyocardial spaces. A maximal end systolic ratio of non-compacted to compacted layers of > 2 is diagnostic. (3) The predominant localisation of the pathology was to mid-lateral (seven of seven patients), apical (six), and mid-inferior (seven) areas. The pathological preparations confirmed the echocardiographic findings. Concomitant regional hypokinesia was not confined to the non-compacted segments. (4) There was colour Doppler evidence of deep perfused intertrabecular recesses.

Conclusions: Four clear cut echocardiographic diagnostic criteria were established. It is suggested that the WHO classification of cardiomyopathies be reconsidered to include IVNC as a distinct cardiomyopathy.

Figure 1

To quantify the extent of non-compaction at the site of maximal wall thickness the end systolic ratio of non-compacted to compacted thickness was determined. The two layers are best visualised at end systole as shown in this short axis view.

Figure 2

Colour Doppler study showed typical forward blood flow from the ventricular cavity into the deep spaces between the prominent trabeculation during diastole (in A represented by a red signal) with a reversed flow back into the ventricle during systole (in B, blue signal).

Figure 3

The structural alterations were predominantly localised to the left ventricular mid lateral wall and to the apex and the mid inferior wall.

Figure 4

Apical four chamber view of three hearts. The anatomical findings (upper panel) are in agreement with the findings of the previously recorded echocardiographic view in the same patient (lower panel).

Figure 5

Histological preparation from the left ventricular apex of a patient with isolated ventricular non-compaction. Note the thin compacted normal outer layer of myocardium and the endocardial (non-compacted) layer. There is scar tissue within the trabeculations (asterisks) and in the subendocardial area but not in the epicardial zone.