Non-compaction of the ventricular myocardium: a cardiomyopathy in search of a pathoanatomical definition.

Ventricular non-compaction is a rare cardiomyopathy characterized by numerous, excessively prominent ventricular trabeculations and deep intertrabecular recesses communicating with the ventricular cavity. The lesion is postulated to result from an intrauterine developmental arrest that stops compaction of the myocardial fiber meshwork. This cardiomyopathy affects the left ventricle, with or without concomitant right ventricular involvement. The disease is now seen with increasing frequency and it is clinically diagnosed by imaging techniques such as echocardiography or cardiac magnetic resonance. Current diagnostic criteria are considered too sensitive, particularly in black individuals. Therefore, this condition has generated considerable controversy and demands a new definition. Non-compaction cardiomyopathy shows variability of hereditary patterns, genetic heterogeneity, diversity in associated phenotypes and a wide spectrum of clinical presentation and pathophysiological findings. Non-compaction can be simply a variant of normal maturation of the ventricular myocardium with only the most severe forms producing a distinct clinical-pathological entity. Ventricular non-compaction most probably is a secondary consequence of an underlying molecular derangement produced by a pathogenetic mutation. It is likely that surgical pathologists will find this entity more frequently due to involvement in transplantation teams.