Left ventricular non-compaction cardiomyopathy: how many needles in the haystack?

### Learning objectives Left ventricular non-compaction cardiomyopathy (LVNC) remains a subject of unsettled debate between those who perceive it to be a primary genetic cardiomyopathy1 and those who believe excessive trabeculation to be a morphological feature shared by distinct pathological processes and therefore not a single disease.2 The defining abnormality is the presence of prominent left ventricular (LV) trabeculae and deep intertrabecular recesses, continuous with the LV cavity and separated from the epicardial coronary arteries.3 This was initially thought to be the consequence of embryological arrest of normal endomyocardial morphogenesis, but contemporary studies dispute this popular theory. This article showcases the most up-to-date research regarding LV trabeculation and non-compaction cardiomyopathy. Practical guidance is offered relating to cardiac diagnostic imaging and clinical management, with ambition to resolve misconceptions about the origins and diagnosis of LVNC. Finally, we aim to provide insights into future research that might illuminate persisting ambiguities. ### In normal development, trabeculae and compact myocardium grow at different rates Around 4 weeks after conception, the primitive heart begins to develop its four chambers. At this early stage, there is no coronary circulation and chamber walls thicker than 50 µm or so are at risk of becoming ischaemic.4 A wall made of thin trabeculae that protrude into the cavity, however, will resist ischaemia bathing in the chamber blood.5 Thus, in the absence of coronary circulation in the fourth and fifth week after conception, trabeculae grow fast, accounting for most of the ventricular mass.6 7 Then, around the transition from embryo to fetus, trabecular growth becomes slow relative to the compact wall, and in this period, the ventricular wall acquires an almost adult-like appearance, or expressed numerically, …