Left ventricular noncompaction and cardiomyopathy: cause, contributor, or epiphenomenon?

PURPOSE OF REVIEW: To discuss unresolved issues pertaining to aetiology and diagnosis of isolated left ventricular noncompaction.

RECENT FINDINGS: Left ventricular noncompaction may be sporadic or familial and is linked to mutations in mitochondrial, cytoskeletal, Z-line, and sarcomeric proteins. Severe childhood manifestations include fetal hydrops or sudden infant death syndrome. Adults with severe phenotypes have a similarly guarded prognosis due to heart failure, arrhythmia and thromboembolism. Conversely, healthy individuals may fulfil current imaging criteria for diagnosis. Left ventricular noncompaction is also observed in families with hypertrophic or dilated cardiomyopathy, casting doubt on its acceptance as a distinct disease entity.

SUMMARY: The extent of myocardial compaction may be a continuous trait within the population. Sensitive imaging techniques may detect subtle variations in morphology that fall within the normal range, underscoring the need for more restrictive diagnostic criteria, as in mitral valve prolapse. Conversely, rather than being a root cause of myocardial dysfunction, left ventricular noncompaction may represent a secondary consequence of a genetic alteration, well-tolerated when the heart is otherwise normal. In the presence of a pathogenic mutation, disruption to myocyte function at a molecular level may be the primary disease determinant, with noncompaction arising as a maladaptive remodelling response that compounds the disease process through subendocardial ischaemia and fibrosis.