Key Questions Relating to Left Ventricular Noncompaction Cardiomyopathy: Is the Emperor Still Wearing Any Clothes?

Abstract

The evidence is increasing that left ventricular noncompaction cardiomyopathy as it is currently defined does not represent a failure of compaction of pre-existing trabecular myocardium found during embryonic development to form the compact component of the ventricular walls. Neither is there evidence of which we are aware to favour the notion that the entity is a return to a phenotype seen in cold-blooded animals. It is also known that when seen in adults, the presence of excessive ventricular trabeculations does not portend a poor prognosis when the ejection fraction is normal, with the risks of complications such as arrhythmia and stroke being rare in this setting. It is also the case that images of "noncompaction" as provided from children or autopsy studies are quite different from the features observed clinically in asymptomatic adults with excessive trabeculation. Our review suggests that the presence of an excessively trabeculated left ventricular wall is not in itself a clinical entity. It is equally possible that the excessive trabeculation is no more than a bystander in the presence of additional lesions such as dilated cardiomyopathy, with the additional lesions being responsible for the reduced ejection fraction bringing a given patient to clinical attention. We, therefore, argue that the term "noncompaction cardiomyopathy" is misleading, because there is neither failure of compaction nor a cardiomyopathic process in most individuals that fulfill widely used diagnostic criteria.

Remodeling of the Embryonic Interventricular Communication in Regard to the Description and Classification of Ventricular Septal Defects

“…This is not true, as the compact part of the ventricular walls is formed, in its larger part, by hyperplasia of the initially thin compact layer. This thin compact layer is present from the outset of formation of the chamber myocardium (Anderson et al, ). It is the initial trabeculations, nonetheless, which do coalesce to form the muscular ventricular septum.…”

Cardiovascular magnetic resonance based diagnosis of left ventricular non-compaction cardiomyopathy: impact of cine bSSFP strain analysis

“…It is characterised by two distinct layers of the left ventricular (LV) myocardiuman endocardial layer of heavily hypertrabeculated myocardium with deep inter-trabecular recesses, and an abnormally thin epicardial layer of compacted myocardium [2]. Despite controversies regarding the development of the myocardial phenotype of LVNC, the abnormal morphology characteristically involves the final segments to undergo compaction during embryogenesisthe apical inferior and lateral segments, with variable basal extension [3,4].…”

Heart development in the lizards (Varanidae) with the greatest extent of ventricular septation

“…This strongly suggests that some trabeculae had undergone compaction. Compaction is considered a key process of the formation of the ventricular walls and septum of mammals and birds (Captur, Syrris, Obianyo, Limongelli, & Moon, 2015; Sedmera, Pexieder, Vuillemin, Thompson, & Anderson, 2000), although the importance of the process may vary between species and its contribution to pathology is debated (R. H. Anderson et al, 2017; Finsterer, Stollberger, & Towbin, 2017).…”