Noncompaction cardiomyopathy embryology

Overview
Noncompaction results from the failure of heart muscle cells to transform from a spongy state to a compacted state during embryogenesis. The process can affect either the left or right ventricle, but generally affects on the left ventricle.

Embryonic Basis of Noncompaction
During development, the majority of the heart muscle is a sponge-like meshwork of interwoven myocardial fibers. As normal development progresses, these trabeculated structures undergo significant compaction that transforms them from spongy to solid. This process is particularly apparent in the [[ventricles]], and particularly so in the left ventricle. Noncompaction cardiomyopathy results when there is failure of this process of compaction. Because the consequence of non-compaction is particularly evident in the left ventricle, the condition is also called left ventricular noncompaction. Less than half the patients with NCC have involvement of the right ventricle.

This abnormality in development begins to occur around the 8 week mark during fetal development. The myocardium at this period of development is often referred to as looking like a sponge as it is still a meshwork of interwoven myocardial fibers. This is beneficial at this stage as there is an increased surface area which allows perfusion of the myocardium from the left ventricular cavity. However as the embryo grows the myocardium should begin to be compact, in the case of NCC though the heart fails to fully compact leaving the myocardium to still have a spongy form. Non-compaction Cardiomyopathy can affect both ventricle walls of the heart separately or together. However, it generally affects only the left ventricle wall and therefore is sometimes known as left ventricular noncompaction.

Some authors have hypothesized that either myocardial ischemia or pressure overload may inhibit the regression of embryonic structures.

Some authors have challenged the hypothesis that NCC is due to an arrest in embryonic development. In one study, three infants who went on to develop NCC did not have the disease diagnosed at birth. It is unclear if limitations of fetal echocardiography may have played a role in failing to make the diagnosis at birth.