Cardiac Magnetic Resonance of Left Ventricular Trabeculation

Abstract

Historically, left ventricular noncompaction (LVNC) was considered to be a rare form of cardiomyopathy; however, during the past decade, there has been a significant increase in reports of patients with LVNC. Using either echocardiography or cardiac magnetic resonance (CMR) imaging, LVNC is relatively straightforward to diagnose in individuals expressing a typical phenotype. However, the diagnosis may be challenging to make in those individuals who express more subtle phenotypes of LVNC. CMR imaging offers a more detailed examination of myocardial structure and composition compared with other imaging modalities, such as echocardiography. With more common use of CMR, there has been increased appreciation of the degree of trabeculation of the LV. The ventricle comprises 2 myocardial layers: the compact myocardium and the trabecular myocardium. During cardiac development, after heart looping, the myocardium becomes deeply trabeculated through a clonal outgrowth of embryonic cardiomyocytes.1 After the coronary arteries form and provide a ready supply of oxygen and nutrients, the LV undergoes compaction accompanied by resolution of the deep trabeculae. Persistence of the LV trabeculae in the postnatal myocardium may be associated with cardiomyopathy, and LVNC is classified as a cardiomyopathy.2,3 Article see p 139 There is a lack of consensus surrounding LVNC diagnostic criteria. The imaging criteria for LVNC differ depending on whether echocardiography or CMR is used. Both imaging modalities use the ratio of the thickness of the trabeculated layer to the thickness of the compacted layer (T/C). However, a commonly used diagnostic criterion for echocardiography requires the T/C to be >2.0 at end systole,4 whereas the diagnostic criterion for CMR is T/C …