Left ventricular noncompaction (LVNC) is a cardiomyopathy associated with sporadic or familial disease, the latter having an autosomal dominant mode of transmission. The clinical features associated with LVNC vary from asymptomatic to symptomatic patients, with the potential for heart failure, supraventricular and ventricular arrhythmias, thromboembolic events, and sudden cardiac death. Echocardiography is the diagnostic modality of choice, revealing the pathognomonic features of a thick, bilayered myocardium; prominent ventricular trabeculations; and deep intertrabecular recesses. Widespread use and advances in the technology of echocardiography and cardiac magnetic resonance imaging are increasing awareness of LVNC, and cardiac magnetic resonance imaging is improving the ability to stage the severity of the disease and potential for adverse clinical consequences. Study of LVNC through research in embryology, imaging, and genetics has allowed enormous strides in the understanding of this heterogeneous disease over the past 25 years.
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History of Left Ventricular Noncompaction
References to a spongy or embryonic myocardium, particularly in association with complex congenital heart disease, have been made in the pathology literature periodically for more than 80 years. The historical aspects of LVNC have been well described in the literature. The histology of persistence of spongy myocardium with embryonic blood supply was first discussed in the literature in 1975 and subsequently described as spongy myocardium with persistent sinusoids in the 1980s. In 1985, Engberding and Bender were the first to make the antemortem diagnosis of isolated LVNC using two-dimensional (2D) echocardiography, which demonstrated a spongy myocardium with prominent sinusoids. Jenni et al. reported biventricular noncompaction in 1986. Chin et al. subsequently reported a series of patients with a persistence of trabecular meshwork and deep intertrabecular recesses communicating with the LV cavity in 1990 and proposed the unifying terminology of LVNC as well as the echocardiographic criteria for diagnosing this entity.
In the past 25 years, understanding of LVNC cardiomyopathy has increased through improved imaging modalities, such as 2D and three-dimensional (3D) echocardiography and cardiac magnetic resonance imaging (CMR), and evolving genetic links, including mutations encoding tafazzin (TAZ) (G4.5) associated with Barth syndrome, ZASP (Z-line, sodium channels [SCNS5]), and mitochondrial and sarcomere protein genes.
Nomenclature of LVNC
The various names used to describe the morphologic profile of LVNC have prevented the development of a standardized nomenclature and impeded the use of diagnostic criteria that would facilitate understanding and promote research. The various names used to describe the morphologic profile of LVNC include “honeycomb,” “persistent sinusoids,” “spongy myocardium,” “persistent embryonic myocardium,” “hypertrabeculation,” “LVNC,” “LVNC/hypertrabeculation syndrome,” and “noncompaction of the ventricular myocardium.” Developmental and evolutionary evidence does not support the terms “hypertrabeculation” and “persistent sinusoids” as being descriptive of noncompacted myocardium. Failure of trabecular remodeling is best described by noncompaction to illustrate failure of myocardial maturation during embryogenesis ( Figure 2 ).
LVNC: Recognition
LVNC was given its recent name in 1990 and is listed as an unclassified cardiomyopathy by the World Health Organization. It was classified as a genetic cardiomyopathy by the American Heart Association in 2006. There is an ongoing debate regarding the classification of LVNC. LVNC is a distinct form of cardiomyopathy that is recognized by multiple imaging modalities ( Figures 3 and 4 , Videos 1 and 2 ; 
view video clips online).
History of Left Ventricular Noncompaction
References to a spongy or embryonic myocardium, particularly in association with complex congenital heart disease, have been made in the pathology literature periodically for more than 80 years. The historical aspects of LVNC have been well described in the literature. The histology of persistence of spongy myocardium with embryonic blood supply was first discussed in the literature in 1975 and subsequently described as spongy myocardium with persistent sinusoids in the 1980s. In 1985, Engberding and Bender were the first to make the antemortem diagnosis of isolated LVNC using two-dimensional (2D) echocardiography, which demonstrated a spongy myocardium with prominent sinusoids. Jenni et al. reported biventricular noncompaction in 1986. Chin et al. subsequently reported a series of patients with a persistence of trabecular meshwork and deep intertrabecular recesses communicating with the LV cavity in 1990 and proposed the unifying terminology of LVNC as well as the echocardiographic criteria for diagnosing this entity.
In the past 25 years, understanding of LVNC cardiomyopathy has increased through improved imaging modalities, such as 2D and three-dimensional (3D) echocardiography and cardiac magnetic resonance imaging (CMR), and evolving genetic links, including mutations encoding tafazzin (TAZ) (G4.5) associated with Barth syndrome, ZASP (Z-line, sodium channels [SCNS5]), and mitochondrial and sarcomere protein genes.
Nomenclature of LVNC
The various names used to describe the morphologic profile of LVNC have prevented the development of a standardized nomenclature and impeded the use of diagnostic criteria that would facilitate understanding and promote research. The various names used to describe the morphologic profile of LVNC include “honeycomb,” “persistent sinusoids,” “spongy myocardium,” “persistent embryonic myocardium,” “hypertrabeculation,” “LVNC,” “LVNC/hypertrabeculation syndrome,” and “noncompaction of the ventricular myocardium.” Developmental and evolutionary evidence does not support the terms “hypertrabeculation” and “persistent sinusoids” as being descriptive of noncompacted myocardium. Failure of trabecular remodeling is best described by noncompaction to illustrate failure of myocardial maturation during embryogenesis ( Figure 2 ).
LVNC: Recognition
LVNC was given its recent name in 1990 and is listed as an unclassified cardiomyopathy by the World Health Organization. It was classified as a genetic cardiomyopathy by the American Heart Association in 2006. There is an ongoing debate regarding the classification of LVNC. LVNC is a distinct form of cardiomyopathy that is recognized by multiple imaging modalities ( Figures 3 and 4 , Videos 1 and 2 ; view video clips online).
Embryology
Detailed description of the embryonic development of the ventricular myocardium is beyond the scope of this review. This has been elegantly described in the literature. Briefly, at 5 to 8 weeks of normal embryonic development, intertrabecular recesses or “sinusoids” form. The recesses are in direct communication with the LV endocardium. As normal cardiac development progresses and myocardial compaction occurs, the intertrabecular recesses transform into capillary beds. The process of trabecular compaction in humans is between 12 and 18 weeks of gestation and starts at the base and progresses toward the apex ( Figure 5 ). Compaction is most pronounced in the left ventricle, and substantial growth and compaction occur throughout postnatal development. From the fourth month of gestation in humans, the compacted layer forms the bulk of the ventricular myocardium.
LVNC is hypothesized to be due to early cessation of compaction of trabecular meshwork during embryogenesis. The result is formation of a compacted epicardial layer with a loose, interwoven “spongy” meshwork and prominent trabeculae and deep intertrabecular recesses that communicate with the LV cavity. Because the apex is the last to undergo compaction, ventricular noncompaction is usually localized toward the apical region. The gestational age at which myocardial maturation arrest occurs may be a determinant of the severity and extent of LVNC, hence the broad spectrum of phenotypic (mild to severe degrees of noncompaction) and clinical (benign condition to HF and sudden cardiac death) expression. The exact molecular mechanism, or mechanisms, responsible for the regulation of ventricular myocardial differentiation, growth, and trabecular compaction is currently lacking precision and clarity.
Diagnostic Criteria and Differential Diagnosis
Several echocardiographic and magnetic resonance imaging definitions for the diagnosis of LVNC have been proposed and used in published studies ( Table 1 ). Two-dimensional echocardiography has been the foundation for establishing diagnosis, increasing awareness and better delineating the phenotypic expressions of LVNC ( Figures 3 and 6–11 , Videos 1–7 ; view video clips online). CMR is a complementary imaging modality. Delayed gadolinium enhancement with CMR identifies myocardial fibrosis, which may have prognostic implications.
| Echocardiographic criteria | |
|---|---|
| Chin et al. | Jenni et al. |
| • LVNC is defined by a ratio of X/Y ≤ 0.5 | • Bilayered myocardium consisting of a thin C layer and a much thicker NC layer with deep endomyocardial recesses: NC/C > 2 |
| • These criteria evaluate trabeculae at the LV apex using the parasternal short-axis and apical views and on the LV free wall thickness at end-diastole | • Predominant location of the pathology is midlateral, midinferior, and apex |
| • Evidence of intertrabecular recesses filled with blood from the LV cavity | |
| • Acquisition of images views: short-axis with measurement of NC/C ratio performed at end-systole | |
| Stöllberger and Finsterer | Authors’ proposal (criteria not validated) |
| • Four or more trabeculations protruding from the LV wall, located apically to the papillary muscles and visible in one imaging plane | • An evaluation of the trabeculations’ sizes (NC myocardium) in relation to C wall thicknesses in multiple imaging windows and at different ventricular levels throughout the cardiac cycle |
| • Trabeculations with the same echogenicity as the myocardium and synchronous movement with ventricular contractions | • Identification of the bilayered myocardium (C and NC) in the short-axis views at the mid and apical levels and in the apical two- and four-chamber and apical long-axis views |
| • Perfusion of the intertrabecular recesses from the LV cavity | • Thicknesses of the C and NC sections of the myocardium are best measured in the short-axis views at end-diastole, with an NC/C ratio > 2 being diagnostic of LVNC |
| • Acquisition of the images in the apical four-chamber view, atypical views to obtain the best quality image to differentiate between false chords, aberrant bands and trabeculations | |
| MRI criteria | |
|---|---|
| Petersen et al. | Jacquier et al. |
| • Ratio between NC and C layers > 2.3 at end-diastole | • Trabeculated LV mass > 20% of global LV mass (measurements made at end-diastole) |
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