Left ventricular non-compaction (LVNC), also known as ventricular hypertrabeculation, is a rare congenital cardiomyopathy. This condition is characterized by a unique and prominent trabecular meshwork and deep intratrabecular recesses, leading to a distinctive appearance of a two-layered myocardium: a thin, compacted epicardial layer and a thick, non-compacted endocardial layer.
Etiology and Genetics
LVNC can occur in isolation or in conjunction with other cardiac anomalies (such as Ebstein, ventricular septal defects or other anomalies). While the exact cause is still under investigation, studies suggest that it may be due to an arrest in the normal process of endomyocardial morphogenesis during fetal development. Genetic factors have been strongly implicated, with many cases displaying an autosomal dominant inheritance pattern.
Several genes associated with LVNC have been identified, including MYH7, MYBPC3, and TTN, among others. Genetic counseling and testing may be considered in some cases to determine risk in siblings and for future offspring.
The clinical presentation of LVNC in newborns varies widely, from asymptomatic to severe heart failure. The variability in presentation is believed to be due to differences in the degree and location of non-compaction, and possibly the co-occurrence of other cardiac abnormalities. Symptoms may include poor feeding, failure to thrive, difficulty breathing, and excessive fatigue or lethargy.
Diagnosis of LVNC is usually established through echocardiography, which reveals the characteristic appearance of a two-layered myocardium. Additional imaging modalities like Cardiac Magnetic Resonance Imaging (CMRI) may be used to confirm the diagnosis.
Specific echocardiographic criteria for LVNC have been proposed, although there is currently no universally accepted standard. The most commonly used criteria include the ratio of non-compacted to compacted myocardium, with a ratio greater than 2.0 in end-systole generally considered diagnostic.
Jenni Criteria: This includes the presence of numerous prominent trabeculations and deep intertrabecular recesses. It defines non-compacted to compacted myocardial ratio greater than 2:1 measured at end-systole in the parasternal short-axis view as diagnostic of LVNC.
Chin et al. Criteria: It includes the presence of two distinct myocardial layers, a thin, compacted epicardial layer, and a much thicker non-compacted endocardial layer with prominent trabeculations and deep intertrabecular recesses.
Stöllberger and Finsterer Criteria: In addition to features of two distinct myocardial layers, it requires the presence of color Doppler flow within the deep intertrabecular recesses.
Petersen et al. Criteria: Non-compacted to compacted myocardial ratio of > 2.3:1 at end-diastole on cardiac magnetic resonance imaging (CMR) was diagnostic of LVNC in their study. Although this criterion was designed for CMR, some practitioners use it for echo as well.