Echocardiographic Diagnosis of Left Ventricular Noncompaction Cardiomyopathy

Clinical Spectrum Of Left Ventricular Noncompaction Cardiomyopathy

A more pragmatic approach maybe to view the phenotype of LVNC to be to that of LV hypertrophy, which can occur in a spectrum ranging from clinical scenarios characterized by physiological adaptive changes to primary genetic cardiomyopathy. The diagnosis of LVNC relies on imaging to identify a specific phenotype that is different to that normally visualized in the myocardium of humans. After a phenotype of LVNC is identified, it is imperative that the phenotype be integrated with the clinical scenario and functional state of the heart. Based on this, one should decide if this constitutes a normal variant, physiological adaptation, or primary myocardial pathology.

The definitions “LVNC-like phenotype” or “prominent trabeculations not meeting the criteria for LVNC” have been proposed by some and should refer to the scenario in which prominent trabeculations are identified but the structure of the heart is normal with normal ejection fraction (EF). The significance of this scenario is not clearly elucidated but thought to represent a normal variant. Whether this normal variant will transition to LVNC cardiomyopathy remains an enigma. Several physiological states are characterized by volume overload of the left ventricle in which the LVNC phenotype has been described. These include anemia, pregnancy, and athletes. ^{, ,} This physiological adaptive change maybe reversible as documented in the experience of Gati and coworkers, who found that the LVNC phenotype reverses after pregnancy in certain individuals.

Pathological LVNC may occur if there is associated congenital heart disease; neuromuscular disease; or other myocardial disease such as hypertrophic cardiomyopathy (HCM), myocarditis, or Fabry disease. The screening of family members of individuals with known genetic myocardial disorders such as HCM and less commonly familial dilated cardiomyopathy (DCM) may results in cases of LVNC cardiomyopathy being identified.

Diagnosis

There are several proposed echocardiographic and cardiac magnetic resonance imaging (CMRI) criteria for diagnosing LVNC. CMRI has superior spatial resolution compared with echocardiography and thus has the advantage of detecting the LVNC phenotype in scenarios in which echocardiographic imaging is suboptimal and is superior at imaging the apex and apicolateral walls. Additional advantages of CMRI include the detection of concomitant late gadolinium enhancement suggestive of myocardial scar and detection of myocarditis. Thus, CMRI should be used ideally in addition to echocardiography, although its major limitations include its cost and availability. Furthermore, it appears that CMRI tends to result in overdiagnosis of LVNC compared with echocardiography with one large study detecting the phenotype in 43% of normal individuals. Thus, detection of the LVNC phenotype in isolation by CMRI does not constitute a diagnosis. Instead, as mentioned previously, detection of the phenotype of LVNC must be integrated with several key clinical features to improve diagnosis.