Non-compaction of the left ventricle

Non-compaction of the left ventricle, also known as spongiform cardiomyopathy or left ventricular non-compaction (LVNC), is an arresta phenotype of myocardial compaction during embryogenesis, leading to hypertrophic ventricular trabeculations and deep inter-ventricularinterventricular recesses.

This abnormality It has been hypothesized to result from arrest of normal myocardial compaction during embryogenesis, although acquired cases have also been described inreported.

Non-compaction of the right ventricularventricle has been described, but it is much rarerrare ³.

Terminology

InThere is controversy as to whether LVNC represents a distinct disease versus a phenotypic manifestation of various cardiomyopathies ⁹. For example, although LVNC is classified as a primary genetic cardiomyopathy by the American Heart Association, it remains unclassified by both the World Health Organization and the European Society of itself,Cardiology ⁹.

At least some of the diagnosisinconsistency is due to the fact that LVNC is mostly diagnosed by morphological criteria on non-invasive imaging (e.g. echocardiography and cardiac MRI), and there no universally-accepted criteria exist.

Additionally, findings of LVNC does not constitutemay be seen in a truespectrum of clinical presentations. It may be seen as a component of cardiomyopathy, such as the morphological traits of which this entity is composed ofin Barth syndrome, or in concert with other myocardial structural/functional abnormalities (e.g. dilated, restrictive, arrhythmogenic right ventricular cardiomyopathies); however, it may be acquired/reversible and/or observed in subjects with normal left ventricular function and size.

It has also been described as an intrinsic component of a cardiomyopathyThus, such as that which is found in patients with Barth syndrome, or in concert with another myocardial structural/functional abnormality such as dilated (DCM), restrictive (RCM), or arrhythmogenic right ventricular (ARVC) cardiomyopathy.

As such, the demonstrationfindings of LVNC morphology doesshould not neccesarily implybe equated with cardiomyopathy or aberrant left ventricular function, and its presenceas the findings The findings should be integrated into a holistic evaluation of cardiac function in deciding a final diagnosis ⁶.

Clinical presentation

While LVNC may be an isolated morphological variant, discovered in patients with otherwise structurally and functionally normal hearts, it may also present as a component of a congenital heart disease or true cardiomyopathy; in this latter instance it may present as congestive heart failure. Other presenting features may include ⁸:

• exertional syncope
  • may be associated with a long QT interval
    • may predispose to a subtype of polymorphic ventricular tachycardia, torsades de pointes 
• atrial fibrillation
• systemic thromboembolic events
  • may lead to transient ischemic attacks or stroke

Pathology

Associations

In most patients with non-compaction of the left ventricle, there are no other cardiac malformations. Familial and sporadic form have been described ¹. However, in at least one study, approximately 12% of patients had associated cardiac malformations ¹:

• ventricular outflow tract / left ventricular outflow tract abnormalities (46%, mainly bicuspid aortic valve)
• Ebstein anomaly (25%)
• more rarely: tetralogy of Fallot or coarctation of the aorta

Radiographic features

Plain radiograph

Chest radiographs are not useful in the diagnosis of non-compaction of the left ventricle. They are more useful in identifying complications of the cardiomyopathy, such as pulmonary oedema and cardiomegaly.

Echocardiography

Echocardiography was traditionally used in the diagnosis of left ventricular non-compaction, with the addition of contrast greatly increasing the sensitivity of this examination. However, cardiac MRI is now considered the modality of choice to make this diagnosis. There are no universally accepted echocardiographic criteria for left ventricular non-compaction. Most common echocardiographic features include ⁷:

• bilayered mural appearance of left ventricle
  • the relatively hypoechoic inner layer of left ventricular wall representing the endocardium/myocardium is hyper-trabeculatedhypertrabeculated
    • referred to as the non-compacted or "NC" layer
  • the non-compacted layer is surrounded by the outer "compacted" layer, representing the epicardium
  • classical definition based on the NC/C thickness ratio
    • increased thickness of the NC layer with an NC/C ratio >2.3 consistent with diagnosis
• regional increase in left ventricular trabeculaction
  • predominantly affects the inferolateral walls and the apex
  • the parasternal short axis (or apical four/two/long axis view) should reveal at least four trabeculations
• pronounced inter-trabecular "crypts" or recesses
  • continuity with left ventricular cavity may be demonstrated by color flow Doppler

Other commonly associated features include:

• left ventricular dysfunction
  • both systolic and diastolic
• intraventricular thrombus
• left atrial enlargement
  • associated with atrial fibrillation

MRI

Cardiac MRI has a better contrast resolution than echocardiography and it is the modality of choice for the diagnosis of spongiform cardiomyopathy. The best diagnostic clueis a ratio of non-compacted telediastolic myocardium to compacted telediastolic myocardium of more than2.3:1 (sensitivity: 86%, specificity: 99%).

Treatment and prognosis

The only definitive treatment of left ventricular noncompactionnon-compaction is cardiac transplantation. Otherwise, prevention of both heart failure and thromboembolic events are the main target of treatments.

Differential diagnosis

Possible differential considerations in certain situations include:

• cardiomyopathies
  • dilated cardiomyopathy
  • hypertrophic cardiomyopathy
  • restrictive cardiomyopathy
  • arrhythmogenic right ventricular cardiomyopathy
• normal variant
  • athletes heart
• congenital heart disease