Left ventricular non-compaction (LVNC) is a very rare congenital cardiomyopathy. It is a disease of endomyocardial trabeculations that increase in number and prominence. This cardiomyopathy carries a high risk of malignant arrhythmias, thromboembolic phenomenon and left ventricular dysfunction. This disease also has other names like spongy myocardium, spongiform cardiomyopathy, hypertrabeculation, persisting myocardial sinusoids or zaspopathy. It can carries associations with complex congenital heart defects or skeletal myopathy. It represents the arrest of the normal maturation process of the myocardium. This disease can present throughout life with progressive left ventricular systolic dysfunction.
This type of congenital cardiomyopathy has not been fully understood so far and remained unclassified by WHO. In 2006, the American Heart Association classified this entity as primary cardiomyopathy of genetic origin. MOGE(S) classification of cardiomyopathies has also described it as a distinct entity.
Although the precise cause is not presently known, it is thought to be due to a developmental disorder involving arrest of compaction of loose myocardial meshwork during fetal ontogenesis. It has been traced back to a single point mutation in the beta-myosin heavy chain gene. Various studies have linked left ventricular non-compaction as an autosomal dominant inherited disorder. It has possible links to mutations in several genes like ZASP, dystrobrevin and tafazzin. It has been known to be a part of various syndromes like the Barth, Noonan, Roifman or Toriello Carey syndrome.
Isolated LVNC now presents with increasing frequency between 0.05 percent and 0.24 percent. Although the left ventricle is commonly affected, the involvement of both ventricles involvement occurs in 22 - 38 % of patients.
The ventricular wall of both ventricles in a normal heart consists of a compacted layer of myocardial fibers set in the matrix of supporting connective tissue. The LVNC consists of a meshwork of numerous prominent muscle band called trabeculations in left ventricular apex.
Patients with LVNC may lead a normal life as the normal left ventricle functions. Patients may present at any age from infancy to old age. The clinical manifestations may involve heart pump failure, arrhythmias, and thromboembolic phenomenon. The most common complaint at admission is pump failure.
Diagnostic criteria for LVNC is a ratio X/Y < 0.5 where X is the distance, measured from the epicardial surface to the trough of the trabecular recess and Y is a distance measured from the epicardial surface to the peak of the trabeculation. This method, originally proposed by Chin et al., evaluates the size of trabeculations relative to the thickness of the compacted wall in different echocardiographic views and at different levels of the LV in end diastole. Jenni and co-worker also proposed a method that involves detection of the two myocardial layers, non-compacted and compacted, in short axis views of the LV in end systole. This method describes the ratio >2 between non compacted to compacted myocardium. The third definition proposed by Stollberger et al. determines the number of prominent trabeculations visible in the apical views of the LV in diastole. Regarding diagnosis, there is a debate going on with regards to features displaced by angiography, echocardiography, computed tomography, and magnetic resonance imaging. One can use any of imaging for confirmation.
Echocardiography is routinely used initially as the non-invasive investigation of choice. Contrast echocardiography may potentially improve the sensitivity of diagnosing non-compaction due to improved contrast between myocardium and blood pool.
The diagnosis of spongy myocardium is challenging, as it has to be distinguished from muscle bundles. In non-compaction left ventricle, there are prominent trabeculations. The adequacy of diagnosis of non-compaction depends very much on experience and knowledge of the investigator. Transthoracic echocardiography is also useful for detecting associated lesions like muscular ventricular septal defects or supra mitral ring along with non-compaction.
Septal indentation in left ventricular hypertrabeculation is a finding mostly in children and its differentiation from left ventricular non-compaction is challenging.
Left ventricular angiography is rarely required for making the diagnosis of non-compaction. But angiography is required in associated complex congenital heart disease.
Other imaging modalities which are being increasingly used these days for diagnosis are computed tomography or cardiac magnetic resonance imaging. MRI provides very useful images. Magnetic resonance cine imaging, using so-called steady-state free precession sequence, is increasingly used because of its ability to image with clarity the compacted and non-compacted layers. This technique provides a better ratio of non compacted to compacted myocardium. It also gives superior visualization of left ventricular thrombi and myocardial fibrosis. Cardiac CT is of limited value in the evaluation of left ventricular function.
Management of symptomatic patients with congestive heart failure is with digoxin, diuretics, angiotensin-converting enzyme inhibitors, beta-blockers and afterload reducing agents. Some patients undergo cardiac transplantation. Cardiac rhythm abnormalities are managed with standard protocol, while some patients may benefit from an implanted cardiac defibrillator for severe ventricular tachyarrhythmias to prevent sudden death.
Hypertrabeculation predisposed patients with reduced left the ventricular function are at risk for clot formation, which further contributes to cerebrovascular events, which certainly adds to comorbidity in patients with LVNC. It is recommended to put these patients on oral anticoagulation once the diagnosis of LV non-compaction is confirmed.
After excluding dilated and hypertrophic cardiomyopathy, one should consider other diagnoses that can present with similar features. Thus, it is essential to distinguish left ventricular non-compaction from acquired changes seen in pulmonary atresia with an intact ventricular septum, layered mural thrombus in the left ventricle, mycotic invasion of the heart, intramyocardial hematoma, or Fabry's disease.
MOGE(S) classification of cardiomyopathies has considered LVNC as a distinct entity; this will hopefully improve knowledge and awareness of the disease.
The previously referenced clinical report predicts a dismal outcome of the disease. But increasing clinical experience has modified the prognosis to some extent by providing devices for life-threatening arrhythmias. Some asymptomatic patients now live up to the seventh decade.
In one case series, the extra-cardiac disease also showed associations with mental and motor retardation. The most common complaint at admission was cardiac failure. The mortality rate was 21 percent and death mainly caused by cardiac failure and sepsis.
Left ventricular non-compaction can lead to cardiac failure, lethal ventricular arrhythmias, mural thrombi leading to cerebrovascular events and sepsis.
Left ventricular non-compaction is an uncommon, congenital cardiomyopathy with a poor outcome. It predisposes the patient to cardiac failure, sepsis, and cerebrovascular events.
Ventricular non-compaction is a distinct genetic heterogeneous disease, that may affect both ventricles. The disorder may be isolated or be associated with other congenital cardiac malformation. It may present as dilated cardiomyopathy or less commonly with restrictive physiology. The prognosis for these patients is generally poor. LVNC patients can die suddenly to arrhythmia, thromboembolic events and left ventricular dysfunction. Some symptomatic patients may benefit from cardiac transplantation. Because of the rarity of the disorder and its diverse presentation, management of the condition is best with a multidisciplinary team.
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