|Year : 2015 | Volume
| Issue : 2 | Page : 35-38
Isolated Non Compacted Left Ventricle: A Diagnostic Dilemma
Mridul Chaturvedi, Omkar Singh, Ayush Agarwal
Department of Medicine, S.N. Medical College, Agra, Uttar Pradesh, India
|Date of Web Publication||16-Jun-2015|
Dr. Omkar Singh
424 Saptrishi Apartments, Sector 16 B, Awas Vikas Colony, Agra, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Since the last two decades isolated non compacted LV is recognized as a distinct congenital cardiomypathy produced due to arrest in the embryogenesis and condensation of normal adult myocardium. Course of the disease is malignant and definitive treatment is still not available. Cases are now more and more sporadically recognized due to availability of definitive echocardiographic diagnostic criteria from different parts of India and other countries. MRI too has superiority for the diagnostic identification of the disease and is also helpful for planning management.
Keywords: Cardiomyopathy, embryogenesis, myocardium, noncompaction
|How to cite this article:|
Chaturvedi M, Singh O, Agarwal A. Isolated Non Compacted Left Ventricle: A Diagnostic Dilemma. Heart India 2015;3:35-8
| Introduction|| |
In the last two decades, left ventricular noncompaction (LVNC) has emerged as a rare, distinct cardiomyopathy based on its distinct morphology. Noncompaction of the ventricular myocardium is a congenital cardiomyopathy, caused by arrest of normal embryogenesis of the endocardium and myocardium. Though it is often associated with other congenital cardiac defects, but it can be present as a separate entity. Clinical manifestations are highly variable, ranging from no symptoms to congestive heart failure (CHF), arrhythmias, and systemic thromboembolization.  Echocardiography (ECHO) has been the diagnostic procedure of choice, but magnetic resonance imaging (MRI) is emerging as an equally valuable diagnostic tool. Various diagnostic criteria have been demonstrated to identify, and high degree of suspicion is needed for the correct diagnosis as it is often missed or delayed.
| Embryology|| |
In early embryogenesis, heart is a loose, interwoven mesh of muscle fibers.  The developing myocardium gradually condenses. Gradual compaction of this spongy meshwork of fibers and intertrabecular recesses, or "sinusoids," occurs between 5 th and 8 th week of embryonic life, from the epicardium to endocardium and from the base of the heart to the apex. ,,,, The coronary circulation develops concurrently during this process, and the intertrabecular recesses are reduced to capillaries.  Normally, trabecular compaction is more complete in left ventricle (LV) than in right ventricle (RV). This compaction process, coinciding with the invasion of the coronary arteries into the myocardium from the epicardium, is more pronounced in the LV than in RV and it results in more trabeculated endomyocardial surface of RV. Noncompaction of LV is believed to be the result of an arrest in endomyocardial morphogenesis. It is characterised by numerous, excessively prominent ventricular trabeculations and deep intertrabecular recesses (creates spongiform appearance, term used in past).
Noncompaction of ventricular myocardium is often associated with other congenital cardiac malformations like obstruction of the right or left ventricular outflow tracts, complex cyanotic congenital heart disease, and coronary artery anomalies. , Rarely, noncompaction of LV myocardium may occur without associated cardiac anomalies and is called isolated noncompaction of left ventricular myocardium, a condition described in infants and children, and very rarely in adults. 
Isolated noncompaction of the ventricular myocardium (INVM), first described by Chin et al.  is characterized by persistent embryonic myocardial morphology found in the absence of other cardiac anomalies to explain the abnormal development. In such cases, the resultant deep recesses communicate only with the ventricular cavity, not the coronary circulation.
| Genetics|| |
Both familial and sporadic forms of noncompaction are reported. Chin et al. studied eight pediatrics cases and demonstrated familial recurrence in half of patients.  Oeshlin et al. study demonstrated familial recurrence in 18% in the largest reported adult population with INVM.  Genetic analysis allows better understanding of this unique cardiomyopathy. There is evidence that LVNC is a genetically heterogeneous disorder. A point mutation in the taffazin (TAZ/G4.5) gene has been identified in a family with severe infantile X-linked isolated LVNC;  however in adult population with LVNC, the cardiomyopathy is not caused by mutations in the G4.5 gene. With a genomic wide linkage analysis in a family with autosomal dominant LVNC, a locus containing the LVNC disease gene was identified to map to chromosome 11p15. ,
There have been reports of mutations in several genes, including taffazin (TAZ/G4.5), LIM domain-binding protein 3 (ZASP/LDB3), α-dystrobrevin (DTNA), and lamin A/C (LMNA). 
| Clinical Presentation|| |
Symptoms are associated with:
- Depressed left the ventricular systolic function,
- Ventricular arrhythmias, and
- Systemic embolization.
Depressed left ventricular functions
The mechanism of systolic dysfunction in noncompaction is not clear though studies suggest that subendocardial hypoperfusion and microcirculatory dysfunction may play roles in ventricular dysfunction and arrhythmogenesis. Diastolic dysfunction in ventricular noncompaction may be due to both abnormal relaxation and restrictive filling caused by the numerous prominent trabeculae.  Chin et al.  suggested that because of the prominent, numerous trabeculae, subendocardial ischemia may result from isometric contraction of the endocardium and myocardium within the deep intertrabecular recesses. Patients may present with dyspnea, chest pain, palpitations, CHF.
The mechanism is unclear, but the similarity of noncompaction of left ventricular myocardium to arrhythmogenic right ventricular dysplasia has been pointed out. Arrhythmias are common in patients with ventricular noncompaction. Atrial fibrillation has been reported in over 25% of adults with INVM. , Ventricular tachyarrhythmia have been reported in as many as 47%. Sudden cardiac death accounted for half of the deaths in the larger series of patients with INVM. ,, Although ventricular arrhythmias occurred in nearly 40% of patients in the initial description of INVM by Chin et al.,  Ichida  et al. described no cases of ventricular tachycardia or sudden death in the largest series of pediatric patients with INVM. Paroxysmal supraventricular tachycardia and complete heart block have also been reported in patients with INVM. ,
Embolic complications may be related to the development of thrombi in the extensively trabeculated ventricle, depressed systolic function, or the development of atrial fibrillation. , Patients can present with transient ischemic attack, cerebrovascular accident, mesenteric infarction, pulmonary embolism and brachial artery embolism. Of interest, no systemic embolic events were reported in the largest pediatric series with INVM. 
An association between INVM and facial dysmorphisms, including a prominent forehead, low-set ears, strabismus, high-arching palate, and micrognathia, was described by Chin et al.  One-third of children with INVM in the series by Ichida et al.  had similar dysmorphic facial features. No associated dysmorphic facial features were observed in two adult populations with INVM. , An association between noncompaction and neuromuscular disorders has also been described,  with as many as 82% of patients having some form of neuromuscular disorder
| Diagnosis|| |
Diagnostic criteria are described concisely in [Table 1].
|Table 1: Diagnostic criteria for the diagnosis of isolated noncompacted cardiomyopathy |
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Findings are usually nonspecific and include left ventricular hypertrophy, repolarization changes, inverted T waves, ST segment changes, axis shifts, intraventricular conduction abnormalities, and atrio-ventricular block. ,,, Oechslin et al.  described left bundle branch block in 44% of adult patients with INVM.
This is an ideal method of choice for LVNC. Diagnostic criteria are ,,,
- Absence of associated cardiac abnormalities.
- Excessively thickened myocardial wall with a thin, compacted epicardial layer and a thick, noncompacted endocardial layer. The endocardial layer consists of prominent trabeculations and deep intertrabecular recesses, which communicate with left ventricular cavity. For assessing the extent of noncompaction, site of maximal thickness should be taken. The non-compacted layer should be at least twice thick of an epicardial layer [Figure 1].
|Figure 1: Short axis image of left ventricular cavity at end systole. To quantify the extent of non-compaction at the site of maximal wall thickness, the end systolic ratio of noncompacted (n) to compacted (c) thickness was determined|
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- Deep intertrabecular recesses communicate with LV thus filled with blood as visualised by color Doppler.
- Predominantly affected segments are apical and midventricular of both inferior and lateral wall. To assess the extent of the non-compaction at the site of maximal thickness, the preferred method is to measure the end-systolic ratio of noncompacted to compacted thickness. As these trabeculations can also be found in LVH caused by hypertensive cardiomyopathy or dilated cardiomyopathy. Therefore, the ratio of noncompacted to compacted layers in IVNC should be compared with the ratio of trabeculated to untrabeculated dimensions. , The color Doppler study can show typical forward and reversed direct blood flow from the ventricular cavity into the spaces between the prominent trabeculations throughout the cardiac cycle.  The obvious limitation of echo is the cases are often misdiagnosed as dilated or hypertrophic cardiomyopathy, heart tumor and thrombus formation in the ventricle.
| Cardiovascular Magnetic Resonance|| |
Magnetic resonance imaging provides good correlation with echo for localization and extent of noncompaction and is useful in cases with poor echocardiographic window. Cardiovascular magnetic resonance (CMR) is considered superior to ECHO in detecting non compaction as it demonstrates the myocardial thickness and prominent trabecular architecture of the LV. In addition, the demonstration of differences in MRI signal intensity in noncompacted myocardium may help identify substrate for potentially lethal arrhythmias. Petersen et al. described the criteria for the diagnosis by CMR: The ratio of noncompacted myocardium to compacted myocardium must be >2.3 during the diastole (sensitivity of 86% and specificity of 99%).  Later, Jacquier et al. described another method to diagnose this entity: A trabeculated left ventricular mass above 20% of total mass with a sensitivity of 91.6% and a specificity of 86.5% is predictive of LVNC. 
Recently, Wan J et al. in 2013 have shown that in patients considered to meet criteria for LVNC, late gadolinium enhancements distributions were strikingly heterogeneous with appearances attributable to three or more different cardiomyopathic processes [Figure 2] and [Figure 3]. 
|Figure 2: A magnetic resonance image of a patient with noncompaction showing T1-weighted coronal image (a), axial image (b) of the left ventricle and T2-weighted image (c). An inner zone of noncompacted myocardium (small white arrows) is distinguishable from a thin outer zone (white arrows) of compacted myocardium in the left ventricle|
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|Figure 3: T2-weighted imaging (c) reveals a high-intensity area at the apex (white arrow) consistent with disturbed microcirculation due to fibrosis, thrombus formation, and hypo kinesis of this area|
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| Management|| |
In LVNC, management is purely symptomatic. As there is increased frequency of arrhythmias, ambulatory electrocardiogram monitoring should be performed annually. β-blocker like carvedilol has some beneficial effect on left ventricular function.  Biventricular pacemakers may have a role in the treatment of LVNC patients with heart failure, reduced left ventricular function, and prolonged intraventricular conduction. Long-term prophylactic anticoagulation is recommended for prevention of systemic embolization in all patients with ventricular noncompaction whether or not thrombus has been found. , Screening ECHO of first degree relatives is recommended because of familial association. Oechslin et al.  reported that patients with higher left ventricular end diastolic diameter on presentation, New York Heart Association class III-IV, permanent or persistent atrial fibrillation, and bundle branch block are candidates for early, aggressive interventions, including consideration of cardioverter defibrillator implantation and evaluation for transplantation.
| Prognosis|| |
Although the prognosis for patients with noncompaction of the ventricular myocardium varies, nearly 60% of patients described in one study  had either died or undergone cardiac transplantation within 6 years of diagnosis. The occurrences of systemic emboli, ventricular arrhythmias, and death were considerably lower in the largest pediatric series with INVM when compared with adults and the initial case series by Chin et al.,  although nearly 90% of patients followed for up to 10 years developed left ventricular dysfunction. The segmental pattern of involvement of noncompaction in children is mostly similar to that seen in adults and systolic dysfunction in children is closely related to the number of affected segments. 
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[Figure 1], [Figure 2], [Figure 3]