Discussion

Non-compaction is a heterogeneous myocardial abnormality of unknown aetiology.Reference Anderson, Jensen and Mohun ² Features include multiple prominent ventricular trabeculations, deep intertrabecular recesses, and a bi-layered myocardium consisting of a thick, spongy, non-compacted endocardial layer and a thin, compacted, epicardial layer.Reference Finsterer, Stollberger and Towbin ³ Abnormal trabeculations are typically most evident in the apical portion of the left ventricle with extension to the lateral left ventricular wall, distal to the papillary muscles.Reference Finsterer, Stollberger and Towbin ^{3 ,} Reference Towbin, Lorts and Jefferies ⁴ The left ventricular cavity communicates with the intertrabecular spaces without evidence of perfusion by the epicardial coronary artery system.Reference Towbin, Lorts and Jefferies ⁴

It has been speculated that arrest of endomyocardial morphogenesis with failure in the compaction pathway represents the pathogenetic mechanism underlying non-compaction; however, this hypothesis is unproven.Reference Towbin, Lorts and Jefferies ⁴ It seems more likely that non-compaction of the ventricular myocardium results from abnormal persistence of the trabecular layer rather than from non-compaction of the ventricular wall.Reference Henderson and Anderson ⁵ Indeed, if persistence of the embryonic sinusoids was the pathogenetic mechanism, direct communication with the coronary arteries would be expected and should have been documented; however, this contradicts the definition of non-compaction.Reference Finsterer, Stollberger and Towbin ^{3 ,} Reference Towbin, Lorts and Jefferies ⁴ Also, as the excessive trabeculations in non-compaction lack embryonic features (sparse Purkinje cells, atrial natriuretic factor negative, and abundant in coronary vasculature), non-compaction cannot be considered a retention of the embryonic design. Therefore, the lesion may result from the compact wall growing into the ventricular lumen in a trabecular fashion.Reference Jensen, van der Wal, Moorman and Christoffels ⁶ Indeed, antenatal echocardiograms did not identify foetal non-compaction in our patient.

Non-compaction was originally reported as an isolated cardiomyopathy.Reference Finsterer, Stollberger and Towbin ^{3 ,} Reference Towbin, Lorts and Jefferies ⁴ However, non-compaction has been subsequently described in all age groups in association with most forms of CHD. Right-sided lesions, especially Ebstein’s anomaly, pulmonic stenosis, pulmonary atresia, tricuspid atresia, and tetralogy of Fallot, are more frequently coupled with non-compaction. Congenital non-compaction has been associated with distinct genetic mutations, albeit a causal relationship between these monogenic disorders and non-compaction remains to be established.Reference Finsterer, Stollberger and Towbin ³ Genetic abnormalities may cause both structural malformations and impair left ventricular myocardial differentiation. Haemodynamic disturbances during foetal life or post-natally may trigger or contribute to alterations of left ventricular architecture in genetically susceptible individuals.Reference Finsterer, Stollberger and Towbin ^{3 ,} Reference Stahli, Gebhard and Biaggi ⁷

Cardiac magnetic resonanceReference Secchi, Di Leo and Papini ⁸ criteria for the diagnosis of non-compaction includeReference Nucifora, Sree Raman and Muser ⁹ : visual appearance of two distinct myocardial layers (a compacted epicardial layer and a non-compacted endocardial layer); marked trabeculation and deep intertrabecular recesses within the non-compacted layer; and non-compacted to compacted end-diastolic myocardial ratio >2.3 and/or non-compacted to global end-diastolic left ventricle mass ratio >0.20.

CHD and non-compaction are mainly seen in children.Reference Tsai, Ebenroth, Hurwitz, Cordes, Schamberger and Batra ^{10 ,} Reference Yu, Wang, Zheng and Zou ¹¹ The efficacy of surgical treatment of these patients is largely unknown. There is evidence suggesting that the presence of non-compaction may increase the risk of operative repair of congenital cardiac malformations.Reference Tsai, Ebenroth, Hurwitz, Cordes, Schamberger and Batra ^{10 ,} Reference Yu, Wang, Zheng and Zou ¹¹ Indeed, children who present with heart failure and poor ventricular function may have worse outcomes (death or intractable heart failure) post-operatively.Reference Yu, Wang, Zheng and Zou ¹¹ In these patients, poor ventricular function may be attributed to non-compaction, CHD, or both. Surgery can effectively relieve heart failure, improve ventricular function, and decrease heart size.Reference Yu, Wang, Zheng and Zou ¹¹ This was the case in our patient, whose left ventricular function was restored post-surgery and balloon angioplasty.

CHD co-exists with non-compaction in 12% of adult cases. The prevalence of non-compaction is highest for Ebstein’s anomaly followed by aortic coarctation, tetralogy of Fallot, and bicuspid or unicuspid aortic valve.Reference Stahli, Gebhard and Biaggi ⁷ Recent data suggest that bicuspid aortic valve is present in 11% of non-compaction cases.Reference Stahli, Gebhard and Biaggi ^{7 ,} Reference Agarwal, Khandheria, Paterick, Treiber, Bush and Tajik ^{12 ,} Reference Towbin ¹³ Notably, only 10 cases of non-compaction with bicuspid aortic valve and coarctation have been reported in the literature (Table 1 and Supplementary figure S1). It should be noted, however, that there are reports showing no increased risk in developing left ventricular non-compaction cardiomyopathy in the setting of bicuspid aortic valve.Reference Shen, Capoulade and Tastet ²⁰

Table 1. Published cases of left ventricular non-compaction associated with bicuspid aortic valve and aortic coarctation.

In conclusion, the pathogenesis of non-compaction is enigmatic and the clinical implications of the disorder, as well as the optimal management, remain debatable. Concomitant bicuspid aortic valve, aortic coarctation, and non-compaction are a recently defined association that needs further investigation. A major query is whether these entities interact to hasten the potential for adverse clinical events. Repair of the cardiovascular abnormalities seems to restore left ventricular function.