Non-compaction of left ventricle is often classified as a cardiomyopathy and is characterized by abnormal deep trabeculations, which is more at the apex . Left ventricular non-compaction can be associated with left ventricular dilatation or hypertrophy. Systolic and diastolic dysfunction can occur and other congenital heart diseases can be associated. Ventricular arrhythmias and complete atrioventricular block can occur and present as syncope or sudden cardiac death.
Genetic transmission has been noted in 30-50% of patients and several genes have been implicated. NOTCH signaling pathway seems to be the final common pathway affected . It was thought that embryological arrest of normal endomyocardial morphogenesis was the cause of non-compaction. But some authors have disputed this theory .
In the early stages of development of the heart when the coronary circulation is yet to develop, thin trabeculae prevent ischemia by providing good surface area for direct absorption from the blood in the cavity. Initially trabecular growth is rapid and accounts for most of the ventricular mass. Later on the trabecular growth becomes slower compared to the compact ventricular wall .
A systematic review and meta-analysis of observational studies found 28 eligible studies enrolling 2501 patients with left ventricular non-compaction . Cardiovascular mortality was 1.92 per 100 person years at a median follow up of 2.9 years in the meta-analysis. The risk was similar to that of dilated cardiomyopathy. Risks of thromboembolism and ventricular arrhythmias in left ventricular non-compaction were similar to dilated cardiomyopathy. But incidence of heart failure hospitalizations was higher than in dilated cardiomyopathy. Left ventricular ejection and not the extent of trabeculation, appeared to be an important determinant of adverse outcome in non-compaction of the left ventricle.
Another study of 339 adults identified between 2000 and 2016 assessed the long term survival . Three imaging criteria used for defining left ventricular non-compaction were Jenni criteria, Chin criteria and Peterson criteria. Jenni criteria for left ventricular non-compaction was end systolic non-compacted to compacted myocardial ratio more than 2 . Chin criteria was the end diastolic ratio between the troughs and peaks of trabeculation to epicardium less than 0.5 . These two were echocardiographic criteria. Peterson criteria was ratio of end diastolic non-compacted to compacted myocardium more than 2.3 on magnetic resonance imaging . Median age was 47.4 years and 59 patients died during a median follow up of 6.3 years. 57% of patients had left ventricular ejection fraction below 50%. Isolated apical noncompaction was noted in 48% . Age, left ventricular ejection fraction below 50% and noncompaction extending from apex to mid or basal segments were the factors associated with all-cause mortality on multivariable Cox regression analysis . An interesting finding in this study from Mayo Clinic, Rochester (MN) was that those with isolated apical noncompaction and normal left ventricular ejection fraction had survival comparable to general population.
Treatment of left ventricular non-compaction follow the same lines as those with heart failure due to dilated cardiomyopathy, with diuretics, beta blockers, angiotensin converting enzyme blockers and other afterload reducing agents. Risk of thromboembolism and anticoagulation may be considered in those with left ventricular dysfunction. Implantable defibrillators may be needed in those with life threatening ventricular arrhythmias .