Left Ventricular Non-Compaction (LVNC)

Overview

Left ventricular non-compaction (LVNC) is a rare genetic disease of the heart muscle, also called Non-compaction cardiomyopathy (NCC),  spongiform cardiomyopathy. Compaction is a process that occurs during the development of the heart when a baby is in the womb. If this process is not complete, the inside of the heart muscle (the one in contact with the blood) will look spongy or “trabeculated”. Normally, it is smooth. Originally, non-compaction was diagnosed very rarely. It seemed to be associated with dangerous heart rhythms and, often, severe weakness of the heart muscle. Sometimes, if the trabeculations are deep, a blood thinning medication is used. In some cases, implantation of a defibrillator may be required to treat dangerous rhythms. In very severe cases, heart transplantation is sometimes required but this is rare.

Symptoms

Symptoms range greatly in severity. Most are a result of a poor pumping performance by the heart. The disease can be associated with other problems with the heart and the body.

Causes

During development, the majority of the heart muscle is a sponge-like meshwork of interwoven myocardial fibers. As normal development progresses, these trabeculated structures undergo significant compaction that transforms them from spongy to solid. This process is particularly apparent in the ventricles, and particularly so in the left ventricle. Noncompaction cardiomyopathy results when there is failure of this process of compaction. Because the consequence of non-compaction is particularly evident in the left ventricle, the condition is also called left ventricular noncompaction. Other hypotheses and models have been proposed, none of which is as widely accepted as the noncompaction model.

Diagnosis

More recently, newer imaging techniques with higher resolution mean that we notice trabeculation in the heart much more often. As such, many patients who will have a much less severe disease course are diagnosed with this condition. Sometimes the term “hyper-trabeculation” is used to distinguish the finding of sponginess from the condition known to cause dangerous rhythms and heart muscle weakness.

Newer genetic tests have also revealed that in many cases where hyper-trabeculation is prominent, mutations of the same genes that cause hypertrophic cardiomyopathy can be found, suggesting some overlap between these conditions. Medications can be used to treat the dangerous rhythms or heart muscle weakness associated with LVNC.

Treatment

The classical triad of complications - heart failure, ventricular arrhythmias and systemic embolic events -  are common in patients with advanced disease, although overall, they are less frequently observed in recent studies than they were in initial reports. Oechslin et al reported that in a group of 34 adults with left ventricular noncompaction, the presence of higher final diastolic diameter of left ventricle, low ejection fraction, functional class III-IV (New York Heart Association), persistent or permanent atrial fibrillation and bundle branch block were related with high risk and poor prognosis, calling to consider the possibility of implantation of an automated cardiac defibrillator and evaluation for transplant. Mortality was similar in left ventricular noncompaction as with patients with nonischemic dilated cardiomyopathy  (3 year survival of 85 to 83 %).

Diagnosis calls for the study of family members, and maybe, genetic counseling. Due to the high prevalence of neuromuscular disorders reported in patients with left ventricular noncompacton, neurological and musculoskeletal evaluations are also recommended.