If you have never heard of non-compaction cardiomyopathy you are in good company. Every so often I have a patient who is diagnosed with a condition I’ve never heard about, and today that was non-compaction cardiomyopathy. Cardiomyopathy I see fairly commonly, but non-compaction was something I’d never heard about. Maybe sometime in med school I should have learned and remembered about cardiac muscle compaction, but if so it did not stick in my memory bank.
It turns out that in the developing fetus the muscle of the heart between 6-18 weeks gestation forms first as strands of muscle that are loosely connected and have cavities between them. This happens especially the thickest part of the heart muscle in the left ventricle which pumps the blood out to the body. It is believed that the purpose of this is to allow the myuocardial cells in these strands of heart muscle to get their oxygen and nutrients directly from blood flowing around them before the coronary arteries develop and the heart’s own vascular supply has formed. Later in development these strands of muscle tissue are compacted into a solid wall of muscle in a process called compaction.
In very rare individuals this process does not occur properly, and the left ventricular wall remains largely made up of loosely associate strands of muscle which are far less functional as a pump than a normal left ventricle. This can lead to development of symptoms of congestive heart failure as the affected individual grows older really anytime between late childhood and mid to older adulthood.
Non-compaction cardiomyopathy was first described in 1984 by Engberding and Bender in an Am. Jol. Cardiology article, and since has been found to be associated with a rare genetic mutation in some cases. Normal individuals can have some strands of myocardial tissue inside the heart and these are called trabeculations. In non-compaction cardiomyopathy the width of the trabeculated lining of the heart is at least twice the thickness of the normal solid heart muscle in the left ventricle. Echocardiography and cardiac MRI are used to confirm this diagnosis, and in about 30% of cases a specific genetic mutation is found. Non-compaction cardiomyopathy is described in excellent detail in this 2011 European Heart Journal Article.
The prognosis in non-compaction cardiomyopathy is highly variable and really poorly understood due to the relatively recent discovery of this as a specific condition and the very few individuals found to have non-compaction cardiomyopathy. Although non-compaction cardiomyopathy is still incompletely understood, it is felt that some other developmental conditions including other cardiac abnormalities especially of the left coronary artery and the various heart valves and pulmonary vessels, as well as non-cardiac neuromuscular defects may be sometimes associated. Complications other than congestive heart failure that may be associated with non-compaction cardiomyopathy include blood clots forming in the trabecula leading to stroke or other embolic event.
Other causes of cardiomyopathy are much more common. Ischemic cardiomyopathy occurs when coronary artery disease leads to a large part of the heart muscle to be damaged or killed in myocardial infarctions (heart attacks) leaving the rest of the heart to compensate. Post-viral cardiomyopathy occurs after some viral infections that damage the heart muscle cells, leaving them functioning poorly. Post-partum cardiomyopathy occurs after childbirth uncommonly. Dilated cardiomyopathy is when the heart becomes stretched to a degree that it cannot pump effectively, usually related to chronic congestive heart failure. Restrictive cardiomyopathy occurs when the epicardium (outer covering of the heart) becomes non-compliant and the heart cannot fill with blood enough to allow normal pump function. All of these other types of cardiomyopathy have been described for much longer, and are relatively much more common than non-compaction cardiomyopathy. Being prompted to hit the internet to see what’s up with a patient found to have a condition I’ve never heard of keeps me in the learning mode and that’s good for me.