Dilated cardiomyopathy

Cardiomyopathy translates to “heart muscle disease,” so cardiomyopathy is a broad term used to describe a variety of issues that result from disease of the myocardium, or heart muscle.

When cardiomyopathy develops as a way to compensate for some other underlying disease like hypertension or valve diseases, it’s called secondary cardiomyopathy, but when it develops all by itself it’s called a primary cardiomyopathy.

Now the most common type is dilated cardiomyopathy which can cause all four chambers of the heart to dilate, or get bigger.

Specifically new sarcomeres or muscle units in the walls are added in series and the chambers grow larger, which leaves the walls relatively thin compared to the large chamber size with less muscle to use for contraction.

In other words, they have really weak contractions, which means less blood’s pumped out each contraction, meaning there’s a lower stroke volume, and if the heart’s failing to pump out as much blood to both the body from the left ventricle, and the lungs from the right ventricle, patients develop biventricular congestive heart failure, and since contraction happens during systole, we say this is a type of systolic heart failure.

Also, when the chambers get larger, they tend to stretch out the valves that separate the atria and ventricles. When stretched, the valves can’t close all the way, so they start to regurgitate blood back into the atria, called mitral valve regurgitation on the left side and tricuspid valve regurgitation on the right—the former of which might be heard on auscultation as a holosystolic murmur, meaning that it happens throughout systole.

In addition to that, you might also hear an S3 heart sound on auscultation which is the result of blood rushing into and slamming into the dilated ventricular wall during diastole.

Arrhythmias can also be a complication, because stretching out the muscle walls can irritate the cells in the conduction system which are within those walls.

Sometimes an x-ray can be helpful for a diagnosing dilated cardiomyopathy. As far as causes go, most of the time, primary dilated cardiomyopathy is idiopathic, meaning there isn’t a clearly identifiable cause.

Some cases, though can be traced back to specific genetic mutations or genetic conditions like Duchenne Muscular Dystrophy and hemochromatosis.

Also in some cases it could be caused by an infection like coxsackievirus B which causes myocarditis, inflammation of the heart muscle, or Chagas disease, a protozoal infection.

Also, alcohol abuse is strongly linked to dilated cardiomyopathy, since alcohol and its metabolites have a direct toxic effect on the myocardium.

Similarly, certain drugs can also be a cause, including chemotherapy drugs like doxorubicin and daunorubicin, but also drugs like cocaine.

Also, wet beriberi, having too little Vitamin B1 (aka thiamine), can lead to dilated cardiomyopathy. Peripartum cardiomyopathy is an important cause as well, where dilated cardiomyopathy can develop in the third trimester of pregnancy or in the weeks following delivery, probably because of issues like pregnancy-associated hypertension, although about half of patients recover following pregnancy.

As you can see - there are a lot of things that can lead to dilated cardiomyopathy - and regardless of the cause, the outcome is less effective systolic function.

Treatment for severe dilated cardiomyopathy can include a left ventricular assist device or an LVAD, which is a mechanical pump that assists the heart in distributing blood, and in extreme cases someone might have a heart transplant.

All right, as a quick recap… Dilated cardiomyopathy is a disease of the myocardium which causes all four chambers of the heart to get bigger.

Because heart walls will be thin compared to the large chambers, this can result in weak contraction, low stroke volume, and congestive heart failure.

It can also cause valve regurgitation and arrhythmias. Treatment, in extreme cases, is to do a heart transplant.