Myocarditis

Definitions & Key takeaways

Myocarditis is an inflammation of the heart muscle, also known as the myocardium. It can be caused by a variety of different infections, including viruses, bacteria, fungi, and parasites. It can also be caused by autoimmune diseases, such as lupus, or by drugs and toxins. Symptoms of myocarditis include chest pain, palpitations, shortness of breath, and fluid retention which might be an indication of heart failure. Treatment for myocarditis involves medications to reduce inflammation, and antibiotics to treat any underlying infections. In some cases, a heart transplant may be necessary.

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With myocarditis, myo means muscle, card means heart, and itis means inflammation. So, myocarditis is inflammation of the myocardium, which is the muscular middle layer of the heart wall, which contracts and relaxes so the heart can pump blood all around the body.
Inflammation in the myocardium layer causes swelling, and that damages the heart muscle cells' ability to contract. That means that less blood gets pumped out of the heart with each heartbeat.
And if myocarditis is severe enough, it can lead to heart failure, which is when the heart can't keep up with the demands of the body.
Once the inflammation resolves, the heart contraction typically returns to normal, but occasionally, when the inflammation is really severe, it can cause fibrosis or scar tissue in the myocardium.
Scar tissue doesn't contract normally, so if that happens, it can cause long-term problems with heart contraction. In North America, viral infections, specifically coxsackievirus bee infections, are the main cause of myocarditis.
Viral infections can trigger lymphocytic myocarditis, which is when lymphocytes, the B and T cells of the immune system, and water make their way into the interstitial space, the space between heart muscle cells.
There are plenty of other infectious causes as well though. One of these is Japanosoma cruzi.
A single-celled protozoan that causes Chager's disease throughout South America. In Chagas disease, under a microscope, it's possible to see groups of amatogotes within the heart muscle cells, which are trapanosomes that are in the intracellular stage.
As a result, the heart muscle cells in the crows will die. There's also Tricinella.
A roundworm that moves from the intestines into various parts of the body causing a variety of problems, including myocarditis.
Myocarditis can also be seen in Lyme disease, which is caused by the bacteria Borrelia bergdorferi, which is spread by deer ticks.
Finally, in immunocompromised individuals, there's toxoplasma gondi. A single-celled parasite harbored by cats that can cause myocarditis.
So, those are the infectious causes, but there are also non-infectious causes of myocarditis as well. These include systemic lupus erythematosis, also known as lupus.
And polymyositis, which is a generalized inflammation of the muscles where the immune system starts to attack the myocardial layer of the heart.
There's also drug associated myocarditis, which means there's an adverse drug reaction that inflames the heart. Drug reactions cause a hypersensitivity myocarditis.
Which is when eosinophils get into the blood vessels in the myocardium. Finally, there's giant cell myocarditis, which causes inflammation in the heart from an unknown cause.
The key finding here is that macrophages, the immune cells that engulf foreign substances, start to fuse together to form a single giant cell, hence the name.
Individuals with myocarditis can have a chest pain that is sometimes positional. Meaning that it can get better or worse depending on the body's position.
It can also cause arrhythmias or irregular heartbeats because the inflammation affects the pacemaker cells traveling through the myocardium.
There can also be more general symptoms like fatigue. Fever And shortness of breath.
In severe cases, when myocarditis starts to develop into heart failure, there can be additional symptoms like fluid retention in the feet and ankles.
Individuals with myocarditis suffer heart muscle damage. Which causes troponin and creatine kinase levels to rise on blood tests.
An electrocardiogram can show sinus tachycardia, a fast heart rate. As well as T wave inversions and saddle-shaped ST segment elevations.
Because it looks a bit like a horse saddle. In addition, a chest X-ray might show an enlarged heart, while echography might show inflamed heart muscle walls.
Ultimately, the diagnosis is based on a biopsy of the cardiac muscle, but doing that procedure comes with some risk, so it's not always done.
The treatment of myocarditis depends on the underlying cause. Viral myocarditis usually improves slowly over time, and other infections are treated with appropriate antibiotics.
If there are signs of heart failure, then they are typically managed with a medication and careful fluid balance. Arrhythmias usually resolve as the inflammation improves as well.
Finally, in severe cases, like some cases of Chager's myocarditis and giant cell myocarditis, a heart transplant may be needed if other treatments don't work.
All right, as a quick recap, in North America, myocarditis is most often caused by viruses like Coxsackie. But in South America, a common cause is Sugar's disease.
Symptoms include positional chest pain and arrhythmias. And classic ECG findings include sinus tachycardia, with saddle-shaped ST segment elevations.
And T wave inversions.