Definition and Overview

Myocarditis is a medical condition wherein the myocardium, or the heart muscle, becomes inflamed. Also known as inflammatory cardiomyopathy, it can develop in otherwise healthy individuals when viral, bacterial, or fungal infections reach the heart. Most cases are mild and many patients do not suffer from any long-term effects of the condition. However, severe cases can lead to serious complications, including chronic heart failure, or when the heart muscle loses its ability to pump.

Inflammation occurs when the body’s immune system activates immune cells and produces certain chemicals to fight infection. This inflammatory process can cause damage to the heart muscle, causing it to swell and thicken. If the damage is extensive and a large portion of the heart becomes affected, its ability to pump blood will be impaired.

Myocarditis can affect people of any age group, but it tends to be more common in young adults. In fact, it is believed that up to 20% of all sudden death cases in young adults are due to the condition.

Causes of Condition

Myocarditis can be caused by:

1.) Parasites, viruses, fungi, and bacteria, including but not limited to:

  • Borrelia

  • Chlamydia

  • Clostridia

  • Coxsackie B viruses

  • Cytomegalovirus (CMV)

  • Epstein-Barr virus (EBV)

  • Hepatitis C

  • Herpes

  • HIV

  • Influenza

  • Meningococci

  • Mycoplasma (bacteria that cause a lung infection)

  • Parvovirus

  • Staphylococcal (staph) bacteria

  • Streptococcal (strep) bacteria

  • Treponema (the cause of syphilis)

2.) The immune system’s response to infection that causes inflammation

3.) Chemicals released during myocardial cell death

4.) Certain medications that cause allergic or toxic reaction

5.) Certain medical treatments, such as radiation therapy

6.) Certain autoimmune diseases, such as lupus, giant cell arteritis, and Wegener’s granulomatosis

7.) Heavy metals, including copper and iron

8.) Organ rejection following heart transplantation

9.) Electric shock

In up to 50% of cases involving children and young adults, the cause of myocarditis is unknown (idiopathic).

Key Symptoms

Myocarditis normally does not produce symptoms in the early stages or in mild cases. However, when the condition progresses to an advanced stage, patients may experience the following signs:

  • Abdominal pain

  • Arrhythmias

  • Chest pain, which may radiate to the upper part of the body

  • Chronic cough

  • Diarrhoea

  • Fainting (rare)

  • Fatigue

  • Fever

  • Headache

  • Joint pain

  • Light-headedness

  • Shortness of breath while lying down and exercising

  • Small amounts of urine

  • Sore throat

If left untreated, the condition can lead to life-threatening complications, such as:

  • Sudden cardiac arrest - Myocarditis can cause dangerous arrhythmias that can prevent the heart from beating. Unless the patient receives immediate medical attention, this condition can lead to death.

  • Stroke or heart attack - Blood clots are more likely to form if the blood is not properly circulating throughout the body. If these clots block an artery leading to the heart or brain, the patient may suffer from a heart attack or stroke.

  • Heart failure - Severe cases of myocarditis can cause the heart to stop functioning.

Who to See and Types of Treatments Available

Patients showing signs and symptoms of myocarditis can consult a general practitioner (GP) for initial assessment and routine medical tests. These include a physical exam and a thorough review of the patient’s medical history and symptoms. This is often followed by blood tests, which measure levels of certain enzymes that the body releases when certain organs are not working properly.

If the results of blood tests indicate heart abnormalities, patients are referred to a cardiologist, a doctor specialising in disorders affecting the heart. To make a definitive diagnosis, the following tests are performed:

  • Cardiac catheterisation

  • Chest x-ray

  • Echocardiogram

  • Electrocardiogram

  • Endomyocardial biopsy

  • Magnetic resonance imaging (MRI)

  • Nuclear heart scan

Treatment is not always necessary as many cases of myocarditis improve on their own or without treatment. For patients with mild symptoms, it is common for doctors to advise patients against competitive sports for up to six months and to take certain medications to strengthen the immune system so that it can effectively fight off infections. If myocarditis developed as a complication of an autoimmune disorder, the patient can be prescribed with drugs that suppress the immune system (corticosteroids).

More aggressive treatment is necessary when the condition progresses to heart failure. Although this is a serious condition, it can be effectively managed with a combination of medicines and implantable devices used to regulate heart rhythms.

Medicines that are commonly prescribed for the treatment of heart failure include:

  • ACE inhibitors and angiotensin receptor blockers - These work by relaxing and opening up the blood vessels to make it easier for the heart to effectively pump blood throughout the body.

  • Beta-blockers - Used to reduce blood pressure and protect the heart from the effects of “fight or flight” chemicals produced by the body.

  • Diuretics and aldosterone antagonists - Used to treat swelling by making the patient pass more urine.

Implantable devices used to regulate heart rhythms include:

  • Pacemakers - A pacemaker is a small device that is implanted in the chest or abdomen. It uses low-energy electrical impulses to help the heart beat at a normal rate.

  • Cardiac resynchronisation therapy (CRT) devices - These devices are used to resynchronise the contractions of the heart’s ventricles by sending tiny electrical impulses to the heart muscle.

  • Implantable cardioverter defibrillators (ICDs) - Devices designed to monitor heart rhythm. If dangerous rhythms are recorded, the device will deliver shocks to prevent serious heart conditions, such as sudden cardiac arrest, from occurring.

To achieve the best possible treatment outcomes, patients are also advised to:

  • Stop smoking

  • Eat a balanced diet

  • Avoid alcoholic drinks as much as possible

  • Cut down on salt

  • Be more active

References:

  • Bonow RO, et al. Myocarditis. In: Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 10th ed. Philadelphia, Pa.: Saunders Elsevier; 2015. http://www.clinicalkey.com.

  • Bozkurt B, et al. Current diagnostic and treatment strategies for specific dilated cardiomyopathies: A scientific statement from the American Heart Association. Circulation. 2016;134:e579.

  • Cooper LT, et al. The role of endomyocardial biopsy in the management of cardiovascular disease: A scientific statement from the American Heart Association, the American College of Cardiology, and the European Society of Cardiology. Circulation. 2007;116:2216.

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