Frequently asked questions about myocarditis: Part one

Myocarditis is a condition in which the heart becomes inflamed due to viral infection, reaction to a drug or an inflammatory condition. Symptoms include fatigue, malaise, chest pain, breathlessness, electrical abnormalities of the heart. It can present acutely, subacutely or as a chronic disease process and can cause an irregular heartbeat. In part one of this two-part series, Dr Sabiha Gati, a vastly experienced consultant cardiologist, answers some of the key questions about this ailment.

How common is viral myocarditis?

Viral infections are the most common cause of myocarditis in the developed world.

Does every viral infection find its way through the heart and circulatory system?

There are roughly 1.5 million new cases of myocarditis every year, with estimates of 10 to 20 cases per 100,000 people. The exact number of viral myocarditis cases is unknown, due to the fact that many cases are subclinical and benign. However, it is estimated that between 1 and 5 per cent of acute viral infection cases my involve myocardium. So, a small number.

Most myocarditis patients are young and healthy. Children, pregnant women and the immunocompromised are most susceptible to this condition.

Does exercise make it more likely you will develop viral myocarditis?

Myocarditis is the cause of between 5 and 10 per cent of sudden cardiac deaths in athletes and up to 20 per cent in military recruits, which suggests that exercise may be a trigger for sudden death in this condition.

Clinical observations suggest that there is a link between high-intensity physical exercise and the development of myocarditis. Although this hasn’t been assessed in humans, the high incidence rate in athletes points to a trend. The higher prevalence in this group can be attributed to the greater exposure to microbes faced by athletes compared to the general population. Contact and team sports also carry an increased infection risk due to the greater chance of droplet infections.

Virus studies in animals suggest that our immunity to respiratory infections reduces with intensive exercise.

How many days after a viral illness should you wait before exercising again?

As well as affecting the heart, viral infections can also cause muscle soreness, joint pain and fatigue. Cold-like symptoms such as coughing, sore throat, runny nose, fever and diarrhoea may also be present. So, it’s important to refrain from exercise while experiencing these symptoms as they could increase the chances of the virus spreading to the blood circulation and potentially affecting the gastro-intestinal tract, and even the heart.

It is recommended that people wait 3-5 days without symptoms before returning to moderate exercise. This is usually enough time for the symptoms of the acute phase of the infection, such as tiredness and a raised body temperature, to pass, though it may extend to 7-10 days in more severe cases.

How long does it normally take to recover from myocarditis?

Exercise and participation in sports is strongly discouraged during the acute phase of myocarditis. The European Society of Cardiology recommends that people with myocarditis only resume exercise after 3-6 months.

The exact rest period is determined by the severity of the disease, heart function, electrical abnormalities and how much fluid there is around the heart. Roughly half of athletes with myocarditis display mild forms which do not result in hospital admission. Such cases usually clear within 4-6 weeks, although intensive exercise is not recommended for at least 3 months before gradually returning to previous levels of intensity.

Are there any long-term effects of myocarditis?

Once myocarditis sets in, it infects the tissue in and around the heart muscle, becoming inflammatory once the immune system reacts to it. The effects of myocarditis depend on the stage of the disease:

• Acute – Direct viral cytotoxicity and focal, diffuse necrosis, destruction of heart.
• Subacute - Human immune activation mediated injury creating autoantibodies that react to the cardiac muscle with inflammatory proteins.
• Chronic – Diffuse myocardial scarring and impairment of heart function and may lead to dilated cardiomyopathy.

Therefore, the long-term effects include heart failure, dangerous electrical abnormalities and an abnormal baseline electrical trace.

In part 2 of this series, Dr Gati continues to answer some of the most important questions about myocarditis including recurrence, symptoms and seeking medical help.

For further consultation on myocarditis or any other heart-related issue, visit Dr Sabiha Gati’s profile, where you can request an appointment with her.