So, What is myocarditis?

Myocarditis is inflammation of the heart muscle, the myocardium. It is most commonly caused by viral infections, although it can also be triggered by autoimmune conditions, certain medications, and, more rarely, reactions to vaccines. The inflammation can weaken the heart’s ability to pump effectively and can interfere with its electrical activity, which is why myocarditis can cause chest pain, palpitations, breathlessness, and in some cases more serious problems such as heart failure or dangerous rhythm disturbances.

In my experience, myocarditis is a condition patients have heard of but rarely understand well, often having read alarming things online. Over more than 20 years as a Consultant Cardiologist at Kingston Hospital, and across my private clinics at Parkside, The New Victoria, Cleveland Clinic London and Heartsure, I have assessed a considerable number of patients referred with possible myocarditis, and the reality is usually far more reassuring than the search results they have read. Most cases are mild, recover well, and need careful monitoring rather than aggressive treatment.

What causes myocarditis

The heart muscle becomes inflamed when something triggers the body’s immune system to attack heart tissue, either directly or indirectly. The most common causes I see in clinical practice are listed below.

• Viral infections, particularly enteroviruses, adenoviruses, influenza, and some coronaviruses
• Autoimmune conditions, such as lupus or sarcoidosis
• Bacterial infections, in rarer cases
• Certain medications and recreational drugs
• Reactions to some vaccines, which are uncommon and usually mild
• Toxins, including excessive alcohol use over long periods

Viral myocarditis is by far the most common cause in the UK. In many patients I see, the condition starts a few days or weeks after a flu-like illness or chest infection that they had not connected to their cardiac symptoms.

From my work with patients over the years, taking a careful history of any recent infection works better than ordering broad blood tests early on, because the timeline of symptoms is often the strongest clue to the cause.

The symptoms of myocarditis

Symptoms vary widely. Some patients have very mild symptoms that resolve on their own, while others can become unwell quickly. The most common presentations I see in clinic are listed below.

• Chest pain, often sharp, central, and worse when lying flat or breathing in
• Palpitations, including a fast or irregular heartbeat
• Breathlessness, particularly on exertion
• Unusual fatigue lasting longer than a typical viral illness
• A general feeling of being unwell, often a few weeks after an infection
• Dizziness or near-blackouts in more severe cases

The chest pain associated with myocarditis is often quite distinctive. Unlike the pressure or tightness of angina, it tends to be sharper, related to breathing or position, and not particularly brought on by exertion. This is one of the patterns I rely on heavily when assessing a patient who has had a recent viral illness.

What I’ve found over many years of assessing chest pain is that sharp pain which worsens when lying flat works better as an early indicator of myocarditis than relying on blood tests alone, because positional symptoms point towards inflammation of the heart or its lining far more reliably than vague tightness.

How serious is myocarditis

Most patients with myocarditis make a full recovery, particularly when the cause is a self-limiting viral infection. However, the severity does vary, and this is why proper assessment is important.

The spectrum looks broadly like this.

• Mild cases, with brief symptoms and full recovery within weeks
• Moderate cases, where symptoms persist for a few months and require monitoring
• Severe cases, where significant heart muscle weakness develops, leading to heart failure
• Rare cases of fulminant myocarditis, where the heart deteriorates rapidly and urgent hospital treatment is required

In my own practice, the great majority of patients I assess for suspected myocarditis fall into the mild or moderate group. I’d estimate that fewer than one in twenty develop significant lasting heart muscle damage, and the rest recover well with appropriate rest, monitoring, and follow-up.

How myocarditis is diagnosed

There is no single test that confirms myocarditis. The diagnosis is built up from the history, the examination, and a combination of investigations. The tests I typically arrange are listed below.

• A 12-lead ECG, which often shows non-specific changes that point towards inflammation
• An echocardiogram, to assess heart muscle function and look for any reduction in pumping efficiency
• Blood tests, including troponin, which is often raised in myocarditis
• Inflammatory markers, such as CRP
• A cardiac MRI, which is the gold-standard non-invasive test for confirming inflammation
• An ambulatory ECG or ZIO patch, if rhythm disturbances are suspected
• Occasionally, a coronary angiogram to rule out narrowed arteries as a cause of the symptoms

Having reviewed the imaging in many of these cases, cardiac MRI works better than echocardiography alone for confirming myocarditis, because it can identify inflammation and scarring within the heart muscle itself, rather than just the consequences of those changes. That said, an echocardiogram remains essential because it is quick, widely available, and gives an immediate picture of how well the heart is pumping.

Myocarditis and exercise, a vital point

One area where I am very firm with patients is exercise. Continuing to train, particularly at high intensity, during active myocarditis is one of the most dangerous things a patient can do. The inflamed heart muscle is unstable, and intense exertion is a recognised trigger for serious rhythm disturbances.

The guidance I give in clinic is generally as follows.

• Avoid all moderate-to-vigorous exercise for at least three to six months
• Return to physical activity gradually, with medical guidance
• Have a follow-up echocardiogram and, where appropriate, MRI before returning to high-intensity sport
• Athletes should not return to competition without specialist cardiac clearance

From my work with patients who are keen runners, cyclists, or gym-goers, I’ve found that the people who pause training fully for three months recover far more reliably than those who try to “ease back in” early. This is one situation where doing less, for longer, is genuinely the safer choice.

Treatment for myocarditis

Treatment depends on the cause and severity. For most patients with mild viral myocarditis, the mainstay of care is rest, time, and follow-up. The approaches I commonly use are listed below.

• Restriction from exercise and physical exertion
• Standard heart failure medications, if there is any reduction in pumping function
• Beta-blockers or other rhythm-control medication, if palpitations are a problem
• Treatment of the underlying cause, where there is one, such as immunosuppression for autoimmune myocarditis
• Hospital admission, in more severe cases requiring closer monitoring
• Cardiac rehabilitation, once recovery is well established, often through the team at Heartsure

Looking back at the patients I’ve followed through to full recovery, structured cardiac rehabilitation works better than informal “getting back to it on your own” because it provides supervised, graded exercise at the point when the heart is recovering but still vulnerable. The patients who use rehab tend to return to full activity more confidently and more safely.

What recovery looks like

Recovery from myocarditis is usually gradual, and patience is essential. The general pattern I observe in clinic is the following.

• The first month is the time for the most caution, with strict avoidance of significant exertion
• Symptoms often start to improve over weeks two to six
• Most patients are noticeably better by three months
• Full recovery often takes six months
• Follow-up imaging is generally arranged at three and six months to confirm the heart has returned to normal

Some patients are left with a slightly reduced exercise tolerance, or occasional palpitations, even after recovery. These usually settle over time, but they should always be reviewed if they persist.

When to seek a cardiology opinion

You should consider a specialist cardiac assessment if you have any of the following.

• Chest pain after a recent viral illness, particularly if positional or sharp
• New palpitations following an infection
• Persistent breathlessness or fatigue beyond what a viral illness would normally cause
• A raised troponin reading on routine testing
• A wish for clearance to return to sport after a previous diagnosis of myocarditis
• Concerns about your heart in the weeks following COVID-19

You can read verified feedback from patients I’ve seen if it helps you decide whether a private cardiology opinion is the right step.

Conclusion

Myocarditis is a condition that sounds frightening, but in most cases is manageable, recoverable, and not as catastrophic as the internet may suggest. The key is proper assessment, accurate diagnosis, and a sensible period of rest before returning to normal activity. With the right tests and follow-up, the great majority of patients recover fully and return to their previous lifestyle, including exercise and sport, in time.

If you have had symptoms following a viral illness, have been told your troponin is raised, or want to discuss return to sport after a previous diagnosis, you can contact me, Dr Arvind Vasudeva, on 020 8977 4826 to arrange a structured cardiac assessment. I consult at Parkside Hospital in Wimbledon, The New Victoria Hospital in Kingston, Cleveland Clinic London and the Heartsure Clinic, and you can book a convenient appointment here through my secretary Hannah.