Difference Between Myocarditis And Pericarditis

Myocarditis and pericarditis are inflammatory heart diseases involving different parts of the heart. The heart is composed of layers, with the middle layer of the heart formed by the myocardium. The myocardium is made up of muscle and is responsible for the pumping of the heart. The outermost layer of the heart is the pericardium, which covers the heart and protects it. 

Both the myocardium and the pericardium can get damaged and irritated leading to inflammation. The two conditions share many common features, causes, and symptoms and they can also occur at the same time (myopericarditis).

The major difference between the two conditions is the location of the inflammation, which can potentially make myocarditis more dangerous. The type of chest pain felt in both conditions is also different. Myocarditis is associated with tightness and squeezing around the chest, whereas pericarditis has a characteristic sharp pain that gets worse with coughing and lying down. In the article, we discuss in detail the two conditions, what similarities they share, and how they differ from one another.

Understanding myocarditis 

Myocarditis is when the muscles of the heart, called the myocardium, become inflamed. This inflammation can cause harm and even death to specialised heart muscle cells known as myocytes. The damage can happen in a specific area (focal) or spread across a larger area (diffuse).

The extent of the inflammation determines the symptoms, ranging from mild chest pain and shortness of breath to abnormal heart rhythms and heart failure. The condition can also be potentially life-threatening.

Causes of myocarditis

The exact cause of myocarditis is unknown. It has been proposed that there is some sort of insult or injury to the heart muscle tissue. This insult, in turn, activates the immune system, leading to inflammation of the myocardium. 

These insults or injuries can be caused by:

• Direct injury to the muscle tissues of the heart, for example, by viruses or cardiotoxins (drugs or toxins that are harmful to the heart)
• Indirect injury to the heart muscles by activation of the immune system by infections or toxins in the body

Many factors have been known to damage the myocardium, but in most cases of myocarditis, the cause is unknown. Some examples of known causes include:

• Infections (from viruses, bacteria, parasites or fungi)
• Toxins such as alcohol and cocaine
• Reactions to medicines like clozapine and penicillin
• Inflammatory conditions such as inflammatory bowel disease
• Autoimmune conditions, like lupus
• Radiation therapy
• Covid-19 and vaccinations. Myocarditis can be a rare side effect of COVID-19 and certain vaccinations. In most cases, it is mild and doesn't require extensive medical treatment.

Symptoms of myocarditis

Myocarditis is often linked to a previous viral infection, but not everyone with myocarditis has this early phase. Some people might experience symptoms like fever, rash, muscle and joint aches, fatigue, respiratory issues, and digestive problems before myocarditis sets in. However, these symptoms can vary, and not everyone experiences the same pattern. If someone shows signs of myocarditis or any health issue, it's best to see a doctor for a thorough evaluation.

Symptoms of myocarditis itself can vary in severity depending on how bad the inflammation gets. If the cause of myocarditis is an infection, symptoms can begin to show within the range of a few days to several weeks after the infection. 

Some symptoms of myocarditis include:

• Chest pain or discomfort –a feeling of tightness or squeezing in the chest. This can occur while resting or when active, and even when lying down 
• Shortness of breath – either when active or at rest 
• Palpitations – feeling like the heart is racing, pounding, or fluttering 
• Unusual fatigue
• Decreased exercise tolerance
• Fainting or passing out
• Rapid or irregular heart rhythms (arrhythmias)
• Rarely, swelling of hands, legs, ankles, and feet (oedema) – occurs in cases of heart failure, when the muscles of the heart are so damaged they are not able to pump properly.

In most cases, the inflammation resolves by itself, and the person can recover completely. Severe cases of myocarditis can lead to the development of complications like cardiogenic shock, heart failure, and dilated cardiomyopathy.

Diagnosis of myocarditis

Your doctor will make the diagnosis of myocarditis based on your symptoms and findings from laboratory testing. 

Some common laboratory tests that your doctor might use to confirm myocarditis include:

1. Electrocardiography (ECG) – measures your heart rate and rhythm and is done to look for any irregularities.
2. Chest X-ray – can determine any differences in the size and structure of the heart.
3. Laboratory markers – blood tests are done to exclude heart attacks. Cardiac enzyme tests show proteins related to heart damage.
4. Echocardiogram – an ultrasound that is done to check heart size and abnormality in the functioning of heart muscles and valves
5. Cardiac MRI – cardiac MRI is a new tool that helps to look for any muscle death and damage and is slowly replacing cardiac biopsy
6. Endomyocardial biopsy – biopsy of the heart muscle tissue is taken and checked for signs of inflammation and muscle death. It can confirm the diagnosis of myocarditis but is rarely performed. 

Treatments for myocarditis

Treatment for myocarditis is based on the cause and complications. Mild myocarditis does not need to be treated and gets better independently with rest. In more severe cases, your doctor can prescribe you the following medications:

• Medicines for treating heart failure – to help the heart pump blood around the body
• Medicines to treat arrhythmias (abnormal heart rhythms)
• Corticosteroids and immunosuppressants – for rare cases where myocarditis is caused by problems with the immune system rather than an external source
• Surgery, for extreme cases. For example, in cases of heart failure, a surgeon may implant devices, such as artificial pumps and pacemakers, to help the heart better pump blood.
• A heart transplant may be required in very extreme cases

Understanding pericarditis

The heart is covered by a protective, thin double layer of tissue called the pericardium. When this layer is irritated and inflamed, it is called pericarditis. It produces a sharp chest pain as the irritated layers of pericardium rub against each other. Pericarditis is usually a mild condition and goes away without any treatment, although long-term complications may occur in more severe cases, hence the need for early detection and treatment.

Causes of pericarditis 

Like myocarditis, the exact cause of pericarditis is hard to determine. In most cases, no cause is found and it is termed idiopathic pericarditis.

The following are some of the causes of pericarditis:

• Infections (from viruses, bacteria, parasites or fungi)
• Autoimmune diseases like lupus and rheumatoid arthritis
• Trauma – chest injuries from incidents like car accidents
• Kidney failure – increased urea in the blood due to kidney failure can lead to a form of pericarditis known as uremic pericarditis
• Reaction to medications – such as penicillin and anti-coagulants
• Cancers like leukaemia, lymphoma, breast cancer, and lung cancer
• Covid-19 and vaccinations – a rare side effect of vaccination; most cases are mild and do not require any medical treatment

Furthermore, certain conditions can activate the immune system and result in inflammation. As a result, there is a higher risk of developing pericarditis after:

• Heart attacks (post-myocardial infarction syndrome / Dressler syndrome)
• Open heart surgery (post-pericardiotomy syndrome) and procedures of the heart, such as cardiac catheterisation
• Radiation therapy

Symptoms of pericarditis

The most characteristic symptom of pericarditis is chest pain, which:

• is sharp and stabbing
• gets worse on coughing, swallowing, taking deep breaths, and lying flat
• gets better by sitting up and leaning forward

Other symptoms that can occur in pericarditis are

• Fever – having a high temperature or feeling hot and shivery
• Difficulty in breathing when lying flat
• Dry cough
• Pain in your neck, left shoulder, and back 
• Palpitations (feeling like your heart is pounding, having a faster heartbeat, and having an irregular heartbeat)
• Anxiety 
• Swelling in ankles, feet, and legs – occurs in cases of a complication, such as constrictive pericarditis
• Shortness of breath on exertion – also occurs in cases of constrictive pericarditis.

Diagnosis of pericarditis

Your doctor will ask you questions regarding your chest pain, do a physical examination, and may also advise one or more of the following tests to diagnose pericarditis and exclude complications:

1. Electrocardiogram (ECG) –  looks at the rhythm of the heartbeat
2. Echocardiogram – a heart ultrasound to check how well your heart is pumping and to check for fluid around the heart 
3. Chest X-ray – shows the size of the heart
4. Cardiac MRI – shows inflammation and thickening of the pericardium, fluid around the heart, and compression of the heart.
5. Cardiac catheterisation – is done when your doctor suspects constrictive pericarditis. It can tell the doctor more about the blood flow and the pressure inside and surrounding the heart.
6. Blood tests – blood tests are done to exclude heart attack and heart failure, and to detect markers of inflammation that are raised in pericarditis

Treatments for pericarditis

Treatment usually depends on the severity of the disease, the presence of complications, and the cause.

• Anti-inflammatory drugs (NSAIDs) – such as ibuprofen. If these do not work, you may be prescribed other medicines such as colchicine or steroids.
• Antibiotics – if the cause of pericarditis is bacterial infection
• Pericardiocentesis or pericardial window – procedures performed to drain any excess fluid from the pericardium in rarer cases of recurring or more severe pericarditis
• Pericardiectomy – surgical removal of most or all of the pericardium. Performed after repeated instances of inflammation cause the pericardium to become stiff and scarred, such as in constrictive pericarditis, where the heart cannot pump properly

Which is more common?

The incidence of myocarditis is difficult to estimate as it is an underdiagnosed condition, mostly mild and often poorly investigated. 

A primary survey done between 1998 and 2017 in the UK, estimated that myocarditis accounted for 0.04% (36.5 per 100,000) of all hospital admissions, and in 2017 there were about 2000 hospital admissions of myocarditis.¹

Acute pericarditis is found in approximately 5% of patients admitted to the emergency department for chest pain unrelated to heart attacks and accounts for 0.1% of hospital admissions. Several studies have shown that from 3 to 28 people per 100,000 get pericarditis each year, making it an uncommon condition.³ Pericarditis most often affects young and middle-aged people assigned male at birth (AMAB), between 16 to 65 years of age.¹

Which is more dangerous? 

Both conditions require thorough evaluation and workup by a doctor. Myocarditis can be more dangerous than acute pericarditis as it is associated with more severe long-term complications.² However, both conditions can have complications that can be potentially life-threatening if not caught and treated early.

In certain cases, inflammation of the myocardium and the pericardium can also occur together. This is termed myopericarditis.

Early diagnosis and treatment of both conditions is crucial in avoiding severe long-term complications.

Pericarditis is mostly mild and resolves on its own without treatment. Some unusual complications of pericarditis include:

• Pericardial effusion – fluid build-up around the heart, which can be clear or have blood or pus in it. This can cause further heart problems.
• Constrictive pericarditis – this is an unusual complication in people suffering from long-term pericarditis. There is permanent thickening and scarring of the pericardium. This leads to the heart being constricted by the thick covering and unable to pump properly.
• Cardiac tamponade – this is an emergency condition that can be potentially life-threatening. There is increased pressure on the heart by fluid build-up around it. The heart is not able to pump, and there is a dramatic decrease in blood pressure. 

Myocarditis involves the muscles of the heart, meaning that if the inflammation is severe enough it can result in permanent damage to the heart muscles. The long-term complications due to this damage can cause:

• Heart failure – a condition where the heart is unable to pump blood properly. Over time, heart failure can progress and require device implants or even a heart transplant. The damage to the muscle puts strain on the heart, and to compensate, the remaining heart muscles get stretched and enlarged, leading to a condition called dilated cardiomyopathy.
• Heart attacks and stroke – as the ability of the heart to pump blood gets impaired, the blood pools and clots. These clots can travel in the blood, causing heart attacks (if a clot gets lodged in the blood vessels supplying the heart) or stroke (if a clot gets lodged in a blood vessel supplying the brain) 
• Arrhythmias – a rapid or irregular heartbeat. Arrhythmias can increase the occurrence of strokes.
• Sudden cardiac death – Certain serious arrhythmias can cause sudden cardiac arrest (the heart stops suddenly). This can be deadly and cause death if not immediately treated.

How to manage both conditions? 

Symptoms of both myocarditis and pericarditis need to be evaluated thoroughly by a doctor.

If you are experiencing symptoms of myocarditis or pericarditis, seek medical care. Your doctor will ask you questions related to the symptoms and about any previous viral illnesses and recent vaccinations. Your doctor will also do a physical exam and investigations like ECG, chest X-ray, echocardiogram, and laboratory markers for heart attack and heart failure to diagnose the conditions. The treatment will depend on the severity and cause of the condition.

When to seek medical attention

It is important to seek immediate medical attention in any case of unexplained chest pain. Many symptoms of myocarditis and pericarditis overlap with each other, and also with other heart and lung conditions such as heart attack, and should not be ignored.

Seek emergency medical help if you are experiencing:

• Sudden chest pain or discomfort that does not go away
• Sudden chest pain that goes into your arms, back, neck, or jaw
• Shortness of breath and sweating
• Chest pain and feeling sick or light-headed

Summary

Inflammatory heart diseases like myocarditis and pericarditis share many similar features, causes, and symptoms. They are usually mild and resolve on their own with rest.

Myocarditis is inflammation of the middle muscular layer of the heart while pericarditis is the inflammation of the outermost protective covering of the heart.  For more information about the two diseases and the effect of Covid-19 and Covid-19 vaccinations on the heart, refer to the links provided below.