Heart inflammation typically causes chest pain, fatigue, and shortness of breath, but the specific sensations depend on which part of the heart is inflamed. The three main types are pericarditis (inflammation of the sac surrounding the heart), myocarditis (inflammation of the heart muscle itself), and endocarditis (inflammation of the heart valves). Each produces a distinct pattern of symptoms, and some can feel alarmingly similar to a heart attack.
Pericarditis: Sharp Pain That Changes With Position
Pericarditis produces the most distinctive and recognizable chest pain of the three types. The pain is sharp and stabbing, centered in the chest or behind the breastbone, and it behaves in a way that sets it apart from other cardiac problems. It gets worse when you cough, swallow, take a deep breath, or lie flat. The hallmark relief position is sitting up and leaning forward, which takes pressure off the inflamed sac around your heart.
This positional quality is what often distinguishes pericarditis from a heart attack. During a heart attack, people typically describe pressure, tightness, or squeezing, often comparing it to “an elephant sitting on my chest.” That sensation doesn’t change much with breathing or body position. Pericarditis pain, by contrast, is sharper and more reactive to movement. It can also radiate to the shoulders or neck, which adds to the confusion, but the deep-breath and lying-down triggers are strong clues.
Myocarditis: A Slower, More Varied Set of Symptoms
Myocarditis, inflammation of the heart muscle, is harder to pin down because it doesn’t always announce itself with dramatic chest pain. Some people feel symptoms build gradually over days. Others experience a sudden onset. The most common symptoms include chest pain, fatigue, shortness of breath (both at rest and during activity), and palpitations, a sensation of your heart racing, fluttering, or beating irregularly.
What makes myocarditis tricky is that it often follows what feels like a routine illness. Up to 80% of patients report a prodromal phase: gastrointestinal symptoms, fever, sweats, chills, body aches, sore throat, or something resembling the flu. This viral-feeling illness typically occurs one to two weeks before cardiac symptoms appear. So the pattern to watch for is a flu-like illness that seems to resolve, followed by new or worsening chest pain, unusual fatigue, or breathlessness that seems out of proportion to your activity level.
In more advanced cases, myocarditis can cause symptoms of heart failure: swelling in the legs, ankles, or feet, lightheadedness, fainting, and an inability to exercise at your normal level. Some people also report abdominal pain and loss of appetite. Young, otherwise healthy people are particularly at risk of dismissing these symptoms as lingering effects of a virus, which is why the post-illness timeline matters.
Endocarditis: Systemic Illness With Subtle Signs
Endocarditis, an infection of the heart valves, feels less like a heart problem and more like a body-wide illness. Fever, chills, night sweats, fatigue, and unexplained weight loss are the primary symptoms. Joint and muscle pain are common. Because these overlap heavily with many infections, endocarditis is often diagnosed late.
One unusual feature is what happens to the skin and nails. Between 15% and 33% of people with endocarditis develop splinter hemorrhages, tiny dark lines under the fingernails or toenails that look like splinters embedded beneath the nail. Small, painless red spots can appear on the palms or soles of the feet. These aren’t symptoms you’d feel in the traditional sense, but they’re visible clues that an infection has reached the bloodstream and heart.
How It Differs From a Heart Attack
The overlap between heart inflammation and a heart attack is real, and distinguishing between them at home isn’t always possible. But there are patterns worth knowing. Heart attack pain tends to feel like pressure, heaviness, or tightness. It often radiates to the left arm, jaw, or back, and it doesn’t change when you shift position or breathe deeply. It also tends to come on during exertion or stress, though not always.
Inflammatory chest pain is more often sharp or stabbing. It reacts to breathing, coughing, or position changes. It may build over hours or days rather than arriving suddenly. And it frequently comes with fever or follows a recent illness, which is unusual for a heart attack. That said, myocarditis can cause heart rhythms unstable enough to mimic the sudden, catastrophic feel of a cardiac event. If you’re experiencing new chest pain, especially with lightheadedness, fainting, or severe shortness of breath, treat it as an emergency regardless of what you think is causing it.
What Happens During Diagnosis
Doctors use blood tests to detect heart inflammation. One key marker is troponin, a protein released when heart muscle cells are damaged. A high-sensitivity troponin level above 18 pg/mL raises suspicion for active myocarditis, while a level at or below that threshold can effectively rule it out with about 96% confidence. Inflammatory markers like C-reactive protein also tend to be elevated. An ECG, echocardiogram, and sometimes a cardiac MRI help confirm the diagnosis and assess how much of the heart is affected.
For pericarditis, the diagnosis is often more straightforward. The combination of sharp, positional chest pain, a characteristic “friction rub” sound heard through a stethoscope, and ECG changes can be enough to confirm it without advanced imaging.
Recovery and Activity Restrictions
Recovery timelines vary significantly by type and severity. Pericarditis often improves within a few weeks with anti-inflammatory treatment, though it can recur. Myocarditis requires a longer and more cautious approach. Current guidelines from the American College of Cardiology recommend that people diagnosed with myocarditis avoid exercise for three to six months to allow inflammation to resolve. The exact duration depends on how severely the heart was affected, how well it’s pumping, and what a follow-up cardiac MRI shows.
This exercise restriction is one of the most practically important things to understand about myocarditis. Exercising on an inflamed heart muscle increases the risk of dangerous arrhythmias. For athletes or physically active people, this means a full stop on training, not just dialing back intensity. Return to activity is gradual and guided by repeat testing to confirm the inflammation has cleared.
Red Flags That Need Immediate Attention
The three classic ways myocarditis presents in an emergency are chest pain, heart failure (severe breathlessness, inability to lie flat, leg swelling), and arrhythmia-related symptoms like fainting or near-fainting. Any of these, especially in someone who recently had a viral illness, warrants urgent evaluation. Hemodynamic instability, meaning your blood pressure drops dangerously or your heart rhythm becomes erratic, can require emergency circulatory support.
For pericarditis, the main concern is a complication called cardiac tamponade, where fluid builds up around the heart and compresses it. Signs include worsening shortness of breath, a feeling of fullness in the chest, and lightheadedness when standing. For endocarditis, high fever that won’t break, new neurological symptoms, or sudden vision changes suggest the infection may be spreading and needs immediate care.