Myocarditis has a highly variable presentation. Both the severity and symptoms can be different from one person to the next.
This makes it difficult to detect.
Acute myocarditis has 3 general presentations:
1) Acute Coronary Syndrome
This looks like a heart attack..
Chest pain, arm pain, jaw pain, difficulty breathing etc.
Usually about 4 weeks after inciting event.
2) Heart failure
This usually presents weeks to months after inciting event.
Swelling legs, difficulty breathing, weight gain are common. Easy to misdiagnose.
3) Scary Things
Arrhythmias, sudden cardiac death, and cardiogenic shock.
These can kill you quickly.
Some people with myocarditis also develop pericarditis. Usually causes chest pain when breathing and pain when laying in certain positions (ex pain when laying on back)
Most myocarditis falls into one of those three, but there's more.