Myocarditis is an infection of the heart muscle, most commonly caused by a virus. Symptoms can be the same as a heart attack and the ECG can be mighty bad.
There are two risks: first you can get fluid around the heart called a pericardial effusion. This squashes the heart and may reduce its pumping ability. In some cases we drain it with a needle under ultrasound control.
Second it can damage the heart muscle itself and sometimes the fibres that attach the valves.
The massive fatigue you often get for weeks is not really understood as the heart may be functioning well. Most likely it is the virus itself.
Once you are not too knackered to work you may well have an echocardiogram to demonstrate no effusion, good muscle activity and normal valves. Once this is done no problem. A friend of mine walked through an initial class one and the CAA didn't even talk to heir cardiologist.
So good luck