It may be particular to the regions of the heart that became inflamed? Not sure, I'm not a cardiologist. I would imagine that the common myocarditis symptoms (chest pain and tightness) would be caused by inflammation of the heart leading to pressure against the pericardium that would be what is noticed as tightness. Perhaps here the inflammation was mainly internal, so didn't result in the more common symptoms. Would need a cardiologist to weigh in on it really though, I'm just thinking out loud.