Acute pericarditis
Acute pericarditis is a type of pericarditis ( inflammation of the sac surrounding the heart , the pericardium ) usually lasting less than 6 weeks . 
<triplet> Acute pericarditis <subj> pericarditis <obj> subclass of <subj> pericardium <obj> afflicts <triplet> pericarditis <subj> inflammation <obj> subclass of <subj> pericardium <obj> afflicts