passages.id: split_4_test_157_passage
passages.type: progene_text
passages.text: We studied three groups of children : (1) 20 patients with idiopathic VT ( aged 3-18 years ; mean 11.2 years ) ; (2) 30 patients with benign PVCs ( aged 1 - 20 years ; mean 10.5 years ) ; and (3) 30 control subjects ( aged 4 - 17 years ; mean 12 years ) .