WorldCom ( WCOM) was the most actively traded issue in the Instinet late session Monday, although the company ? which saw its debt further lowered into the realm of junk earlier ? was treading water after falling 9% in regular trading. Shares of the long-distance company were unchanged at $1.45 each after S&P lowered by two notches its long-term corporate credit rating. A couple of wireless companies were also atop the volume list but unchanged: U.S. Unwired ( UNWR) held steady at $2.99 while Triton PCS ( TPC) was even with its 4 p.m. close at $5.59. Elsewhere, Vasomedical ( VASO) gave back 16 cents to $2.68 after almost doubling in the regular session on expanded FDA approval for its chest pain therapy. The company's shares rose 82% to close at $2.84 at 4 p.m. EDT on the FDA's decision, which could expand the number of patients eligible for the treatment by up to 20%. Other stocks falling in the late session included Tuesday Morning ( TUES), down 13.4% to $18.52; Chattem ( CHTT), down 7.6% to $33.15 after announcing a secondary offering; and Tellium ( TELM), which gave back 5 cents to $1.16 after rising 10 cents to $1.21 in the regular session. On the upside, Dynegy ( DYN) was gaining 25 cents to $8.80; ValueVision Media ( VVTV) was up 50 cents to $19.20 after affirming sales goals; and Neoforma ( NEOF) was gaining 23 cents to $12.23 after saying several companies had agreed to use its e-commerce product.