An expert witness testified Thursday that even short term use of the painkiller Vioxx can double the risk of heart attach and death, a finding that the drug’s manufacturer Merck & Co. misrepresented. University of Washington biostatistician Richard Kronmal said company sponsored tests showed that patients who took the drug suffered serious side effects to blood vessels amost immediately. After reviewing Merck’s own data, Kronmal stated, “It clearly is a drug that has severe effects on the vascular system.”