NEW YORK (Reuters) - Pfizer Inc. said it has found an increased risk of heart attacks with patients taking its top-selling painkiller Celebrex, a drug that is in the same class as Vioxx, but has no plans to remove it from the market. Pfizer announced Friday that it found the increased risk in one of two long-term cancer prevention trials, while the other trial showed no increased risk. The National Cancer Institute, which was conducting the study for Pfizer, suspended the use of Celebrex after discovering that patients taking 400mg to 800mg of the drug daily had a 2.5 times greater risk of experiencing major heart problems than those who were not.