WHITEHOUSE STATION, N.J. (AP) — Merck and Co. said Wednesday that European regulators agreed to review an application for one version of Merck’s drug candidate vernakalant, which is intended to treat abnormal heart rhythms. The European Medicines Agency accepted Merck’s application for the intravenous version of the drug. Vernakalant is designed to treat acute atrial fibrillation, a rapid and irregular heartbeat that can cause strokes. Merck is also developing an oral form of the drug. Rival drugmaker Sanofi-Aventis is seeking European Union approval of a competing drug called Multaq. The Food and Drug Administration approved Multaq in July, and Sanofi-Aventis said it was the first new drug approved for atrial fibrillation in a decade. Sanofi-Aventis, which is based in France, estimated there are 4.5 million patients in Europe and 2.5 million in the U.S.