(Reuters) -Alnylam Pharmaceuticals said on Monday it would not pursue expanded use of its drug to treat a potentially fatal heart disease in the U.S. after the Food and Drug Administration declined to approve the medication despite a favorable recommendation from its advisers. The regulator, in its so-called complete response letter, said the drug patisiran did not meaningfully improve the condition of patients with heart muscle issues or cardiomyopathy caused by ATTR amyloidosis, characterized