An estimated 64 million Americans have elevated levels of lipoprotein(a), or Lp(a), a type of cholesterol that can increase the risk of heart attack and other cardiovascular problems. Having high Lp(a) doesn’t show up on routine tests because lifestyle factors like diet and exercise don’t seem to affect it and there have been no drugs to treat it — until now. Lepodisiran — an experimental drug made by the pharmaceutical company Eli Lilly — has…