This study is enrolling participants with elevated lipoprotein (a) levels, a cholesterol like substance, to test an investigational study medication called olpasiran. Investigational means it has not yet been approved by the US Food and Drug Administration (FDA) for commercial use but has been approved for use in this study. Olpasiran is a subcutaneous injection given every 12 weeks. This study is randomized, which means participants are randomly assigned, like the flip of a coin, to either receive olpasiran or placebo. Placebo looks like the study medication but has no active ingredients. Neither the participants nor the study doctor or study team will know if you are getting study medication or placebo. Participation in this study will last up to 4 1/2 years and include about 14-24 study visits. Study procedures include physical exams, medical history and medication review, electrocardiograms (tracing of the electrical activity of your heart), blood work, questionnaires and medication administration.