Low-dose rivaroxaban was effective in secondary prevention of atherosclerotic cardiovascular disease (ASCVD) in the COMPASS trial. There is no established role, however, for oral anticoagulants in primary prevention. We evaluated whether coronary artery calcium (CAC) scoring identifies a high-risk primary prevention adult population who may benefit from low-dose rivaroxaban to prevent ASCVD events. We modeled expected outcomes of low-dose rivaroxaban in 5,196 Multiethnic Study of Atherosclerosis (MESA) cohort participants not already on antiplatelet or anticoagulant therapy. We applied relative risk ratios from COMPASS to absolute MESA event rates in order to estimate number needed to treat (NNT) to avoid a composite of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke, as well as number needed to harm (NNH) to cause 1 hospitalized bleed; with both NNT and NNH stratified by calculated ASCVD risk and by baseline CAC. MESA participants with CAC ≥300 had crude ASCVD event rate of 20 per 1000 patient-years, which is comparable to that observed in the COMPASS control-arm. CAC was independently associated with the composite ASCVD outcome (p <0.001 for trend). However, CAC was not independently associated with adjusted hazard ratio for hospitalized major bleeding. Predicted 5-year NNT (modeled from COMPASS) was 75 in persons with CAC 100-299 and 45 with CAC ≥300 despite NNH values of 252 and 98, respectively. In conclusion, CAC helps to distinguish estimated ASCVD benefit from estimated bleeding harm, thereby identifying very high-risk primary prevention adults without established cardiovascular disease who may derive net-benefit from low-dose rivaroxaban.
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