Comparison of Frequency of Atherosclerotic Cardiovascular Disease Events Among Primary and Secondary Prevention Subgroups of the Systolic Blood Pressure Intervention Trial.

The Pooled Cohort Equation (PCE) predicts 10-year risk of first-time atherosclerotic cardiovascular disease (ASCVD) events and was incorporated in analyses of a primary and secondary prevention population in the Systolic Blood Pressure Intervention Trial (SPRINT). Whether PCE enhances risk prediction among secondary prevention populations is unknown. We sought to compare ASCVD events by level of PCE-predicted risk among primary and secondary prevention SPRINT populations. SPRINT randomized adults with hypertension and ≥1 CVD risk factor or previous CVD events to systolic blood pressure control targeting <120 mm Hg or 135 to 139 mm Hg. We calculated the hazard ratio (HR) of ASCVD events among secondary versus primary (reference) prevention subgroups overall and by predicted 10-year ASCVD risk categories (<10%, 10% to <20%, 20% to <30%, and ≥30%) and within risk subgroups, comparing to the lowest risk category. Among 8,151 participants, 16% with previous CVD, mean age was 66 years and 35% were women. The HR for ASCVD events overall was 2.51 (1.96, 3.20). HR was 2.97 (1.47, 5.99) among <10% 10-year risk and 2.23 (1.38, 3.59) among ≥30% risk. Within subgroups comparing ≥30% to <10% risk (reference) categories, the HR was 2.85 (1.76, 4.63) for primary and 2.14 (1.07, 4.30) for the secondary prevention. In conclusion, history of previous events was a potent risk factor for subsequent ASCVD events. The PCE does not enhance risk prediction among secondary prevention populations and may differentially underestimate risk in secondary prevention populations with lowest predicted risk.