Abstract 161: Do Baseline Risk Factor Differences Explain the Variation in Results Between SAMMPRIS and WASID?

Introduction: When enrollment in SAMMPRIS was stopped, the 30-day rate of stroke or death and the 1-year rate of the primary endpoint in the medical arm were 5.8% and 12.2%, respectively. The comparative rates in patients in WASID who met the SAMMPRIS entry criteria were 10.6% and 21.9%. While the lower rates in the SAMMPRIS trial have been attributed to aggressive medical management, an alternative hypothesis is that SAMMPRIS patients may have been at lower risk due to a lower burden of vascular risk factors. Methods: We compared risk factors at study entry in the 227 patients in the medical arm of SAMMPRIS with the 143 patients in WASID who met the SAMMPRIS entry criteria. Results: Compared with WASID patients, SAMMPRIS patients were younger (mean age 59.5 years vs. 62.5 years; p=0.009) but had higher percentages of hypertension (89% vs. 76%; p<0.001)*, hyperlipidemia (89% vs 69%; p<0.001)*, stenosis in the 80-99% range (55% vs. 35%; p<0.001), anterior circulation stenosis (68% vs. 48%; p<0.001), white race (71% vs. 61%; p=0.06), and on an antithrombotic agent at the time of the qualifying event (62% vs. 52%; p=0.08). SAMMPRIS patients had higher mean systolic blood pressure (146.8 mmHg vs. 139.1, p< 0.001), higher body mass index (30.7 kg/m 2 vs. 29.4, p=0.045) but lower LDL (98 mg/dl vs. 125, p<0.001). There were no significant differences in the frequency of female gender, stroke as the qualifying event, diabetes, smoking, history of previous stroke, time from qualifying event to study entry, and history of CAD. Conclusion: Compared to WASID patients meeting the SAMMPRIS entrance criteria, SAMMPRIS patients were slightly younger but had a higher burden of other important vascular risk factors including severity of stenosis, which was the most important predictor of subsequent stroke in WASID. These data suggest that the improved prognosis in the medical arm of SAMMPRIS compared with WASID patients is related to the aggressive medical management used in SAMMPRIS and not to a lower burden of risk factors in SAMMPRIS patients. * the increased frequency of hypertension and hyperlipidemia in SAMMPRIS might reflect the change in the JNC definition of hypertension after the start of WASID and the fact that many more patients are prescribed statins now than when WASID was done