Outcomes After Coronary Artery Calcium and Other Cardiovascular Biomarker Testing Among Asymptomatic Medicare Beneficiaries

Background— Biomarkers improve cardiovascular disease (CVD) risk prediction, but their comparative effectiveness in clinical practice is not known. We sought to compare the use, spending, and clinical outcomes in asymptomatic Medicare beneficiaries evaluated for CVD with coronary artery calcium (CAC) or other cardiovascular risk markers. Methods and Results— We used a 20% sample of 2005 to 2011 Medicare claims to identify fee-for-service beneficiaries aged ≥65.5 years with no CVD claims in the previous 6 months. We matched patients with CAC with patients who received high-sensitivity C-reactive protein (hs-CRP; n=8358) or lipid screening (n=6250) using propensity-score methods. CAC was associated with increased noninvasive cardiac testing within 180 days (hazard ratio, 2.22, 95% confidence interval, 1.68–2.93, P &lt;0.001, versus hs-CRP; hazard ratio, 4.30, 95% confidence interval, 3.04–6.06, P &lt;0.001, versus lipid screening) and increased coronary angiography and revascularization. During 3-year follow-up, CAC was associated with higher CVD-related spending ($6525 versus$4432 for hs-CRP, P &lt;0.001; and $6500 versus$3073 for lipid screening, P &lt;0.001) and fewer CVD-related events when compared with hs-CRP (hazard ratio, 0.74, 95% confidence interval, 0.58–0.94, P =0.017) but not compared with lipid screening (hazard ratio, 0.84, 95% confidence interval, 0.64–1.11, P =0.23). Conclusions— CAC testing among asymptomatic Medicare beneficiaries was associated with increased use of cardiac tests and procedures, higher spending, and slightly improved clinical outcomes when compared with hs-CRP testing. </jats:sec

Abstract 202: Association Between Implantable Ventricular Assist Device Receipt at Medicare Destination Therapy Centers and Mortality: An Instrumental Variable Analysis

Background: Comparing the effectiveness of contemporary implantable ventricular assist devices (VAD) with medical therapy using observational data is challenging because of treatment selection bias. Objective: To use instrumental variable analysis to examine 1-year mortality of elderly Medicare beneficiaries with advanced heart failure receiving contemporary implantable VADs compared with conservative management. Methods: We identified the first hospitalization for heart failure for at least 14 days between January 1, 2009, and December 31, 2011, among all Medicare beneficiaries 65 to 80 years of age, as well as receipt of an implantable VAD during that hospitalization. We estimated risk-adjusted differences in 1-year mortality for VAD versus medical therapy using a 2-stage least squares instrumental variable analysis method. The date that a hospital was certified by Medicare to implant VADs as permanent circulatory support (“destination therapy facility”) was used as an instrument for VAD receipt, since this variable directly influences the use of VAD therapy. Patients were censored at the date of heart transplantation or death, or at the end of the study period. Results: Of 33,483 beneficiaries hospitalized, 827 (2.5%) underwent VAD implantation at 104 hospitals, 30 of which became destination therapy centers between 2009 and 2011. Among VAD recipients, 71 (8.5%) proceeded to heart transplantation. Unadjusted 1-year mortality rates were 26.5% for VAD versus 51.9% for medical therapy (risk difference,-25.4%; P &lt; 0.001). The adjusted risk difference was -23.6% (95% CI -27.0% to -20.1%, P &lt; 0.001). Using instrumental variable analysis, VAD receipt was associated with a significantly larger decrease in 1-year mortality (risk difference, -40.6%, 95% CI -52.2% to -29.0%; P &lt; 0.001). Conclusions: When confounding was controlled with instrumental variable analysis, VAD implantation among elderly Medicare beneficiaries, on the margin, was associated with a 41% reduction in 1-year mortality compared with medical therapy, consistent with randomized trial results. Use of a hospital’s “destination therapy” certification date as an instrumental variable may facilitate future comparative effectiveness analyses of VAD therapy. </jats:p