Abstract P042: Associations Between Echocardiographic Arterial Compliance and Incident Cardiovascular Disease in African Americans: The ARIC Study
Authors: Melissa C Caughey, Laura R Loehr, Susan Cheng, Christy L Avery, Scott D Solomon, Ervin R Fox, Alan L Hinderliter
Journal: Circulation (2014)

Background: The stroke volume to pulse pressure ratio (SVPP), derived by echocardiography, is a validated estimate of arterial compliance. SVPP has been shown to predict fatal coronary disease in Europeans; however, its prognostic value in African Americans and associations with incident cardiovascular disease (CVD) are unknown. Methods: We analyzed a subset (N=2059) of African Americans (mean age 59 ± 6 years, 65% female) in the ARIC study, who were free of prevalent cardiovascular disease and imaged by echocardiography in 1993-1995. Echocardiographic arterial compliance was determined 2 ways: by the SVPP, and a simplified arterial compliance index (ACI). Stroke volume was calculated by multiplying the aortic velocity-time integral (VTI) with the cross-sectional area of the left ventricular outflow tract (CSA). Pulse pressure was derived by subtracting the diastolic from systolic blood pressure. SVPP = VTI*CSA /PP. The ACI was calculated using the VTI as a surrogate for stroke volume: ACI = VTI / PP, as 75% of echocardiograms were missing CSA. Cox regression was used to model associations between ACI and subsequent CVD (defined as first incident stroke, coronary event, or heart failure), after controlling for age, sex, body mass index, smoking, diabetes, hypertension, total cholesterol, and glomerular filtration rate. A complete-case sensitivity analysis of participants with measured CSA (N=519) was conducted, to compare ACI and SVPP hazard ratios of CVD. Finally, missing stroke volume measurements were imputed by Monte Carlo Markov Chains, and risks between simulated SVPP and CVD assessed. Results: Over a mean follow up of 13 ± 4 years, 544 participants (26%) developed CVD. The lowest (representing greater arterial stiffness) compared to highest ACI quartile was associated with increased CVD risk (HR=2.67, 95%CI: 1.97 - 3.63). For each 1-unit decrease in ACI quartile, the HR of CVD increased 39% (HR = 1.39, 95%CI: 1.26 - 1.53). In the complete case analysis, the CVD hazard ratio contrasting lowest to highest quartiles was 1.88 (95% CI: 1.12 - 3.17) for ACI, and 1.81 (95%CI: 1.10 - 2.99) for SVPP. Each 1-unit decrease in arterial compliance quartile increased HR of CVD by 30% (HR = 1.30, 95%CI: 1.10 - 1.54) for ACI, compared to 24% (HR = 1.24, 95%CI: 1.05 - 1.45) for SVPP. By multiple imputation, a 1-unit decrease in simulated SVPP quartile increased CVD risk 18% (HR = 1.18, 95%CI: 1.08 - 1.28). Conclusions: This is the first study to examine the prognostic value of echocardiography-derived arterial compliance in African Americans. We observed that the ACI and SVPP were associated with incident CVD in African Americans, after controlling for cardiac risk factors and anthropometry. Risks associated with SVPP, a validated measurement of arterial compliance, and the ACI, a novel simplified index, show close agreement in complete-case analyses of incident CVD in African Americans.