Splenic switch-off in regadenoson 82Rb-PET myocardial perfusion imaging: assessment of clinical utility.

BACKGROUND: Splenic switch-off (SSO) is a phenomenon describing a decrease in splenic radiotracer uptake after vasodilatory stress. We aimed to assess the diagnostic utility of regadenoson-induced SSO. METHODS: We included consecutive patients who had clinically indicated Regadenoson Rb-82 PET-MPI for suspected CAD. This derivation cohort (no perfusion defects and myocardial flow reserves (MFR) ≥ 2) was used to calculate the splenic response ratio (SRR). The validation cohort was defined as patients who underwent both PET-MPI studies and invasive coronary angiography (ICA). RESULTS: The derivation cohort (n = 100, 57.4 ± 11.6 years, 77% female) showed a decrease in splenic uptake from rest to stress (79.9 ± 16.8 kBq⋅mL vs 69.1 ± 16.2 kBq⋅mL, P < .001). From the validation cohort (n = 315, 66.3 ± 10.4 years, 67% male), 28% (via SRR = 0.88) and 15% (visually) were classified as splenic non-responders. MFR was lower in non-responders (SRR; 1.55 ± 0.65 vs 1.76 ± 0.78, P = .02 and visually; 1.18 ± 0.33 vs 1.79 ± 0.77, P < .001). Based on ICA, non-responders were more likely to note obstructive epicardial disease with normal PET scans especially in patients with MFR < 1.5 (SRR; 61% vs 34% P = .05 and visually; 68% vs 33%, P = .01). CONCLUSION: Lack of splenic response based on visual or quantitative assessment of SSO may be used to identify an inadequate vasodilatory response.

Racial/Ethnic Disparities and Determinants of Sufficient Physical Activity Levels.

Introduction: Adequate physical activity is an integral requirement for achieving cardiovascular health. Physical inactivity is the fourth leading cause of death worldwide. Hence, it is important to identify racial/ethnic groups that are less likely to achieve sufficient physical activity levels, and to address barriers to meeting physical activity requirements. Methods: Cross-sectional data from the 2006-2015 National Health Interview Survey (NHIS) were used to compare self-reported sufficient physical activity among different racial/ethnic groups: non-Hispanic (NH) Whites, NH Blacks, NH Asians, and Hispanics in the United States. Sufficient physical activity was defined as ≥ 150 minutes per week of moderate-intensity physical activity, ≥ 75 minutes per week of vigorous-intensity physical activity, or ≥ 150 minutes per week of moderate and vigorous physical activity. Results: The study sample consisted of 296,802 individuals, mean age ± standard error age 46.4 ± 0.10 years, 52% women, 70% NH White, 12% NH Black, 5% NH Asian, and 14% Hispanic. The prevalence of sufficient physical activity in the overall population was 46%, while it was 48% among NH Whites, 39% among NH Blacks, 45% among NH Asians, and 40% among Hispanics. In multivariable-adjusted models (odds ratio; 95% confidence interval), NH Blacks (0.79; 0.64,0.97), NH Asians (0.72; 0.62,0.85) and Hispanics (0.71; 0.61,0.82) were significantly less likely to engage in sufficient physical activity compared with NH Whites. Older age, women, and low income were inversely associated with sufficient physical activity, while a college education or higher was associated directly with it. Conclusions: NH Black and Asian Americans and Hispanic adults were less likely to engage in sufficient physical activity levels compared with Whites. It is important to address barriers to meeting physical activity thresholds to help achieve optimal cardiovascular health.