In recent years, cardiovascular immuno-imaging by positron emission tomography (PET) has undergone tremendous progress in preclinical settings. Clinically, two approved PET tracers hold great potential for inflammation imaging in cardiovascular patients, namely FDG and DOTATATE. While the former is a widely applied metabolic tracer, DOTATATE is a relatively new PET tracer targeting the somatostatin receptor 2 (SST2). In the current study, we performed a detailed, head-to-head comparison of DOTATATE-based radiotracers and [¹⁸F]F-FDG in mouse and rabbit models of cardiovascular inflammation. For mouse experiments, we labeled DOTATATE with the long-lived isotope [⁶⁴Cu]Cu to enable studying the tracer’s mode of action by complementing in vivo PET/CT experiments with thorough ex vivo immunological analyses. For translational PET/MRI rabbit studies, we employed the more widely clinically used [⁶⁸Ga]Ga-labeled DOTATATE, which was approved by the FDA in 2016. DOTATATE’s pharmacokinetics and timed biodistribution were determined in control and atherosclerotic mice and rabbits by ex vivo gamma counting of blood and organs. Additionally, we performed in vivo PET/CT experiments in mice with atherosclerosis, mice subjected to myocardial infarction and control animals, using both [⁶⁴Cu]Cu-DOTATATE and [¹⁸F]F-FDG. To evaluate differences in the tracers’ cellular specificity, we performed ensuing ex vivo flow cytometry and gamma counting. In mice subjected to myocardial infarction, in vivo [⁶⁴Cu]Cu-DOTATATE PET showed higher differential uptake between infarcted (SUV_max 1.3, IQR, 1.2–1.4, N = 4) and remote myocardium (SUV_max 0.7, IQR, 0.5–0.8, N = 4, p = 0.0286), and with respect to controls (SUV_max 0.6, IQR, 0.5–0.7, N = 4, p = 0.0286), than [¹⁸F]F-FDG PET. In atherosclerotic mice, [⁶⁴Cu]Cu-DOTATATE PET aortic signal, but not [¹⁸F]F-FDG PET, was higher compared to controls (SUV_max 1.1, IQR, 0.9–1.3 and 0.5, IQR, 0.5–0.6, respectively, N = 4, p = 0.0286). In both models, [⁶⁴Cu]Cu-DOTATATE demonstrated preferential accumulation in macrophages with respect to other myeloid cells, while [¹⁸F]F-FDG was taken up by macrophages and other leukocytes. In a translational PET/MRI study in atherosclerotic rabbits, we then compared [⁶⁸Ga]Ga-DOTATATE and [¹⁸F]F-FDG for the assessment of aortic inflammation, combined with ex vivo radiometric assays and near-infrared imaging of macrophage burden. Rabbit experiments showed significantly higher aortic accumulation of both [⁶⁸Ga]Ga-DOTATATE and [¹⁸F]F-FDG in atherosclerotic (SUV_max 0.415, IQR, 0.338–0.499, N = 32 and 0.446, IQR, 0.387–0.536, N = 27, respectively) compared to control animals (SUV_max 0.253, IQR, 0.197–0.285, p = 0.0002, N = 10 and 0.349, IQR, 0.299–0.423, p = 0.0159, N = 11, respectively). In conclusion, we present a detailed, head-to-head comparison of the novel SST2-specific tracer DOTATATE and the validated metabolic tracer [¹⁸F]F-FDG for the evaluation of inflammation in small animal models of cardiovascular disease. Our results support further investigations on the use of DOTATATE to assess cardiovascular inflammation as a complementary readout to the widely used [¹⁸F]F-FDG.

Background: Macrophages, innate immune cells that reside in all organs, defend the host against infection and injury. In the heart and vasculature, inflammatory macrophages also enhance tissue damage and propel cardiovascular diseases. Methods: We here use in vivo positron emission tomography (PET) imaging, flow cytometry, and confocal microscopy to evaluate quantitative noninvasive assessment of cardiac, arterial, and pulmonary macrophages using the nanotracer ⁶⁴ Cu-Macrin—a 20-nm spherical dextran nanoparticle assembled from nontoxic polyglucose. Results: PET imaging using ⁶⁴ Cu-Macrin faithfully reported accumulation of macrophages in the heart and lung of mice with myocardial infarction, sepsis, or pneumonia. Flow cytometry and confocal microscopy detected the near-infrared fluorescent version of the nanoparticle ( ^VT680 Macrin) primarily in tissue macrophages. In 5-day-old mice, ⁶⁴ Cu-Macrin PET imaging quantified physiologically more numerous cardiac macrophages. Upon intravenous administration of ⁶⁴ Cu-Macrin in rabbits and pigs, we detected heightened macrophage numbers in the infarcted myocardium, inflamed lung regions, and atherosclerotic plaques using a clinical PET/magnetic resonance imaging scanner. Toxicity studies in rats and human dosimetry estimates suggest that ⁶⁴ Cu-Macrin is safe for use in humans. Conclusions: Taken together, these results indicate ⁶⁴ Cu-Macrin could serve as a facile PET nanotracer to survey spatiotemporal macrophage dynamics during various physiological and pathological conditions. ⁶⁴ Cu-Macrin PET imaging could stage inflammatory cardiovascular disease activity, assist disease management, and serve as an imaging biomarker for emerging macrophage-targeted therapeutics.

Background: The COVID-19 pandemic has resulted in a high degree of psychological distress among health care workers (HCWs). There is a need to characterize which HCWs are at an increased risk of developing psychological effects from the pandemic. Given the differences in the response of individuals to stress, an analysis of both the perceived and physiological consequences of stressors can provide a comprehensive evaluation of its impact. Objective: This study aimed to determine characteristics associated with longitudinal perceived stress in HCWs and to assess whether changes in heart rate variability (HRV), a marker of autonomic nervous system function, are associated with features protective against longitudinal stress. Methods: HCWs across 7 hospitals in New York City, NY, were prospectively followed in an ongoing observational digital study using the custom Warrior Watch Study app. Participants wore an Apple Watch for the duration of the study to measure HRV throughout the follow-up period. Surveys measuring perceived stress, resilience, emotional support, quality of life, and optimism were collected at baseline and longitudinally. Results: A total of 361 participants (mean age 36.8, SD 10.1 years; female: n=246, 69.3%) were enrolled. Multivariate analysis found New York City’s COVID-19 case count to be associated with increased longitudinal stress (P=.008). Baseline emotional support, quality of life, and resilience were associated with decreased longitudinal stress (P<.001). A significant reduction in stress during the 4-week period after COVID-19 diagnosis was observed in the highest tertial of emotional support (P=.03) and resilience (P=.006). Participants in the highest tertial of baseline emotional support and resilience had a significantly different circadian pattern of longitudinally collected HRV compared to subjects in the low or medium tertial. Conclusions: High resilience, emotional support, and quality of life place HCWs at reduced risk of longitudinal perceived stress and have a distinct physiological stress profile. Our findings support the use of these characteristics to identify HCWs at risk of the psychological and physiological stress effects of the pandemic.