Combined Function Test Research Articles

5962Incremental prognostic value of hybrid PET-CT assessed myocardial blood flow, coronary stenosis severity and adverse plaque characteristics

Abstract Background Management of patients with suspected coronary artery disease (CAD) can be optimized with prognostic information derived from non-invasive imaging such as positron emission tomography (PET) perfusion imaging and coronary computed tomography angiography (CCTA). The aim of the present study was to determine the incremental prognostic value of combined functional testing using PET perfusion imaging and anatomical testing using CCTA-derived stenosis severity and morphological assessment of CCTA-derived plaque morphology. Methods In this retrospective study, 539 patients referred for hybrid [15O]H2O PET – CCTA imaging because of suspected CAD were investigated. PET perfusion imaging was used to determine hyperemic myocardial blood flow (MBF), whereas CCTA images were evaluated for obstructive stenosis and high-risk plaque morphology. Major adverse coronary events (MACE) included all-cause death, non-fatal myocardial infarction (MI), urgent revascularization and late non-urgent revascularization (i.e. not guided by initial diagnostic work-up with non-invasive imaging). Kaplan Meier analysis and Cox proportional hazard regression were used to evaluate the independent prognostic value of PET-derived MBF, CCTA-derived stenosis and CCTA-derived high-risk plaque. Results During a mean follow-up of 6.8 [4.8–7.9] years, 79 (14.7%) patients experienced MACE, including 23 (4.3%) deaths, 19 (3.5%) MIs, 8 (1.5%) urgent revascularizations and 29 (5.4%) late non-urgent revascularizations. Annualized event rates for normal vs. abnormal results of PET perfusion imaging, CCTA-derived stenosis and high-risk plaque morphology were 1.2% vs 4.1%, 0.6% vs 4.4%, and 1.7% vs 5.6%, respectively (p<0.001 for all). The combined use of these three imaging parameters resulted in excellent long-term risk prediction, with a MACE-free survival of 97% in patients with no positive imaging findings. In contrast, MACE-free survival was only 69% in patients in whom all imaging findings were positive (figure 1). Multivariate Cox proportional hazard regression demonstrated incremental prognostic value of PET perfusion imaging, CCTA-derived stenosis and CCTA-derived high-risk plaques for the occurrence of MACE (p<0.05 for all) MACE-free survival stratified by PET-CT Conclusion PET-derived myocardial blood flow and CCTA-derived stenosis severity and high-risk plaque morphology are independent long-term predictors of adverse cardiac events and provide incremental prognostic value. Combined functional, anatomical and morphological assessment may allow for improved risk stratification in patients with suspected CAD.

Assessment of a combined anterior pituitary function test in beagle dogs: Rapid sequential intravenous administration of four hypothalamic releasing hormones

A combined anterior pituitary (CAP) function test was assessed in eight healthy male beagle dogs. The CAP test consisted of sequential 30-second intravenous administrations of four hypothalamic releasing hormones in the following order and doses: 1 μg of corticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropinreleasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin, cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Each releasing hormone was also administered separately in the same dose to the same eight dogs in order to investigate any interactions between the releasing hormones in the combined function test. Compared with separate administration, the combined administration of these four hypothalamic releasing hormones caused no apparent inhibition or synergism with respect to the responses to CRH, GHRH, and TRH. The combined administration of these four hypothalamic releasing hormones caused a 50% attenuation in LH response compared with the LH response to single GnRH administration. The side effects of the combined test were confined to restlessness and nausea in three dogs, which disappeared within minutes after the administration of the releasing hormones. It is concluded that with the rapid sequential administration of four hypothalamic releasing hormones (CRH, GHRH, GnRH, and TRH), the adenohypophyseal responses are similar to those occurring with the single administration of these secretagogues, with the exception of the LH response, which is lower in the CAP test than after single GnRH administration.