Are you stressed?

Splenic switch-off as a novel marker for adenosine response in nitrogen-13 ammonia PET myocardial perfusion imaging: Cross-validation against CMR using a hybrid PET/MR device

“…It should be also noted that while the results of our study may be applicable to patients undergoing dipyridamole stress, the splenic switch-off sign is not observed after administration of regadenoson due to its selective receptor affinity or during dobutamine stress. 7,9 Furthermore, since this study demonstrated the feasibility of detecting SSO in PET MPI as defined by visual SSO in CMR, further assessment of this sign using invasive coronary angiography and coronary computed angiography as an anatomical correlate is needed. Finally, our binary system of categorizing patients as responders and non-responders might be an over-simplification as a more graded adenosine response is suggested by some studies, depending on receptor density and responsiveness of adenosine receptors, as well as the distribution of SIR and activity ratios in our study suggest a graded response of splenic perfusion to adenosine stress.…”

“…Its validity as a marker for adenosine response is based on the assumption that while adenosine receptor stimulation results in splanchnic vasodilation, the splenic circulation is not affected by this mechanism, potentially even showing an opposite reaction in the form of vasoconstriction. 7 , 8 The utility of SSO for identifying inadequate adenosine response in CMR was first described in the CE-MARC study cohort, where significantly more false-negative than true negative exams failed to show the sign. 9 A subsequent study in a real-world population also showed an increased prevalence of SSO in true positive as compared to false-negative CMR exams, although not reaching statistical significance.…”

Image-derived and physiological markers to predict adequate adenosine-induced hyperemic response in Rubidium-82 myocardial perfusion imaging

“…1,2 The accuracy of the stress myocardial blood flow and reserve assessments, however, is significantly lowered if adequate pharmacological stressing is not achieved. 3 Previous studies have suggested that 3-20% of all stress MPI might have false-negative findings caused by inadequate pharmacological stressing of the patients. [3][4][5] The most frequently used pharmacological stressors are regadenoson, dipyridamole, and adenosine; they all activate the adenosine receptor A 2A in coronary arteries and initiate a dilatation of these vessels, which in turn increases myocardial blood flow up to fourfold.…”

“…3 Previous studies have suggested that 3-20% of all stress MPI might have false-negative findings caused by inadequate pharmacological stressing of the patients. [3][4][5] The most frequently used pharmacological stressors are regadenoson, dipyridamole, and adenosine; they all activate the adenosine receptor A 2A in coronary arteries and initiate a dilatation of these vessels, which in turn increases myocardial blood flow up to fourfold. 6 Coffee, caffeine, and other methylxanthines act as non-selective antagonists at the adenosine receptors and are expected to dose-dependently attenuate vasodilator-induced myocardial hyperaemia and may, therefore, reduce the sensitivity of radionuclide MPI for the detection of inducible perfusion abnormality in patients with coronary artery disease.…”

“… 7 The easy identification of adequate hemodynamic response in the patients persists to be a problem; however, several physiological, image-derived, and hybrid markers have been suggested to identify the adequate response. 3 , 8 , 9 This study aimed to evaluate seven of the proposed markers ability to predict adequate adenosine-induced hyperemic response in subjects with or without caffeine consumption prior to MPI. The seven markers can be classified as image-derived markers (splenic response ratio (SRR) and splenic stress-to-rest intensity ratios (SIR)) and markers of changes in physiological response between rest and stress MPI (heart rate (ΔHR), the percentwise change in HR (Δ%HR), changes in the rate pressure product (ΔRPP), and changes in the systolic blood pressure (ΔSBP)).…”