Splenic Switch‐Off for Determining the Optimal Dosage for Adenosine Stress Cardiac MR in Terms of Stress Effectiveness and Patient Safety

Abstract

Background: Adenosine stress MRI is well established for the evaluation of known and suspected coronary artery disease. However, a proportion of patients might be "under-stressed" using the standard adenosine dose. Purpose: To compare three different adenosine dosages for stress MRI in terms of stress adequacy based on splenic switch-off (SSO) and limiting side effects. Study Type: Prospective. Population: In all, 100 patients were randomized in group 1 (33 pts), group 2 (34 pts), and group 3 (33 pts), receiving dosages of 140 μg/kg/min, 175 μg/kg/min, or 210 μg/kg/min, respectively. SSO was evaluated visually and quantitatively. Sequence: Stress perfusion was performed using a 1.5T scanner in three short axes using a standard single-shot, saturation recovery gradient-echo sequence. Assessment: Three blinded experienced operators evaluated SSO on stress and rest perfusion acquisitions in the three groups. The signal intensity of the spleen and myocardium and the presence of inducible ischemia and late gadolinium enhancement were assessed. Statistical Analysis: T-test, analysis of variance (ANOVA), chi-squared test, and Pearson's correlation coefficient. Results: SSO was present more frequently in patients receiving 175 μg/kg/min and 210 μg/kg/min (31/33 [94%] and 27/29 [93%], respectively) compared to those receiving the standard dose (19/33 [58%], P < 0.05). A positive stress result was noted in 3/33 (9%) patients receiving 140 μg/kg/min vs. 9/33 (27%) patients receiving 175 μg/kg/min and 10/31 (33%) patients receiving 210 μg/kg/min (P < 0.05 for all, P < 0.05 for group 1 vs. groups 2, 3). The relative decrease of splenic signal intensity at hyperemia vs. baseline was significantly lower in group 1 compared to groups 2 and 3 (−33% vs. −54%, −56%, respectively; P < 0.05). No adverse events during scanning were noted in groups 1 and 2, whereas in group 3 four examinations were stopped due to severe dyspnea (n = 2) and AV-blockage (n = 2). Data Conclusion: A dosage of 175 μg/kg/min adenosine results in a higher proportion of SSO, which may be an indirect marker of adequate coronary vasodilatation and simultaneously offers similar safety compared to the standard 140 μg/kg/ min dosage. Level of Evidence: 1 Technical Efficacy Stage: 2

A polygenic stacking classifier revealed the complicated platelet transcriptomic landscape of adult immune thrombocytopenia

“…The analysis of variance (ANOVA) algorithm measures the difference between the means of two groups of samples. 55 ANOVA uses F-test to calculate the statistical significance of rejecting the null hypothesis of the mean equality. The F-test assumes that the data follow the F-distribution.…”

Assessment of Splenic Switch‐Off With Arterial Spin Labeling in Adenosine Perfusion Cardiac MRI

“…8,9 Splenic switch-off, defined as stress to rest splenic perfusion attenuation in response to A 2A A 2B receptor-mediated vasoconstriction of the afferent splenic arteries during adenosine infusion, 10 has been proposed as an indicator of stress adequacy in cardiac MRI. [11][12][13][14][15] To date, it has been assessed in first-pass perfusion imaging studies since the spleen is commonly captured by the acquired short-axis slices. [11][12][13][14][15] The main disadvantage of using first-pass images for the assessment of splenic switch-off is that stress adequacy is usually determined during the study interpretation once the exam has finished.…”

“…[11][12][13][14][15] To date, it has been assessed in first-pass perfusion imaging studies since the spleen is commonly captured by the acquired short-axis slices. [11][12][13][14][15] The main disadvantage of using first-pass images for the assessment of splenic switch-off is that stress adequacy is usually determined during the study interpretation once the exam has finished. [11][12][13][14][15] Therefore, the utility of the technique seems limited to the detection of false-negative findings.…”

“…[11][12][13][14][15] The main disadvantage of using first-pass images for the assessment of splenic switch-off is that stress adequacy is usually determined during the study interpretation once the exam has finished. [11][12][13][14][15] Therefore, the utility of the technique seems limited to the detection of false-negative findings. The use of a noncontrast technique would be beneficial for the real-time evaluation of splenic switch-off to objectively determine the vasodilator effect of the drug, thus providing an opportunity for optimizing the stress response by increasing the adenosine dose before gadolinium administration.…”

“…Previous work has shown that a higher adenosine dose increases the proportion of patients with splenic switch off in comparison to the standard 140 μg/kg/min dose. 15 In this context, T1 mapping has been previously investigated 16 ; however, T1 estimations do not provide a direct measure of splenic perfusion. Arterial spin labeling (ASL) provides noncontrast perfusion measurements by using magnetically labeled arterial blood water spins as endogenous tracers.…”