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

Abstract

Background No methodology is available to distinguish truly reduced myocardial flow reserve (MFR) in positron emission tomography myocardial perfusion imaging (PET MPI) from seemingly impaired MFR due to inadequate adenosine response. The adenosine-induced splenic switch-off (SSO) sign has been proposed as a potential marker for adequate adenosine response in cardiac magnetic resonance (CMR). We assessed the feasibility of detecting SSO in nitrogen-13 ammonia PET MPI using SSO in CMR as the standard of reference. Methods and Results Fifty patients underwent simultaneous CMR and PET MPI on a hybrid PET/MR device with co-injection of a gadolinium-based contrast agent and nitrogen-13 ammonia during rest and adenosine-induced stress. In CMR, SSO was assessed visually (positive vs negative SSO) and quantitatively by calculating the ratio of the peak signal intensity of the spleen during stress over rest (SIR). In PET MPI, the splenic signal activity ratio (SAR) was calculated as the maximal standard uptake value of the spleen during stress over rest. The median SIR was significantly lower in patients with positive versus negative SSO in CMR (0.57 [IQR 0.49 to 0.62] vs 0.89 [IQR 0.76 to 0.98]; P < .001). Similarly, median SAR in PET MPI was significantly lower in patients with positive versus negative SSO (0.40 [IQR 0.32 to 0.45] vs 0.80 [IQR 0.47 to 0.98]; P < .001). Conclusion Similarly to CMR, SSO can be detected in nitrogen-13 ammonia PET MPI. This might help distinguish adenosine non-responders from patients with truly impaired MFR due to microvascular dysfunction or multivessel coronary artery disease.

Extracardiac findings with increased perfusion during clinical O-15-H2O PET/CT myocardial perfusion imaging: A case series

“…It has been shown that the presence of splenic switch-off indicates sufficient adenosine-induced coronary vasodilatation, whereas absence of splenic switch-off is not a reliable marker of failed adenosine response. 38 , 39 This information can be extremely helpful in distinguishing patients with balanced hypoperfusion from non-responders.

Figure 5 A Patient with pronounced splenic switch-off after adenosine stress.

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Combining body mass index with waist circumference to assess coronary microvascular function in patients with non-obstructive coronary artery disease

“…Patients younger than 18 years, having coronary revascularization, or with contraindications against adenosine/dipyridamole or PET were excluded. 15 Contraindications for the use of adenosine/ dipyridamole were second-or third-degree atrioventricular block, hypotension, bradyarrhythmias, asthma, or hypersensitivity to dipyridamole/adenosine. This study was approved by the Ethics Review Committee of the First Hospital of Shanxi Medical University and a written informed consent was obtained from all patients prior to study participation.…”

“…We also did not measure the patients' body fat percentage, lean body mass, or fat distribution. Fourth, we justified the cut-off for CMD based on 15 O-H 2 O rather than 13 N-ammonia. Although 13 N-ammonia and 15 O-water provide similar absolute MBF information over a wide range of blood flows in human, it remains uncertain how these thresholds for hyperemic flows using 15 O-H 2 O compare with 13 N-ammonia.…”

“…Fourth, we justified the cut-off for CMD based on 15 O-H 2 O rather than 13 N-ammonia. Although 13 N-ammonia and 15 O-water provide similar absolute MBF information over a wide range of blood flows in human, it remains uncertain how these thresholds for hyperemic flows using 15 O-H 2 O compare with 13 N-ammonia. Moreover, we did not perform follow-up surveillance for future cardiovascular events.…”

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.…”