Evaluation of splenic switch off in a tertiary imaging centre: validation and assessment of utility.

Aims: Adenosine can induce splenic vasoconstriction (splenic switch-off, SSO). In this study, we aim to evaluate the utility of identifying a lack of SSO for detecting false-negative adenosine stress perfusion cardiac magnetic resonance (CMR) scans.
Methods and Results: We visually analysed 492 adenosine stress perfusion CMR scans reported as negative in a cohort of patients with no previous history of coronary artery disease. A lack of SSO was identified in 11%. We quantified the phenomenon by drawing regions of interest on the spleen and comparing intensity between stress and rest scans, the spleen intensity ratio (SIR). Inter-rater agreement for qualitative determination of SSO was κ = 0.81 and inter-class correlation for quantitative determination of SSO was 0.94. The optimal threshold for SIR as an indicator of SSO was 0.40 (sensitivity = 82.5%, specificity = 92.3%, AUC = 0.91). 23 065 CMR scans and 9926 invasive coronary angiogram reports were retrospectively examined to identify patients with negative CMR scans who required coronary intervention in the subsequent 12 months (false negatives). We compared these scans with true positives who had positive adenosine stress perfusion CMR scans followed by coronary intervention. The rate of lack of SSO was 20.7% in the false-negative group versus 13.1% in true positives (P = 0.37).
Conclusion: The lack of SSO is prevalent, easily measureable, and has potential to improve on haemodynamic criteria as a marker of adenosine understress in CMR perfusion scans.
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