Prognostic utility of splenic response ratio in dipyridamole PET myocardial perfusion imaging
Cardiac magnetic resonance perfusion studies with adenosine stress have shown that splenic response can identify patients with inadequate pharmacologic stress. We investigate the incremental prognostic impact of splenic response ratio (SRR) in patients with normal Rubidium (Rb)-82 PET myocardial perfusion imaging (MPI).
Consecutive patients undergoing dipyridamole Rb-82 PET MPI for the evaluation of coronary artery disease were screened. Spleen and liver Rb-82 activity was measured and the SRR was calculated: SRR = (Spleen stress/Liver stress)/(Spleen rest/Liver rest). Major adverse cardiac events (MACE) were determined at 1 year of follow-up in patients with normal summed stress score and normal summed difference score.
Of the 839 patients screened, the spleen was visualized in 703 (84%) of scans. There was significantly higher MACE observed in splenic non-responders vs splenic responders in both the normal SSS (7.8% vs 2.9%, P = .027) and the normal SDS groups (7.4% vs 2.2%, P = .014). In multivariate analysis in patients with normal SDS, splenic response was a significant, independent predictor of MACE (HR 2.97, 95% CI 1.10 to 8.04, P = .033).
SRR is a novel imaging metric to identify patients with sub-maximal vasodilator stress and an incremental prognostic marker in patients with normal SDS and SSS (Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT01128023).
KeywordsMajor adverse cardiac events myocardial perfusion imaging positron emission tomography prognosis summed difference score splenic response ratio
Major adverse cardiac events
Myocardial blood flow reserve
Myocardial perfusion imaging
Positron emission tomography
Summed difference score
Splenic response ratio
Summed stress score
Karan Bami, Shrankhala Tewari, Fadi Guirguis, Linda Garrard, and Ann Guo have nothing to disclose. Terrence D. Ruddy has research grants from GE HealthCare and Advanced Accelerator Applications. Robert A. deKemp reports grants, consulting fees, and license revenues from Jubilant DraxImage and University of Ottawa Heart Institute (UOHI), outside the submitted work. Rob S. B. Beanlands reports grants and honoraria from Lantheus Medical Imaging, grants and honoraria from Jubilant DraxImage, and grants from GE Healthcare, outside the submitted work. Rob S. B. Beanlands is a Career Investigator supported but the Heart and Stroke Foundation of Ontario and a Tier 1 Research Chair supported by the University of Ottawa. Benjamin J. W. Chow holds the Saul and Edna Goldfarb Chair in Cardiac Imaging Research. He receives research support from CV Diagnostix and educational support from TeraRecon Inc. Girish Dwivedi was supported by a CIHR new investigator salary support award while at UOHI. Currently he is Wesfarmers Chair in Cardiology at University of Western Australia with an Adjunct Professor appointment at UOHI. The study was performed at UOHI.
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