Abstract 17358: Prognostic Value of Splenic Response Ratio in Rubidium-82 Positron Emission Tomography Myocardial Perfusion Imaging
Introduction: Cardiac magnetic resonance perfusion studies with adenosine stress have shown that splenic response may be a valuable tool to identify patients with inadequate pharmacologic stress. However, the prognostic impact of splenic response ratio (SRR) in patients with normal myocardial perfusion is unknown.
Purpose: We explored the prognostic value of SRR in patients undergoing dipyridamole stress rubidium-82 positron emission tomography (PET) myocardial perfusion imaging (MPI).
Methods: Splenic tracer activity concentrations (Bq/cm3) were measured in 839 consecutive patients undergoing PET MPI. We calculated SRR with stress and rest values using the liver as a control organ: SRR = (Spleen stress/Liver stress) / (Spleen rest/Liver rest). Patients with SRR ≤ 0.71 were classified as splenic responders, and above this as non-responders. This cutoff was obtained from SRR values in the derivation cohort (n = 50) showing normal stress MPI and normal myocardial flow reserve. The validation cohort (n = 653) was grouped into those with normal sum stress score (SSS = 0) and normal sum difference score (SDS <2). Major Adverse Cardiac Event (MACE), which included a composite endpoint of cardiac death, non-fatal acute coronary syndrome or late revascularization, was determined at 1 year of follow up.
Results: Splenic response was quantifiable in 84% of scans. In the normal SSS group, 219 (73%) were splenic responders, similar to the 312 (72%) with normal SDS. There was significantly higher MACE observed in splenic non-responders versus splenic responders in the normal SSS (6.1% vs 1.4%, p = 0.02) and the normal SDS groups (7.4% vs 2.2%, p = 0.01). The log-rank test showed that MACE free survival at 1 year was significantly lower in splenic non-responders in the normal SDS group (Figure 1).
Conclusion: SRR may be a novel tool to identify patients with sub-maximal vasodilator stress during PET. Splenic nonresponse emerged as a prognostic marker in patients with normal SDS and SSS.
Author Disclosures: K. Bami: None. S. Tewari: None. F. Guirguis: None. L. Garrard: None. A. Guo: None. T.D. Ruddy: Research Grant; Modest; GE HealthCare. R.S. Beanlands: None. R.A. deKemp: None. B.J. Chow: Research Grant; Modest; GE Healthcare. Other; Modest; TeraRecon Inc.. G. Dwivedi: None.
- © 2016 by American Heart Association, Inc.