Incremental prognostic value of SPECT-MPI in chronic kidney disease: A reclassification analysis

Background: Traditional cardiovascular (CV) risk factors have limited predictive value of CV mortality in patients with chronic kidney disease (CKD, creatinine clearance less than 60 mL/minute per 1.73 m²). The aim of this study was to evaluate incremental and independent prognostic value of single-photon emission computerized tomography-myocardial perfusion imaging (SPECT-MPI) across continuum of renal function. Methods: We retrospectively studied 11,518 (mean age, 65 ± 12 years; 52% were men) patients referred for a clinical indication of SPECT-MPI between April 2004 and May 2009. Primary end point was composite of cardiac death and non-fatal myocardial infarction (CD/MI). We examined the relationship of total perfusion defect (TPD) and CD/MI in multiple Cox regression models for CV risk factors and GFR. The incremental predictive value of TPD was examined using Harrell’s c-index, net reclassification index (NRI), and integrated discrimination index (IDI). Results: Over a median follow-up of 5 years (25th to 75th percentiles, 3.0-6.5 years), 1,692 (14.5%) patients experienced CD/MI (740 MI and 1,182 CD). In a multivariable model adjusted for traditional CV risk factors and GFR, the presence of a perfusion defect was independently associated with increased risk of CD/MI (HR = 2.10; 95% CI 1.81, 2.43, p < .001). Using Cox regression, TPD improved the discriminatory ability beyond traditional CV risk factors and GFR [from AUC = 0.725, (95% CI 0.712-0.738) to 0.784, (95% CI 0.772-0.796), p < .0001]. Furthermore, TPD improves risk stratification of CKD patients over and above traditional CV risk factors and GFR [NRI = 14%, 95% CI (12%-16%, p < .001) and relative IDI = 60%, 95% CI (51%, 66%, p < .001)]. Conclusions: Across the spectrum of renal function, SPECT-MPI perfusion defects independently and incrementally reclassified patients for their risk of CD/MI, beyond traditional CV risk factors.