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Quantitative vs. Visual Prognostic SPECT
Study Questions:
What is the ability of automated myocardial perfusion imaging analysis in comparison to visual analysis in major adverse cardiac event (MACE) prediction?
Methods:
The investigators identified 19,495 patients (64 ± 12 years, 56% male) undergoing stress Tc-99m SPECT-MPI from the multicenter REFINE SPECT (REgistry of Fast Myocardial Perfusion Imaging with NExt generation SPECT), and were followed for 4.5 ± 1.7 years for MACE. Perfusion abnormalities were assessed visually and categorized as normal, probably normal, equivocal, and abnormal. Stress total perfusion deficit (TPD), quantified automatically, was categorized as TPD = 0%, TPD >0% to <1%, ≤1% to <3%, ≤3% to <5%, ≤5% to ≤10%, or TPD >10%. MACE consisted of death, nonfatal myocardial infarction, unstable angina, or late revascularization (>90 days). Kaplan-Meier and Cox proportional hazards analyses were performed to test the performance of visual and quantitative assessment in predicting MACE.
Results:
During the follow-up, 2,760 MACE occurred (14.2%). MACE rates increased with worsening of visual assessment: normal (2.0%), probably normal (3.2%), equivocal (4.2%), and abnormal (7.4%) (all p < 0.001). MACE rates increased with increasing stress TPD from 1.3% (TPD = 0%) to 7.8% (TPD >10%) (p < 0.0001). Adjusted hazard ratio (HR) for MACE increased even in equivocal assessment (HR, 1.56; 95% confidence interval [CI], 1.37-1.78 and in the TPD category of ≤3% to <5% (HR, 1.74; 95% CI, 1.41-2.14) (all p < 0.001). MACE in patients with normal visual assessment still increased from 1.3% (TPD = 0%) to 3.4% (TPD ≥5%) (p < 0.0001).
Conclusions:
The authors concluded that quantitative analysis allows precise granular risk stratification in comparison to visual reading, even for cases with normal clinical reading.
Perspective:
This registry study reports that increasing abnormality on both visual and automated perfusion quantification was associated with increased MACE risk over long-term follow-up (median follow-up of 5 years), in both unadjusted and adjusted multivariable analyses. Furthermore, the MACE rates increased progressively with each increasing interval of both visual and quantitative assessment (stress TPD) on a fine granular scale, including several intervals below standard diagnostic threshold (SSS <4 and stress TPD <5%). These data suggest that quantitative parameters provide additional independent prediction of the patient’s outcome and in the future, it may be reasonable to report a quantitative probability estimation of annual-MACE risk for a given patient.
Clinical Topics: Cardiovascular Care Team, Noninvasive Imaging, Prevention, Computed Tomography, Nuclear Imaging
Keywords: Angina, Unstable, Diagnostic Imaging, Myocardial Infarction, Myocardial Ischemia, Myocardial Perfusion Imaging, Risk, Secondary Prevention, Technetium, Tomography, Emission-Computed, Single-Photon
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