Accurate detection of extensive coronary artery disease depends on reliable imaging benchmarks — and until now, a critical one was missing for the newest cardiac PET tracer. Establishing normal reference limits for transient ischemic dilation using 18F-flurpiridaz fills a practical clinical gap that has limited confident interpretation of this next-generation imaging modality since its FDA approval.
Drawing on the multicenter phase III flurpiridaz-301 trial — one of the largest prospective cardiac imaging datasets with paired invasive coronary angiography — researchers performed a secondary analysis of 746 patients with suspected coronary artery disease who underwent rest-stress 18F-flurpiridaz PET, Tc-99m SPECT myocardial perfusion imaging, and invasive angiography. Using a 5-mm Gaussian post-reconstruction filter, the 97.5th percentile transient ischemic dilation threshold was set at 1.18 for exercise stress and 1.25 for pharmacologic stress. Notably, PET-derived values rose in a graded, progressive fashion across angiographically confirmed coronary disease severity categories, while corresponding SPECT thresholds landed lower — a technically important distinction when labs transition between modalities.
These findings carry meaningful implications for cardiac imaging programs now adopting 18F-flurpiridaz following its regulatory clearance. Transient ischemic dilation reflects stress-induced subendocardial ischemia causing apparent left ventricular cavity enlargement; without modality-specific thresholds, labs risk misclassifying normal studies as pathologic or, worse, missing high-risk disease. The graded association with angiographic severity strengthens the biomarker's construct validity. However, critical caveats apply: this is a secondary analysis of a trial with specific enrollment criteria, the population skewed toward clinically referred patients rather than a general screening cohort, and the thresholds were derived with a particular reconstruction filter — meaning labs using different software pipelines cannot directly apply these cutoffs. The filter sensitivity finding is particularly pragmatic, signaling that standardization of post-processing workflows will be essential before these reference values can be universally adopted. Overall, this is incremental but genuinely necessary calibration work for a modality poised to reshape nuclear cardiology.