Transient ischemic dilation with 18F-flurpiridaz positron emission tomography: Establishing thresholds for a novel radiotracer.

BACKGROUND

Transient ischemic dilation (TID) of the left ventricule (LV) is a specific marker of extensive coronary artery disease (CAD). Normal limits for TID using 18F-flurpiridaz have not been established.

METHODS

We performed a secondary analysis of the multicenter phase III flurpiridaz-301 trial, which included patients with suspected CAD who underwent rest-stress 18F-flurpiridaz positron emission tomography (PET), Tc-99m single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI), and invasive coronary angiography (ICA). TID was calculated using ungated left ventricular volumes. Stress-specific reference thresholds were derived in patients without angiographic CAD. The effects of stress modality, CAD severity, and postreconstruction Gaussian filtering on TID measurements were evaluated.

RESULTS

Among 746 patients with evaluable PET, SPECT, and angiographic data, stress-specific TID reference thresholds (97.5th percentile) for 18F-flurpiridaz PET using a 5-mm Gaussian filter were 1.18 for exercise stress and 1.25 for pharmacologic stress. Corresponding Tc-99m SPECT thresholds were lower. PET-derived TID values increased progressively with angiographically defined CAD severity, demonstrating a graded association across disease categories. Application of post-reconstruction Gaussian filtering resulted in lower PET-derived TID values compared with unfiltered images, with modest differences between 5-mm and 8-mm filters.

CONCLUSIONS

This study suggests stress-specific reference thresholds for TID using 18F-flurpiridaz PET in a large multicenter cohort. PET-derived TID values were higher than those observed with Tc-99m SPECT, varied by stress modality, and were influenced by postreconstruction filtering. These findings highlight the importance of tracer-, stress-, and protocol-specific reference standards for accurate clinical interpretation of TID.