The Effect of Heart Rate on Exposure Window and Best Phase for Stress Perfusion Computed Tomography: Lessons From the CORE320 Study.

Objectives: The aim of this study is to evaluate the effect of heart rate on exposure window, best phase, and image quality for stress computed tomography perfusion (CTP) in the CORE320 study.
Methods: The CTP data sets were analyzed to determine the best phase for perfusion analysis. A predefined exposure window covering 75% to 95% of the R-R cycle was used.
Results: Of the 368 patients included in the analysis, 93% received oral β blockade before the rest scan. The median heart rate during the stress acquisition was 69 bpm (interquartile range [IQR], 60-77). The median best phase was 81% (IQR, 76-90), and length of exposure window was 22% (IQR, 19-24). The best phase was significantly later in the cardiac cycle with higher heart rates (P < 0.001), and higher heart rates resulted in a small, but higher number of poor quality scans (6%, P < 0.001). The median effective dose of the stress scan was 5.3 mSv (IQR, 3.8-6.1).
Conclusions: Stress myocardial CTP imaging can be performed using prospective electrocardiography triggering, an exposure window of 75% to 95%, and β-blockade resulting in good or excellent image quality in the majority (80%) of patients while maintaining a low effective radiation dose.