Extensive and balanced reduction of myocardial blood flow in patients with suspected obstructive coronary artery disease: 15O-water PET study

Detection of obstructive coronary artery disease (CAD) by stress myocardial perfusion imaging (MPI) is conventionally based on relative differences in perfusion. This may lead to either underestimation of the extent of myocardial ischemia, or the ischemia might be completely missed in case of balanced perfusion reduction. Using absolute quantification of myocardial blood flow (MBF) by positron emission tomography (PET), we evaluated how common are extensive and balanced myocardial perfusion abnormalities in symptomatic patients with suspected obstructive CAD.Among 758 consecutive symptomatic patients undergone coronary computed tomography angiography (CTA), 286 patients subsequently underwent quantitative 15O-water adenosine-stress PET MPI to assess the hemodynamic significance of suspected obstructive stenosis. Out of these, 46 (16%) patients had reduced (≤2.3 ml/g/min) absolute stress MBF in all three standard coronary territories (LAD, LCX, RCA). Subsequently, relative stress MBF in each coronary territory was calculated, considering a territory with the highest absolute stress MBF as a reference region. Among the 46 patients, 72% had significant regional heterogeneity in myocardial perfusion (defined as having ≥1 territory with relative stress MBF80%) while the remaining 28% (4.5% of the whole MPI cohort) showed balanced perfusion reduction (all relative MBF values ≥80%).Among symptomatic patients with suspected obstructive stenosis on coronary CTA, quantitative PET revealed that 16% of patients had reduced stress MBF involving all three coronary artery territories, of whom approximately one third showed balanced reduction. Thus, in 4.5% of the patients the perfusion abnormalities could have been missed by conventional relative MPI analysis.