Diagnosis of multivessel coronary artery disease using 13N-ammonia positron emission tomography and contributing factors of reduced global MFR in the real-world clinical practice

Quantitative 13N-ammonia positron emission tomography (PET) allows measurement of myocardial blood flow (MBF) and myocardial flow reserve (MFR). A reduced global MFR may indicate multivessel coronary artery disease (MVD), but its specificity is limited in real-world clinical practice. We aimed to classify the causes of reduced global MFR and to identify factors associated with the diagnosis of MVD. Among patients who underwent 13N-ammonia PET and invasive coronary angiography (ICA) between April 2014 and October 2018, 81 patients with reduced global MFR (< 2.0) were included. Causes of reduced MFR were categorized based on PET, echocardiography, and ICA findings. Patients were stratified into MVD and non-MVD groups and compared in terms of clinical characteristics, cardiovascular risk factors, echocardiography parameters, and PET imaging. Univariate and multivariate analyses were performed to identify independent predictors of MVD. MVD was identified in 51% of patients, while 49% were classified as non-MVD. Global MFR did not differ significantly between the MVD and non-MVD groups (1.44 ± 0.32 vs. 1.53 ± 0.34; p = 0.220). On multivariate analysis, the presence of a perfusion defect with a fill-in pattern on qualitative PET imaging was the only independent predictor of MVD (OR 13.80; p = 0.002). Among non-MVD patients, contributors to reduced global MFR included high resting MBF in 22, insufficient pharmacological stress in 12, influence of body motion artifacts in 12, severe single-vessel disease in 7, and heart failure in 5. Multiple contributing factors were suspected in 19 patients. Five patients were classified as “others,” but were suspected of having coronary microvascular dysfunction. In real-world clinical practice, global MFR can be reduced by multiple factors. Among patients with reduced global MFR, the presence of a perfusion defect with a fill-in pattern on qualitative PET imaging is the strongest indicator of MVD.