Prognostic value of global and regional myocardial blood flow assessed by 15O-water positron emission tomography in patients with suspected coronary disease

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Coronary computed tomography angiography (CCTA) combined with positron emission tomography (PET) myocardial perfusion imaging (MPI) using 15O-water is an effective non-invasive method to detect or exclude obstructive coronary artery disease (CAD) in patients with intermediate pre-test disease probability. Prognostic value of myocardial blood flow (MBF) has been demonstrated previously with other radiotracers for PET-MPI such as 13N-labeled ammonia and 82Rubidium, but the prognostic value of 15O–water and the optimal cut-off value are unclear. \n \nWe evaluated consecutive patients from 2006 to 2014 who had sequential CCTA and 15O-water PET-MPI performed at Turku PET Centre. PET-MPI was performed only if obstructive CAD (≥ 50% stenosis) was suspected based on coronary CTA. All patients (n=530) who were performed 15O-water PET-MPI during adenosine stress were included in this study. Major adverse events (AE), including cardiovascular (CV) mortality, myocardial infarction (MI) and unstable angina pectoris (UAP) were recorded from hospital records and from the National Institute for Health and Welfare (Finland) during an average follow-up of 6.2 years. \n \nBased on our study, global stress MBF 2.2 ml/g/min is the optimal prognostic cut-off value. During mean follow-up of 6.2 years there were 46 events (9 CV deaths, 23 MIs and 14 UAPs) corresponding to an annual event rate of 1.4%. Out of 530 patients, 121 had reduced global stress MBF (<2.2 ml/g/min). Out of 409 patients who had preserved global stress MBF (≥2.2 ml/g/min), 187 showed regional ischemia defined as regional stress MBF < 2.3 ml/g/min, whereas 222 had no regional ischemia. Patients with reduced global stress MBF had significantly higher annual AE rate than patients with normal global stress MBF (2.7% vs. 1.1%, p = 0.001). Regional ischemia in the presence of preserved global stress MBF was associated with an intermediate annual event rate of 1.5% (p = 0.001 vs. reduced global stress MBF). Patients having preserved global stress MBF without regional ischemia had the lowest event rate (0.7%, p = 0.002 vs. preserved global stress MBF with regional ischemia, or reduced global stress MBF). Globally reduced stress MBF by 15O-water PET MPI is associated with an increased risk of adverse events. Compared with regional ischemia, reduced global MBF identifies patients with the highest adverse event risk.

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