Objectives

Established reference values for 13N-ammonia PET myocardial perfusion imaging (MPI) in patients without flow-limiting coronary artery disease (CAD).
Identified body mass index (BMI) as the most important predictor of resting myocardial blood flow (rMBF), stress MBF (sMBF), and myocardial flow reserve (MFR).
Demonstrated that median and reference limits for sMBF and rMBF decrease with increasing BMI, while MFR exhibits stable lower reference limits across a wide range of BMI.

Methodology

Retrospective single-center study of patients who underwent 13N-ammonia PET-MPI.
Excluded patients with evidence of myocardial ischemia or scar, known cardiomyopathy, impaired left ventricular function, non-response to vasodilators, and those who underwent a stress-rest protocol.
Multiple linear regression analyses were performed to identify independent predictors of rMBF, sMBF, and MFR.
Predictor importance was calculated.
Median, lower reference limit (LRL), and upper reference limit (URL) for rMBF, sMBF, and MFR were calculated based on the presence of predictors.

784 patients were included.
Median rMBF was 0.75 mL∙min−1∙g−1 (LRL=0.49 mL∙min−1∙g−1; URL=1.33 mL∙min−1∙g−1).
Median sMBF was 2.41 mL∙min−1∙g−1 (LRL=1.42 mL∙min−1∙g−1; URL=3.73 mL∙min−1∙g−1).
Median MFR was 3.09 (LRL=2.11; URL=4.65).
BMI was the single most important independent predictor of rMBF, sMBF, and MFR (predictor importance of 72%, 87%, and 41%, respectively; standardized β=-0.434, -0.566 and −0.174, respectively).
Additional predictors were sex and hypertension for rMBF, sex for sMBF, and hypertension and coronary artery calcium score (CACS) for MFR.

The study is limited by its observational, single-center design, and potential residual confounding cannot be excluded.
The lack of outcome data is a major limitation, and future studies are needed to evaluate the prognostic value of the established reference limits.
The retrospective nature of the study resulted in a lack of conclusive data on renal function, preventing evaluation of its potential effect on MBF.
The results are limited to PET MPI with 13N-ammonia, and the impact of different scanners or software solutions was not assessed.