Impact of cardiovascular risk factors on myocardial blood flow in patients with presumably unobstructed coronary arteries: Results from the Stuttgart myocardial perfusion registry

Background Non-invasive quantification of myocardial blood flow (MBF) has emerged as a valuable tool for the detection of coronary artery disease. Recently, fully automated MBF assessment using cardiac magnetic resonance imaging (CMR) has become available. However, data on the influence of cardiovascular risk factors and patients´ characteristics (such as age, BMI, and gender) on MBF remain limited and partially conflicting. Purpose The aim of this study was to assess the impact of cardiovascular risk factors on MBF in individuals without evidence of regional inducible ischemia, indicating the absence of obstructive epicardial coronary artery disease. Methods This analysis included consecutive patients who underwent vasodilator stress CMR at our institution between 2023 and 2025. First-pass myocardial perfusion was assessed both visually and quantitatively using an MRI sequence with fully automated inline MBF quantification. All included patients had a negative stress CMR by routine qualitative criteria, defined as the absence of ischemic late gadolinium enhancement (LGE), perfusion defects, valvular disease, or structural heart abnormalities. Patients with insufficient vasodilator response—defined as stress MBF (SMBF) <1.43 ml/g/min in all AHA segments and a heart rate increase of <15 bpm—were excluded. In a subanalysis, resting MBF (RMBF) was adjusted for the rate-pressure product to minimize the influence of hemodynamic variation at rest. Results A total of 1082 individuals (median age 63 [56–70] years; 51.8% male) were included in this analysis. Among them, 240 individuals (median age 61 [52–68] years; 47.5% male) had no known cardiovascular risk factors. The presence of cardiovascular risk factors was significantly associated with abnormal stress myocardial blood flow (SMBF <2.25 ml/g/min), with the strongest associations observed for arterial hypertension (RR: 1.575, p<0.001), diabetes mellitus (RR: 1.616, p<0.001), and hyperlipidemia (RR: 1.248, p=0.004). Obese patients (BMI ≥25) showed significantly lower SMBF and RMBF compared to non-obese individuals (SMBF: 2.3 [1.9–2.7] vs. 2.7 [2.3–3.2] ml/g/min, p<0.001; RMBF: 0.8 [0.7–1.1] vs. 1.0 [0.8–1.3] ml/g/min, p<0.001). Women demonstrated significantly higher MBF values than men (SMBF: 2.7 [2.2–3.1] vs. 2.2 [1.9–2.6] ml/g/min, p<0.001; RMBF: 1.0 [0.8–1.4] vs. 0.8 [0.6–1.0] ml/g/min, p<0.001). Finally, both SMBF and myocardial perfusion reserve (MPR) declined linearly with increasing age (SMBF: y = 3.44 − 0.0153×age, R² = 0.062; MPR: y = 4.27 − 0.0207×age, R² = 0.051). Conclusions Automated CMR-based MBF quantification reveals a significant influence of cardiovascular risk factors and individual patient characteristics on myocardial perfusion in patients with presumably unobstructed coronary arteries. These findings underscore the potential role of coronary microvascular dysfunction and highlight the complexity of defining universal MBF cut-off values.