173 Quantitative Perfusion CMR in ANOCA were observed in 6%. Visual assessment of the total 49 perfusion scans showed that 45 scans (91.8%) had no perfusion defects in stress, 2 scans (4.1%) had a presumable defect (1 ANOCA patients vs. 1 healthy control), 1 scan (2.0%) showed a definite perfusion defect (1 in ANOCA patients vs. 0 in healthy controls), and 1 scan (2.0%) was not assessable during stress (overall p = 0.536). During rest perfusion scan, only one definite perfusion defect was observed in an ANOCA patient. No late gadolinium enhancement was observed in any of the scans. Quantitative assessment of perfusion by CMR Figures 1 and 2 depict typical examples of acquired images in healthy controls and in ANOCA patients, respectively. In a healthy control, no perfusion defect was visible on either the conventional grayscale first-pass perfusion images or the QP CMR results, which showed an MPR of 2.58. Contrarily, in an ANOCA patient, also no perfusion defect was visible on first-pass perfusion images, but QP CMR revealed a reduced MPR of 1.58. Figure 3 shows the results of the global perfusion CMR during rest, stress and the global MPR in the overall groups. No significant difference was observed in global rest MBF (1.16 ± 0.23 ml/g/min vs 1.22 ± 0.20 ml/g/min, respectively p = 0.398) (Fig. 3A), while global perfusion during stress was significantly lower in ANOCA patients (2.43 ± 0.72 ml/g/min vs 2.99 ± 0.65 ml/g/min, respectively p = 0.006) (Fig 3B). Also, MPR was significantly lower in ANOCA patients compared to healthy controls (2.24 ± 0.79 vs 2.68 ± 0.64, respectively p = 0.036) (Fig. 3C). Global MPR in both patients and controls were dichotomized into a normal MPR (≥ 2.19) or abnormal MPR (< 2.19). A total of 17 participants (34.7%) were classified with an impaired global MPR, with a significant higher prevalence of an abnormal MPR in ANOCA patients (n = 12, 50%) compared to healthy controls (n = 5, 20%, p = 0.027). Figure 1. Normal Quantitative Perfusion in Healthy Control. Example of acquired images in a healthy control Abbreviations: MBF: Myocardial Blood Flow; MPR: Myocardial Perfusion Reserve 8
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