Background: Resting myocardial blood flow (rMBF) within regions of myocardial scar as measured by positron emission tomography (PET) has not yet been assessed with the radiotracer Rubidium82 (Rb82) or correlated with scar thickness. Cardiac magnetic resonance imaging (cMRI) offers high spatial resolution and identifies myocardial scar with late gadolinium enhancement (LGE). Using Rb82 PET, we sought to characterize rMBF in regions of myocardial scar of varying thicknesses determined by cMRI. Methods/Results: Patients with a history of myocardial infarction, a resting Rb82 PET study and a cMRI were identified. On cMRI, regions of infarction, defined as >50% LGE with akinesis, were sub-categorized as 50-75% LGE or >75% LGE, corresponding with increasing transmural scar thickness. PET zones of infarct based on size and %LGE by cMRI were quantified for mean and minimum rMBF. Mean rMBF (cc/min/g) in infarct zones with >75% LGE was 0.32±0.07 with a minimum rMBF of 0.19±0.03. In infarct zones with 50-75% LGE, rMBF was 0.45±0.14 (50-75% vs. >75%, p=0.002). Conclusions: We identified rMBF within cMRI confirmed regions of myocardial scar of varying thicknesses. rMBF has an inverse relationship with the extent of LGE on cMRI, with the most severe regions (>75% LGE) having mean and minimal rMBF (cc/min/g) of 0.32±0.07 and 0.19±0.03, respectively.
Keywords: Magnetic resonance imaging (MRI); Myocardial blood flow; Myocardial infarction; Positron emission tomography (PET).
2022, The Japanese Society of Nuclear Cardiology.