Viable Myocardium Detected by the Combination of Hybrid PET/MR and SPECT Imaging for the Prediction of the Efficacy of PCI in Patients With Chronic Total Occlusion.

Percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) represents a major challenge in interventional cardiology. However, the results of the current large-scale CTO study showed that PCI failed to improve the long-term prognosis (MACE) over medical therapy. Is CTO intervention necessary and how to select appropriate patients for intervention? Previous studies have found the presence and improvement of viable myocardium(VM) in patients with CTO after PCI，and the amount of preoperative VM is critical to the choice of treatment for patients.

Several diagnostic techniques have been introduced to assess myocardial viability and LV recovery, allowing the identification of ischemic myocardium with potentially reversible systolic dysfunction, such as hibernating myocardium, among which 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography ( 18F-FDG PET) as the "gold standard" for clinical assessment of VM. However, single FDG-PET assessment of VM has limitations and cannot accurately identify hibernating myocardium. 99mTc-Methoxyisobutylisocyanide single-photon emission computed tomography (99mTc-MIBI SPECT), as a validated method for assessing myocardial perfusion, is recommended by guidelines for the assessment of VM in combination with FDG-PET. In recent years, contrast-enhanced cardiac magnetic resonance imaging (cardiac magnetic resonance imaging CMR) has been increasingly used to assess myocardial viability due to its high spatial resolution, which allows the acquisition of cardiac function and myocardial scarring.

However, there are fundamental differences between the two methods in assessing VM and LV function, with LGE-CMR primarily describing an increase in extracellular space associated with scar tissue, whereas FDG-PET uptake represents the true metabolic signals of viable cardiomyocytes. They are complementary.

Hybrid PET/MRI has recently been used as a novel modality for evaluating cardiac diseases, allowing a truly synchronous/simultaneous acquisition of complementary information such as high-resolution anatomy and myocardial metabolism in merged images. However, few studies about PET/MRI were done in patients with CTO.

Our study aims to investigate the effect of CTO-PCI by assessing VM detected by the combination of PET/MR and SPECT and to investigate the predictive value of viable myocardial area on the efficacy of CTO-PCI.