Abstract
Purpose
Papillary muscle ischemia (PMI) is caused by micro-vessels' occlusion in the broad endocardium because papillary muscle perfusion is supply from micro-vessels of peripheral coronary arteries and is easy to fail by the increase in peripheral vascular resistance. However, the clinical significant is not understood because PMI could not be detected by existing perfusion imaging such as SPECT and MRI. We propose the detection method of PMI using 13N-ammonia PET (NH3-PET), and investigate the association with the global myocardial flow reserve (Global-MFR) reflecting coronary microvascular dysfunction.
Methods
Data of adenosine-stress NH3-PET for consecutive 260 patients with coronary artery disease (CAD) or suspected CAD was retrospectively analyzed. Using high-resolution cine imaging derived from NH3-PET, PMI was defined as the absence of the PM accumulation at stress conditions. Myocardial flow was generated from the time activity curve of left ventricle input and myocardial uptake using 3-compartment model and the first 2 minutes' dataset of list mode images. Global-MFR was calculated by stress to rest flow ratio. Summed stress score (SSS) was used as an estimate of the extent of myocardial ischemia. 150 out of 260 patients (58%) with SSS ≥4 or with the past history of coronary artery diseases were classified as ischemic group, and 110 patients (42%) with SSS<4 were classified as non-ischemic group.
Results
PMI was seen in 68 of 260 patients (26.6%). The frequency of PMI was higher in the ischemic group than the non-ischemic group (37.8% vs. 10.1%, p<0.0001). Global-MFR was significantly lower in patients with PMI than those without (1.87±0.55 vs. 2.39±0.80, p<0.0001). In both ischemic and non-ischemic group, global-MFR was significantly reduced in patients with PMI. (Ischemic group: 1.83±0.56 vs. 2.12±0.52, p=0.0043, Non-ischemic group: 2.06±0.45 vs. 2.63±0.91, p=0.040).
Typical case of PMI
Conclusion
High-resolution cine imaging derived from NH3-PET makes it possible to detect PMI in about a quarter of patients with CAD or suspected CAD. PMI associates with reduced Global-MFR regardless of the presence of myocardial ischemia, suggesting that PMI is an important sign of early ischemia confined to the papillary muscle or the broad microvascular injury.
Positive contrast high-resolution 3D-cine imaging of the cardiovascular system in small animals using a UTE sequence and iron nanoparticles at 4.7, 7 and 9.4 T