Abstract
1524
Objectives: The cardiac sympathetic nerves play a key role in regulating heart function. It has been demonstrated in severe coronary artery stenosis that sympathetic tissues are more susceptible to ischemia than myocardial muscle cells. Cardiac sympathetic nerve injury may be a more sensitive marker of postischemic cardiac damage than changes in blood perfusion during early stage coronary artery events.Therefore, we sought to validate N-11C-methyl-dopamine (11C-MDA) as an agent to image cardiac sympathetic nerve injury, and analyze the sympathetic nerve receptors in acute and chronic myocardial ischemia.
Methods: . Chronic and acute myocardial ischemia was surgically setup in Bama minipigs, and was evaluated by ECG and serum enzyme levels of 4 weeks later. Paired 11C-MDA and 13N-ammonia PET scans were performed at baseline, 1, 3 and 6 months (mon) after surgery to relate cardiac sympathetic nerve injury to blood perfusion, which were also compared with the 11C-MDA PET results of acute myocardial ischemia model. Finally, the animals were sacrificed and the left ventricular myocardium was routinely sectioned. Results. The ECG-ST segment was depressed, and levels of the serum enzymes increased at 1 mon post-surgery. Cardiac uptake of tracer was quantified as the defect volume. Both before and 1mon after surgery, the PET images of 11C-MDA and 13N-ammonia were similar. However, the left ventricular myocardial defect volume on 11C-MDA PET was significantly greater than 13N-ammonia at 3 and 6 mon post-surgery (P < 0.05). Compared with 11C-MDA PET images of chronic myocardial ischemia,11C-MDA PET images of the acute myocardial ischemia defect volume on was larger (P < 0.05). In addition, the left ventricular biopsy of 6-mon chronic and acute myocardial ischemia model showed myocardial infarction in some areas. Conclusions. Compared with 13N-ammonia, the extent of the myocardial defect visualized by 11C-MDA is much greater, which be suggested by blood perfusion images, and the recovery from myocardial sympathetic nerve injury is much slower than the restoration of blood perfusion. Compared with the images of acute myocardial ischemia models, the damage of neural receptor in chronic myocardial ischemia recovered more slowly and the scope of acute ischemia injury was larger.11C-MDA PET may provide additional biological information during recovery from ischemic heart disease in acute and chronic myocardial ischemia.