N-¹¹C-Methyl-Dopamine PET Imaging of Sympathetic Nerve Injury in a Swine Model of Acute Myocardial Ischemia: A Comparison with¹³N-Ammonia PET

OBJECTIVE: Using a swine model of acute myocardial ischemia, we sought to validate N-(11)C-methyl-dopamine ((11)C-MDA) as an agent capable of imaging cardiac sympathetic nerve injury. METHODS: Acute myocardial ischemia was surgically generated in Chinese minipigs. ECG and serum enzyme levels were used to detect the presence of myocardial ischemia. Paired (11)C-MDA PET and (13)N-ammonia PET scans were performed at baseline, 1 day, and 1, 3, and 6 months after surgery to relate cardiac sympathetic nerve injury to blood perfusion. RESULTS: Seven survived the surgical procedure. The ECG-ST segment was depressed, and levels of the serum enzymes increased. Cardiac uptake of tracer was quantified as the defect volume. Both before and immediately after surgery, the images obtained with (11)C-MDA and (13)N-ammonia were similar. At 1 to 6 months after surgery, however, (11)C-MDA postsurgical left ventricular myocardial defect volume was significantly greater compared to (13)N-ammonia. CONCLUSIONS: In the Chinese minipig model of acute myocardial ischemia, the extent of the myocardial defect as visualized by (11)C-MDA is much greater than would be suggested by blood perfusion images, and the recovery from myocardial sympathetic nerve injury is much slower than the restoration of blood perfusion. (11)C-MDA PET may provide additional biological information during recovery from ischemic heart disease.