Assessment of myocardial metabolic state after hypothermic heart preservation for transplantation utilizing radioiodinated free fatty acid imaging.

: Myocardial turnover of 15-p-iodo(123I)-phenylpentadecanoic acid (123I-IPPA) was assessed in 14 swine experiments before and after orthotopic heart transplantation. Two preservation techniques were used: simple hypothermic storage (group 1; n = 7) and a perfusion technique (group 2; n = 7) with pressure maintained at 28 cm H2O (20 mm Hg) and a myocardial temperature of 8 to 10 degrees C. Hearts in both groups were initially perfused with hypothermic isosmolar potassium cardioplegic solution to acquire immediate diastolic arrest. The perfusate in group 2 was an extracellular formulation supplemented with glucose, mannitol, insulin, and oxygen. The ischemic interval for both groups was 6 hours including orthoptic transplantation. Pretransplant and posttransplant planar gamma imaging was performed using 3 to 5 mCi 123I-IPPA. Fatty acid turnover was assessed using time-activity curves analyzed by monoexponential least squares curve fitting generating t1/2 (half-lives in minutes). Increases in t1/2 were observed in hearts of both groups after transplantation, that is, lateral (290% +/- 72% and 104% +/- 49% increase, p = 0.03), septal (140% +/- 34% and 39% +/- 29% increase, p = 0.02), and apical (273% +/- 111% and 133% +/- 44% increase, p = 0.06) walls within groups 1 and 2, respectively. We conclude that 123I-IPPA turnover is useful in assessing the immediate metabolic state of posttransplant myocardium. It can also be concluded that preservation techniques based on continuous hypothermic perfusion are better able to maintain normal metabolic substrate utilization immediately after transplantation than are simple hypothermic storage techniques.