Prostacyclin production in free versus native IMA grafts

The long-term patency of the internal mammary artery (IMA) in coronary artery surgery has been superior to that of other grafts. We tested the IMAs as free grafts in an experimental study with 8 dogs. The right IMA was dissected free as a naked artery without surrounding tissue, and the left IMA was dissected with surrounding tissue using electrocautery. Both free IMA grafts were anastomosed first to the left IMA one after another and then to the left anterior descending coronary artery. The grafts were harvested 6 months later, and the prostacyclin (PGI2) production of the free IMA grafts and of the intact IMAs was measured. Radioimmunoassay was used to measure 6-keto-prostaglandin F1 alpha, the stable metabolite of PGI2. The PGI2 production of the right free IMA without surrounding tissue was 21.1 +/- 8.5 pg/mg and of the left IMA with surrounding tissue was 17.9 +/- 7.9 pg/mg (expressed in picograms of 6-keto-prostaglandin F1 alpha per milligram of tissue wet weight). The control value of the intact IMA was 18.3 +/- 6.5 pg/mg. Thus, PGI2 production of both free IMAs did not differ significantly from each other and from controls. This study showed that free IMAs were able to produce as much PGI2 as were control IMAs and that the type of dissection did not affect the result.