Quantitative measurement of endothelium derived nitric oxide production of the internal mammary artery bypass graft during extracorporeal circulation.

Objective: This study was undertaken to determine the extent of endothelium derived nitric oxide (EDNO) production of the internal mammary artery (IMA) bypass graft and of the native coronary circulation by measuring its stable metabolite (NO2: nitrite) in different sampling sites: internal mammary free cut end flow, in the coronary sinus prior and after anastomosis completion, and to compare them to the nitrite level of the normal plasma.

Methods: Nitrite level was determined with fluoroscopy using 4 hydroxycoumarin nitrozation in 50 consecutive patient undergoing onpump myocardial revascularization.

Results: Nitrite levels in the normal plasma were found to be 31.2 micromol. Nitrite level in systemic and coronary circulation after total heparinization, prior to extracorporeal circulation (ECC) was found to be 60.8 micromol (lower quartile /l.q./: 46.6 micromol, upper quartile /u.q./: 70.0 micromol,) and 58.3 micromol,(l.q.:47.8 micromol, u.q.:70.0 micromol) respectively, and of the IMA bypass graft free cut end flow was 54.4 micromol,(l.q.:42.0 micromol, u.q.:66.8 micromol) while in the coronary sinus, after completion the IMA anastomosis, it was 45.71 micromol (l.q.: 35.0 micromol, u.q.: 55.0 micromol), (all geometric mean).

Conclusions: Total heparinization enhances EDNO production. Nitrite concentration in the IMA free cut end flow is similar or greater, than that of the native coronary circulation, however, after IMA bypass graft construction significant reduction (P<0.001) could be measured in the coronary sinus.