[Usefulness of OPCAB from the viewpoint of fluctuations in the level of blood natriuretic peptides].

Fluctuations in the level of blood natriuretic peptides (ANP and BNP) were compared between 41 patients who underwent conventional coronary artery bypass (CCAB) and 19 patients who underwent off-pump coronary artery bypass (OPCAB). A blood sample was collected before surgery, and 6, 12 and 24 hours; 2, 3, 5 and 7 days; and 1 month after the end of extracorporeal circulation. There were no significant differences in left ventricular ejection fraction (LVEF) before and after surgery in either group or between the two groups. On average, 3.3 +/- 1.0 bypass grafts were used for the CCAB group, and 2.2 +/- 0.8 grafts for the OPCAB group. Furthermore, the maximum postoperative creatine phosphokinase-MB (CK-MB) level for the CCAB group was 49.1 +/- 17.5 IU/l, whereas that for the OPCAB group was significantly lower at 23.2 +/- 24.8 IU/l. The preoperative level of blood ANP for the CCAB group was 24.6 +/- 19.9 pg/ml while that for the OPCAB group was 39.3 +/- 29.5 pg/ml, but there was no significant difference between the two groups. In both groups, the level of blood ANP reached a peak three days after the end of extracorporeal circulation and then decreased after that point. Although the level of blood ANP for the OPCAB group decreased to 51.4 +/- 26.4 pg/ml one month after the end of extracorporeal circulation, that for the CCAB group one month after the end of extracorporeal circulation remained significantly high at 61.3 +/- 30.6 pg/ml, when compared to that before surgery. Furthermore, the preoperative level of blood BNP for the CCAB group was 40.0 +/- 35.2 pg/ml and that for the OPCAB group was 75.5 +/- 59.7 pg/ml, but there was no significant difference between the two groups. Then, in both groups, the level of blood BNP reached a peak 2-5 days after the end of extracorporeal circulation and then decreased after that. Whereas the level of blood BNP for the OPCAB group decreased to 96.4 +/- 56.0 pg/ml one month after the end of extracorporeal circulation, that for the CCAB group one month after the end of extracorporeal circulation remained significantly high at 160.3 +/- 106.2 pg/ml when compared to that before surgery. The levels of ANP and BNP increased postoperatively for both OPCAB and CCAB groups since the following events caused a great degree of stress on the heart: general anesthesia, cardiac herniation, stabilizer compression, regional blood flow blockage and reperfusion injury. Although the level of natriuretic peptides for the CCAB group remained high one month after the end of surgical stress, that for the OPCAB group returned to near the preoperative level one month later, thus supporting the notion that OPCAB is less invasive.