[Benefit of off-pump coronary artery bypass grafting evaluated from the change of the regional myocardial oxygen metabolism during bypass grafting]

Abstract

Recently, off-pump coronary artery bypass grafting (off-pump CABG: OPCAB) has been considered a safe alternative to conventional CABG (CCAB) for myocardial revascularization, because OPCAB improves operative mortality and morbidity from the view of reduction of multi-organ complications, duration of hospital stay, risks of blood transfusion and operative costs. This study was performed to estimate the benefit of OPCAB by examining the change of myocardial oxygen metabolism during OPCAB. Twenty five patients who had undergone OPCAB including the internal thoracic artery (LITA) on the segment 8 of the left anterior descending coronary artery (LAD) were studied in this series, and divided in 2 groups [17 angina pectoris (AP) cases, 8 old myocardial infarction (OMI) cases]. With 3-wave length near infrared spectroscopy (TOS-96: TOSTEC, Tokyo, Japan), the tissue hemoglobin (Hb) volume in the myocardium [Hb index (HbI) = 10 x calibrated absorption at 801 nm/clinical absorption intensity at 801 nm] and the myocardial tissue oxygen saturation (rSo2) on the surface of the left ventricle surrounded by LAD and the 2nd diagonal branch were measured at 5 minutes before and after OPCAB to LAD, and myocardial oxygen metabolism (OM) was calculated [OM = (20-1.34 x systemic Hb x rSo2/100) x HbI]. During OPCAB, several hemodynamic data, systemic Hb and arterial gas findings were not changed. In both groups, the HbI and the OM were significantly increased [HbI: AP group; 1.04 +/- 0.23 to 1.57 +/- 0.41 (p < 0.0001), OMI group; 0.99 +/- 0.28 to 1.55 +/- 0.39 (p = 0.0051), OM: AP group; 11.6 +/- 3.1 to 17.5 +/- 6.0 (p = 0.0010), OMI group; 10.6 +/- 2.3 to 16.1 +/- 2.8 (p = 0.0007)]. The rSo2 was not changed and remained within normal limit during OPCAB. These findings suggested that the regional myocardial oxygen metabolism would be improved immediately just after OPCAB and this finding might be one of the reasons why OPCAB shows the good mortality and morbidity compared with CCAB.