Clinical value of intra-operative transit-time flow measurement for coronary artery bypass grafting: a prospective angiography-controlled study.

OBJECTIVE: Transit-time flow measurement (TTFM) is the most widely used method for intra-operative graft quality control in coronary artery bypass surgery. Although it may provide the opportunity for the surgeon to promptly revise the graft before the patient is discharged from the operating room, controlled clinical data on the ultimate usefulness of the TTFM are scarce. Clear cut-off values for when to revise grafts have not been set. METHODS: A total of 204 consecutive grafts (left internal mammary artery (n=46), vein graft (n=155), and radial artery (n=3)) underwent TTFM in 75 elective coronary artery bypass grafting (CABG) patients. The following parameters were recorded: mean graft flow (MGF), pulsatility index (PI), and insufficiency ratio (IR). After a mean follow-up of 199 ± 42 days, coronary angiography was performed for assessment of graft patency. RESULTS: A total of 166 grafts were found to be patent (85%), and 29 (15%) were completely occluded. The median and interquartile range (IQR) of MGF for the occluded grafts at the time of surgery was 38 ml min(-1) (IQR, 2549 ml min(-1)) and for the patent grafts 45 ml min(-1) (IQR, 31-71 ml min(-1); p=ns]. The corresponding PI values were 3.3 (IQR, 2.8-5.0) and 2.2 (IQR, 1.7-3.2; p=0.003), and the IR values were 1.6 (IQR, 0.6-6.1) and 0.2 (IQR, 0-2.2; p=0.03). By receiver operating characteristic (ROC) analysis, the highest sensitivity (72%) and specificity (70%) were associated with a PI value>3.0. However, 49 out of 70 such grafts (70%) were found to be patent. Furthermore, 10 out of 16 (63%) grafts, that had a combination of low flow (MGF<15 ml min(-1)) and high PI (>3.0), were patent at control angiography. CONCLUSIONS: TTFM predicts graft failure within the 6 months after CABG. However, specific cut-off recommendations for when to revise a graft cannot be set on the basis of TTFM. The cut-off values suggested in the literature lead to unnecessary graft revisions in the majority of cases, and, on the other hand, many technical defects probably remain unnoticed. Better methods to assess the quality of coronary artery bypass grafts are needed.

Levosimendan facilitates weaning from cardiopulmonary bypass in patients undergoing coronary artery bypass grafting with impaired left ventricular function.

BACKGROUND: Levosimendan is a compound with vasodilatory and inotropic properties. Experimental data suggest effective reversal of stunning and cardioprotective properties. METHODS: This prospective, randomized, placebo-controlled, double-blind study included 60 patients with 3-vessel coronary disease and left ventricular ejection fraction (LVEF) of less than 0.50. Levosimendan administration (12 microg/kg bolus, followed by an infusion of 0.2 microg/kg/min) was started immediately after induction anesthesia. Predefined strict hemodynamic criteria were used to assess the success of weaning. If weaning was not successful, CPB was reinstituted and an epinephrine infusion was started. If the second weaning attempt failed, intraaortic balloon pumping (IABP) was instituted. RESULTS: The groups had comparable demographics. The mean (standard deviation) preoperative LVEF was 0.36 (0.8) in both groups. The baseline cardiac index was 1.8 (0.3) L/min/m(2) in the levosimendan group and 1.9 (0.4) L/min/m(2) in the placebo group. The mean duration of CPB to primary weaning attempt was 104 (25) minutes in the levosimendan and 109 (22) minutes in the placebo group. Primary weaning was successful in 22 patients (73%) in the levosimendan group and in 10 (33%) in the placebo group (p = 0.002). The odds ratio for failure in primary weaning was 0.182 (95% confidence interval, 0.060 to 0.552). Four patients in the placebo group failed the second weaning and underwent IABP compared with none in the levosimendan group (p = 0.112). CONCLUSIONS: Levosimendan significantly enhanced primary weaning from CPB compared with placebo in patients undergoing 3-vessel on-pump coronary artery bypass grafting. The need for additional inotropic or mechanical therapy was decreased.