RESULTS
Between 2003 and 2014 a total of 1210 patients underwent OPCAB in our institution under the same surgeon. One-vessel disease and other revascularization strategies different to SIMA or BIMA were excluded. We identified 1023 patients who fulfilled the inclusion criteria, 681 of them in the SIMA group and 382 in the BIMA group. As the two groups were significantly different with respect to their baseline characteristics, propensity score matching (with a match tolerance of 0.05) was performed, reducing the cohort to 684 patients.
BIMA was offered to younger patients (mean age 59.4 ± 9.1 vs. 69.4 ± 7.7 for the SIMA group, p = 0.001), predominantly male (91% vs. 78%, p = 0.001) and with less comorbidities such as diabetes (21% vs. 32%, p = 0.001), chronic obstructive respiratory disease (COPD, 10% vs. 17%, p = 0.002), previous neurological disease (5% vs. 10%, p = 0.001), peripheral vascular disease (10% vs. 19%, p = 0.001) or previous myocardial infarct (45% vs. 55%, p = 0.005). Obesity (BMI > 30) was similar in the two conduit strategies (40% vs. 44%, p = 0.07).
After the propensity matching, the baseline characteristics were comparable, although age remained significantly lower in the BIMA group (59.4 ± 9.1 vs. 69.5 ± 7.9, p = 0.001). (Table 1) Rest of the preoperative characteristics for the non-matched and matched groups are listed in Table 1.
Revascularisation with BIMA was used for elective cases but also in-house urgent referrals (41%) and emergency cases (2%). Twenty-three patients had an intra-aortic balloon pump (IABP) inserted before the operation for unstable angina, and BIMA strategy was offered to three of them. After the propensity matching, the timing for surgery and use of preoperative IABP were also comparable. (Table 2)
The choice of conduits was not influenced by the extent of the disease. As determined by the preoperative coronary angiogram, the use of SIMA or BIMA was equivalent for three vessels disease (83% vs. 80%, p = 0.18), two vessels disease (17% vs. 20%, p = 0.18) and left main stem (LMS) disease (32% vs. 37%, p = 0.11). However, BIMA was most frequently used for patients with normal left ventricular ejection fraction (LVEF) (71% vs. 56%, p = 0.001) and less frequently in those in with impaired LVEF (Fair LVEF 27% vs. 38%; Poor LVEF 2% vs. 6%, p < 0.05). (Table 2). LVEF was also included in the propensity score matching, however the use of BIMA continued to seem to be preferred in patients with good LVEF and an adjusted Cox analysis was conducted to analyse the impact on survival. (Table 2)
Mean number of distal anastomoses performed was equivalent in the two groups, even before matching (SIMA 3.7 ± 0.8 (1 - 5), BIMA 3.7 ± 0.8 (2 - 6), p = 0.11). As expected, the number of arterial conduits used was superior in the BIMA group (2.8 ± 0.6 (2 - 5)) when compared to the SIMA group (1.1 ± 0.3 (1 - 2), p = 0.001; note that the patients recorded as two arterial conduits in the SIMA group had a sequential graft with the LIMA to the LAD and first diagonal). Venous conduits were more commonly used in the SIMA group (2.5 ± 0.8 (0 - 4) vs. 0.8 ± 0.8 (0 - 3) in the BIMA group, p = 0.001). A third arterial conduit (RA) was used in 67 cases (20%). Total arterial revascularization was achieved in 109 cases (42%). (Table 3)
Complete revascularization was achieved in 99.4% of the cases; in the remaining 0.6%, a vessel (PDA or OM) was deemed to be too small to be grafted during the intraoperative analysis. The rate of conversion from OPCAB to ONCAB during the same period of the study was 0.7% (8 cases, which were excluded from the study). Reasons for conversion were: ventricular arrhythmias (4 cases), intraoperative cardiac arrest (2 cases) or difficult exposure of an intramyocardial OM vessel (2 cases).