Results:
There were 4536(75.72%) males. Mean age of the study population was 57.50±8.53 years. Most common diagnosis was triple vessel disease (n=4613, 77%). Mean numbers of grafts inserted were 3 ±0.83. LIMA was used in 5972 patients (99.7%). Most common grafting strategy was pedicle left internal mammary artery graft (LIMA) to left anterior descending artery (LAD) and saphenous vein to other territory. Total arterial revascularization in the form of LIMA (in situ, pedicle)-RIMA (skeletonized) or LIMA (in situ, pedicle)-Radial ‘Y’ configuration was performed in 620 (10.35%) patients. Emergency surgery was performed in 560 (9.34%) patients and coronary endarterectomy performed in 886 (14.8%) patients. Most common grafting strategy for endatrectomy vessel was direct anastomosis (of LIMA or saphenous vein) followed by grafting upon on lay patch of saphenous vein. Other demographic and preoperative variables are shown in Table 1.
Out of 5990 off pump coronary bypass surgeries, total 132 (2.2%) patients were re-explored. The most common cause of re-exploration was bleeding (n=110, 83.33%) followed by cardiac tamponade (n=15, 11.36%) and unspecified (n=5, 3.8%). The most common site of bleeding was from graft/anastomosis (53.8%), followed by sternum including LIMA bed (31.1%), others (10.6%, pacing wire site, thymus etc.) and none (4.54%). Mean time to re-exploration was 9.75±8.65 hours (Median 5.5 hour, range 1-36 hour). Other intraoperative and postoperative variables are shown in Table 2.
We found that pre-operative low platelet count (p=0.000), emergency surgery (p=0.008), and number of grafts (p=0.000), were significant risk factors for re-exploration on univariate as well as multivariable analysis(F (4,594)=27.72, p=0.000, R2 =0.497) while age, sex, body surface area, diabetes, hypertension, peripheral vascular disease, pre-operative hemoglobin, pre-operative prothrombin time, pre-operative serum creatinine as well as serum bilirubin, pre-operative ejection fraction, total arterial revascularization, LIMA use and endarterectomy were not found risk factors for re-exploration after OPCABG (p>0.05,Table 3,4). Patient who re-explored had significantly increase morbidity in the form of increase drain output (p=0.00), number of blood product transfusion (p=0.00), more ICU stay (p=0.00), more ventilation time (p=0.00), more IABP use (p<0.001), renal dysfunction (p=0.002), deep sternal wound infection (p<0.001) and hospital stay (p=0.00).
30- Day mortality in the study population was 1.41%. 30-day mortality was significantly more in patient who underwent re-exploration (13.63 % vs 1.14%, p=0.000). The most common cause of the death was sepsis (66.6%) with multi organ dysfunction followed by low cardiac output syndrome. On multiple regression analysis (Table 4), preoperative platelet count, emergency surgery, euroscore II, number of grafts, preoperative ejection fraction, postoperative serum bilirubin and creatinine, no of blood products used, re-exploration and time to re-exploration found to be an independent risk factor for mortality (F(28,3076)=40.54,R2=0.519, p=0.000 for model fit) while age, sex, body surface area, previous MI, diabetes, hypertension, chronic obstructive pulmonary disease, preoperative prothrombin time , preoperative serum bilirubin, preoperative serum creatinine, total arterial coronary bypass grafting, presence of atrial fibrillation and performing coronary endarterectomies were not found statistically significant factors for mortality.
We analyzed effect of time delay on re-exploration because on multiple regression analysis B coefficient was highest for time to re-exploration. On receiver operating curve analysis, we found that the optimum cut off for time to re-exploration was of 14 hours with sensitivity 81.3% and specificity of 80% and AUC of 0.798 (figure 1).
As shown in Table 5, while comparing groups of patients who underwent re-exploration early (time to re-exploration after completion of primary operation <14 hour as per cut-off) and delayed, later group had significantly high mortality (30.55% vs 7.29%, p=0.000), higher drain output (995.54±380.2 vs 1458.16±543.20, p=0.00), higher number of blood products received (11.14±11.89 vs 23.69±10.09, p=0.000), more frequently underwent coronary endarterectomy (6 vs12, p=0.000), higher incidence of tamponade (3 vs 12, p=0.000), higher ventilation time (13.05± 6.39 vs 41.10±81.08) and high ICU stay (5.03±3.74 vs 8.53±6.03, p=0.02).