Early outcomes of on-pump versus off-pump coronary artery bypass grafting

Objectives: To see the early post-operative outcomes of off-pump versus on-pump coronary artery bypass graft surgery. Methods: This retrospective analytical study was conducted at Ch. Pervaiz Elahi Institute of Cardiology Multan, Pakistan. Our Primary outcome variables were; necessity of inotropic support, nonfatal myocardial infarction, ICU stay, nonfatal stroke, new renal failure requiring dialysis and death within 30 days after operation. There were two groups of patients; Group-I (On-pump group) and Group-II (Off-pump Group). SPSS V17 was used for data analysis. Independent sample t-test and Mann Whitney U test were used to compare quantitative Variables. Chi-square test and Fisher’s exact test were used to analyze qualitative variables. P-value ≤ 0.05 was considered significant. Results: Three hundred patients were included in this study. There were no significant difference regarding risk factors except hyper-cholestrolemia which was high in off pump group (p-value 0.05). Angiographic and Echocardiographic characteristics e.g. preoperative ejection fraction, LV function grade and severity of CAD was same between the groups. Mortality risk scores and Priority status for surgery were also same. Regarding post-operative outcomes; Post-op CKMB Levels, need and duration of inotropic support, mechanical ventilation time and ICU stay was significantly less in Off-Pump group (p-value 0.001, <0.0001, 0.006, 0.025 and 0.001 resp.). Peri-operative chest drainage was significantly high in On-pump CABG group (p-value 0.027). Incidence of post-op complications was not statistically different between the groups. Conclusions: At 30 days follow-up, Incidence of myocardial infarction, necessity and duration of inotropic support, ICU stay period and peri-operative bleeding were significantly less in off-pump group. The incidence of neurologic, pulmonary and renal complications was same between the off-pump and on-pump groups.

complications associated with the use of cardiopulmonary bypass, 5,6 such as systemic inflammatory response, 7 cerebral dysfunction, 8,9 myocardial depression, and hemodynamic instability. 10 Several previous trials have compared offpump CABG with on-pump CABG. 4,11,12 However, none of the previous trials had sufficient power to accurately assess moderate but clinically important differences in rates of death, myocardial infarction, stroke, and renal failure. Furthermore, the skills of the participating surgeons can also influence the outcome of a specific surgical procedure. 13,14 So we conducted this study to compare the early outcomes of off pump versus on pump coronary artery bypass graft surgery to see whether off pump or on pump surgery is better in our center.

METHODS
It was a retrospective analytical study conducted at Ch. Pervaiz Elahi Institute of Cardiology Multan, Pakistan. The data of patients operated from January 2012 to December 2014 was retrieved from cardiac surgery database of the hospital. Patients having similar pre-operative characteristics were selected for study to minimize the effect of these on postoperative outcomes. Patients who were scheduled to undergo CABG were eligible to participate in this study if they required isolated CABG with median sternotomy. Exclusion Criteria: Patients having any clinically significant valvular disease (i.e., moderate, moderate to-severe, or severe valve disease), requiring immediate surgery, with small target vessels (<1.1 mm in internal diameter) or diffuse coronary artery disease were excluded from the study.
Our primary outcomes were; necessity of inotropic support, nonfatal myocardial infarction, ICU stay, nonfatal stroke, new renal failure requiring dialysis and death within 30 days after operation. All deaths in these 30 days were considered to be the result of cardiovascular causes.

RESULTS
There was no significant difference regarding demographic characteristics of patients except BMI that was significantly high in patients of group I. Risk factors of Ischemic Heart Disease were same between the two groups. Similarly Angio-graphic, Echocardiographic, mortality risk scores and Priority status for surgery all were same between groups (Table-I). No of grafts applied for revascularization was high in on-pump group, these were 2.92±0.61 versus 2.78±0.68 in off-pump group. But this difference was not statistically significant. Regarding post-operative outcomes, post-op CKMB Levels, need and duration of inotropic support, mechanical ventilation time and ICU stay was significantly less in Off-Pump group. Peri-operative chest drainage was also significantly high in on-pump CABG group (p-value 0.027). Regarding immediate postoperative complications pulmonary complications occurred in 4.7% (7.0) patients in on-pump CABG group and in 2.7% (4.0) patients in Off-pump group. Incidence of neurologic complications was also high in on-pump CABG group (Table-II).

DISCUSSION
Trend of Off-pump CABG has been increasingly in use in Western countries since the early 1990s, when Benetti 5 and Buffolo 15

demonstrated excellent
Early outcomes of on-pump versus off-pump CABG benefits possibly associated with the avoidance of cardiopulmonary bypass. 16 About 15% to 20% of CABG procedures in the Western world and most CABG operations in Asia are performed off-pump without the use of cardiopulmonary bypass. Multiple randomized trials, observational studies have compared peri-operative mortality, and surgical complications and outcomes, for Off pump CABG and on-pump CABG. 16 Many studies, typically conducted in low-risk patients, found no significant differences in peri-operative mortality, but did find a reduced need for blood transfusions, ventilation and shorter hospital stay times with off pump CABG. 17,18 Meta-analyses reports also showed similar results, 19,20 Large observational studies reported significant reductions in peri-operative mortality and morbidity, and similar peri-operative outcomes. [21][22][23] Whereas many other studies have concluded that off pump-CABG is associated with a high risk of long term mortality; probably this may be due to high risk of incomplete revascularization in off pump CABG group. As many studies have shown lower rates of complete revascularization in off pump CABG patients. 24,25 In our study, the number of grafts were less in off-pump group but this difference was statistically not significant (p-value 0.06) so it can be neglected.
Off pump CABG has demonstrated decreased blood loss and need for transfusion, decreased length of stay, less myocardial enzyme leak, less inflammation, and less renal and neurologic impairment in addition to decreased cost. 12,26,27 Reston and colleges 28 in their meta-analysis report of comparing short term and midterm outcomes of off-pump CABG, found that off pump CABG is associated with reduced length of hospital stay, operative morbidity, and operative mortality as compared with on pump CABG.
Our study supports the results of these studies as in our study, peri-operative chest drainage was significantly low in Off-Pump Group. We found significant difference regarding post-op CK-MB levels, need and duration of inotropic support, mechanical ventilation time and ICU stay time, all were high in on-pump CABG group. However we do not find any significant difference in immediate post-operative complications in both groups pulmonary and neurologic complications were a bit high in on-pump CABG group but this difference was not statistically significant. In our study, operative mortality was high in on-pump CABG group, there were two deaths in this group in a one month follow up in this group but there was no mortality in Off-pump CABG group.
The results of our study revealed that off pump CABG is a safe and better option as regards to early extubation, respiratory complications and early recovery and a lower risk of short term mortality.

CONCLUSIONS
At 30 days follow-up, Incidence of myocardial infarction, necessity and duration of inotropic support, ICU stay period and peri-operative bleeding were significantly less in off-pump group. And the incidence of neurologic, pulmonary and renal complications was same between the offpump and on-pump groups.