Off-Pump Coronary Artery Bypass Grafting Surgery : A Narrative Review

Coronary Artery Bypass Grafting (CABG) Surgery is considered the standard treatment for revascularization in Coronary Artery Disease. The Off-Pump Coronary Artery Bypass Graft (OPCAB) which evades the use of Cardiopulmonary Bypass (CPB) became a popular CABG procedure, due to the adverse effect of CPB. Hypothetically, OPCAB may improve the rates of perioperative Myocardial Injury, Neurocognitive Impairment, Stroke and Mortality. However, some studies showed no superior outcomes for OPCAB compared to on-pump CABG. This study aims to evaluate the short-term and long-term outcomes of OPCAB versus On-Pump CABG. The results showed that OPCAB is probably a safe procedure for patients, especially for those with high-risk conditions. OPCAB procedure showed superior short-term outcomes in terms of Myocardial Infarction, Systemic Inflammatory Response, Postoperative Cognitive Dysfunction, Renal Failure, Stroke, Pulmonary Complication, Postoperative Transfusion, Hospital stay length and infection than On-pump CABG. However, regarding long-term outcomes, Off-Pump CABG had a higher rate of incomplete revascularization and repeat revascularization and a higher risk of long-term mortality as well as lower graft patency. Furthermore, the result showed that the higher experience of the surgeons in OPCAB improves the outcome of the Surgery.

Effect of continuous positive airway pressure associated to exercise on the breathing pattern and heart rate variability of patients undergoing coronary artery bypass grafting surgery: a randomized controlled trial

Continuous positive airway pressure (CPAP) has been used to improve gas exchange and diaphragmatic function, among others benefits. Moreover, it can be used to increase exercise tolerance and positively influence ventilatory function and breathing pattern (BP) during exercise. However, there is no information about the long-term effects of CPAP, as an adjunct to an inpatient cardiac rehabilitation (CR) program, on BP and heart rate variability (HRV) of patients after coronary artery bypass grafting surgery (CABG). Twenty patients were allocated to receive, after randomization, standard inpatient CR without CPAP (control group - CG) or CR with CPAP between 10 to 12 cmH2O (CPAP group - CPG) associated with the exercises. Participants were assessed preoperatively and on the discharge day, in the sitting rest position. Outcome measurements included BP variables, collected by respiratory inductive plethysmography, and HRV, collected by polar precision performance. The CPG presented lower values of percent rib cage inspiratory and expiratory contributions to tidal volume (%RCi and %RCe) at discharge time, compared to CG. No statistical differences between groups were observed for HRV variables and both groups presented lower values of these indices, compared to preoperative ones. In this context, the patients who received CPAP throughout the whole rehabilitation program were discharged with a better BP, which could indicate more synchronized breathing. CPAP did not influence cardiac autonomic modulation in the long term.

Sudden, new-onset aortic regurgitation during off pump coronary bypass surgery

During off pump coronary artery bypass grafting surgery, it is common to observe mitral or tricuspid regurgitation due to heart displacement. But it's very unusual to notice new onset aortic regurgitation in OPCABG.

Application of electrical impedance tomography for postoperative lung recruitment in patients undergoing off pump coronary artery bypass grafting surgery / 上海交通大学学报（医学版）

Objective • To find out the optimal positive end expiratory pressure (PEEP) by electrical impedance tomography (EIT) for better lung recruitment and ventilation distribution in patients undergoing off pump coronary artery bypass grafting surgery (OPCAB). Methods • 105 patients underwent OPCAB from Jan. 2017 to Dec. 2017 were analysed. Patients were randomly divided into two groups, i.e. experiment group (54 cases) and control group (51 cases). Four regions of interest (ROI) were recorded by EIT. PEEP were 3 cmH2O in control group while PEEP were increased stepwise by 2 cmH2O from 0 cmH2O to 14 cmH2O in experiment group. The optimal PEEP for lung recruitment was applied in experiment group. Postoperative oxygenation index (PaO2/FiO2) and pulmonary complication were compared between two groups. Results • The overall mortality was 2 (1.90%). The incidence of postoperative pulmonary complication, pulmonary infection, atelectasis, pleural effusion were 18.10%, 2.86%, 18.10%, 18.10%, respectively. The optimal PEEP zone was 6-9 cmH2O. PaO2/FiO2 was significantly increased with the optimal PEEP in experiment group (P=0.00). There were significant differences in postoperative pulmonary complication between two groups (P=0.02). Conclusion • EIT can directly monitor ventilation distribution and titrate suitable PEEP for better lung recruitment in patients undergoing OPCAB. It can significantly reduce postoperative pulmonary complication, improve oxygenation, and decrease ICU stay and ventilation duration.

Application of electrical impedance tomography for postoperative lung recruitment in patients undergoing off pump coronary artery bypass grafting surgery / 上海交通大学学报（医学版）

Objective·To find out the optimal positive end expiratory pressure (PEEP) by electrical impedance tomography (EIT) for better lung recruitment and ventilation distribution in patients undergoing off pump coronary artery bypass grafting surgery (OPCAB). Methods?·?105 patients underwent OPCAB from Jan. 2017 to Dec. 2017 were analysed. Patients were randomly divided into two groups, i.e. experiment group (54 cases) and control group (51 cases). Four regions of interest (ROI) were recorded by EIT. PEEP were 3?cmH2O in control group while PEEP were increased stepwise by 2?cmH2O from 0?cmH2O to 14?cmH2O in experiment group. The optimal PEEP for lung recruitment was applied in experiment group. Postoperative oxygenation index (PaO2/FiO2) and pulmonary complication were compared between two groups. Results?·?The overall mortality was 2 (1.90%). The incidence of postoperative pulmonary complication, pulmonary infection, atelectasis, pleural effusion were 18.10%, 2.86%, 18.10%, 18.10%, respectively. The optimal PEEP zone was 6-9?cmH2O. PaO2/FiO2was significantly increased with the optimal PEEP in experiment group (P=0.00). There were significant differences in postoperative pulmonary complication between two groups (P=0.02). Conclusion?·?EIT can directly monitor ventilation distribution and titrate suitable PEEP for better lung recruitment in patients undergoing OPCAB. It can significantly reduce postoperative pulmonary complication, improve oxygenation, and decrease ICU stay and ventilation duration.

Dexmedetomidine decreases the inflammatory response to myocardial surgery under mini-cardiopulmonary bypass

Cardiopulmonary bypass (CPB) with extracorporeal circulation produces changes in the immune system accompanied by an increase in proinflammatory cytokines and a decrease in anti-inflammatory cytokines. We hypothesize that dexmedetomidine (DEX) as an anesthetic adjuvant modulates the inflammatory response after coronary artery bypass graft surgery with mini-CPB. In a prospective, randomized, blind study, 12 patients (4 females and 8 males, age range 42-72) were assigned to DEX group and compared with a conventional total intravenous anesthesia (TIVA) group of 11 patients (4 females and 7 males). The endpoints used to assess inflammatory and biochemical responses to mini-CPB were plasma interleukin (IL)-1, IL-6, IL-10, interferon (INF)-γ, tumor necrosis factor (TNF)-α, C-reactive protein, creatine phosphokinase, creatine phosphokinase-MB, cardiac troponin I, cortisol, and glucose levels. These variables were determined before anesthesia, 90 min after beginning CPB, 5 h after beginning CPB, and 24 h after the end of surgery. Endpoints of oxidative stress, including thiobarbituric acid reactive species and delta-aminolevulinate dehydratase activity in erythrocytes were also determined. DEX+TIVA use was associated with a significant reduction in IL-1, IL-6, TNF-α, and INF-γ (P<0.0001) levels compared with TIVA (two-way ANOVA). In contrast, the surgery-induced increase in thiobarbituric acid reactive species was higher in the DEX+TIVA group than in the TIVA group (P<0.01; two-way ANOVA). Delta-aminolevulinate dehydratase activity was decreased after CPB (P<0.001), but there was no difference between the two groups. DEX as an adjuvant in anesthesia reduced circulating IL-1, IL-6, TNF-α, and INF-γ levels after mini-CPB. These findings indicate an interesting anti-inflammatory effect of DEX, which should be studied in different types of surgical interventions.

Therapeutic effects of Enhanced External Counter Pulsation (EECP) on clinical symptoms, echocardiographic measurements, perfusion scan parameters and exercise tolerance test in coronary artery disease patients with refractory angina.

Background: The purpose of this study was finding relationship between the therapeutic effects of Enhanced External Counterpulsation on treatment resistant angina among the patients, who are unsuitable for invasive interventions. Aims & Objective: To study the therapeutic effects of Enhanced External Counter Pulsation (EECP) on clinical symptoms, echocardiographic measurements, perfusion scan parameters and exercise tolerance test in coronary artery disease patients with refractory angina. Material and Methods: In an interventional study 50 patients (34 men and 16 women) under EECP therapy were investigated for one year. This machine is composed of three pairs of cuffs which work by attaching cuffs to lower limbs and it is contracted during diastole from distal to proximal and makes pressure to vessels of lower limbs. Treatment effects of EECP on clinical signs were evaluated on the base of Canadian cardiovascular society classification for angina severity, drugs consumption and SF36 quality of life questionnaire. Para clinical assessments including echocardiography, perfusions scan and exercise tolerance test parameters were also assessed prior to EECP, at the end of the treatment and at 12 months thereafter. Any differences in background measurements were recorded and analyzed. Results: Decrement of angina severity and improvement of life quality before and after one month EECP therapy was significant (p<0.001, p=0.01). The rate of nitrate consumption and other medications causes no significant difference concerning dosage decrease (p>0.05). There was significant difference between ejection fraction of before, one month and one year after treatment only in severe IHD (p=0.016, p=0.038, respectively). Left ventricle end diastolic and end systolic diameters were also significantly decreased after one month (p= 0.031), and this improvement remained up to one year. Difference between ischemia severity in perfusion scan before and one month afterwards was significant as well (p= 0.044). The exercise tolerance test duration after one month also increased (p<0.001) and did not change statistically after one year. Conclusion: This study demonstrated that EECP is a useful method, while effective and safe for patients with severe refractory angina pectoris resistant to drug therapy and aggressive interventions such as PCI or CABG are not suitable.

Clinical analysis of acute kidney injury in 1113 patients after cardiac valve replacement surgery / 中华肾脏病杂志

Objective To investigate the incidence and risk factors of acute kidney injury(AKI)after different types of cardiac valve replacement surgery. Methods A single cohort of 1113 patients who received cardiac valve replacement surgery from April 2009 to March 2010 in Zhongshan Hospital,Fudan University were prospectively analyzed.Multivariate Logistic regression analysis was used to evaluate possible risk factors associated with post-operative AKI.Akl was defined as a relative 50% increase or an absolute increment of 26.4 μmol/L in Scr within 48 hours and/or urine volume <0.5ml·kg-1·h-1 up to 6h.Results Of the 1113 patients, the incidence of AKI was 33.24%.In-hospital mortality of AKI patients was 6.49%,which was 5.373 times higher than that of non-AKI patients(P<0.01).The incidence of AKI in patients who simultaneously received cardiac valve replacement and coronary artery bypass grafting was 75.00%,which was significantly higher as compared to other types of valve replacement surgery(P<0.01).Unconditional multivariate Logistic regression analysis revealed that male,old age,long extracorpeal circulation (CPB)time(≥120 min)and combined with coronary artery bypass grafting surgery were the independent predictors of AKI episodes,and the corresponding OR values were 1.455,2.110,1.768 and 2.994 respectively. Conclusions AKI is a common and serious complication after cardiac valve replacement surgery.Patients who received combined cardiac surgery as valve replacement and coronary artery bypass grafting have higher incidence of AKI.Old age,male,long CPB time(≥120 min)and combined with coronary artery bypass grafting surgery are the independent risk factors of post-operative AKI for patients undergoing cardiac valve replacement surgery.

Surgical myocardial revascularization of patients with ischemic cardiomyopathy and severe left ventricular disfunction

Objective: To determine long-term survival, identify preoperative factors predictive of a favorable outcome, and assess functional improvement after coronary artery bypass grafting in patients with advanced left ventricular dysfunction. Methods: Between 1995 and 2001, 244 patients who underwent coronary artery bypass grafting and had a preoperative left ventricular ejection fraction less than or equal to 35 percent were included. left ventricular ejection fraction was determined by uniplanar or biplanar ventriculography during left heart catheterization. Indication for surgery was predominance of tissue viability. Functional improvement was evaluated through echocardiography and gated scintigraphy at exercise/ rest. Survival was determined by Kaplan-Meier analysis. Results: Mean left ventricular ejection fraction was 29±4 percent (ranged from 9 percent to 35 percent). An average of 3.01 coronary bypass grafts per patient were performed. In-hospital mortality was 3.7 percent (9 patients). The 4-year survival rate was 89.7 percent. Multivariate correlates of favorable short- and long-term outcome were preoperative New York Heart Association Funcional classification for congestive heart failure class I/II, lower PAsP, higher left ventricular ejection fraction and gated left ventricular ejection fraction Ex/Rest ratio >5 percent. Left ventricular ejection fraction rise from 32±5 percent to 39±5 percent, p <0.001. Gated left ventricular ejection fraction at exercise/ rest increased markedly after surgery: from 27±8 percent/ 23±7 percent to 37±5 percent/ 31±6 percent, p <0.001. Conclusions: In selected patients with severe ischemic left ventricular dysfunction and predominance of tissue viability, coronary artery bypass grafting may be capable of implement preoperative clinical/ functional parameters in predicting outcome as left ventricular ejection fraction and gated left ventricular ejection fraction at exercise/ rest.

Pre-operative high sensitive C-reactive protein predicts cardiovascular events after coronary artery bypass grafting surgery: A prospective observational study.

C-reactive protein is a powerful independent predictor of cardiovascular events in patients with coronary artery disease. The relation between C-reactive protein (CRP) concentration and in-hospital outcome, after coronary artery bypass grafting (CABG), has not yet been established. The study aims to evaluate the predictive value of pre-operative CRP for in-hospital cardiovascular events after CABG surgery. High-sensitivity CRP (hs-CRP) levels were measured pre-operatively on the day of surgery in 66 patients scheduled for elective on pump CABG surgery. Post-operative cardiovascular events such as death from cardiovascular causes, ischemic stroke, myocardial damage, myocardial infarction and low output heart failure were recorded. During the first 30 days after surgery, 54 patients were free from observed events and 14 developed the following cardiovascular events: 10 (15%) had myocardial damage, four (6%) had low output heart failure and two (3%) suffered stroke. No patients died during the follow-up period. Serum concentration of hs-CRP ≥ 3.3 mg/l (cut-off point obtained by ROC analysis) was related to higher risk of post-operative cardiovascular events (36% vs 6%, P = 0.01), myocardial damage (24% vs 6%, P = 0.04) and low output heart failure (12% vs 0%, P = 0.04). Multivariate logistic regression analysis showed that hs-CRP ≥ 3.3 mg/l ( P = 0.002, O.R.: 19.3 (95% confidence interval (CI) 2.9-128.0)), intra-operative transfusion of red blood cells ( P = 0.04, O.R.: 9.9 (95% C.I. 1.1-85.5)) and absence of diuretics in daily antihypertensive treatment ( P = 0.02, O.R.: 15.1 (95% C.I. 1.4-160.6) were independent predictors of combined cardiovascular event. Patients having hs-CRP value greater or equal to 3.3 mg/l pre-operatively have an increased risk of post-operative cardiovascular events after on pump coronary artery bypass grafting surgery.

Effect of cardiopulmonary bypass on the pharmacokinetics of propranolol and atenolol

The pharmacokinetics of some β-blockers are altered by cardiopulmonary bypass (CPB). The objective of this study was to compare the effect of coronary artery bypass graft (CABG) surgery employing CPB on the pharmacokinetics of propranolol and atenolol. We studied patients receiving oral propranolol with doses ranging from 80 to 240 mg (N = 11) or atenolol with doses ranging from 25 to 100 mg (N = 8) in the pre- and postoperative period of CABG with moderately hypothermic CPB (32°C). On the day before and on the first day after surgery, blood samples were collected before β-blocker administration and every 2 h thereafter. Plasma levels were determined using high-performance liquid chromatography and data were treated by pharmacokinetics-modelling. Statistical analysis was performed using ANOVA or the Friedman test, as appropriate, and P < 0.05 was considered to be significant. A prolongation of propranolol biological half-life from 5.41 ± 0.75 to 11.46 ± 1.66 h (P = 0.0028) and an increase in propranolol volume of distribution from 8.70 ± 2.83 to 19.33 ± 6.52 L/kg (P = 0.0032) were observed after CABG with CPB. No significant changes were observed in either atenolol biological half-life (from 11.20 ± 1.60 to 11.44 ± 2.89 h) or atenolol volume of distribution (from 2.90 ± 0.36 to 3.83 ± 0.72 L/kg). Total clearance was not changed by surgery. These CPB-induced alterations in propranolol pharmacokinetics may promote unexpected long-lasting effects in the postoperative period while the effects of atenolol were not modified by CPB surgery.

Early detection of ruptured bulla by capnography during off pump coronary artery bypass grafting surgery: A case report / 대한마취과학회지

Capnography is monitoring of concentration or partial pressure of CO2 in respiratory gases. It provides information about CO2 production, pulmonary perfusion, alveolar ventilation, respiratory patterns and elimination of CO2 from the anesthesia circuit and ventilator. Thus it gives us a rapid and reliable method to detect life threatening conditions such as malposition of tracheal tube, ventilatory failure, circulatory failure and defective breathing circuits. Authors experienced that change of capnogram during off pump coronary artery bypass grafting surgery helped early detecting ruptured bulla and prevented intraopertive or postoperative pneumothorax.

The relationship of serum creatinine and cardiac troponin I after off-pump coronary artery bypass graft surgery

BACKGROUND: Renal dysfunction is an independent risk factor of cardiac dysfunction and one of common complications after cardiac surgery. This study was designed to evaluate the relationship between serum creatinine (s-Cr) and cardiac troponin I (cTnI) in off-pump coronary artery bypass graft surgery (OPCAB). METHODS: Data, from 13 patients underwent OPCAB, were analyzed in prospective fashion. The levels of s-Cr and cTnI were evaluated before and after OPCAB. The correlations of s-Cr and TnI were analyzed in the patients with cardiac dysfunction assessed by low cardiac output or stroke volume at end of surgery. RESULTS: Patients with preoperatively elevated s-Cr (female, > or =1.2 microg/L; male, > or =1.5microg/L) showed higher incidence of elevated s-Cr and elevated cTnI (> or =0.68microg/L) on arrival at intensive care unit (POD-0), postoperative 12 hours (POD-1) and postoperative 36 hours (POD-2) (P< 0.05). Patients with preoperatively elevated cTnI showed higher incidence of elevated cTnI at POD-0, POD-1 and POD-2 (P< 0.05). In 7 patients with low cardiac index (< 2.0 L/min/m2) or stroke volume index (<40 mL/beat/m2) at end of surgery, the increases of s-Cr and cTnI showed positive correlation at POD-0, POD-1 and POD-2 (correlation coefficient 0.818, 0.864 and 0.785, respectively). CONCLUSIONS: The increases of s-Cr and cTnI showed positive correlation in low cardiac output after OPCAB. The results suggested that elevated s-Cr may be an independent predictor of elevated cTnI representing perioperative myocardial injury.

Evaluation on the effect of low intensity exercise training in coronary artery disease. Including the evaluation on significance of exercise training after CABG surgery / 体力科学

A study was conducted to evaluate the effects of exercise training for cardiac rehabilitation. 69 patients with coronary artery disease were assigned to a low intensity exercise training program, which lasted for 3 months. The target heart rate for the exercise program was set at 50-60% of maximal heart rate. For comparison, the study patients were divided into 2 groups. 25 patients who had undergone CABG were assigned to group A and 42 patients who had not undergone CABG were assigned to group B. A symptom-limited treadmill exercise test was performed before and after the exercise training program in each patient. Oxygen uptake (VO<SUB>2</SUB>), SBP, HR and PRP were measured at rest, submaximal workload and workload at the end point during the treadmill exercise test.<BR>In addition, FAT, LVI and PCI were calculated. The parameters measured before and after exercise training were compared in order to assess the effects of the exercise training program. Our findings showed that exercise training was effective for improving exercise tolerance and submaximal exercise capacity in patients with coronary artery disease, particularly those who had undergone CABG.