The surgical treatment of coronary artery disease dates back to the 1940s, when Vineberg proposed in 1946 to improve myocardial blood supply by burying the distal end of the internal mammary artery (LIMA) into the myocardium. In 1962, Sabiston first performed a right coronary artery bypass graft (CABG) using the saphenous vein. In 1966 and 1968, Kolessov and Favaloro reported their experience with LIMA and SV, respectively. The work done by these predecessors pioneered the surgical treatment of coronary heart disease. Later, the increasing sophistication and improvement of extracorporeal circulation and myocardial protection techniques led to the worldwide availability of traditional CABG surgery. The first off-pump coronary bypass (OPCAB) was performed by Kolessov in the Soviet Union in 1964, and 32 cases were completed by 1969, with 6 cases still alive 20 years later. 143 OPCAB results were reported by Ankeney in 1972, which were performed mainly by blocking the blood flow above and below the anastomosis; Trapp et al. reported 63 cases in which the procedure was performed without extracorporeal circulation but still with coronary perfusion. Later Benetti, Buffolo et al. reported their more than ten years of surgical experience with OPCAB bulk cases, with better results. Most of the selected cases were those with single anterior descending branch lesions, or combined with right coronary lesions, or combined with other associated high-risk factors. During this period, OPCAB surgery was reported individually, but it was far from mainstream. Until recent years, with the successful development and clinical application of non-extracorporeal surgical devices such as sternal retractors and Stablizer, this surgical approach has gradually come to the forefront and become widely accepted, posing a great challenge to traditional CABG surgery and accounting for an increasing proportion of CABG. 1. Advantages and indications of OPCAB: It is well known that conventional extracorporeal cardiac arrest with coronary artery bypass grafting (CCABG) has been used clinically for many years, and the surgical technique is mature and the efficacy is very accurate. However, the intraoperative and postoperative systemic inflammatory reactions caused by extracorporeal circulation itself cannot be avoided. These complex inflammatory responses can be mediated and activated by complement, cytokines, kininogen/bradykinin pathways, neutrophil release of oxygen radicals, protein coagulation cross-linking and fibrinolysis, cytotoxicity, and microembolism, resulting in a diffuse multi-organ inflammatory response, leading to liver, kidney, brain, lung, and gastrointestinal tract damage, disruption of coagulation mechanisms, impaired function due to myocardial ischemic edema, and interstitial pulmonary edema. Although these damages can be controlled within safe limits with the research and development of extracorporeal circulation and cardiac and cerebral protection technologies, they will certainly have an impact on postoperative monitoring, management and rehabilitation. In addition, although the establishment of extracorporeal circulation provides a guarantee for the safety of surgery, the complications associated with its operation cannot be completely avoided, some of which (e.g., aortic hemorrhage, blood gas embolism, etc.) may also threaten the successful completion of surgery. Many patients require intraoperative and postoperative blood transfusions, which may lead to complications. OPCAB, on the other hand, removes the systemic inflammatory response brought about by extracorporeal circulation itself, which subsequently reduces the occurrence of organ-specific complications, and also reduces the cost of extracorporeal circulation, greatly decreases the possibility of blood transfusion, and shortens the time of ventilatory assistance, ICU stay and hospitalization. The advantages are especially evident in high-risk patients who cannot or are at risk of using extracorporeal circulation. Of course, the indications for CCABG are also applicable to OPCAB, including: (1) those who are difficult to control by medical treatment and unsuitable for percutaneous transluminal coronary angioplasty (PTCA); (2) multiple lesions in multiple branches with PTCA failure or restenosis; (3) coronary artery stenosis of 50% or more with distal stenosis patency and target vessel internal diameter ≥1,5mm; (4) early OPCAB Recently, OPCAB can be performed in patients with stenosis of the left main artery or the high anterior descending branch and gyrus branch equivalent to the left main artery if the heart can tolerate moving. Relative contraindications to OPCAB: (1) poor coronary vascular condition, diffuse lesion, or severe calcification, lumen inner diameter ≤1.3mm, requiring endothelial debridement; (2) blood pressure drops during OPCAB, or the lumen inner diameter is ≤1.3mm. (3) coronary artery myocardial bridge; (4) other intracardiac surgery such as valve replacement, ventricular wall tumor removal, thrombus removal, etc.; (5) severe pulmonary hypertension; (6) huge left ventricle with cardiac insufficiency. 3, OPCAB preoperative preparation and anesthesia characteristics: OPCAB preoperative preparation process is similar to CCABG, the application of β-blockers, calcium antagonists, and nitrates to control symptoms. A certain room temperature is maintained in the operating room, and routine monitoring of arteriovenous pressure, electrocardiogram, and peripheral oxygen saturation is performed. The safe performance of OPCAB is largely dependent on the anesthesiologist’s control of hemodynamics. Unlike CCABG, OPCAB involves moving the heart to obtain good field exposure, and this movement or change in position will inevitably affect the hemodynamic status, which requires close cooperation with the anesthesiologist and, sometimes, the application of certain pharmacological support such as: lidocaine, phenylephrine, dopamine, atropine, etc. During surgery, the patient is often adjusted in the trendelenburg position in order to better visualize the target vessels. This produces volume redistribution and helps to reduce the occurrence of hemodynamic disturbances. Continuous nitroglycerin drip during surgery is beneficial in reducing myocardial ischemia. In addition, maintaining the heart rate at 50-60 beats/MIN intraoperatively is beneficial for vascular anastomosis, but for patients with larger hearts, it is safer to control the heart rate at about 80 beats/MIN. (1) Median sternal incision, which is suitable for multiple coronary artery lesions. The LIMA, SV or radial artery are free for bypass vessels under direct vision after opening the chest. Systemic heparinization (1 mg/kg) is performed and then the pericardium is suspended according to the anastomosis site. Nierich et al. reported that a wet gauze pad placed between the left ventricle and the pericardium could elevate and rotate the left ventricle to the center of the incision, exposing the anterior descending branch (LAD); the diagonal branch could be elevated by fixing 2-3 pericardial traction wires to rotate the heart right for anastomosis. To expose the posterior left ventricular wall and limbic branches, the patient is placed in the Trendelenburg position and rotated to the right, which allows the apical portion of the heart to be placed outside the chest cavity to facilitate the procedure. Local fixation of the anastomosis site was earlier accomplished by threading and pulling on the upper and lower ends of the anastomosis site, which is now rarely used because of the potential for damage to the coronary vessels. In order to obtain a more stable hemodynamic state and better exposure, the Octopus cardiac stabilizer is now used, which allows the epicardial tissues on both sides of the anastomosis site to be adsorbed and fixed, making the anastomosis easier to perform, especially for deeper anastomoses. Attention should be paid during suspension, moving the heart and local fixation: excessive displacement of the heart causing right ventricular compression can affect blood pressure, and in general, redistribution of body fluids in the trendelenburg position is sufficient to correct cardiac output. Adjust the dosage of vasoactive drugs if necessary. In cases of multiple coronary artery lesions, which target vessel is anastomosed first depends on the degree and location of vessel obstruction. The anastomosis of the LIMA-LAD or the severely diseased vessel is often performed first, which improves and stabilizes the hemodynamic status and provides some protection for the anastomosis of subsequent vessels. However, a completely obstructed vessel is done first to allow collateral perfusion of the next vessel to be anastomosed. An elastic blocking band is worn proximal or distal to the anastomosis site before the anastomosis in order to prepare for blocking the coronary flow. During anastomosis of the right coronary artery, a coronary blocking plug (Intraluminal shunt) is placed in the incision to maintain blood perfusion distal to the anastomosis and to prevent slowing of the heart rate, especially in patients with pre-existing right coronary flow. A sterile carbon dioxide nebulizer or oxygen nebulizer is also used to help expose the operative field. In a hemodynamic analysis by Nierich [14], it was concluded that the per-pulse volume of median open-heart OPCAB was reduced to different degrees for different anastomotic sites, but within tolerable limits, and that the cardiac output could be adequately ensured by the “trendelenburg” position. The cardiac output can be adequately ensured by the “trendelenburg” position. (2) The left anterolateral incision (MIDCAB) is indicated for the anastomosis of a single branch of the LIMA-LAD lesion. A special chest opener is used to expose and free the internal mammary artery, and a special local brake is required for the anastomosis. The purpose of this incision is to further reduce trauma and improve the appearance. However, the indications are narrow, especially for those with thoracic and pulmonary lesions and those who cannot tolerate unilateral ventilation; in addition, it is difficult to manage intraoperative hemodynamic disturbances. The use of this procedure should be carefully considered in the selection of cases. If poor coronary vascular conditions, calcification or diffuse lesions are found during intraoperative exploration, CCABG should be used instead in a timely manner. Comparison and evaluation of OPCAB and CCABG: Since OPCAB avoids extracorporeal circulation, the most important factor of systemic damage caused by CCABG, it has advantages in terms of pathological basis and clinical efficacy. OPCAB has a certain advantageous position in terms of pathological basis and clinical efficacy. (1) OPCAB can reduce systemic inflammatory response: In a comparative study of systemic inflammatory response between OPCAB and CCABG, Struber et al. demonstrated that the degree of cytokine-mediated inflammatory response was significantly lower in patients with OPCAB than in those with CCABG; Ascione et al. , C3a, C5a and their responses, concluded that the systemic inflammatory response and postoperative infection rate were lower in OPCAB. In addition, myocardial damage from hypoxic arrest and ischemia-reperfusion injury caused by CCABG is also a disadvantage of CCABG. Biridi et al. demonstrated that the release of troponin I, a protein specific for myocardial injury, and myocardial damage were significantly reduced in OPCAB patients. bouchard tested OPCAB patients postoperative blood lactate and CK-MB levels were significantly lower than those in the CCABG group, suggesting a protective effect on cardiac and renal function. diegelar, on the other hand, confirmed that neurological complications after CABG were mainly related to extracorporeal circulation and microembolism. The absence of the side effects of extracorporeal circulation on various organ systems allows organ function to be maintained in an optimal state during the intraoperative and early postoperative periods when coronary revascularization is performed, and its corresponding complications are mitigated to a minimum, especially in those high-risk patients. (2) Since OPCAB has been developed and popularized only in recent years, its long-term efficacy has not yet been reported in large numbers. In a retrospective analysis of 700 OPCAB cases, Benetti showed that this procedure can be an alternative treatment for coronary artery disease, especially in patients of advanced age or with associated disease, and is superior to CCABG in terms of protection of cardiac function, ICU and hospital stay, transfusion volume, and cost/effect ratio compared with the same period. Yokoyama compared the clinical outcomes of OPCAB in 242 high-risk patients including advanced age (>80 years), EF ≤0.25, history of neurological disease, renal insufficiency, COPD, and reoperation, and found that in this group of patients there was a significant advantage over Calafiore reported 460 procedures, of which 5.7% were converted to extracorporeal circulation due to poor intraoperative exposure of fine, calcified, or diffuse coronary lesions, with a mortality rate of 1.1% and a 1-year patency rate of 96.1%. stamou reported that the application of OPCAB for reoperation of single-branch lesions In another report, he also noted a lower incidence of atrial fibrillation after OPCAB. In addition, OPCAB in patients with concomitant malignancy has unparalleled advantages of CCABG. However, Omeroglu estimated the long-term (5-8 years) graft patency rate in 70 patients randomly selected from 696 OPCAB cases by coronary angiography, of which 95.59% were anterior descending branches and 47.06% were venous bridges, and multivariate analysis showed that the main causes of graft obstruction were the type of graft material (venous bridges (low patency rate) and hyperlipidemia, with significant improvement in left ventricular function (P=0.04) The rates of re-intervention or reoperation were 0.97% and 1.4%, respectively, suggesting that OPCAB can achieve intermediate and long-term outcomes that are indistinguishable from those of conventional surgery. Of course, there is disagreement as to whether precise anastomosis and long-term patency rates are affected by multiple lesions, especially the gyral branch, due to its poorly revealed nature. In addition, the majority of OPCAB patients have a lower number of bypass vessels in the graft than CCABG, with the possibility of incomplete revascularization. Compared with CCABG, OPCAB has obvious advantages for high-risk patients because it avoids extracorporeal circulation, reduces surgical trauma and systemic inflammatory response, shortens postoperative ventilator-assisted time, ICU stay and hospitalization time, reduces surgical costs, and has low early postoperative complication rate and mortality, but its long-term efficacy and patency rate need further observation. At present, OPCAB is still not a complete substitute for CCABG. In addition to its limited indications, extracorporeal circulation should be prepared while performing this procedure. Preoperative comprehensive evaluation of lesion vascular conditions, application of cardiac stabilization devices, good anesthesia coordination, and skillful surgical technique are necessary to ensure successful implementation of OPCAB.