The efficacy of minimally invasive coronary artery bypass grafting (mics cabg) for patients with coronary artery diseases and diabetes: a single center retrospective study

This study was ethically approved by the Ethics Committee of Beijing Anzhen Hospital, Capital Medical University, China.

A total of 639 bypass operations were conducted in the Minimally Invasive Cardiac Surgery Center, Beijing Anzhen Hospital, China, between January 2017 and December 2021.

Our study included some of these bypass operations, and the inclusion criteria were as follows: (1) Patients with a history of Type II diabetes lasting one year or more; (2) Patients diagnosed with single, multiple, or left main CAD through coronary angiography; (3) Patients with complete clinical data. The exclusion criteria were as follows: (1) Patients with valve diseases, ventricular aneurysms, or other diseases requiring simultaneous cardiac surgery; (2) Patients suffering from severe lung disease who require simultaneous lung resection surgery; (3) Patients with carotid stenosis requiring simultaneous carotid artery stent surgery and emergency operation [13, 14]. After selection, 173 cases were enrolled (65 MICS CABG and 108 CCABG cases, respectively). The cases were matched based on gender, age, Body Mass Index (BMI, kg/m²), body surface area (m²), history of hypertension, smoking history, drinking history, history of Atrial Fibrillation (AF), history of cerebral infarction, history of cardiac surgery, heart function grading (NYHA grading), creatinine clearance rate (mL/min), brain natriuretic peptide (BNP, ng/L), Creatine Kinase Isoenzyme (CK-MB, ng/mL), Cardiac Troponin (TnI, µg/L), arterial partial pressure of oxygen (PO₂) before operation, and preoperative Left Ventricular Ejection Fraction (LVEF, %). Finally, 52 MICS CABG cases and 52 CCABG cases were successfully matched. Table 1 summarizes the preoperative characteristics of the enrolled patients.

Patients in the CCABG group were placed in a supine position. Subsequently, under general anaesthesia, the sternum was split in the middle through sternotomy incision, gradually spreading the sternum and releasing the Left Internal Mammary Artery (LIMA). The pericardium was not opened at this point. Simultaneously, the Saphenous Vein Graft (SVG) was prepared for backup. The pericardium was opened and suspended after completing the transplantation of blood vessels. The target vessel was fully exposed using a cardiac stabilizer. End-to-side anastomosis was performed on LIMA to the anterior descending artery, while SVG sequential anastomosis was performed on other target vessels. During proximal anastomosis, aortic sidewall forceps were employed on the ascending aorta with no or mild calcification. The ascending aorta with severe calcification was punched with an aortic connector. A flow meter was used to detect graft flow after each target vessel’s revascularization.

Patients in the MICS CABG group were also placed in a supine position and their left shoulder-back side was raised by 30°. Subsequently, general anesthesia was administered, and a dual lumen tracheal intubation was performed to assist the patients with breathing. Following that, the pleura was accessed through the 4th or 5th intercostal space on the left side after making an incision on the anterolateral side of the left chest wall. An IMA retractor (THORATRAK MICS Retractor System) was used to retract the left rib, and the patients were then ventilated with one lung to obtain free access to the LIMA while preparing SVG for backup. Following that, the pericardium was opened and suspended after opening the intercostal space on both sides using a hinged retractor (ValveGate). A cardiac surface fixator (TS2000 Medtronic Inc) was applied to complete anastomosis from the LIMA to the anterior descending artery. The anastomosis site of the proximal ascending aorta was exposed. Proximal venous anastomosis was performed using a specially designed ascending aortic wall forceps. Sequential SVG anastomosis was performed using an apex fixator (29,800 Medtronic Inc) and a cardiac surface fixator. The flow meter was used to detect graft flow after revascularization.

Aspirin and clopidogrel were discontinued before the operation as part of the preoperative anti-platelet regimen. Patients who received PCI and were diagnosed with coronary stent stenosis via coronary angiography or left main artery disease before surgery, were treated with a single anti-platelet regimen (100 mg/d aspirin) up until two days before the operation. The patients underwent extubation in the Intensive Care Unit (ICU) after surgery and later received a daily oral anti-platelet regimen of aspirin (100 mg) and clopidogrel (75 mg) after being transferred back to the general ward. The standard anti-platelet regimen for patients after discharge is lifelong aspirin and clopidogrel for at least one year.

According to the previous history of hypoglycemic drugs, the preoperative blood glucose control regimen was to stop the thiazolidinediones and DPP-4 inhibitors, continue to take metformin and alpha-glucosidase inhibitors, and increase the use of SGLT-2 inhibitors hypoglycemic drugs after admission. The target of blood glucose management is 6.0 to 8.0mmol/L for Fasting Blood-Glucose (FBG) before three meals, and strict attention should be paid to avoid hypoglycemia. Patients with persistent FBG ≥ 10.0mmol/L were treated with subcutaneous insulin injection. The patients received a daily oral hypoglycemic drug regimen after being transferred back to the general ward, and Regular Insulin (RI) was applied for at least 3 days to control blood glucose fluctuations. On the 4th day after surgery, it was decided whether to stop RI according to the FBG and blood glucose fluctuations.

Antibiotics were used on the day of surgery, and the conventional antibiotics were second- or third-generation cephalosporin antibiotics.

The diagnosis of CAD was confirmed by coronary angiography. Diabetes was defined as typical diabetic symptoms (including polydipsia, polyuria, polyphagia, and unexplained weight loss) accompanied by Random Blood Glucose (RBG) ≥ 11.1mmol/L, FBG ≥ 7.0mmol/L, Oral Glucose Tolerance Test (OGTT) 2 h blood glucose ≥ 11.1mmol/L, or glycosylated hemoglobin (HbA1c) ≥ 6.5%. All-cause mortality was defined as death caused by various reasons, including cardiogenic death in patients who were in stable conditions in the past. Myocardial Infarction (MI) was defined as follows: (1) Myocardial enzymes, such as Cardiac Troponin (TnI) and/or Creatine Kinase Isoenzyme (CK-MB), reaching more than twice the upper limit of the normal reference range; and (2) Significant changes in the ST segment of the electrocardiogram. Revascularization events refer to those performed by PCI or CABG after discharge. New York Heart Association (NYHA) classify the impaired state of heart function into four grades according to the degree of activity that induces symptoms of heart failure. It includes Class I: No limitations. Ordinary physical activity does not cause undue fatigue, dyspnoea or palpitations (asymptomatic LV dysfunction); Class II: Slight limitation of physical activity. Ordinary physical activity results in fatigue, palpitation, dyspnoea or angina pectoris (mild CHF); Class III: Marked limitation of physical activity. Less than ordinary physical activity leads to symptoms (moderate CHF) and Class IV: Unable to carry on any physical activity without discomfort. Symptoms of CHF present at rest (severe CHF). Major Adverse Cardiovascular and Cerebrovascular Events (MACCEs) includes death, nonfatal myocardial infarction, revascularization and cerebral apoplexy. The reference range of the creatinine clearance rate (eGRF) was > 90 mL/L; with 60–90 mL/min, 30–60 mL/min, 15–30 mL/min, and < 15 mL/min indicating minor renal impairment, medium renal impairment, heavy renal impairment, and dialysis, respectively. The reference range of BNP was 0-100 ng/L, with 100–300 ng/L and > 300 ng/L indicating cardiac dysfunction and acute heart failure, respectively. On the other hand, the reference range of PO₂ was 80–100 mmHg, with 60–80 mmHg and < 60 mmHg indicating mild hypoxemia and Type I respiratory failure, respectively. The three-level FitzGibbon grading standardization (Grade A: Completely unobstructed; Grade B: Stenosis < 50% of the target coronary artery diameter; and Grade O: Graft vessel occlusion) was used to evaluate the transplanted blood vessels, that is, stenosis at the proximal/distal anastomosis or the main stem of the graft.

The key outcomes included MACCEs, all-cause death, MI, cerebral apoplexy, revascularization, adverse wound healing events during postoperative follow-up and one-year patency of the graft by coronary CTA. The perioperative complications in the hospital was also recorded.

The contact information of all patients was recorded at discharge, and they were all reminded (together with their families) to undergo coronary artery CTA at our facility or another hospital after one year for graft patency evaluation. we conducted patient follow-up through telephone inquiry, focusing on survival, MACCEs incidence, repeated revascularization incidence and incision healing.

The preoperative confounding factors were filtered based on PSM. Patients were divided into two groups (MICS CABG and CCABG) in a 1:1 ratio based on gender, age, BMI (kg/m²), body surface area (m²), history of hypertension, smoking history, drinking history, history of AF, history of cerebral infarction, history of cardiac surgery, heart function grading (NYHA grading), creatinine clearance rate (mL/min), BNP (ng/L), CK-MB (ng/mL), TnI (µg/L), PO₂, and preoperative LVEF (%). The caliper value was set at 0.05 and the Standardized Difference (SD) at < 10% to ensure the variables between the two groups matched appropriately. All statistical analyses were performed using IBM SPSS Statistics® for Windows (v 26.0). Normally distributed measurement data were expressed as mean ± standard deviation, and inter-group comparisons were performed using an independent sample t-test or analysis of variance. Non-normally distributed measurement data were presented as Median (M) and Interquartile Ranges [IQR, upper and lower quartiles (P25, P75)], and the Wilcoxon rank sum test was performed for inter-group comparisons. On the other hand, counting data were expressed as frequency (rate or constituent ratio), and inter-group comparisons were performed using a chi-square test, a Fisher’s exact probability test, or the Wilcoxon rank sum test. Kaplan-Meier survival curves were constructed to evaluate MACCEs incidence, and the log-rank test was employed to compare inter-group data. The impact of confounding variables on MACCEs incidence was minimized using a multivariate Cox proportional hazard regression model. Variables with significant statistical differences (P ≤ 0.05) or reported effects on the research results were included in the multivariate Cox proportional hazard regression model for correction. Overall, results with P ≤ 0.05 were considered statistically significant.