Patients and Methods
From 24 November 2016 to 23 December 2019, 186 patients who had been diagnosed with multivessel or left main coronary artery disease by coronary angiography were referred for surgical revascularization. After preoperative examination and exclusion of other cardiovascular abnormalities, elective MICS CABG via small left thoracotomy was performed by surgeons who had passed the steep learning curve of this procedure. This study was approved by the ethics committee of Peking University Third Hospital.
Contraindications for this procedure included an unstable preoperative hemodynamic status, severe pulmonary dysfunction, severe obesity, thoracic cavity deformity, and porcelain ascending aorta (A.o) calcification as indicated by computed tomography (CT). The patients’ preoperative characteristics are listed in Table 1.
The preoperative antiplatelet regimen was administration of 100 mg of oral aspirin per day from admission to the day before the operation. In patients who had undergone percutaneous coronary intervention (PCI) <1 year preoperatively while the stent remained patent, a dual antiplatelet regimen of 100 mg of aspirin and 75 mg of clopidogrel per day was adopted until the day before the operation.
An individualized surgical plan for revascularization was established preoperatively according to each patient’s variables and coronary anatomy. All 186 patients were intent to achieve complete myocardial revascularization with the use of two grafts to bypass two or more of three coronary systems: the left anterior descending artery (LAD), left circumflex artery (LCX), and right coronary artery (RCA).
The patient was placed in the supine position with a soft pad under the left scapula, which elevated the left chest by 10 cm. The patient was then intubated with a double-lumen endotracheal tube. An external defibrillator pad was placed for emergency defibrillation. A Swan-Ganz catheter was placed via the right internal jugular vein into the pulmonary artery for intraoperative hemodynamic monitoring. After draping, a 7- to 8-cm-long incision, two-thirds lateral to the left middle clavicle line, was made via the fifth intercostal space after establishing single-lung ventilation. The chest wall was lifted with a retraction system, and the LITA was carefully identified and harvested in a pedicled manner under direct vision from the innominate vein superiorly to its bifurcation or trifurcation inferiorly. The thymus and pericardial fat tissue were dissected and removed with cautery for exposure of the A.o before pericardiotomy. Heparin (1 mg/kg) was administered to achieve an activated clotting time of >250 seconds. Heparin was supplemented at 30-minute intervals to keep the activated clotting time at >250 seconds. After pericardiotomy, the target vessel was identified and exposed. At the same time, an endoscopic or open procedure to harvest the SV was performed by the surgical staff. The SV was prepared in heparinized solution after ligation of its branches.
An apical suction device was used to position the heart, and the target vessel was then stabilized with a vacuum-assisted Octopus Nuvo epicardial stabilizer (Medtronic, Minneapolis, MN, USA). After arteriotomy, an intracoronary shunt was routinely inserted into the vessel to minimize acute ischemia. Handsewn distal anastomosis was accomplished with a running 7-0 or 8-0 Prolene suture (Ethicon, Inc., Somerville, NJ, USA). The routine revascularization strategy was the LITA to LAD first, then proximal anastomosis to the A.o with the SV or radial artery (RA), followed by sequential grafting with a single SV or RA graft 14 to bypass the trunk or branch of the LAD, LCX, or RCA.
Placement of traction sutures on the right pericardium lateral to the A.o, together with insertion of a moist sponge between the right pericardium and A.o, pushed the A.o leftward and facilitated exposure of the proximal A.o. The proximal anastomosis was performed using 6-0 running propylene suture (Ethicon, Inc.) with the aid of a long-shaft side clamp to connect the SV with the A.o. The presence of an eggshell A.o that had not been visible in the preoperative CT scan excluded the possibility of proximal A.o anastomosis. In such cases, the SV graft was anastomosed to the left axillary artery via a horizontal incision placed 1 cm under the clavicle, then passed through the first intercostal space as a sequential graft to bypass the target vessels. Epicardial coronary arteries with a caliber of >1.5 mm and proximal stenosis of >70% were grafted intraoperatively. In two patients, the left RA was used because of shortage of the SV. The distribution of the grafts and target vessels are listed in Table 2.
After neutralization of heparin with protamine, the pericardium was closed. An indwelling catheter was inserted percutaneously and passed underneath the pleura under direct visualization to block the intercostal nerves and thus allow for continuous injection of analgesics postoperatively. A #28 left chest drainage tube was inserted via the sixth intercostal space lateral to the incision. The patients were extubated in the intensive care unit and received an oral dual antiplatelet regimen of daily aspirin (100 mg) and clopidogrel (75 mg). The standard regimen after hospital discharge was lifelong continuation of the aspirin and ≥1-year continuation of the clopidogrel.
The patients underwent invasive coronary artery and graft angiography via the left RA or femoral artery before hospital discharge. The postoperative angiograms were reviewed by three coronary surgeons. Each graft was viewed in at least two orthogonal planes and scored on the worst appearance of the graft. Graft assessment was standardized by the FitzGibbon gradation as the presence of stenosis at either the proximal/distal anastomosis or trunk of the graft: grade A, perfectly patent; grade B, patent with stenosis reducing the caliber to <50% of the target coronary artery; and grade O, occluded graft. Grade A and B grafts were deemed patent. The CR rate was the ratio of the number of grafts constructed intraoperatively to the number of grafts intended to be constructed. Complementary PCI was performed with a drug-eluting stent if indicated.
The patients were followed up via the WeChat app by a single physician assistant after discharge. Major adverse cardiovascular and cerebral events (MACCE) and all causes of death were recorded.