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Robotic Coronary Artery Bypass Grafting


Robotic Coronary Artery Bypass Grafting
Introductory Considerations
The goal of any minimally invasive procedure is to achieve the least surgical trauma possible and to carry out the intervention in a port-only approach. After unsuccessful attempts to perform endoscopic coronary bypass surgery using long-shafted thoracoscopic instrumentation, the first totally endoscopic coronary bypass grafting (TECAB) was carried out in 1998 using a surgical robot. Since then, TECAB has been further developed from single-vessel to multivessel surgical revascularization1,2 and is performed in beating heart and stopped heart versions. TECAB can be combined with percutaneous coronary intervention in so-called integrated or hybrid procedures. A second, third, and fourth generation of surgical robots is available, and procedure-specific robotic instrumentation has improved vision, exposure of target vessels, and overall ergonomic features of the procedure.

1. Patient Selection, Indications, and Contraindications
At the current stage, any patient with a clear indication for surgical coronary revascularization can be considered for TECAB. It is, however, highly important to respect the contraindications listed in Box 7.1. In general, TECAB is elective surgery, and redo procedures are difficult using open techniques and are long and tedious in the endoscopic setting. Any factor that leads to distortion or reduction of the pleural cavities, such as thoracic deformities, a severely enlarged heart, or reduced lung volume, needs to be respected. Wise judgment needs to be applied as to whether to expose patients to a potentially longer pump time, myocardial ischemic time, and overall procedure time. This is especially true for patients with multiple comorbidities. Because TECAB involves a significant technical learning curve, we strongly recommend to start with simpler versions of the operation in low-risk patients.


2. Preoperative Workup
All patients should receive the same workup as for open coronary artery bypass grafting (CABG). The usual battery of preoperative examinations consists of the clinical history and physical examination, basic blood tests (complete blood count [CBC], basic metabolic panel [BMP], international normalized ratio [INR], type, and screen), carotid Doppler studies, ankle-brachial index (ABI), pulmonary function studies, and echocardiography. To address TECAB-specific questions, computed tomography (CT) angiography of the chest, abdomen, and pelvis is carried out. The parameters that should be assessed for this procedure by the surgeon, surgical team, and radiologist on this CT are listed in Box 7.2.


3. Anesthesia
Basic cardiac anesthesia principles are applied but experienced anesthesiologists with specific skills should lead the case. Box 7.3 lists specific anesthesia aspects. Transesophageal echocardiography (TEE) is necessary for monitoring heart function and regional wall motion, as well as for adequate positioning of the endoballoon in arrested heart TECAB. Good communica- tion with the anesthesia team is key, especially in regard to when to start single-lung ventilation, level of CO2 inflation pressure, occurrence of leg ischemia if femoral arterial heart-lung machine perfusion is chosen, migration of the endoballoon in arrested heart TECAB, heart rate control and assessment of regional wall motion in beating heart TECAB, and respiratory management after a longer heart-lung machine run under single-lung ventilation.

4. Necessary Hardware and Procedure Versions
·  Currently, only one surgical robot is available on the market that allows performance of TECAB (Intuitive Surgical, Sunnyvale, CA). Surgeons who perform TECAB mostly use the third generation (Si version) of the da Vinci system. Fig. 7.1 shows the surgeon sitting behind the robotic console. Using so-called masters, the surgeon performs maneuvers with his or her hands, which are translated into intrathoracic movements of a robotic three-dimensional (3D) camera and the robotic instruments. Foot pedals are part of the machine for switching between camera and instrument control, as well as for electrocautery. The surgeon looks into a 3D binocular. At the time of this writing, not all instruments used for TECAB are available for the fourth generation (Xi version).
·  TECAB can be performed with and without use of the heart-lung machine. The former version is usually called AH (arrested heart) TECAB; the latter is commonly referred to as BH (beating heart) TECAB. We strongly recommend developing both methods because it gives a robotic surgery team the best level of flexibility and allows for best tailoring of the operation to the patient’s needs.
·    BH-TECAB can avoid side effects of the heart-lung machine but target vessel exposure and anastomotic suturing are technically more demanding than in AH-TECAB. Surgeons should master anastomotic techniques in the arrested heart version before moving to the beating heart technique. We also recommend cannulating the patient prophylactically for a potential heart-lung machine run in BH-TECAB, which may be necessary if there is limited intrathoracic space and if the patient develops myocardial ischemia, hemodynamic instability, or ventricular arrhythmia. Installing the heart-lung machine acutely in these situations is difficult with the robot docked, may take too much time if there is significant hemodynamic compromise, and may be associated with additional vascular complications. In our experience, having the immediate safety net of a heart-lung machine available has proven to be very valuable.
 
The surgeon operates the robotic instruments from a console. A third and fourth generation of operation robots are currently available.


In AH-TECAB, anastomotic suturing is easier, but AH-TECAB requires specific skill sets in remote access perfusion and the use of endoballoon or transthoracic clamping. These skills should be developed in procedures other than TECAB (e.g., atrial septal defect [ASD] II repair or minithoracotomy mitral valve repair) before application in totally endoscopic CABG. In our hands, placement of bypass grafts to the right coronary artery (RCA) and circumflex coronary artery territories only works reasonably using the arrested heart technique because the heart is completely flaccid and can be adequately rotated.

Procedural Steps
Step 1. Positioning, Prepping, and Draping
The patient is placed on the operating table in the supine position. The arms are tucked to the body, and the left chest is slightly elevated using a towel roll. Because the team needs to be prepared for conversion to an open procedure, the patient is prepped and draped as for open CABG, and the equipment for conducting open CABG should always be available.

Step 2. Port Placement and Robot Docking
The ports are usually placed on the patient’s left chest and should be inserted by the most experienced team member, because correct port placement plays a key role in the operation. Insertion requires complete left lung collapse and must be confirmed by the anesthesia team before placement. The camera port is placed in the fifth intercostal space on the anterior axillary line, and CO2 is insufflated at a pressure of 8 mm Hg. Should hemodynamic compromise (e.g., hypotension) occur during this phase, the CO2 pressure should be lowered. The thoracic cavity is then inspected and, under scope vision, the left and right instrument ports are inserted cranially and caudally four fingerbreadths away from the camera port, midway between the anterior axillary line and midclavicular line. The surgical robot is then docked and a robotic cautery spatula (right arm) and DeBakey forceps (left arm) are inserted. Fig. 7.2 depicts the port arrangement and instruments inserted, and Fig. 7.3 shows the robotic arms docked to the patient.

Step 3. Internal Mammary Artery Takedown
Using the camera-up view with the 30-degree angled robotic camera, the internal mammary artery (IMA) is identified by its visible pulsations. The electrocautery is set at 15 to 20 W, and the endothoracic fascia and muscle covering the IMA are removed (Fig. 7.3). The IMA is then harvested in a skeletonized fashion using mechanical takedown and cauterization of the side branches close to the chest wall (Fig. 7.4). Clipping is necessary only for large branches and in case of side branch bleeding. If both IMAs are harvested, the right pleura is entered via generous robotic endoscopic retrosternal dissection and opening of the right pleura. In double-IMA harvesting, the right IMA should be taken down before the left IMA. After heparinization, the IMA can be clipped distally, divided using robotic Pott’s scissors, and dropped into the left chest for autodilation.
 
Figure 7.2 Port arrangement in TECAB.

Figure 7.3 The robotic arms are docked to the patient’s left chest, with the camera port inserted into the fifth intercostal space on the anterior axillary line and the right instrument port inserted into the third intercostal space midway between anterior axillary line and midclavicular line. The left instrument port is placed in the seventh intercostal space midway between anterior axillary line and midclavicular line.
Figure 7.4 The internal mammary artery is harvested in a skeletonized technique using a robotic electrocautery spatula at a power of 15 to 20 Watts and a robotic deBakey forceps.


Step 4. Assistance Port Placement
After IMA harvesting under scope visualization, a 5-mm assistance port is placed in the left parasternal region, opposite to the camera port. Since introduction of this step, significant time gains in TECAB have been noted. This port allows the insertion and removal of material needed throughout the procedure (e.g., bulldogs, suture material, Silastic tapes, suction tubing).

Step 5. Pericardial Fat Pad Removal and Pericardiotomy
To gain access to the pericardial fat pad and the pericardium, the scope view is switched to the camera-down mode. Using an electrocautery spatula on the right and a long tip forceps on the left, the fat pad is resected, starting with its cranial sternal portion and then moving caudally. If the fat pad is large, starting the heart-lung machine can significantly improve intrathoracic space and facilitate removal. The pericardium is opened above the right ventricular outflow tract, incised (heading toward the substernal part of the pericardial reflection), and then taken out laterally. Cranially, the pericardium is opened, moving toward the phrenic nerve, which needs to be clearly identified. The phrenic nerve and left atrial appendage, which is close, need to be respected.

Step 6. Remote Access Cardiopulmonary Bypass and Application of the Endoballoon
·    If the preoperative CT angiogram shows no or only mild grades of aortoiliac atherosclerosis, we feel comfortable using femorofemoral cannulation for the cardiopulmonary bypass. Usually, the left groin is exposed. We keep dissection of the femoral artery and vein limited to prevent lymphatic leaks. A distal leg perfusion line is inserted in all cases, and leg perfusion is monitored by near-infrared spectroscopy (NIRS) throughout the whole procedure. A 25 F venous drainage cannula is then advanced into the superior vena cava under TEE guidance and connected to the heart-lung machine tubing. A 21 F or 23 F arterial perfusion cannula with a side arm is inserted into the femoral artery and connected to the arterial line of the cardiopulmonary bypass circuit.
·    For safe use of the ascending aortic endoballoon for cardioplegia, we specifically look into a lack of ascending, arch, and descending thoracic aortic atherosclerosis. The maximum ascending aortic diameter we accept is 38 mm. The aortic valve should be competent and free of thickening or stenosis. The balloon is completely de-aired and inserted through the side arm of the arterial perfusion cannula. The guidewire is advanced into the aortic root under TEE guidance, and the endoballoon is then placed above the aortic valve. The catheter is connected to the heart-lung machine tubing, and the pressure lines for measurement of aortic root pressure and balloon pressure are de-aired and connected to corresponding manometers. Aspiration or injection of air through the catheter into the aortic root has to be avoided by all means.
·   The heart-lung machine is started slowly in all procedures. With adequate venous drainage, low blood pressure, and lack of ventricular ejections, the endoballoon is inflated, and its correct position in the aortic root is confirmed by TEE. After endoballoon inflation, cardioplegia is induced. For initial rapid induction, adenosine (6 mg diluted in 20 mL of saline solution) may be injected. We start cooling only after a stable balloon position has been achieved. Cardioplegia is repeated every 20 minutes. If a percutaneous retrograde cardioplegia catheter has been inserted, both antegrade and retrograde cardioplegia can be given following customary protocols.
·  In cases of moderate to severe aortoiliac atherosclerosis, we strictly avoid femoral arterial retroperfusion. Instead, the left axillary artery is exposed in the left infraclavicular region and an 8-mm prosthetic side arm is anastomosed to the artery and connected to the arterial line of the cardiopulmonary bypass circuit. Axillary cannulation ensures antegrade perfusion from the descending thoracic aortic level downstream and may reduce the risk of retrograde aortoiliac dissection. The endoballoon catheter can in most cases still be inserted through a separate 19 F cannula placed into the common femoral artery.
·    If severe-grade aortoiliac atherosclerosis is present, or if protruding and mobile atheroma is seen on TEE, the endoballoon is contraindicated. In these cases, we use a BH-TECAB approach. BH-TECAB patients are still cannulated, and the cannulae are placed at an activated clotting time (ACT) level of 300 seconds. Should a pump run become necessary, we raise the ACT to 480 seconds. Supportive cardiopulmonary bypass is extremely helpful—for example, in BH multivessel TECAB, in cases of ischemia during target vessel occlusion, if space inside the chest is limited, or if bleeding problems are encountered. During supportive pump runs, significant diffuse bleeding from portholes, the IMA bed, and other structures may be observed and may require intermittent evacuation of pleural blood using transthoracic suction.

Step 7. Exposure of Target Vessels
 The robotic endostabilizer can be used as an exposure device in BH-TECAB and AH-TECAB. For positioning of this device, a 12-mm port is placed subcostally into the left chest using a port incision two fingerbreadths lateral to the xiphoid angle. Insertion of the port can be guided by the robotic camera using the up view. The subcostal port is docked to the fourth arm of the da Vinci system.
 For all work on the coronary target vessels, the scope view is camera down. With the subcostally placed endostabilizer, the left anterior descending artery (LAD) and circumflex coronary artery systems can be well reached. The endostabilizer is activated using a dedicated foot pedal, and the suction pods are placed alongside the target area of the target vessel. In this way, local immobilization can be achieved in BH-TECAB, and the target vessel can be moved into a comfortable position in both BH-TECAB and AH-TECAB.
    The right coronary artery system can be accessed by inserting the endostabilizer through a 12-mm left-sided instrument port. With this port arrangement, the subcostal port can be used as the left robotic instrument arm. The acute margin of the right ventricle is lifted up using the endostabilizer, and excellent access to the posterior descending artery and posterolateral artery can be gained. To date, we have applied this method only in AH-TECAB.
    After appropriate exposure of the target vessel, the epicardium is incised with robotic Pott’s scissors.

Step 8. Robotic Endoscopic Graft to Coronary Anastomosis
·    Before starting the anastomosis, final preparations are carried out on the bypass graft. After occlusion with a bulldog, the graft is trimmed in an oblique manner distally and opened further, to a total length of 4 mm. Free flow must be checked.
·    For incision of the target vessel, we use a DeBakey forceps and robotic lancet beaver knife. The incision is enlarged to approximately 4 mm using robotic Pott’s scissors. A 7-cm double- armed polypropylene suture is then brought in through the assistance port. For suturing the anastomosis, two robotic black diamond microforceps are used.
·    The suture is started at the toe of the anastomosis on the back wall with an inside-out stitch. The needle is parked away in the epicardium. With the other needle, the suture is continued on the back wall, stitching the graft inside out and the coronary artery outside in. After three throws in parachute technique, the graft is brought down to the anastomotic level, and suturing becomes easier. It is very important to apply adequate suture tension to avoid leaks on the back wall, which are harder to correct than if they occur on the front wall. Fig. 7.5 shows the suturing of the anastomotic back wall. Figs. 7.6 and 7.7 depict the further suturing sequence. After going around the heel, the needle is parked away again, and the contralateral needle is taken to suture around the toe of the anastomosis and complete the suture line. Gentle probing of lumen patency with the tips of the microforceps is possible. The whole suture line needs to be carefully inspected for slings, which can be corrected using one of the suture needles. A video of the suturing technique is also available at.
·  At the current stage, grafts can be placed to all coronary territories. The most common TECAB versions are left internal mammary artery to left anterior descending artery (LIMA to LAD), right internal mammary artery (RIMA) to LAD combined with LIMA to the diagonal, ramus, or circumflex artery branches, and LIMA to LAD combined with RIMA to the RCA territory. The latter is a Y graft construct.
·   There are some specifics to consider when suturing on the arrested heart or beating heart. In AH-TECAB, the target vessel can be incised as cardioplegia is initiated, which may reduce the risk of injury to the back wall. Backbleeding from the target vessel may be present, caused by inadequate venous drainage or low endoaortic balloon pressure leading to retrograde aortic root flow. Correction of the venous drainage cannula position, additional inflation of the endoballoon, or placement of a Silastic tape is an appropriate measure to take to reduce backbleeding. Suturing should only be started if a clear view of the target vessel is ensured.
·  In BH-TECAB, Silastic tapes are placed proximally and distally to the graft landing zone. Only the proximal one is occluded. The target vessel is then opened and an intraluminal shunt is inserted first, completely into the distal vessel. It is then pulled into the proximal vessel and the Silastic tape is loosened. In BH-TECAB, the stitching maneuvers must be very gentle to avoid lacerations of the coronary artery wall. An esmolol drip may improve the comfort of suturing. The surgeon has to deal with magnified bouncing movements of the operative field; intense simulation training in dry and wet laboratory models is strongly recommended before moving into the clinical setting.
 
Figure 7.5 Suturing of the back wall of the anastomosis in videoscopic view. Two robotic microforceps are used. Suture material is a 7 cm-long double-armed 7/0 polypropylene suture.

Figure 7.6 After completing the back wall and hell of the anastomosis, the toe and anterior wall suture are complete.
Figure 7.7 The multiwristed robotic instruments allow for comfortable robotic knot tying.


Step 9. Final Maneuvers
·    Transit time ultrasound flow measurements of the bypass are carried out in all cases using a specifically designed endoscopic flow probe. The probe is brought in through the subcostal port. Blood collections in the left pleural space are evacuated using a flexible suction tube brought in through the assistance port.
· After pump runs, the patient is weaned from cardiopulmonary bypass, leaving the robot docked and leaving instruments parked in the IMA bed. This is done because the heart will be filled after decannulation, and re-insertion of instruments may be difficult. The combination of single-lung ventilation and the use of cardiopulmonary bypass may lead to transient, significant respiratory compromise, which is usually self-limited.
·    Once the patient is oxygenating stably and pump function is adequate, protamine is given. A final robotic inspection of the thoracic cavity follows. This phase requires ongoing thorough attention of the console surgeon and tableside team. Once adequate hemostasis has been achieved, the robotic system is undocked but the ports are left in place. This is important to avoid CO2 losses during final manual inspections with the robotic camera. The ports are removed in a stepwise manner under scope inspection. They are cauterized and packed with Surgicel. A chest tube is inserted through the camera porthole. This should be done with the left lung inflated to avoid graft injuries during this last phase of the operation.

Postoperative Care
Postoperative care basically follows the principles of care after coronary bypass surgery through a sternotomy. After single-lung ventilation, atelectasis may be present, which usually can be managed with respiratory therapy. Attention should be paid to peripheral arterial and venous circulation after remote access cannulation. Pain may be quite intense, specifically around the camera port side area, but usually goes away within the first few postoperative days. Sternal precautions do not need to be prescribed.

Keywords:      coronary artery disease, coronary artery bypass grafting, minimally invasive surgery, endoscopic surgery, robotic surgery

References
1.  Bonatti J, Schachner T, Bonaros N, et al. Robotic assisted endoscopic coronary bypass surgery. Circulation. 2011;124:236–244.
2.  Bonatti J, Lee JD, Bonaros N, et al. Robotic totally endoscopic multivessel coronary artery bypass grafting: procedure development, challenges, results. Innovations. 2012;7:3–8.