MMCTS
(March 15, 2006). doi:10.1510/mmcts.2004.000935
Copyright © 2006 European Association for Cardio-thoracic Surgery
Procedure
Closed-chest, robotically assisted CABG
Volkmar Falk*,
Stephan Jacobs and
Friedrich-Wilhelm W. Mohr
Department of Cardiac Surgery, Heartcenter, University of Leipzig, Germany
* Corresponding author: * Volkmar Falk, Klinik für Herzchirurgie, Universität Leipzig, Herzzentrum, Strämpellstr. 39, 04289 Leipzig, Germany Tel.: +49-341-865-1422/1423; fax: +49-341-865-1452. E-mail: falv{at}medizin.uni-leipzig.de
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Summary
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Total endoscopic coronary artery bypass grafting is a robotic assisted procedure to graft the left internal thoracic artery to the left anterior descending coronary artery without opening the chest. Through four 1-cm port incisions the procedure can be performed on the beating heart using a telemanipulation system and an endoscopic vacuum stabilizer to locally immobilize the heart.
Key Words: Coronary artery bypass grafting • Robotics • Telemanipulation
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Introduction
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Since its introduction in the 1960s, coronary artery bypass grafting (CABG) has become one of the most frequently performed surgical procedures. CABG provides excellent long-term results for various clear-cut indications with a major favorable impact on patient outcome and recurrence of adverse cardiac events [1]. The success of catheter-based techniques for treating ischemic coronary syndromes, combined with the shift towards less invasive approaches by other surgical specialties, has renewed interest in minimally invasive approaches for cardiac surgery. Off-pump coronary artery bypass grafting (OPCAB) was developed in order to avoid the effects of cardiopulmonary bypass and limited access bypass grafting through alternate incisions such as minimally invasive direct coronary artery bypass (MIDCAB) was established. With the introduction of computer enhanced instrumentation systems such as the da Vinci® surgical telemanipulator (MMCTSLink 17), total endoscopic coronary artery bypass grafting (TECAB) has become possible. This robotic assisted procedure is applied to graft the left internal thoracic artery (ITA) to the left anterior descending coronary artery (LAD) without opening the chest. Through four 1-cm port incisions the procedure can be performed on the beating heart using a telemanipulation system and an endoscopic vacuum stabilizer to locally immobilize the heart.
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Surgical technique
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Standard monitoring for cardiac surgery is applied. A central line and arterial line are placed. Defibrillator pads are placed on the back and to the right chest. A double-lumen endotracheal tube is used to allow for single lung ventilation. After draping the instrument arms and camera arm, camera and scope calibration are performed and the endostabilizer is prepared. The room temperature is set for off pump surgery and the use of a warm touch blanket is recommended. Patient positioning is demonstrated in Video 1. A holding arm for the endostabilizer is mounted to the OR table rail on the patient's right side and the operating table is rotated 10 to 15° to raise the patient's left side.
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Video 1 Patient positioning. The patient is placed in a supine position with a small positioning roll placed caudal of the left scapula to lift the thorax and drop the left shoulder. The patient is draped in a way to allow for standard sternotomy and saphenous vein harvesting or a left lateral minithoracotomy if required. To the left the patient is draped to allow access to the lower axillary line for port placement.
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After single right-lung ventilation is initiated the camera port is placed in the 5th intercostal space 2 cm medial of anterior axillary line. CO2-insufflation is begun for adequate visualization and to create working space, as hemodynamically tolerated. Although insufflation pressures in the range of 10–12 mmHg are usually well tolerated, an increase in right ventricular filling pressures, a decrease of intrathoracic blood volume index and right ventricular ejection fraction is to be expected. As a result, cardiac output and blood pressure may decrease despite a compensatory increase in heart rate.
A 30° scope angled up is inserted and the thoracic cavity is scanned for anatomical landmarks and to exclude the presence of adhesions. The surgical cart is then brought to the table and the camera attached to the central arm. Under direct vision, the right instrument port is placed in the third intercostal space medial to anterior axillary line (Video 2), the left instrument port is placed in the seventh intercostal space medial to anterior axillary line (Videos 3 and 4).
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Video 2 The right instrument port is created in the third intercostal space medial to the anterior axillary line. Insertion of the trocar is monitored by endoscopic vision.
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Video 3 The left instrument port is placed in the seventh intercostal space medial to the anterior axillary line. To avoid any external collisions, all anesthesia equipment is mounted distant to the patient. Depending on the individuals physiognomy ports are created in a flat triangle (with the central camera port placed a little bit lower than the two instrument ports) or in an almost linear fashion following the anterior axillary line.
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Video 4 External view of the telemanipulation system with optimal joint setup for LITA harvesting. The ideal position for the setup joints of the instrument arms is 90° between the primary and secondary axis (‘shoulder’) and 45° between the secondary and tertiary axis (‘elbow’). For the camera arm, the net-sum of angles should be 0° resulting in straight alignment of the scope and the central column. With this setup there should be no necessity to move the setup joints during the procedure. The remote centers should be placed correctly within the ports to provide the highest precision and lowest friction.
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The instrument arms are centered for optimal range of motion, by adjusting the respective setup joints, and the instruments are inserted. The instruments are moved along the entire length of ITA to evaluate for external collisions between patient's body and instrument arms; instrument arms and camera arm. Variations in body habitus may alter port location. Before dissection of the left internal thoracic artery (LITA) the anatomic structures are identified (Video 5).
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Video 5 Anatomic landmarks such as the phrenic nerve and the subclavian artery are easily identified.
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LITA take-down starts by retracting and incising the facia immediately covering the LITA with low power monopolar cautery (Video 6).
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Video 6 Start of LITA dissection by splitting the intrathoracic fascia.
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The LITA is always in view while bluntly dissecting off the anterior thoracic wall moving from the lateral to medial edge keeping a pedicle without the facia (Video 7).
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Video 7 Splitting of the fascia frees the LITA and facilitates dissection.
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A small pedicle is kept intact by keeping the lateral veins. Getting into and following the correct tissue plane minimizes the cautery required (Video 8).
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Video 8 After splitting the fascia, the lateral edge of the pedicle is developed and side branches are cut using low energy cautery.
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Using this method, the path of the LITA is always known. A small section of medial pedicle edge is left attached at the level of the fourth rib (Video 9).
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Video 9 After LITA dissection is completed the graft is left attached to the chest wall at the level of the fourth rib to minimize interference with later steps during the procedure such as pericardiotomy or insertion of the stabilizer.
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The precision of the instruments does also allow for a skeletonizing take-down technique. Dissection is usually performed from the first intercostal space to the level of the bifurcation. Side branches may be clipped or cauterized. The pedicle is not detached from the chest wall until the anastomosis is finally performed to avoid torsion of the graft and any interference during pericardiotomy. The next step is pericardial lipectomy (Video 10).
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Video 10 Epicardial fat is removed beginning medially by taking down the mediastinal attachments. Care must be taken to avoid injury of the phrenic nerve.
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The mediastinal and diaphragmatic attachments of the pericardium are bluntly dissected to allow the pericardial sac to drop and to facilitate insertion of the endostabilizer later during the procedure. The pericardiotomy is performed with a longitudinal incision in the pericardium over the suspected course of the left anterior descending artery (LAD) as shown in Video 11.
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Video 11 The pericardium is opened longitudinally. Care must be taken not to extend the pericardiotomy too far laterally over the apex as the heart may drop out of the pericardial sac.
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Identification of the LAD is facilitated by identifying anatomical landmarks such as the apex of the heart, the groove between the medial aspect of the left atrial appendage and pulmonary artery and the ventricular septum that can be identified by differences in the contractile pattern of the right and left ventricles. The ideal site for the anastomosis is then determined by absence of visible atheromatous plaques and avoiding proximity to bifurcations (Video 12).
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Video 12 Initial identification of the LAD. Note that range of motion is tested in the anastomotic region to ensure freedom from collisions or singularities and to allow for set up changes at this point if required.
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It may be necessary to flip the endoscope from 30°, angled up to 30°, angled down to enhance visualization (Video 13).
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Video 13 After changing from 30° angled up to a 30° angled down view, better visualization of the LAD is achieved.
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At this time, the ideal length of the graft can be assessed. The distal end is then prepared for the anastomosis. This is done leaving the concomitant veins intact to provide counter traction during LITA preparation and keep the orientation of the graft. The distal end of the LITA is skeletonized and the concomitant veins are clipped (Video 14).
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Video 14 In-situ dissection of the distal end of the LITA in preparation for the anastomosis. It is of utmost importance to free the distal end (up to 2 cm) of all adventitial tissue to facilitate suturing.
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After heparinization (an ACT of 300 s is recommended) a vascular clamp is placed approximately 2 cm proximal to the transection site (Video 15).
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Video 15 Placement of a vascular clamp on ITA pedicle. The clamp may be attached to the chest wall in order to provide additional counter traction and to facilitate exposure of the graft during the initial stitches for the anastomosis.
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The LITA is clipped distally and cut and spatulated in preparation for the anastomosis (Video 16). Graft patency is confirmed by briefly releasing the vascular clamp (Video 17).
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Video 16 In-situ spatulation of the distal ITA. Markers on the scissors allow for assessment of the length of the cut.
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Video 17 Flow check of ITA (wide angled view). In case of insufficient flow, the procedure should be converted. Further endoscopic manipulation of a graft with insufficient flow is not recommended.
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The LITA pedicle is left attached to the chest wall so as to keep the orientation of the graft until the anastomosis is performed. A 12-mm subxyphoid cannula is inserted under endoscopic vision (Schematic 1). Before introduction of the endostabilizer, temporary silastic occlusion tapes and a 7-cm 7-0 double-armed Prolene suture are inserted and stored in the mediastinum. The endostabilizer – MMCTSLink 91 – is then introduced under endoscopic vision (Video 18).
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Video 18 Insertion of stabilizer through a subxyphoidal port.
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The left instrument arm may be removed to provide more access during this portion and re-docked to the cannula after the holding arm is attached to the endostabilizer. The patient side surgeon positions the endostabilizer above the LAD target site and locks the position of the holding arm. Vacuum lines and an irrigating saline line are connected and the multilink irrigator is advanced into the field of view. The console surgeon then positions the stabilizer feet parallel to the LAD target site. After suction is applied, the feet are locked into position (Video 19). The irrigation tube is placed in proximity to the anastomotic site (Video 20).
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Video 19 Placement of stabilizer. It is important to follow a sequel where first the stabilizer is attached loosely on the epicardium using suction only. The stabilizer pads should have an equal distance and run parallel to the LAD. Only then the stabilizer is locked into position.
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Video 20 Set up of internal irrigator. Flushing is performed by the table side surgeon upon request.
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After blunt dissection of the anastomotic target site (Video 21), the silastic tapes are placed proximal and distal to the anastomotic site (Videos 22 and 23). The silastic tapes are then tightened and the LAD is occluded (Video 24).
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Video 21 Blunt dissection of the LAD. Within the anastomotic region the target vessel should be free of adventitial tissue.
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Video 22 Placement of proximal silastic occlusion tape. After the epicardium has been cut superficially with the blunt knife, the dull needle is placed with minimum force through the underlying muscle.
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Video 23 Placement of distal silastic occlusion tape. Care must be taken to leave enough space (2 cm) between the two occlusion tapes.
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Video 24 The LAD is occluded by lowering the self-locking plate onto the vessel and anchoring the silastic tape. Readjustments may become necessary after arteriotomy.
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Using a 15° sharp blade the arteriotomy is performed (Video 25) and enlarged with EndoWrist® Potts scissors (Video 26) (MMCTSLink 92).
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Video 25 Incision of the LAD. The initial incision should be very limited to allow control of residual bleeding from septal branches or incomplete vascular occlusion. Spots of visible atheroma should be avoided.
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Video 26 Enlargement of arteriotomy using scissors is recommended.
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At this point a shunt may be introduced. However, this requires release of the occlusion tapes and is therefore not recommended. Transection of the LITA is completed at this time and the graft is brought in close proximity of the target site (Video 27).
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Video 27 The LITA pedicle is transected and approximated to the anastomotic site. If graft length is critical a stay suture to the epicardium may prevent excess tension at the anastomotic site.
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A detailed description of the preferred anastomotic technique is outlined in Schematics 2,3,4,5,6,7,8,9. The anastomosis is best performed by beginning at the middle of the medial wall (12 o'clock position) suturing inside-out on the LITA and outside-in on the LAD towards and around the heel. This way, there is less resistance for needle penetration through graft tissue (Video 28).
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Schematic 2 Anastomotic technique.
With the proximal aspect of the coronary artery to the right, the anastomosis is started with the first stitch inside-out of the ITA back-wall and outside-in on the coronary artery at the 12 o'clock position (Courtesy of Intuitive Surgical).
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Schematic 3 Anastomotic technique.
The second needle is anchored in the epicardium to maintain tension on the suture. The suturing is continued using the first needle towards the heel. Magnification may lead to inadequate spacing; as with conventional anastomotic techniques, 12 stitches are usually sufficient for a robotic anastomosis (Courtesy of Intuitive Surgical).
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Schematic 4 The anastomosis is continued around the heel to the 5 o'clock position (ITA inside-out, coronary artery outside-in). The first needle is then secured in the epicardium to maintain suture tension (Courtesy of Intuitive Surgical).
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Schematic 5 Anastomotic technique.
(A) With the second needle the anastomosis is continued towards the toe going outside-in on the ITA and inside-out on the coronary artery (B) around the toe and onto the 5 o'clock position (C) where the sutures meet (Courtesy of Intuitive Surgical).
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Schematic 6 Anastomotic technique.
The suture is tensioned by pulling on the tails of the suture ensuring that the back wall of the suture is tensioned adequately (Courtesy of Intuitive Surgical).
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Schematic 7 Anastomotic technique.
It is helpful to leave a small tail of suture with the needle to facilitate needle removal (Courtesy of Intuitive Surgical).
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Schematic 8 Anastomotic technique.
When the suture is properly tensioned and formed the anastomosis is finished by tying the knots (Courtesy of Intuitive Surgical).
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Schematic 9 Anastomotic technique.
Finally, the vascular clamp is released (Courtesy of Intuitive Surgical).
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Video 28 Construction of the anastomosis is done in a standard fashion.
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The anastomosis is completed using the second needle going inside-out on the LAD and outside-in on the LITA around the toe (Video 29).
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Video 29 Anastomosis toe stitches. During suturing it is important to tension the suture after each stitch in order to avoid anastomotic leakage.
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Care has to be taken to continuously tension the suture. After the needles are broken off, an instrument knot is tied (Video 30).
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Video 30 Knot tying should be performed after breaking the needles. Since there is only limited tactile feedback, visual control is of utmost importance.
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The occlusion tapes and the vascular clamp are released and evacuated through an instrument port. The pedicle may be fixed to the epicardium by stay sutures. For graft patency control transient time Doppler flow measurements can be performed endoscopically if a probe without handle is available. This probe can be advanced through the stabilizer port. Alternatively, intraoperative angiography has been performed using a mobile angio-unit. The quality of these angiograms may however vary. We still perform post-operative standard angiography on all patients within a few days after surgery to ensure patency of the graft. More recently, epicardial endoscopic ultrasound has been suggested for quality control in TECAB. This technique may not only be helpful to determine the quality and the flow through the anastomosis but may serve as a valuable tool for identifying the best location for the anastomotic site on the target vessel in the absence of haptic feedback. Endoscopic high frequency echo probes are, however, not widely available yet.
After pleural effusion is drained under vision, the stabilizer and instruments are withdrawn and the left lung is ventilated (Video 31). A chest tube is inserted through one of the port holes, all other holes are closed and protamine is given.
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Video 31 Finished anastomosis and stabilizer removal (stabilizer unlocking and removal).
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In case a four-arm system is used, the fourth arm is introduced after harvesting of the LITA in the third intercostal space in the anterior axillary line. It may be used to provide counter traction during epicardial fat removal, pericardiotomy and to present the pedicle during the anastomosis.
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Results
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The TECAB procedure is performed infrequently. Initially it was performed on the arrested heart using the Port-Access (MMCTSLink 93) with femoro-femoral bypass, endoaortic balloon clamping and cardioplegic arrest. CPB time and cross-clamp time were in the range of 80–120 and 40–60 min, respectively. The reported patency rate for the TECAB procedure on the arrested heart ranged from 95 to 100% prior to discharge and 96% at 3 months follow-up angiography [1,2]. It was demonstrated in these initial series, that equal patency rates as compared to standard bypass procedures could be achieved endoscopically in selected patients. However, operating times were in the range from 4 to 6 h for a single bypass graft. In a more recent multicenter analysis angiographic patency rate was 98.2% (61/62) and the conversion rate was 23% (27/111), mostly related to problems with the Port-Access system or peripheral cannulation.
Endoscopic coronary artery bypass grafting on the beating heart is technically more challenging [3,4]. In a multicenter registry the data of five centers were accumulated. Based on an intention-to-treat the conversion rate (elective conversion to a MIDCAB procedure) was 33% (37/117). Conversions were mostly due to the inability to locate or dissect the LAD, calcified target vessels and rarely other conditions such as arrhythmia or hemodynamic instability. In most centers take-down of the LITA is now a routine procedure that can be performed in 30 to 40 min and is comparable to the times required in MIDCAB procedures. Time is lost for setting up the stabilizer and preparing the anastomotic area. LAD occlusion times are usually in the range of 25–40 min and thus exceed those reported for MIDCAB procedures. Operating times for a beating heart TECAB procedure thus range from 2.5 to 3.5 h in most centers. The patency rates for completed beating heart TECAB procedures are in the range of 92–94% (Photo 1). In our own experience the relatively long LAD occlusion times have not resulted in an increase of cardiac enzymes postoperatively as compared to MIDCAB or OPCAB.
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Photo 1 Post-operative angiogram demonstrating patent LIMA to LAD graft after TECAB on the beating heart.
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It can be concluded that the use of telemanipulation systems is safe, and allows for true endoscopic coronary artery bypass grafting. The use of the systems is currently restricted to a few indications (single vessel bypass grafting of the LAD, occasionally double vessel grafting) but it is conceivable that it may be used for endoscopic multi-vessel procedures in the near future [5]. Ergonomic man-machine interfaces and multi-level servo controlling allow for precise tissue handling despite the lack of fine tactile feedback.
However, operating times are still long and conversions to MIDCAB or open surgery are frequently necessary. A number of steps that occur between ITA take-down and performing the anastomosis are challenging due to the lack of assistance, limited space, the lack of fine tactile feedback and a limited number of instruments. Among the difficulties are the handling of excessive epicardial fat, determination of the optimal site for an anastomosis, target vessel calcification, and back-bleeding from septal branches. In addition, difficulties with positioning of the stabilizer or incomplete immobilization, render beating heart closed chest bypass grafting difficult. A low threshold for conversion is mandatory to avoid any risk for the patient. Elective conversion is safe and should not be considered a failure.
As with all new technologies, a learning curve has to be overcome and a structured training is considered essential for the procedural success. This includes a principal understanding of the system architecture of telemanipulation systems and the underlying human–machine interface technology. A team approach is crucial for success and it is important that the table side surgeon understands the basic mechanisms of joint motion of the manipulators in order to provide a setup that allows an unrestricted range of motion. Take-down of the ITA should be routinely accomplished, before aiming at a complete TECAB procedure.
With refinements in telemanipulator technology, the development of adjunct devices to enhance exposure and the fast developments in image guidance, the technique of computer enhanced endoscopic cardiac surgery will further evolve and may prove beneficial for selected patients. The application of multi-modal 3D imaging and computational modeling of the range of motion of the robotic arms in an individual patient data-set may optimize preoperative planning of the procedure [6]. New devices for facilitated anastomosis may facilitate endoscopic coronary artery bypass grafting in the future [7].
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References
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- Falk V, Diegeler A, Walther T, Bannusch J, Bucerius J, Raumans J, Autschbach R, Mohr FW. Total endoscopic coronary artery bypass grafting. Eur J Cardiothorac Surg 2000;17:38–45.[Abstract/Free Full Text]
- Dogan S, Aybek T, Andresen E, Byhahn C, Mierdl S, Wetpahl K, Matheis G, Moritz A, Wimmer-Greinecker G. Totally endoscopic coronary artery bypass grafting on cardiopulmonary bypass with robotically enhanced telemanipulation: report of forty-five cases. J Thorac Cardiovasc Surg 2002;123:1125–1131.[Abstract/Free Full Text]
- Kappert U, Cichon R, Schneider J, Gulielmos V, Tugtekin SM, Matschke K, Schramm I, Schüler S. Closed chest coronary artery bypass surgery on the beating heart with the use of a robotic system. J Thorac Cardiovasc Surg 2000;120:809–811.[Free Full Text]
- Falk V, Diegeler A, Walther T, Jacobs S, Raumans J, Mohr FW. Total endoscopic off-pump coronary artery bypass grafting. Heart Surg Forum 2000;3:29–31.[Medline]
- Stein H, Cichon R, Wimmer-Greinecker G, Ikeda M, Hutchinson D, Falk V. Totally endoscopic coronary artery bypass surgery using the da Vinci surgical system: a feasibility study on cadaveric models. Heart Surg Forum 2003;6:E183–190.[Medline]
- Falk V, Mourgues F, Adhami L, Jacobs S, Thiele H, Nitzsche S, Mohr FW, Coste-Manière E. Cardio navigation-planning, simulation and augmented reality in robotic assisted endoscopic bypass grafting. Ann Thorac Surg 2005;79:2040–2048.[Abstract/Free Full Text]
- Falk V, Walther T, Stein H, Jacobs S, Walther C, Rastan A, Wimmer-Greinecker G, Mohr FW. Facilitated endoscopic beating heart coronary bypass grafting using a magnetic coupling device. J Thorac Cardiovasc Surg 2003;126:1575–1579.[Abstract/Free Full Text]
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Summary
Introduction