Ann Thorac Surg 2006;81:455-459
© 2006 The Society of Thoracic Surgeons
Original article: General thoracic
Experience With the "Da Vinci" Robotic System for Thymectomy in Patients With Myasthenia Gravis: Report of 33 Cases
Federico Rea, MD
a
,
*
,
Giuseppe Marulli, MD
a
,
Luigi Bortolotti, MD
a
,
Paolo Feltracco, MD
b
,
Andrea Zuin, MD
a
,
Francesco Sartori, MD
a
a Division of Thoracic Surgery, University of Padua, Padua, Italy
b Division of Anesthesiology, University of Padua, Padua, Italy
Accepted for publication August 22, 2005.
* Address correspondence to Dr Rea, Division of Thoracic Surgery, University of Padua, Via Giustiniani, 2-35128 Padua, Italy (Email: federico.rea{at}unipd.it).
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Abstract
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BACKGROUND: Our initial experience in applying robotic-assisted technologies for the treatment of myasthenia gravis (MG) in patients without thymoma is reported.
METHODS: from April 2002 to October 2004, 33 patients (24 females and 9 males; mean age, 41 years), with clinical nonthymomatous myasthenia gravis, underwent robotic thoracoscopic thymectomy using the "da Vinci" (Intuitive Surgical, Inc, Mountain View, CA) system and adopting a 3 port, left-sided approach.
RESULTS: Mean operative time was 120 minutes. No intraoperative complications or surgical mortality is reported and postoperative complications occurred in two patients (6%). Mean hospital stay was 2.6 days (range, 2–14 days). Histologic analysis of surgical specimens revealed 23 hyperplasia, 4 normal thymus, 4 atrophy, and 2 thymomas; in 12 patients (36.3%) ectopic thymic tissue was found. Follow-up evaluation of the first 24 patients (mean, 23.8 months; range, 12–31 months) showed that 4 patients (16.7%) had complete remission and 18 (75%) had significant clinical improvement for a global benefit rate of 91.7%.
CONCLUSIONS: In patients with MG, robot-assisted thymectomy can be performed safely and efficiently. The improved visualization and dexterity of this instrument and its advanced technology may facilitate the minimally invasive approach to the thymus. We prefer to use the left-sided approach because it provides an enhanced visualization of the aortic window and it reduces the probability of phrenic nerves injury. A longer follow-up is necessary to verify long-term clinical results.
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Introduction
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Myasthenia gravis (MG) is an autoimmune disease that affects neuromuscular transmission and determines chronic weakness and fatigue at various levels of the striated muscles. Symptoms range from ocular disturbances characterized by ptosis and diplopia, to mild, moderate, or severe generalized weakness involving respiratory muscles in the final stage. The thymus gland seems to have an important function in the complex pathogenesis of this disorder as it is implicated in mechanisms of self-tolerance and autoimmunity. Since 1941, when Blalock and colleagues [1] first reported results of transsternal thymectomy in patients affected by MG, thymectomy has had a significant role in the treatment of MG. Though thymectomy is currently a widely accepted therapeutic option in the integrated management of MG, the selection of patients, the extent of thymic resection, and the surgical approach remain controversial [2]. A number of techniques can be used to remove the thymus. They range from the basic transsternal thymectomy [3] to the more aggressive extended transcervical and transsternal maximal thymectomy [4], the transcervical approach alone [5], and the video-assisted thoracoscopic approach [6, 7]. When compared, each approach has its benefits and drawbacks. Less common approaches include a partial sternotomy (involving either the upper [8] or lower [9] sternum), the bilateral thoracoscopic approach combined with a cervical incision (video-assisted thoracoscopic extended thymectomy [VATET]) [10], and the transcervical-subxifoid-videothoracoscopic "maximal" thymectomy [11]. Our past experience encompasses the following approaches: the basic transsternal thymectomy, transcervical thymectomy, and video-assisted thoracoscopic surgery. Recently, our institution purchased the da Vinci robotic system (Intuitive Surgical, Inc, Mountain View, CA), enabling us to develop a program of video-assisted robotic thymectomy in patients with MG without thymoma.
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Material and Methods
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From April 2002 to October 2004 at the Division of Thoracic Surgery in Padua, 33 patients affected by MG underwent a left-sided thoracoscopic thymectomy using the da Vinci robotic system. Diagnosis of MG was based on clinical criteria and one or more of the following finds: the results of electromyography, of edrophonium chloride (Tensilon; ICN Pharmaceuticals, Inc, Costa Mesa, CA) test, and the dosage of circulating acetylcholine receptor antibodies. Preoperative evaluation included neurologic assessment, chest radiogram, and computed tomography (or magnetic resonance in selected patients), electrocardiogram, and spirometry. Preoperative clinical severity of MG was described according to the Osserman classification [12] (Table 1), while postoperatively the De Filippi classification [13] (Table 2) was used to establish the clinical and therapeutic changes after surgery. Both evaluations were conducted by a team of neurologists. Preoperative preparation included a reduction or an interruption of steroid treatment whenever possible; plasmapheresis was used in patients at risk of postoperative respiratory failure (involvement of respiratory muscles or recent worsening of symptoms). All procedures were carried out by a single surgeon (FR), with extensive video-assisted thoracic surgery (VATS) experience and specialized training in robot-assisted surgery, and by a selected team (assistant doctor, nurses, and a mechanical engineer) qualified in robotic surgery. Informed consent was obtained from human subjects.
Surgical Technique
Surgery was performed in the following manner. The patient was under general anesthesia and had a double-lumen endotracheal tube for selective single lung ventilation during the time of operation. The patient is positioned left side up at a 30-degree angle with a bean bag. A camera port for the three-dimensional 0-degree stereo endoscope is introduced through a 15 mm incision in the fifth intercostal space on the midaxillary line and two additional thoracic ports are inserted; one in the third intercostal space on the midaxillary region and another in the fifth intercostal space on the midclavicular space. Two arms of the da Vinci system are then attached to the two access points and another arm is attached to the port-inserted endoscope. The left arm has an EndoWrist (Intuitive Surgical) instrument that grasps the thymus; the right arm has an Endo-dissector device (Intuitive Surgical) with electric cautery function used to perform the dissection. During surgery the hemithorax was inflated through the camera port with CO2 ranging in pressure from 6 to 10 mm Hg. The dissection starts inferiorly at the left pericardiophrenic angle and continues along the anterior border of the phrenic nerve. All anterior mediastinal tissue, including fat, is isolated from the phrenic nerve. The left inferior horn of the thymus is then located and dissected from the pericardium. Subsequently, the thymic gland is separated from the retrosternal area until the right mediastinal pleura and the right inferior horn are found. At this point, the lower part of the thymus is mobilized upwards, the left innominate vein is identified, and the dissection continues along the border of the innominate vein up to the point where the thymic veins are identified, clipped, and divided. The dissection continues upward to the neck until the superior horns are identified and divided from the inferior portion of the thyroid gland by a blunt dissection. The thymus gland, the anterior mediastinal, and the neck fatty tissue are resected radically and the specimen is placed in an Endobag (Espire Medical Ltd, Clevedon, North Somerset, Great Britain) so that it can be removed through trocar incision. After the hemostasis, a 28F drainage tube is inserted through the port of the fifth intercostal space, the lung is reinflated, and the other wounds are closed. The patient is extubated in the operating room and, after an adequate period of observation, returns to the floor of the surgical thoracic ward. The chest drainage tube is removed 24 hours after surgery and, if neurologic evaluation is satisfactory, the patient is discharged 48 to 72 hours after surgery.
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Results
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There were 24 (72.7%) female and 9 (27.3%) male patients; mean age at the time of operation was 41 years (range, 14 to 73 years) and mean duration of symptoms was 20 months (range, 2 to 120 months). Seven (21.2%) patients had preoperative treatment with plasmapheresis as they were at high risk of developing postoperative respiratory failure. The preoperative characteristics of patients are reported in Table 3. Mean operative time was 120 minutes (range, 60 to 240 minutes) and all patients were extubated in the operating room within 1 hour from surgery. Surgery took longer in the early stages of our experience and in the cases where patients had an increased amount of perithymic fatty tissue induced by a prolonged preoperative steroid therapy. No intraoperative mortality or complications were experienced; no conversion to median sternotomy and no extra accesses were required. Postoperative complications occurred in two cases (6%): one patient, in our early experience, had a Chilothorax on the second postoperative day and required long hospitalization (two weeks) to have conservative treatment; another patient had a hemothorax caused by bleeding from one access, which also required conservative treatment. Mean time of hospitalization after surgery was 2.6 days (range, 2 to 14 days). Pathologic examination yielded the following results: 23 patients (69.7%) had thymic hyperplasia, 4 patients (12.1%) had atrophic thymus, 4 patients (12.1%) had a normal thymus, and 2 patients (6.1%) had a small (< 2 cm), well-encapsulated thymoma (stage I by Masaoka classification, type A and type AB by the World Health Organization histologic classification, respectively).
The mean weight of the specimens (thymus and perithymic tissue) was 53.6 grams (range, 22 to 155 grams). Evidence of the ectopic thymic tissue located in the mediastinal fat was found in 12 patients (36.3%). Clinical results were evaluated in those patients with at least 1 year of follow-up (24 patients). Mean follow-up was 23.8 months (range, 12 to 31 months). Short-term results showed a complete remission (class 1) in 4 patients (16.7%) who experienced an absence of symptoms and required no medication; clinical improvement (class 2 and 3) was seen in 18 patients (75%) with fewer symptoms and/or requiring less medication than prior to surgery. After thymectomy, there was no change in clinical outcome (class 4) in two patients (8.3%) and no patient worsened (class 5) in clinical status. Global improvement rate of thymectomy (class 1, 2, 3) reached 91.7% (Table 4). One patient with ectopic thymic tissue had complete remission, 8 patients had clinical improvement, while 2 patients had no changes.
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Comment
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In MG, thymectomy has proven to be a widely accepted therapeutic option in adjunct to medical management, yielding positive results in terms of improvement and remission of symptoms. Numerous thymectomy techniques [3–11] have been proposed and published depending on the different degree of invasiveness, generating the existing controversies as to which is the best surgical approach for this disease. In recent years, advances in endoscopic and minimally invasive surgical techniques have made thymectomy possible. They have also reduced patient morbidity and mortality, infection rate, postoperative hospital stay, and pain medication; moreover, better cosmetic results have led to a greater acceptability of these surgical procedures. Furthermore, results of the more invasive transsternal (classic or extended) approach and the minimally invasive transcervical, VATS, or combined approach are comparable in terms of clinical improvement or remission, thus demonstrating that all methods are effective if the thymectomy is radical and extended to the perithymic tissue. The recent technique of VATS thymectomy has been performed successfully using the left-sided or right-sided approach. This approach combines the advantages of minimally invasive techniques (fewer complications, minimal thoracic trauma, early improved pulmonary function, a shorter recovery period, and optimal cosmetic results) and an excellent view of the anterior mediastinum so that an extended thymectomy can be performed, similar to the one in the transsternal approach. Excellent clinical results, comparable with other techniques, have been attained at intermediate follow-up [7, 14]. Disadvantages of the VATS technique include a two-dimensional view of the operative field and the fact that the arms do not articulate, making it difficult to operate around corners in a fixed three-dimensional space. The development of robotic systems in recent years has made some of these problems surmountable. Lately, robotic systems were also successfully introduced in thoracic surgery for the treatment of various diseases [15, 16], in particular for the disease of the anterior mediastinum. The system is comprised of a device with an intuitive, three-dimensional vision that affords obtaining the best possible view of the operative site; its surgical EndoWrist articulates and rotates 360 degrees, thus improving maneuverability around anatomic structures [17]. In our experience, all of the above-mentioned characteristics make thoracoscopic robot-assisted thymectomy safer and more radical than conventional VATS thymectomy. In fact, in our previous standard VATS experience, we found it particularly difficult to dissect the thymus in the neck region and to reach the perithymic fat in the contralateral hemithorax. In contrast, the current robotic system offers specific advantages over conventional VATS especially in remote and difficult-to-reach areas of the mediastinum. Moreover, the intuitive three-dimensional vision, a scale motion with tremor filtering, and the EndoWrists with articulated movements that permit a full 7 degrees of freedom, make it safer and more comfortable to dissect vascular (anonymous vein) and nervous (phrenic nerve) structures. Our view seems to be in line with other authors [18, 19]. We prefer the left-sided approach proposed by Mineo and colleagues [7] as it offers an enhanced visualization of the aortic window and reduces the probability of phrenic nerve injury. In fact, the left-sided approach offers an excellent view of the left phrenic nerve, while the right phrenic nerve is partially protected by the superior vena cava. Mean operative time can be likened to conventional VATS thymectomy. In fact, after the first few cases that had a longer duration due to the learning curve, the average time of surgery was reduced to approximately 100 minutes. Clinical postoperative results are good considering the short term of mean follow-up (23.8 months). The rates of remission and total improvement are similar to those obtained with the VATS approach [7] and are similar to those obtained with the transsternal approach [3] at the same length of follow-up. These good preliminary results can be explained by the short mean duration of preoperative symptoms (20 months) and the completeness of thymectomy associated with the high percentage of ectopic thymic tissue found in the surrounding mediastinal fat. Various authors [3, 20] point to the fact that better clinical results are obtained from young patients with a short duration of the disease; we believe that the robotic procedure has the advantage of being more easily and readily accepted by both neurologists and young patients as it gives good cosmetic results and is a less invasive approach. Other authors [21–24] highlight the importance of ectopic thymic tissue in the maintenance of disease. In literature the rates of detection of ectopic thymic tissue range from 22% to 39.5% [7, 24]; in our experience this percentage reached 36.3%. The initial fixed cost of the system represents its major drawback, but we believe this cost to be justified if the robotic device is used in several different surgical sectors. Another disadvantage of robotic surgery is its current lack of tactile feedback, but this is compensated by the superior image of the three-dimensional camera. Even the learning curves associated with robotic technology could be considered a disadvantage but learning curves are part of any new technology. In conclusion, our experience has demonstrated the feasibility of this minimally invasive technique. The three-dimensional view and high dexterity of robotic surgical instruments make robotic thymectomy safer than conventional VATS, and equally radical and less invasive than the transsternal approach. We prefer the left-sided approach because it allows enhanced visualization of the aortic window and reduces chances of phrenic nerve injury. Additionally, the minimal cosmetic damage produced and the short hospitalization render this type of surgery more acceptable for patients. Disadvantages of this approach include the initial high costs of the robotic system, early increased operative time, and learning curves associated with robotic technology. An accurate follow-up is necessary to verify long-term clinical results, but this innovative procedure could become one of the most appropriate techniques for thymectomy in MG patients.
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Requirements for Recertification/Maintenance of Certification in 2006
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Diplomates
of the American Board of Thoracic Surgery who plan to participate in
the Recertification/Maintenance of Certification process in 2006 must
hold an active medical license and must hold clinical privileges in
thoracic surgery. In addition, a valid certificate is an absolute
requirement for entrance into the recertification/maintenance of
certification process. if your certificate has expired, the only
pathway for renewal of a certificate is to take and pass the Part I
(written) and the Part II (oral) certifying examinations.
The American Board of Thoracic Surgery will no longer
publish the names of individuals who have not recertified in the
American Board of Medical Specialties directories. The Diplomate's
name will be published upon successful completion of the
recertification/maintenance of certification process.
The CME requirements are 70 Category I credits in either
cardiothoracic surgery or general surgery earned during the 2 years
prior to application. SESATS and SESAPS are the only self-instructional
materials allowed for credit. Category II credits are not allowed. The
Physicians Recognition Award for recertifying in general surgery is not
allowed in fulfillment of the CME requirements. Interested individuals
should refer to the Booklet of Information for a
complete description of acceptable CME credits.
Diplomates should maintain a documented list of their
major cases performed during the year prior to application for
recertification. This practice review should consist of 1 year's
consecutive major operative experiences. If more than 100 cases occur
in 1 year, only 100 should be listed.
Candidates
for recertification/maintenance of certification will be required to
complete all sections of the SESATS self-assessment examination. It is
not necessary for candidates to purchase SESATS individually because it
will be sent to candidates after their application has been
approved.
Diplomates may recertify the year
their certificate expires, or if they wish to do so, they may recertify
up to two years before it expires. However, the new certificate will be
dated 10 years from the date of expiration of their original
certificate or most recent recertification certificate. In other words,
recertifying early does not alter the 10-year validation.
Recertification/maintenance of certification is also open
to Diplomates with an unlimited certificate and will in no way affect
the validity of their original certificate.
The
deadline for submission of applications for the
recertification/maintenance of certification process is May 10 each
year. A brochure outlining the rules and requirements for
recertification/maintenance of certification in thoracic surgery is
available upon request from the American Board of Thoracic Surgery, 633
N St. Clair St, Suite 2320, Chicago, IL 60611; telephone:
(312) 202-5900; fax: (312) 202-5960; e-mail: mailto:info{at}abts.org.
This booklet is also published on the website: www.abts.org.
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References
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Top
Abstract
Introduction
