Gen Thorac Cardiovasc Surg (2014) 62:342–350 DOI 10.1007/s11748-014-0398-6
CURRENT TOPICS REVIEW ARTICLE
Minimally invasive surgery of mitral valve (MIS-MV) Mikihiko Kudo • Ryohei Yozu
Received: 6 December 2013 / Published online: 11 April 2014 Ó The Japanese Association for Thoracic Surgery 2014
Abstract Following the revision of the therapeutic guideline of ACC/AHA in (Circulation 114:450–527, 2006), the incidence of mitral valve repair in asymptomatic patients with moderate or severe mitral valve regurgitation has increased. For mitral valve repair, the quality and outcomes as well as lower invasive procedure are important to obtain the confidence of cardiologists and ensure request of early phase operation from cardiologists. With recent innovations of technologies and the development of revolutionary techniques, minimally invasive surgery of the mitral valve (MIS-MV) has become a widespread surgical option of mitral valve repair. It is vital, however, that careful preoperative assessment, and planning of the approach and perfusion strategy are put in place to perform MIS-MV safely. Keywords Minimally invasive cardiac surgery Mitral valve repair Right minithoracotomy Minimally invasive surgery of mitral valve (MIS-MV)
Introduction Conventional cardiac surgery generally entails exposure of the heart and great vessels through a median full sternotomy. In contrast, minimally invasive surgery of the mitral valve (MIS-MV) enables surgeons to perform cardiac
This review was submitted at the invitation of the editorial committee. M. Kudo (&) R. Yozu Department of Cardiovascular Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan e-mail: [email protected]
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operations via a substantially smaller incision. The aim of MIS-MV is to promote a more rapid postoperative recovery period, to reduce postoperative pain, and to provide cosmetically patient’s satisfaction [2]. Other general advantages of MIS-MV are that they provide access to the relevant parts of the heart while reducing the need for extensive dissection of surrounding tissue. Current reports indicate that MIS-MV is not inferior to conventional surgery and also provides several advantages as compared with conventional approaches [3]. MIS-MV has begun to accrue popularity over recent years for several reasons, including the prospects of less invasive surgical techniques, faster recovery time, and improved cosmetic results. After 1996, Cohn, Cosgrove, and others were able to perform aortic and mitral valve surgery through smaller incision [4–11]. Concurrently, other evolving technologies such as port-access techniques using endoaortic balloon occluders were developed [12– 14]. Widespread use of these techniques, however, was curtailed due to complexity, and potential complication. In addition, there were concerns regarding safety, and possible inferiority of outcomes as a result of complex operations being performed through limited skin incision [15, 16]. In contrast, MIS-MV continued to progress with various technological innovations. As a result, MIS-MV is increasingly used, and minimally invasive mitral valve repair has now extended to the asymptomatic population following the revision of the ACC/AHA guideline [1] in 2006. For MIS-MV, minimally invasive procedures as well as increased quality of life and postoperative outcomes are important to obtain the confidence of cardiologists and to acquire a request for early phase operation from the cardiologists. Careful preoperative assessment and planning of the approach and perfusion strategy are necessary to perform MIS-MV safely.
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Fig. 1 Sternal incisions for upper sternotomy (a) and lower sternotomy (b). Parasternal incision (c). Right minithoracotomy (d)
Minimally invasive approach to mitral valve In the past, the mitral valve has been approached through a median full sternotomy. Technological innovations in surgical endoscopy, instrumentation, tissue telemanipulation, and cardiopulmonary bypass (CPB) technology have allowed for mitral valve surgery to be performed via progressively smaller incisions including hemithoracotomy and minithoracotomy. Satisfactory exposure, access to CPB, and myocardial protection should be easily achieved in MIS-MV. With the introduction of this technique, the first most common MIS-MV approaches were upper hemisternotomy, lower hemisternotomy and right parasternal.
Partial sternotomy Upper hemisternotomy technique The upper hemisternotomy technique begins via 6–10 cm vertical midline incision over the upper portion of the sternum, starting just above the level of the manubriosternal and angled down towards the level of the third or fourth intercostal space (Fig. 1a). Cannulation of the aorta and right atrium can be performed through this hemisternal incision. After cross-clamping of the aorta, cardioplegia is administrated through the aortic root and/or coronary sinus. The right superior pulmonary vein can then be used for left ventricle (LV) venting. Pericardial stay sutures are applied to elevate the heart and optimize visualization. This technique provides excellent visualization, has good cosmetic results and, does not require
specially designed instruments and retractors. Gillinov et al. [8] have reported excellent results with this technique in 462 patients undergoing MIS-MV. Of those having mitral valve surgery, 87 % had mitral valve repair. Operative mortality was 0.8 %. Conversion to full sternotomy was necessary in 2.4 % cases. Blood use was low with 80 % of patients receiving no blood transfusions. They concluded that all primary mitral procedures can be accomplished safely via partial upper hemisternotomy. Lower hemisternotomy technique The lower hemisternotomy technique is performed via a 10-cm incision beginning at the level of the third intercostal space and extending down to the xiphoid process. There are two different versions of this technique. The sternum can either be ‘T’d’ off at the third interspace or a ‘J’ incision performed by making an incision through the middle of the sternum to the level of the third interspace (Fig. 1b). Following this, the ‘J’ incision continues into the interspace on the right side, sparing the entire left sternal table (Fig. 1c). If the ‘T’ incision is performed, direct aortic cannulation can be facilitated by retracting the upper sternal segment. However, if the ‘J’ incision is performed, arterial cannulation may need to be performed via the femoral artery. As with upper hemisternotomy, this approach facilitates very good visualization, has excellent cosmetic results, and minimal sternal complications. Karagoz et al. [11] reported their results of lower ministernotomy surgery in 54 patients undergoing MIS-MV (mitral valve repair in 17 % of cases) as compared with 11 patients who underwent MIS-MV with the upper ministernotomy technique and 29 patients who underwent mitral valve
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surgery via conventional sternotomy. In their experience, lower ministernotomy was faster than the conventional technique, however, there was no significant difference in outcomes [11]. McClure et al. have reported excellent results in a series of 1000 MIS-MV (lower hemisternotomy was used in 75 % and mitral valve repair in 92 % of cases). They reported that operative mortality was 0.8 %, median hospital stay was 5 days, and the 15-year survival rate was 79 % in this series [17]. In this report, partial sternotomy did not require special operative set-up (patient’s positioning) nor instruments and it was easy to convert to a full sternotomy if necessary [17]. Right parasternal approach The right parasternal approach was one of the first approaches used during the early introduction of minimally invasive aortic valve surgery (Fig. 1d). Cosgrove and Sabik [4] described excellent results with this approach in the late 1990s. This approach was performed using a vertical upper right parasternal incision in which the second, third, and sometimes fourth costal cartilages were removed and the right internal mammary vessels routinely ligated and divided. Cohn, [18], Minale et al. [16] reported low mortality and morbidity rate in this approach. Greelish et al. documented the safety of minimally invasive mitral valve repair in 358 patients with parasternotomy/partial sternotomy. The operative mortality was 0/358 patients. A low Fig. 2 Chitwood clamp (a). Modified Cosgrove flex clamp (b). The arrows indicate the modified point. By grasping with forceps this portion, a manipulation of flexible shaft becomes easier
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incidence of homologous blood use, low requirement for post-hospital rehabilitation, and general morbidity following this approach have also been reported [19]. This approach lost popularity as a result of lung and chest wall herniation. This unfavorable complication often required surgical intervention for mesh closure of the hernia, resulting in other techniques becoming more popular.
Right minithoracotomy approach Following the introduction of various small incisions, right minithoracotomy became the primary approach in current MIS-MV, increasing the popularity of MIS-MV. The right minithoracotomy approach to MIS-MV initially began as a procedure based on the small right minithoracotomy approach with incision through the fourth intercostal space with peripheral cannulation and balloon occlusion of the ascending aorta [20, 21] (Fig. 1e). The femoral artery was used for arterial cannulation with a cannula consisting of a side port to allow an endovascular clamp catheter, to be placed into the ascending aorta. Once occluded, cardioplegia was induced through the end of the catheter or retrograde cardioplegia induced through a coronary sinus catheter which was implanted by an anesthesiologist prior to surgery. Grossi et al. [22] have reported 1-year followup results after mitral valve repair with port-access technology. Both echocardiographic results and New York
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Heart Association functional improvements were compatible with results achieved with the conventional full sternotomy approach [22]. They consequently asserted that minithoracotomy should be more widely adopted. Casselman et al. [23] have reported the results of total endoscopic mitral valve repair using endoaortic balloon occluders developed by themselves. They reported good results and high patient satisfaction [23]. Suri et al. [24] reported a propensity score analysis of early outcomes between a port-access group of patients and conventional full sternotomy patients in mitral valve repair. The port-access group independently predicted a significantly diminished duration of postoperative ventilator support (p = 0.045); however, there were no significant differences in other outcomes including postoperative blood transfusion, reoperation for hemorrhage, or length of stay in hospital [24]. Poisoning of the percutaneous coronary sinus catheter and endoaortic clamp were, however, challenging in the portaccess group. As an alternative to the use of the endoaortic balloon occluders, direct aortic cross-clamping with a long vascular clamp through a stab incision in the second intercostal space was developed as a far safer method (Fig. 2a) [25]. This technology enabled a smaller skin incision; however, adequate training of surgeons specifically in this technique was required. Cross-clamp positioning proved to be occasionally a difficult and challenging technique. The pulmonary artery and left atrial appendage were vulnerable to damage. From these reasons, it is recommended that a
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modified Cosgrove flex clamp, improved by our Department be used (Fig. 2b) [26]. This device easily manipulates a shaft with flexibility for the surgeon and is safely inserted into the same intercostal space of minithoracotomy under the direct surgeon’s vision without the need for other ports through the chest. CPB is established with peripheral cannulation by use of femoral arterial perfusion and bicaval venous drainage via right internal jugular vein and femoral vein. Cardioplegia can be induced directly into the aortic root using an antegrade catheter or retrograde catheter via the coronary sinus. Although the procedure was initially performed under direct vision, visual assistance technology was added using a port in the same intercostal space (Fig. 3a, b, c). This approach provides patients with cosmetic satisfaction following surgery (Fig. 4). Theoretically, sternal wound infection does not occur with right minithoracotomy, which is an advantage of that approach. In contrast, close attention must be paid to the following findings. Maselli et al. [27] evaluated micro-embolic events that can occur during MIS-MV, using a continuous automated intraoperative transcranial Doppler, comparing balloon endovascular aortic occlusion and transthoracic aortic clamping technique. In a low-risk population for embolic events occurrence, they found that endovascular balloon aortic clamping resulted in less micro-embolic signals than transthoracic aortic clamping [27]. As the MIS-MV continues to become more popular, mitral valve repair via right minithoracotomy has evolved. Patracek et al. [28] have reported a case of MIS-MV
Fig. 3 Surgical setting of MISMV (a). Internal jugular cannulation (b). Femoral arterial and venous cannulation (c)
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without aortic cross-clamping for high-risk patients. In this technique, they performed MIS-MV using hypothermic fibrillatory arrest without including cardioplegia, thus significantly simplifying the operation [28]. Galloway et al. [29] have reported their excellent long-term outcomes of mitral valve repair with right minithoracotomy in 1,071 patients. Hospital mortality was low at 1.2 %. Eight-year freedom from reoperation was 91 % for conventional and 95 % for MIS-MV patients (p = 0.24), and for all valverelated complications was 86 % for conventional and 90 % for MIS-MV patients (p = 0.14) [29]. In a recent metaanalysis of 35 studies (including 2 randomized studies) comparing outcomes of mitral valve surgery between right thoracotomy and conventional full sternotomy, there was no difference in 30-day mortality rate between the 2 groups. The right minithoracotomy group had less blood transfusion (1.9 units), shorter ventilation time (2.1 h), shorter ICU stay (0.5 day) and shorter hospital stay (1.6 days). In addition, the right minithoracotomy group had lower incidences of sternal wound infection as compared with conventional group (0.04 vs. 0.27 %) and postoperative atrial fibrillation (18 vs. 22 %). The incidence of 30-day stroke, however, was higher in the right minithoracotomy group than in the conventional group (2.1 vs. 1.2 %) [30]. The right minithoracotomy group also had significantly longer CPB and aortic cross-clamping times (144 vs. 111 and 95 vs. 74 min, respectively) [30]. Seeburger et al. [31] reviewed their 1,230 cases of MISMV for anterior (n = 156), posterior (n = 672), and Fig. 4 Surgical scars of MIMVR in a male patient (upper) and a female patient (lower)
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bileaflet prolapse (n = 402) [31]. Patient repair rate was 94 % and 5-year freedom from reoperation was 96 %. McClure et al. [17] reported that 6 out of 929 MIS-MV cases were intraoperatively converted to mitral valve replacement due to technical failure, and that 15-year freedom from reoperation was 90 %, with 5 and 10 years’ freedom rates from recurrent moderate or severe MR of 87 and 69 %, respectively [17]. Speziale et al. randomized patients with Barlow disease into 2 groups: the directvision with right thoracotomy group and the conventional full sternotomy group. They reported similar successful repair rates and freedom from moderate or severe MR in the mean follow-up period of 12 months [32]. Raanani et al. [33] compared the quality of mitral valve repair for posterior leaflet prolapse between right minithoracotomy and conventional full sternotomy, and showed a trend of increased rate of recurrent moderate or severe MR (18 vs. 9 %) in the minithoracotomy group, although the difference was not statistically significant. In contrast, Suri et al. [34] reported no difference in residual MR rates by intraoperative and early postoperative echocardiography in their propensity-matched comparisons of MIS-MV and conventional mitral valve repair for all prolapse subset.
Robotic mitral valve surgery Advancements in closed-chest CPB and telemanipulation technology have spurred a growing interest within the past
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Fig. 5 Mini-valve system: this system is composed of a minithoracotomy spreader with a tilted blade, a left atrial retractor that moves flexibly, and an additional blade for the posterolateral left atrial wall. A 5 blade size is available depending on the left atrial size
decade in robotic mitral valve surgery. The difficulty is that widespread practice of this technology often requires retraining surgeons who are not familiar with these new and evolving techniques [35]. Chitwood et al. [36] described their results of robotic mitral valve repair in 300 patients with the Da Vinci surgical system (Intuitive Surgical, Inc, Sunnyvale, CA, USA). There were 2 (0.7 %) 30-day postoperative mortalities and 6 (2.0 %) late postoperative mortality. Complications included 2 (0.7 %) stroke, 2 transient ischemic attack, 3 (1.0 %) myocardial infarction, and 7 (2.3 %) reoperation for bleeding. Fiveyear survival was 96.6 %, with 93.8 % freedom from reoperation [36]. In addition, Mihaljevic et al. compared the outcomes of robotic mitral valve repair with those of conventional full sternotomy, partial sternotomy, and right minithoracotomy. They showed that all approach groups had no hospital death and that the robotic group had the shortest hospital stay among the 4 different approach groups [37].
WL Gore & Associates, Inc, Flagstaff, Ariz) sutures for ruptured or elongated chordae tendineae of MV is becoming popular with good long-term results [40]. Both leaflet resection and neochordae construction are effective techniques for MIS-MV. The difficult aspect of chordal replacement is using ePTFE sutures, which are vital in determining the correct length of artificial chorda. Various techniques have been reported in order to solve this problem [41, 42]. For example, Oppell and Mohr [43] reported the ‘loop technique’ in which a premeasured ePTFE chordal loop is made and fixed easily to the prolapsed region of the leaflet. In this manner, broad-range mitral valve repair is possible and it can be revised easily. This technique may be useful through both MIS-MV and conventional approaches, and simplifies chordal replacement in MIS-MV approaches [44, 45]. On the other hand, Macarthur et al. reported nonresectional single-suture leaflet-remodeling technique of inverting the prolapsed or flail segment tissue into the LV [46, 47]. This technique revealed the results equal to the resection-suture technique, thus significantly shortening the time consumed when performing MIS-MV.
Repair technique of MIS-MV Various repair techniques have been proposed in MIS-MV [38]. The gold standard has been the resection-suture technique of the prolapsed leaflet [39]. Chordal replacement with expanded polytetrafluoroethylene (ePTFE) (Gore-Tex;
Innovation for MIS-MV In optimal operative setting for MIS-MV, innovation of instruments including a left atrial retractor is vital. As a
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Fig. 6 Endoscopic view. Prolapsed leaflet (a) and papillary muscle (b). This device moves flexibly to various positions of the surgeon’s choice. MIS-MV with ‘loop technique’(c, d)
previous report [48], our Department developed a novel left atrial retractor system, including a minithoracotomy spreader, a left atrial blade, and an additional retractor for the posterior wall of the left atrium (Fig. 5). The advantage of this system is flexibility. It moves flexibly to various positions, and by retraction of the anterior mitral leaflet toward the anterior wall of the LV, even papillary muscles can be exposed easily and clearly on the straight view through the small working port (Fig. 6a, b). This function enables comfortable manipulation to the papillary muscle in chordal replacement with ‘loop technique’ (Fig. 6c, d). The approaches in MIS-MV vary from direct vision to complete totally endoscopic and robotic surgery. Many surgeons prefer direct-vision approach under the endoscopic assist because those are more accessible and the operating time is shorter than two other methods. In the future, further technological innovation will enable the MIS-MV of less invasive.
Conclusion Avoiding a full sternotomy has been consistently reported to have beneficial effects such as reduced blood
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transfusion, ventilation time, and hospital stay [32–34]. The mastery of skills of the team is necessary for MIS-MV than for conventional approaches. So, not only the surgeons but also all other staff in the operating room must be well trained and familiar with this approaches. Recently, a great deal of innovation has contributed to establishing MIS-MV via right minithoracotomy. New innovative instruments and optimal operating setting in mitral valve repair facilitate both direct-vision and endoscopic assist approaches in complex lesions, thus contributing to the acceptance of MIS-MV as routine surgery. Conflict of interest interest.
The author declares that he has no conflict of
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CURRENT TOPICS REVIEW ARTICLE
Minimally invasive surgery of mitral valve (MIS-MV) Mikihiko Kudo • Ryohei Yozu
Received: 6 December 2013 / Published online: 11 April 2014 Ó The Japanese Association for Thoracic Surgery 2014
Abstract Following the revision of the therapeutic guideline of ACC/AHA in (Circulation 114:450–527, 2006), the incidence of mitral valve repair in asymptomatic patients with moderate or severe mitral valve regurgitation has increased. For mitral valve repair, the quality and outcomes as well as lower invasive procedure are important to obtain the confidence of cardiologists and ensure request of early phase operation from cardiologists. With recent innovations of technologies and the development of revolutionary techniques, minimally invasive surgery of the mitral valve (MIS-MV) has become a widespread surgical option of mitral valve repair. It is vital, however, that careful preoperative assessment, and planning of the approach and perfusion strategy are put in place to perform MIS-MV safely. Keywords Minimally invasive cardiac surgery Mitral valve repair Right minithoracotomy Minimally invasive surgery of mitral valve (MIS-MV)
Introduction Conventional cardiac surgery generally entails exposure of the heart and great vessels through a median full sternotomy. In contrast, minimally invasive surgery of the mitral valve (MIS-MV) enables surgeons to perform cardiac
This review was submitted at the invitation of the editorial committee. M. Kudo (&) R. Yozu Department of Cardiovascular Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan e-mail: [email protected]
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operations via a substantially smaller incision. The aim of MIS-MV is to promote a more rapid postoperative recovery period, to reduce postoperative pain, and to provide cosmetically patient’s satisfaction [2]. Other general advantages of MIS-MV are that they provide access to the relevant parts of the heart while reducing the need for extensive dissection of surrounding tissue. Current reports indicate that MIS-MV is not inferior to conventional surgery and also provides several advantages as compared with conventional approaches [3]. MIS-MV has begun to accrue popularity over recent years for several reasons, including the prospects of less invasive surgical techniques, faster recovery time, and improved cosmetic results. After 1996, Cohn, Cosgrove, and others were able to perform aortic and mitral valve surgery through smaller incision [4–11]. Concurrently, other evolving technologies such as port-access techniques using endoaortic balloon occluders were developed [12– 14]. Widespread use of these techniques, however, was curtailed due to complexity, and potential complication. In addition, there were concerns regarding safety, and possible inferiority of outcomes as a result of complex operations being performed through limited skin incision [15, 16]. In contrast, MIS-MV continued to progress with various technological innovations. As a result, MIS-MV is increasingly used, and minimally invasive mitral valve repair has now extended to the asymptomatic population following the revision of the ACC/AHA guideline [1] in 2006. For MIS-MV, minimally invasive procedures as well as increased quality of life and postoperative outcomes are important to obtain the confidence of cardiologists and to acquire a request for early phase operation from the cardiologists. Careful preoperative assessment and planning of the approach and perfusion strategy are necessary to perform MIS-MV safely.
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Fig. 1 Sternal incisions for upper sternotomy (a) and lower sternotomy (b). Parasternal incision (c). Right minithoracotomy (d)
Minimally invasive approach to mitral valve In the past, the mitral valve has been approached through a median full sternotomy. Technological innovations in surgical endoscopy, instrumentation, tissue telemanipulation, and cardiopulmonary bypass (CPB) technology have allowed for mitral valve surgery to be performed via progressively smaller incisions including hemithoracotomy and minithoracotomy. Satisfactory exposure, access to CPB, and myocardial protection should be easily achieved in MIS-MV. With the introduction of this technique, the first most common MIS-MV approaches were upper hemisternotomy, lower hemisternotomy and right parasternal.
Partial sternotomy Upper hemisternotomy technique The upper hemisternotomy technique begins via 6–10 cm vertical midline incision over the upper portion of the sternum, starting just above the level of the manubriosternal and angled down towards the level of the third or fourth intercostal space (Fig. 1a). Cannulation of the aorta and right atrium can be performed through this hemisternal incision. After cross-clamping of the aorta, cardioplegia is administrated through the aortic root and/or coronary sinus. The right superior pulmonary vein can then be used for left ventricle (LV) venting. Pericardial stay sutures are applied to elevate the heart and optimize visualization. This technique provides excellent visualization, has good cosmetic results and, does not require
specially designed instruments and retractors. Gillinov et al. [8] have reported excellent results with this technique in 462 patients undergoing MIS-MV. Of those having mitral valve surgery, 87 % had mitral valve repair. Operative mortality was 0.8 %. Conversion to full sternotomy was necessary in 2.4 % cases. Blood use was low with 80 % of patients receiving no blood transfusions. They concluded that all primary mitral procedures can be accomplished safely via partial upper hemisternotomy. Lower hemisternotomy technique The lower hemisternotomy technique is performed via a 10-cm incision beginning at the level of the third intercostal space and extending down to the xiphoid process. There are two different versions of this technique. The sternum can either be ‘T’d’ off at the third interspace or a ‘J’ incision performed by making an incision through the middle of the sternum to the level of the third interspace (Fig. 1b). Following this, the ‘J’ incision continues into the interspace on the right side, sparing the entire left sternal table (Fig. 1c). If the ‘T’ incision is performed, direct aortic cannulation can be facilitated by retracting the upper sternal segment. However, if the ‘J’ incision is performed, arterial cannulation may need to be performed via the femoral artery. As with upper hemisternotomy, this approach facilitates very good visualization, has excellent cosmetic results, and minimal sternal complications. Karagoz et al. [11] reported their results of lower ministernotomy surgery in 54 patients undergoing MIS-MV (mitral valve repair in 17 % of cases) as compared with 11 patients who underwent MIS-MV with the upper ministernotomy technique and 29 patients who underwent mitral valve
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surgery via conventional sternotomy. In their experience, lower ministernotomy was faster than the conventional technique, however, there was no significant difference in outcomes [11]. McClure et al. have reported excellent results in a series of 1000 MIS-MV (lower hemisternotomy was used in 75 % and mitral valve repair in 92 % of cases). They reported that operative mortality was 0.8 %, median hospital stay was 5 days, and the 15-year survival rate was 79 % in this series [17]. In this report, partial sternotomy did not require special operative set-up (patient’s positioning) nor instruments and it was easy to convert to a full sternotomy if necessary [17]. Right parasternal approach The right parasternal approach was one of the first approaches used during the early introduction of minimally invasive aortic valve surgery (Fig. 1d). Cosgrove and Sabik [4] described excellent results with this approach in the late 1990s. This approach was performed using a vertical upper right parasternal incision in which the second, third, and sometimes fourth costal cartilages were removed and the right internal mammary vessels routinely ligated and divided. Cohn, [18], Minale et al. [16] reported low mortality and morbidity rate in this approach. Greelish et al. documented the safety of minimally invasive mitral valve repair in 358 patients with parasternotomy/partial sternotomy. The operative mortality was 0/358 patients. A low Fig. 2 Chitwood clamp (a). Modified Cosgrove flex clamp (b). The arrows indicate the modified point. By grasping with forceps this portion, a manipulation of flexible shaft becomes easier
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incidence of homologous blood use, low requirement for post-hospital rehabilitation, and general morbidity following this approach have also been reported [19]. This approach lost popularity as a result of lung and chest wall herniation. This unfavorable complication often required surgical intervention for mesh closure of the hernia, resulting in other techniques becoming more popular.
Right minithoracotomy approach Following the introduction of various small incisions, right minithoracotomy became the primary approach in current MIS-MV, increasing the popularity of MIS-MV. The right minithoracotomy approach to MIS-MV initially began as a procedure based on the small right minithoracotomy approach with incision through the fourth intercostal space with peripheral cannulation and balloon occlusion of the ascending aorta [20, 21] (Fig. 1e). The femoral artery was used for arterial cannulation with a cannula consisting of a side port to allow an endovascular clamp catheter, to be placed into the ascending aorta. Once occluded, cardioplegia was induced through the end of the catheter or retrograde cardioplegia induced through a coronary sinus catheter which was implanted by an anesthesiologist prior to surgery. Grossi et al. [22] have reported 1-year followup results after mitral valve repair with port-access technology. Both echocardiographic results and New York
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Heart Association functional improvements were compatible with results achieved with the conventional full sternotomy approach [22]. They consequently asserted that minithoracotomy should be more widely adopted. Casselman et al. [23] have reported the results of total endoscopic mitral valve repair using endoaortic balloon occluders developed by themselves. They reported good results and high patient satisfaction [23]. Suri et al. [24] reported a propensity score analysis of early outcomes between a port-access group of patients and conventional full sternotomy patients in mitral valve repair. The port-access group independently predicted a significantly diminished duration of postoperative ventilator support (p = 0.045); however, there were no significant differences in other outcomes including postoperative blood transfusion, reoperation for hemorrhage, or length of stay in hospital [24]. Poisoning of the percutaneous coronary sinus catheter and endoaortic clamp were, however, challenging in the portaccess group. As an alternative to the use of the endoaortic balloon occluders, direct aortic cross-clamping with a long vascular clamp through a stab incision in the second intercostal space was developed as a far safer method (Fig. 2a) [25]. This technology enabled a smaller skin incision; however, adequate training of surgeons specifically in this technique was required. Cross-clamp positioning proved to be occasionally a difficult and challenging technique. The pulmonary artery and left atrial appendage were vulnerable to damage. From these reasons, it is recommended that a
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modified Cosgrove flex clamp, improved by our Department be used (Fig. 2b) [26]. This device easily manipulates a shaft with flexibility for the surgeon and is safely inserted into the same intercostal space of minithoracotomy under the direct surgeon’s vision without the need for other ports through the chest. CPB is established with peripheral cannulation by use of femoral arterial perfusion and bicaval venous drainage via right internal jugular vein and femoral vein. Cardioplegia can be induced directly into the aortic root using an antegrade catheter or retrograde catheter via the coronary sinus. Although the procedure was initially performed under direct vision, visual assistance technology was added using a port in the same intercostal space (Fig. 3a, b, c). This approach provides patients with cosmetic satisfaction following surgery (Fig. 4). Theoretically, sternal wound infection does not occur with right minithoracotomy, which is an advantage of that approach. In contrast, close attention must be paid to the following findings. Maselli et al. [27] evaluated micro-embolic events that can occur during MIS-MV, using a continuous automated intraoperative transcranial Doppler, comparing balloon endovascular aortic occlusion and transthoracic aortic clamping technique. In a low-risk population for embolic events occurrence, they found that endovascular balloon aortic clamping resulted in less micro-embolic signals than transthoracic aortic clamping [27]. As the MIS-MV continues to become more popular, mitral valve repair via right minithoracotomy has evolved. Patracek et al. [28] have reported a case of MIS-MV
Fig. 3 Surgical setting of MISMV (a). Internal jugular cannulation (b). Femoral arterial and venous cannulation (c)
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without aortic cross-clamping for high-risk patients. In this technique, they performed MIS-MV using hypothermic fibrillatory arrest without including cardioplegia, thus significantly simplifying the operation [28]. Galloway et al. [29] have reported their excellent long-term outcomes of mitral valve repair with right minithoracotomy in 1,071 patients. Hospital mortality was low at 1.2 %. Eight-year freedom from reoperation was 91 % for conventional and 95 % for MIS-MV patients (p = 0.24), and for all valverelated complications was 86 % for conventional and 90 % for MIS-MV patients (p = 0.14) [29]. In a recent metaanalysis of 35 studies (including 2 randomized studies) comparing outcomes of mitral valve surgery between right thoracotomy and conventional full sternotomy, there was no difference in 30-day mortality rate between the 2 groups. The right minithoracotomy group had less blood transfusion (1.9 units), shorter ventilation time (2.1 h), shorter ICU stay (0.5 day) and shorter hospital stay (1.6 days). In addition, the right minithoracotomy group had lower incidences of sternal wound infection as compared with conventional group (0.04 vs. 0.27 %) and postoperative atrial fibrillation (18 vs. 22 %). The incidence of 30-day stroke, however, was higher in the right minithoracotomy group than in the conventional group (2.1 vs. 1.2 %) [30]. The right minithoracotomy group also had significantly longer CPB and aortic cross-clamping times (144 vs. 111 and 95 vs. 74 min, respectively) [30]. Seeburger et al. [31] reviewed their 1,230 cases of MISMV for anterior (n = 156), posterior (n = 672), and Fig. 4 Surgical scars of MIMVR in a male patient (upper) and a female patient (lower)
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bileaflet prolapse (n = 402) [31]. Patient repair rate was 94 % and 5-year freedom from reoperation was 96 %. McClure et al. [17] reported that 6 out of 929 MIS-MV cases were intraoperatively converted to mitral valve replacement due to technical failure, and that 15-year freedom from reoperation was 90 %, with 5 and 10 years’ freedom rates from recurrent moderate or severe MR of 87 and 69 %, respectively [17]. Speziale et al. randomized patients with Barlow disease into 2 groups: the directvision with right thoracotomy group and the conventional full sternotomy group. They reported similar successful repair rates and freedom from moderate or severe MR in the mean follow-up period of 12 months [32]. Raanani et al. [33] compared the quality of mitral valve repair for posterior leaflet prolapse between right minithoracotomy and conventional full sternotomy, and showed a trend of increased rate of recurrent moderate or severe MR (18 vs. 9 %) in the minithoracotomy group, although the difference was not statistically significant. In contrast, Suri et al. [34] reported no difference in residual MR rates by intraoperative and early postoperative echocardiography in their propensity-matched comparisons of MIS-MV and conventional mitral valve repair for all prolapse subset.
Robotic mitral valve surgery Advancements in closed-chest CPB and telemanipulation technology have spurred a growing interest within the past
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Fig. 5 Mini-valve system: this system is composed of a minithoracotomy spreader with a tilted blade, a left atrial retractor that moves flexibly, and an additional blade for the posterolateral left atrial wall. A 5 blade size is available depending on the left atrial size
decade in robotic mitral valve surgery. The difficulty is that widespread practice of this technology often requires retraining surgeons who are not familiar with these new and evolving techniques [35]. Chitwood et al. [36] described their results of robotic mitral valve repair in 300 patients with the Da Vinci surgical system (Intuitive Surgical, Inc, Sunnyvale, CA, USA). There were 2 (0.7 %) 30-day postoperative mortalities and 6 (2.0 %) late postoperative mortality. Complications included 2 (0.7 %) stroke, 2 transient ischemic attack, 3 (1.0 %) myocardial infarction, and 7 (2.3 %) reoperation for bleeding. Fiveyear survival was 96.6 %, with 93.8 % freedom from reoperation [36]. In addition, Mihaljevic et al. compared the outcomes of robotic mitral valve repair with those of conventional full sternotomy, partial sternotomy, and right minithoracotomy. They showed that all approach groups had no hospital death and that the robotic group had the shortest hospital stay among the 4 different approach groups [37].
WL Gore & Associates, Inc, Flagstaff, Ariz) sutures for ruptured or elongated chordae tendineae of MV is becoming popular with good long-term results [40]. Both leaflet resection and neochordae construction are effective techniques for MIS-MV. The difficult aspect of chordal replacement is using ePTFE sutures, which are vital in determining the correct length of artificial chorda. Various techniques have been reported in order to solve this problem [41, 42]. For example, Oppell and Mohr [43] reported the ‘loop technique’ in which a premeasured ePTFE chordal loop is made and fixed easily to the prolapsed region of the leaflet. In this manner, broad-range mitral valve repair is possible and it can be revised easily. This technique may be useful through both MIS-MV and conventional approaches, and simplifies chordal replacement in MIS-MV approaches [44, 45]. On the other hand, Macarthur et al. reported nonresectional single-suture leaflet-remodeling technique of inverting the prolapsed or flail segment tissue into the LV [46, 47]. This technique revealed the results equal to the resection-suture technique, thus significantly shortening the time consumed when performing MIS-MV.
Repair technique of MIS-MV Various repair techniques have been proposed in MIS-MV [38]. The gold standard has been the resection-suture technique of the prolapsed leaflet [39]. Chordal replacement with expanded polytetrafluoroethylene (ePTFE) (Gore-Tex;
Innovation for MIS-MV In optimal operative setting for MIS-MV, innovation of instruments including a left atrial retractor is vital. As a
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Fig. 6 Endoscopic view. Prolapsed leaflet (a) and papillary muscle (b). This device moves flexibly to various positions of the surgeon’s choice. MIS-MV with ‘loop technique’(c, d)
previous report [48], our Department developed a novel left atrial retractor system, including a minithoracotomy spreader, a left atrial blade, and an additional retractor for the posterior wall of the left atrium (Fig. 5). The advantage of this system is flexibility. It moves flexibly to various positions, and by retraction of the anterior mitral leaflet toward the anterior wall of the LV, even papillary muscles can be exposed easily and clearly on the straight view through the small working port (Fig. 6a, b). This function enables comfortable manipulation to the papillary muscle in chordal replacement with ‘loop technique’ (Fig. 6c, d). The approaches in MIS-MV vary from direct vision to complete totally endoscopic and robotic surgery. Many surgeons prefer direct-vision approach under the endoscopic assist because those are more accessible and the operating time is shorter than two other methods. In the future, further technological innovation will enable the MIS-MV of less invasive.
Conclusion Avoiding a full sternotomy has been consistently reported to have beneficial effects such as reduced blood
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transfusion, ventilation time, and hospital stay [32–34]. The mastery of skills of the team is necessary for MIS-MV than for conventional approaches. So, not only the surgeons but also all other staff in the operating room must be well trained and familiar with this approaches. Recently, a great deal of innovation has contributed to establishing MIS-MV via right minithoracotomy. New innovative instruments and optimal operating setting in mitral valve repair facilitate both direct-vision and endoscopic assist approaches in complex lesions, thus contributing to the acceptance of MIS-MV as routine surgery. Conflict of interest interest.
The author declares that he has no conflict of
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