Minimally Invasive Mitral Valve Surgery via Mini-Thoracotomy: Current Update
In recent years, minimally invasive mitral valve surgery (MIMVS) has established itself as an alternative and increasingly used option for patients with mitral valve (MV) pathology. MIMVS is associated with a very low perioperative morbidity and mortality rate in appropriately selected patients, comparable to a full sternotomy approach. Besides superior cosmetic results, patients after MIMVS enjoy shorter recovery times and earlier returns to full activity. A number of approaches are branded as minimally invasive, but the most widely used one entails peripheral cardiopulmonary bypass and a small right anterolateral mini-thoracotomy. The operative technique and outcomes of this approach are summarized in the current update.
KeywordsMinimally invasive Mitral valve repair Mini-thoracotomy Endoscopic
Most patients with degenerative mitral valve (MV) disease are otherwise healthy adults with few comorbidities. Although such patients understand the need for surgical MV repair, they are also apprehensive of the recovery following a full sternotomy approach. Understandably, many patients seek less invasive approaches which would allow them to return sooner to their active life style and work environment. This is reflected by a growing demand among patients and referring physicians for a minimally invasive mitral valve surgery (MIMVS) approach. In addition, MIMVS has gained increasing acceptance within the cardiac surgical community. For example, 45.2 % of MV procedures in 2013 were performed by a minimally invasive access in Germany according to the German Society for Thoracic and Cardiovascular Surgery .
The term MIMVS refers to a constellation of surgical approaches and techniques that minimize surgical trauma through smaller incisions when compared to conventional sternotomy . A number of incisions including parasternal, transternal, and left posterior thoracotomy, among others, have been attempted in the past. Currently, the most common and widely used approach is via a right anterolateral mini-thoracotomy. The other well-established alternatives include a robotically assisted, port access right thoracic approach and a partial sternotomy approach.
While minimally invasive access should be predominantly reserved for less complex pathologies during the initial part of the surgeon’s learning curve (e.g., isolated posterior leaflet prolapse) , this approach can be safely and effectively employed for complex pathologies particularly in high-volume centers (e.g., Barlow’s disease) [4, 5, 6, 7, 8, 9, 10•, 11]. Aside from cosmetic aspects and patient satisfaction, MIMVS facilitates expedited postoperative recovery and an earlier resumption of normal activities, while reducing postoperative pain, blood loss, and overall length of stay in the hospital [5, 7, 8, 9]. The objective of this review is to summarize the current state of MIMVS and to report the results of the largest current series on this subject.
Development of minimally invasive mitral valve surgery
With the success of laparoscopic and thoracoscopic techniques in general surgery and thoracic surgery procedures, enthusiasm for minimally invasive cardiac surgery developed with the goal of avoiding full median sternotomy and sternotomy-related complications. It was not until the mid-1990s that Navia and Cosgrove  described their approach via a small right parasternal incision and Cohn et al.  reported their series utilizing partial sternotomy for cardiac valve surgery. With the innovation of the port access approach [14, 15] in the late 1990s, it was shown that minimally invasive, closed-chest cardiopulmonary bypass (CPB) with cardioplegic arrest was as feasible, safe, and effective as conventional open CPB . The use of peripheral CPB, long endoscopic instruments, and either transthoracic aortic clamping  or endoaortic balloon occlusion  led several pioneering groups around the world [9, 19, 20, 21] to develop a safe mini-thoracotomy platform, which constitutes the most common approach for MIMVS currently in use. Some centers used robotic technology to perform MIMVS via even smaller incisions with comparable results with respect to mortality and morbidity when compared to either conventional sternotomy or mini-thoracotomy [22, 23, 24]. The current update, however, focuses solely on the right anterolateral mini-thoracotomy approach and its outcomes compared to conventional sternotomy.
Operative technique of MIMVS
The remainder of the procedure can be performed under direct vision through the mini-thoracotomy or via a thoracoscopic port in the third intercostal space, with the latter being our preferred method. Using long endoscopic instruments, the MV is inspected and assessed in a standardized stepwise approach . Essentially, the entire armamentarium of MV repair techniques can be utilized via the minimally invasive approach. This includes ring annuloplasty, triangular or quandrangular leaflet resection, chordal transfer, artificial chords, edge-to-edge (“Alfieri”) repair , cleft closure, commissural plication, and calcium debridement.
After the leaflet repair is completed, a full prosthetic ring is usually implanted to restore and to remodel the size and shape of the mitral annulus (Fig. 1c). Ring size selection is based on the measurement of the anterior mitral leaflet (AML) with regard to both the intertrigonal distance and to the anterior-posterior height of the anterior leaflet. Approximately 12 to 16 annular mattress sutures are needed to implant the annuloplasty ring. The sutures are knotted at the prosthetic ring with the help of a knot pusher or with an automatic suture knotting device. The repair is then tested by filling the left ventricle (LV) with saline solution until a seal is achieved to test for sufficient closure of the MV. Use of a laparoscopic irrigator/suction device can be very helpful for performing the water test. Residual small leaks or secondary lesions are addressed as necessary. The LA is closed with a standard technique while deairing with saline. The cross-clamp is removed during low-flow CPB, and adequate rhythm is restored. Repeat TEE imaging is then performed to determine the immediate results of the repair, and any residual mitral regurgitation (MR) quantified as more than mild is addressed by valve re-exploration and re-repair or replacement as guided by the TEE findings.
“Respect” approach using neochordal technique
Resectional techniques used for MV repair were first introduced by Carpentier and have demonstrated excellent long-term results . Newer techniques have been proposed with the aim to preserve MV leaflet tissue, which was made possible with Gore-Tex chordae made out of expanded polytetrafluoroethylene (ePTFE) pioneered by Frater . In the mid-1980s, David reported the use of ePTFE neochordae to support the free edge of the prolapsing segment of the MV leaflet . This technique provided excellent results but was not adopted widely due to difficulties in achieving a reproducible and optimal neochordal length. Over time, however, the use of neochords has become the preferred technique in most centers, particularly with regard to the AML. Perier coined the phrase “respect rather than resect” to stress the importance of respecting the MV leaflet tissue as much as possible and reducing leaflet resection to a bare minimum in order to achieve maximum leaflet coaptation . The widespread adoption of the non-resectional “respect” method came after Mohr introduced the use of premeasured ePTFE loops of certain length (“Leipzig loop technique”) to greatly facilitate implantation of neochordae .
In recent years, a growing number of minimally invasive MV surgeons have embraced this versatile technique because of its reproducibility and simplicity of application and excellent results [32•]. Briefly, artificial chords are prepared as a set of four loops out of an ePTFE suture that are attached to one pledget. The pledget is then fixed to the corresponding papillary muscle opposing the prolapsing segment of the MV leaflet. Sometimes two or even three sets of loops are needed to fix a complex pathology, such as a bileaflet prolapse. Length of the loops ranges from 10 to 26 mm and is determined intraoperatively using a caliper. The ends of the loops are then sutured to the edges of the prolapsing segment of the MV leaflet, serving as neochords in place of torn native chords (Fig. 1b).
The non-resectional “respect” method can be employed for both posterior mitral leaflet (PML) and AML pathologies. For posterior leaflet prolapse, ePTFE chords are used so that the PML remains nearly vertical, posterior, and parallel to the posterior wall of the LV in the inflow region, which transforms the PML into a smooth buttress against which the AML comes into apposition. That is, the AML acts like a “door” and the PML as a “doorframe.” The loops for AML prolapse are therefore approximately 1 cm longer, and its length is truly sized against the native neighboring chords. The potential benefits of non-resectional technique include preserved leaflet mobility, larger surface of coaptation, no significant changes to annular geometry, and the ability to implant the largest possible prosthetic annuloplasty ring with lowest possible transmitral inflow gradients . Placement of the premeasured neochordal loops in the minimally invasive setting is oftentimes easier to perform than a leaflet resection, and this aspect, together with very good long-term results, explains the increasing adoption of this technique among minimally invasive MV surgeons.
Patient selection for minimally invasive mitral valve surgery
Recently reported results of minimally invasive mitral valve surgery performed via mini-thoracotomy in various subgroups of patients
Primary inclusion criterion
Number of patients
30-day mortality (%)
Major adverse events
Perier et al. (2013) 
99.3 % repair rate
1.5 % converted to sternotomy
0.6 % with major CVA
Reser et al. (2014) 
99.3 % repair rate
2.8 % converted to sternotomy
1.6 % with major CVA
Gammie et al. (2009) 
96.3 % repair rate
4 days median hospital stay
1.1 % re-exploration rate
Davierwalla et al. (2013) [32•]
Patients requiring MV surgery
2829 MV repairs and 609 MV replacements
98.4 % repair rate for degenerative MR
1.4 % converted to sternotomy
93 % freedom from re-operation at 10 years
Borger et al. (2014) 
94.5 % repair rate
0.7 % converted to sternotomy
Murzi et al. (2014) 
82 % repair rate
1.1 % converted to sternotomy
6.3 % with major CVA
Arcidi et al. (2012) [39•]
80 % repair rate
2.4 % with major CVA
Santana et al. (2013) 
EF ≤ 35 %
31 MV repairs and 40 MV replacements
1.4 % with major CVA
Seeburger et al. (2014) 
139 MV repairs and 52 MV replacements
1.6 % converted to sternotomy
8 % needed CVVH
MIMVS under fibrillatory arrest in patients with prior sternotomy
Patients who have had a previous sternotomy may be operated on with a minimally invasive approach, although such procedures should probably be performed only after the surgeon has gained a significant experience with MIMVS surgery. Because the adhesions around the aorta often preclude a safe dissection for aortic cross-clamping, hypothermic fibrillation is usually used as a means of myocardial protection. This is accomplished by keeping the heart decompressed and the coronaries perfused against an intact aortic valve with cold oxygenated blood. Cooling the systemic temperature to 26–28 °C also decreases myocardial oxygen consumption. If aortic insufficiency is greater than mild, this approach is contraindicated because of poor visualization of the operative field. There are a few important principles that help one to safely perform fibrillatory arrest cases and prevent adverse neurologic events. The lateral approach facilitates a better exposure of the MV and does not require a significant distortion of the heart, which may render the aortic valve incompetent. Maintenance of the higher perfusion pressure on CPB helps to achieve better coronary perfusion as well as myocardial protection and keeps the aortic valve closed under a better seal. The surgeon avoids testing MV competence with saline injection to prevent air propelling into the LV but instead fills the LV with blood by briefly lifting the left atrial retractor and making the aortic valve incompetent for testing purposes only. Also, CO2 insufflation at 5 L/min into the thoracic cavity throughout the operation displaces the air and thus minimizes the risk of inadvertent air embolism.
Chitwood et al. [39•] utilized this method (fibrillatory arrest at 26 °C) in 77 % of their 167 redo cases (from 1996 through 2006) and reported a mortality of 3 % with no serious complications or increased risk of stroke, which occurred in four patients (2.4 %). Also, Petracek et al. [10•] in their series of 504 patients (from 2006 to 2009) used fibrillatory arrest under moderate hypothermia for their minimally invasive MV cases. In this series, 128 patients (25 %) had previous cardiac operation and only 2 suffered stroke (2 %) while 4 patients died (operative mortality 3.1 %). Although technically challenging, performing MIMVS under fibrillatory arrest in patients after previous sternotomy has several potential benefits. First, there is less extensive mediastinal dissection and less bleeding, resulting in a reduced need for blood transfusions as compared to redo sternotomy. Second, there may be a lower stroke risk by avoidance of aortic cross-clamping in patients with atherosclerotic changes in the ascending aorta. Third, one avoids mediastinal infections and sternal wound complications in high-risk redo cases.
Preoperatively, MIMVS patients undergo screening coronary artery catheterization, which is done preferably via a radial or left femoral artery access in order to have the right groin area free of hematoma when performing femoral cannulation. Alternatively, ECG-gated cardiac CT angiography can be obtained to assess coronary anatomy. CT angiography of the abdomen and pelvis may also be helpful in patients older than 65 years of age or those with significant smoking history, hypertension, or peripheral arterial disease to rule out significant aortoiliac atherosclerosis. These higher risk patients, however, have an increased risk of coronary artery disease and generally require preoperative coronary catheterization as a screening test.
Postoperatively, patients are transferred to the ICU or recovery room with pacing wires, a pericardial drain, and a pleural drain. Generally, they are transferred to the floor on the first postoperative day, and drains are removed on postoperative day 1 or 2. Pacing wires are removed on postoperative day 2 or 3 in the absence of conduction system disturbances. Discharge home generally occurs on postoperative day 4 or later. The majority of patients return to their normal daily and professional activities within 4 to 6 weeks after surgery.
Outcomes after MIMVS compared to conventional sternotomy
As the minimally invasive approach evolved in terms of technology and surgical experience, certain initial challenges such as deairing and limited surgical field exposure have been largely overcome. In addition, emergency conversion to sternotomy is a very uncommon event . It is not surprising, therefore, that in large comparative studies the outcomes of MIMVS are equal to those of conventional sternotomy. In a recent meta-analysis representing more than 20,000 patients from 45 studies, Sundermann et al.  compared outcomes between right lateral mini-thoracotomy and conventional sternotomy in patients undergoing MV surgery. The authors found that 30-day all-cause mortality (1.4 vs 1.7 %) and stroke rate (1.7 vs 1.6 %) were similar between both surgical techniques, as were rates of re-exploration (3.8 vs 3.2 %) and postoperative renal failure (2.1 vs 2.1 %, all p values non-significant). However, CPB time (142.6 ± 26.5 vs 107.7 ± 25.2 min), cross-clamp time (93.7 ± 31.3 vs 74.2 ± 27.5 min), and procedure time (258 ± 41.8 vs 210.7 ± 34.4 min) were significantly longer in the MIMVS group. Also, the rate of aortic dissection was significantly higher in the mini-thoracotomy group, but the total number of dissections was low (4 vs 0 in a total of 9823 reported cases). In contrast, MIMVS patients had significantly shorter hospital stay (7.6 ± 3.2 vs 9.4 ± 3.4 days), length of stay in the intensive care unit (44 ± 30 vs 66 ± 47 h), and respirator dependence (12.3 ± 11.2 vs 22.3 ± 29.1 h). Mini-thoracotomy patients were also found to have less blood drainage volume (674 ± 288 vs 775 ± 292 mL) and blood transfusion need (37 vs 45 %), as well as a lower rate of postoperative new atrial fibrillation (25 vs 29 %).
The economic implications of the above observations are difficult to assess as costs were calculated and compared in only a few studies. However, it appears that MIMVS results in fewer costs than conventional MV procedures. For example, Iribarne et al.  compared the cost and effectiveness of a MIMVS versus traditional sternotomy approach (847 patients who underwent isolated MV surgery from 2003 to 2008) and found a significant reduction in mean total hospital cost in the MIMVS group of $9054 ± 3302.
In regard to the MV repair rate, large meta-analysis studies [43, 45] show that minimally invasive access is not associated with a reduced rate of MV repair. There even appears to be a trend towards a higher repair rate in MIMVS patients in many published comparative series, but selection bias and/or surgical experience may explain this finding.
Adoption of MIMVS
Experienced MV surgeons can achieve excellent results with a minimally invasive approach after an appropriate and adequate training. The fundamental basis for this involves a continuous evolution stemming from a full understanding of MV pathophysiology, sufficient prior experience in conventional MV repair surgery, command of various repair techniques, and then gradual transition to the minimally invasive approach.
'It has been demonstrated, however, that MIMVS is associated with a true learning curve. Although marked variation exists between individual surgeons, a substantial number of operations (anywhere between 75 and 125) are required to achieve optimal results . In experienced hands, minimally invasive access does not lower the threshold for MV replacement with expected MV repair rates of 86 to 99 % [32•, 34, 46]. Some believe that the ultimate iteration of MIMVS is robotic MV repair utilizing several small incisions for port access. Selected centers [22, 23, 24] have achieved equal or better results with such a robotic approach, although these operations tend to be longer and the technology is more expensive than the thoracoscopic platform. Nevertheless, patient satisfaction is very high with this technique.
In conclusion, MIMVS can be safely and effectively performed with excellent short- and long-term outcomes. In the hands of experienced mitral surgeons, MV repair rates and durability are very high via the minimally invasive approach. MIMVS is associated with low mortality and morbidity rates, shortened hospital stay and recovery, and increased patient satisfaction.
Compliance with Ethics Guidelines
Conflict of Interest
Serguei I. Melnitchouk, Jacob P. Dal-Bianco, and Michael A. Borger each declare no potential conflicts of interest.
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
References and Recommended Reading
Papers of particular interest, published recently, have been highlighted as: • Of importance
- 5.Goldstone AB, Atluri P, Szeto WY, Trubelja A, Howard JL, MacArthur Jr JW, et al. Minimally invasive approach provides at least equivalent results for surgical correction of mitral regurgitation: a propensity-matched comparison. J Thorac Cardiovasc Surg. 2013;145:748–56.PubMedCentralCrossRefPubMedGoogle Scholar
- 10.•Petracek MR, Leacche M, Solenkova N, Umakanthan R, Ahmad RM, Ball SK, et al. Minimally invasive mitral valve surgery expands the surgical options for high-risks patients. Ann Surg. 2011;254:606–11. This paper describes minimally invasive mitral valve surgery approach by use of fibrillatory arrest in order to avoid aortic cross-clamping and cardioplegic myocardial arrest in patients with prior sternotomy. Authors report low mortality and morbidity on 504 consecutive patients who underwent mitral valve surgery via this approach. They conclude that this approach expands the surgical options for high-risk patients and yields to superior results than the conventional median sternotomy approach.CrossRefPubMedGoogle Scholar
- 24.Suri RM, Burkhart HM, Daly RC, Dearani JA, Park SJ, Sundt 3rd TM, et al. Robotic mitral valve repair for all prolapse subsets using techniques identical to open valvuloplasty: establishing the benchmark against which percutaneous interventions should be judged. J Thorac Cardiovasc Surg. 2011;142:970–9.CrossRefPubMedGoogle Scholar
- 26.Maisano F, Schreuder JJ, Oppizzi M, Fiorani B, Fino C, Alfieri O. The double-orifice technique as a standardized approach to treat mitral regurgitation due to severe myxomatous disease: surgical technique. Eur J Cardiothorac Surg : Off J Eur Assoc Cardiothorac Surg. 2000;17:201–5.CrossRefGoogle Scholar
- 32.•Davierwala PM, Seeburger J, Pfannmueller B, Garbade J, Misfeld M, Borger MA, et al. Minimally invasive mitral valve surgery: “The Leipzig experience”. Ann Cardiothorac Surg. 2013;2:744–50. This is a report on a total of 3438 patients who underwent minimally invasive mitral valve surgery at the Leipzig Heart Center where it became a routine procedure. Authors report excellent results of the procedure that can be performed safely and effectively with very few perioperative complications.PubMedCentralPubMedGoogle Scholar
- 38.Murzi M, Miceli A, Di Stefano G, Cerillo AG, Farneti P, Solinas M, et al. Minimally invasive right thoracotomy approach for mitral valve surgery in patients with previous sternotomy: a single institution experience with 173 patients. J Thorac Cardiovasc Surg. 2014;148:2763–8.CrossRefPubMedGoogle Scholar
- 39.•Arcidi Jr JM, Rodriguez E, Elbeery JR, Nifong LW, Efird JT, Chitwood Jr WR. Fifteen-year experience with minimally invasive approach for reoperations involving the mitral valve. J Thorac Cardiovasc Surg. 2012;143:1062–8. This systematic review and meta-analysis of comparative studies was performed to update the current evidence on mitral valve surgery through a lateral mini-thoracotomy versus median sternotomy. More than 20,000 patients from 45 studies were included in this study, allowing the authors to conclude that MIMVS and conventional mitral valve surgery have a similar perioperative outcome. Mitral valve surgery via a right lateral mini-thoracotomy seems to be favorable with regard to resource-related outcome.CrossRefPubMedGoogle Scholar