EARLY OUTCOME OF THORACOSCOPIC MINIMALLY INVASIVE VERSUS CONVENTIONAL MITRAL VALVE SURGERY IN MITRAL VALVE DISEASES

Document Type : Original Article

Authors

1 Cardiothoracic Surgery Department, National Heart Institute

2 Cardiothoracic Surgery Department, Faculty of Medicine, Al-Azhar University.

Abstract

Background: Minimally Invasive Mitral Valve Surgery (MIMVS) is fast becoming an established treatment option for the treatment of mitral valve disease internationally. Increased recognition of advantages, of minimizing surgical trauma and its direct impact on reduced postoperative pain, quicker recovery, improved cosmosis and earlier return to work has spurred the minimally invasive cardiac surgical revolution.
Objectives: Comparing the postoperative pain, cost, hospital stay, recovery speed and pulmonary function between minimally invasive and conventional mitral surgery. Moreover, assessment of thirty day mortality and early post-operative morbidity in both techniques.
Patients and methods: This study was conducted on 50 patients requiring mitral valve surgery classified into 2 equal groups:
Group A (Minimally invasive group), who were approached through a right Anterolateral video-assisted minithoracotomy.
Group B (Sternotomy group), who were approached through a conventional median sternotomy.
Results: There was no statistical difference between the two groups in baseline pre-operative characteristics regarding their age, sex, NYHA class, EF%, LA dimension and spirometric study. There was no operative mortality in both groups. Incision length, ventilation time, blood drainage, blood transfusion, ICU stay, total hospital stay were less in group A.
Conclusion: In patients with mitral valve disease, MIMVS can be an alternative to conventional mitral valve surgery with comparable short-term mortality and in-hospital morbidity.

Keywords


EARLY OUTCOME OF THORACOSCOPIC MINIMALLY INVASIVE VERSUS CONVENTIONAL MITRAL VALVE SURGERY IN MITRAL VALVE DISEASES

 

By

 

Ahmed M. Mahgoub(1), Tamer S. Elbanna(1), Abdelrahman M. Abdelrahrman(2), Mohamed Shafik(2) and Mohamed E. Abdulraouf(2)

 

(1) Cardiothoracic Surgery Department, National Heart Institute

(2) Cardiothoracic Surgery Department, Faculty of Medicine, Al-Azhar University.

 

ABSTRACT

Background: Minimally Invasive Mitral Valve Surgery (MIMVS) is fast becoming an established treatment option for the treatment of mitral valve disease internationally. Increased recognition of advantages, of minimizing surgical trauma and its direct impact on reduced postoperative pain, quicker recovery, improved cosmosis and earlier return to work has spurred the minimally invasive cardiac surgical revolution.

Objectives: Comparing the postoperative pain, cost, hospital stay, recovery speed and pulmonary function between minimally invasive and conventional mitral surgery. Moreover, assessment of thirty day mortality and early post-operative morbidity in both techniques.

Patients and methods: This study was conducted on 50 patients requiring mitral valve surgery classified into 2 equal groups:

Group A (Minimally invasive group), who were approached through a right Anterolateral video-assisted minithoracotomy.

Group B (Sternotomy group), who were approached through a conventional median sternotomy.

Results: There was no statistical difference between the two groups in baseline pre-operative characteristics regarding their age, sex, NYHA class, EF%, LA dimension and spirometric study. There was no operative mortality in both groups. Incision length, ventilation time, blood drainage, blood transfusion, ICU stay, total hospital stay were less in group A.

Conclusion: In patients with mitral valve disease, MIMVS can be an alternative to conventional mitral valve surgery with comparable short-term mortality and in-hospital morbidity.

Key words: Minimal invasive, Scar, Pain, Cost.

 

 

INTRODUCTION

     Historically, most mitral valve surgery has been performed using conventional full median sternotomy (Antunes, 2015). In the late 1990s, a new procedure termed minimally invasive mitral valve surgery (MIMVS) was suggested(Ailawadi et al., 2016) MIMVS is fast becoming an established treatment option for the treatment of mitral valve disease internationally (Schmitto et al., 2010).

     Merits of MIMVS in well trained hands are enormous. Routine use of MIMVS showed less surgical trauma with its sequelae reaching earlier resumption of normal activities (Atluri et al., 2013).

PATIENTS AND METHODS

    This study is prospective cohort study including 50 patients requiring mitral valve surgery. All the patients completed the study. The patients were classified into 2 equal groups:

● Group A: Minimally invasive group. This group were approached through a right Anterolateral video-assisted minithoracotomy.

● Group B: Sternotomy group. This group were approached through a conventional median sternotomy.

      Patients were selected from National Heart Institute, and underwent mitral valve surgery from April 2014 to August 2015 in National Heart Institute. All patients approved to have the surgery and signed consents.

    All patients with acute mitral regurgita-tion, concomitant aortic valve disease, concomitant ischemic heart disease, previous open heart surgery or prior right lung surgery or radiotherapy to the right side of the chest, pulmonary artery pressure more than 80mm and impaired preoperative pulmonary function were excluded from the study. Duplex of femoral vessels was done for group A and those with contraindication to femoral cannulation were excluded from the study.

Conventional general anesthesia, standard cardiopulmonary bypass, antegrade cold blood cardioplgia and standard left atriotomy were conducted in all patients regardless the surgical approach. In group B, Standard aortic and bicaval cannulation while in group A, Femoral (venous and arterial) cannulation with TEE guidance was done and patients underwent 4-6 cm video-assisted right anterolateral mini-thoracotomy.

Statistical analysis:

    Data were collected, verified and edited on a personal computer then analysed by SPSS, EPICalc software program to get the final result. Arithmetic mean and standard deviation were collected. t-test was used to compare values. The chi-square test (X2) was used for qualitative values. P value < 0.05 was considered significant.

RESULTS

     The two groups were matched with no statistically significant difference regard-ing age, sex, body mass index (BMI) (Table 1), NYHA class, preoperative echocardiography and preoperative spirometeric studies.

 

 

Table (1): Demographic data.

Groups

Parameters

Group A

Group B

P value

Age

39.24 ± 11.061

48.76 ± 11.36

0.004

Gender (Males)

13/25 (52.0%)

12/25 (48.0%)

0.777

BMI

28.48 ± 4.823

28.08 ± 4.15

0.755

 

 

     Total cross-clamp time (TCCT) and total bypass time (TBT) were longer in group A, but with no statistically significant difference (Table 2).

     Group “A” included 18 cases of mitral valve replacement, 6 cases of mitral valve replacement plus tricuspid valve repair, 1 case of mitral valve repair. In group “B”, there was 18 cases of mitral valve replacement, 7 cases of mitral valve replacement plus tricuspid valve repair, no case of mitral valve repair.

 

 

Table(2): TBT and TCCT.

Groups

Surgical procedures

Group A

Group B

P-value

TBT (min)

Mean ± SD

135.92 ± 28.34

119.48 ± 22.57

0.028

Range

95 - 215

72 - 185

TCCT (min)

Mean ± SD

101.36 ± 18.34

87.20 ± 18.82

0.010

Range

70 - 147

55 - 145

 

 

     There was a high stastically significant difference between the two groups regarding  length of the surgical incision, ventilation time, amount of blood drainage, postoperative spirometric study and total hospital stay.

    There was a statistically significant difference between both groups in blood transfusion units and ICU stay (Table 3).

    Post-operative pain score using the visual analogue scale was high stastically significant with less pain in group A (Table 4).

     Comparison between pre and postopera-tive echocardiography revealed no stastically significant difference (Table 4).

MIMVS group was more expensive than conventional group with no stastically significant difference (Table 4).

 

 

 

Table(3): Postoperative data.

Groups

ICU courses

Group A

Group B

P value

Ventilation (hours)

Range

0-5

2.84 ± 1.93

6 - 24

10.72±4.96

>0.01

Mean ± SD

Blood loss (ml)

Range

120 - 400

241.42 ± 76.61

160 - 1160

489.87 ±188.86

>0.01

Mean ± SD

Blood transfusion

Range

0 - 2

0.12 ± 0.43

0 - 3

0.6 ± 0.95

>0.05

Mean ± SD

ICU stay (day)

Range

1 - 7

2.56 ± 1.42

2 - 10

3.76 ± 1.74

>0.05

Mean ± SD

Incision (cm)

Range

Mean ± SD

5 – 7

16 – 24

>0.01

5.60 ± 0.65

20.16 ± 2.32

Table (4): Follow-up data.

Groups

Postoperative data

Group A

Group B

p-value

Range

Mean ± SD

56.72 ± 6.07

56.08 ± 3.46

0.649

Range

40 - 67

51 - 65

PAP

Mean ± SD

43.48 ± 9.01

46.24 ± 10.37

0.320

Range

30 - 70

25 - 67

FVC(L)

Mean ± SD

2.21 ± 0.61

1.46 ± 0.46

0.001

Range

1.41 - 4.54

0.96 - 2.7

FVC%

Mean ± SD

57.72 ± 12.15

38.46 ± 10.70

0.001

Range

39.1 - 80.2

27.6 - 65.2

FEV1(L)

Mean ± SD

2.05 ± 0.63

1.37 ± 0.43

0.001

Range

1.41 - 4.19

0.95 - 2.7

Post-operative pain

Mean ± SD

3.44 ± 1.00

7.56 ± 1.45

>0.01

Total hospital Stay

(days)

Mean ± SD

6.04 ± 1.10

11.20 ± 2.45

>0.01

Range

5 - 10

6 - 15

Operative Cost

(Thousand LE)

Mean ± SD

17.84 ± 0.67

14.61 ± 1.08

0.001

Range

16.9 - 19

13 - 16

 

 

 

DISCUSSION

    The age groups in this study were relatively younger which may be attributed to earlier and repeated affection by rheumatic fever, which is endemic in most developing countries including Egypt.

    De Praetere et al. (2015)found no statistically significant difference in demographics of patients undergoing MIMVS in his study. Holzhey et al. (2011)report MIMVS in patients over 70 years.

   Preopearative echocardiography showed patients with isolated mirtal valve disease (stenosis or regurge) or mitral and tricuspid valve disease with no prefere-nces in assigning patients for each group Mariscalco and Musumeci (2014) found that mitral valve surgery can be routinely done endoscopically.

     Ailawadi et al. (2016)reported that patients with depressed LV function, more than mild aortic regurge, depressed RV function and PAP more than 80 mmHg should be approached with caution in MIMVS. We found that the smaller the left atrium, the easier the procedure in contrast to the conventional technique.

     Glauber et al. (2015)showed that one of the disadvantages of MIMVS is that it needs a learning curve for the surgeon and team to be able to perform the procedure through a smaller incision in a faster time.In this study, the cross clamp time and the total bypass time were longer in MIMVS group but without statistically significant difference,

      Modi et al. (2008) and Moscarelli et al. (2016) found that there was no significant difference between cross clamp time and the total bypass time between both groups.

     In our study, there were attempts for extubating the patients in the operating theatre which already done in six patients. The postoperative ventilation time and total ICU stay in MIMVS group was significantly lower Modi et al. (2008) and Shah et al. (2013)showed that post-operative mechanical ventilation and total ICU stay are significantly lower in patients undergoing minimally invasive mitral valve surgery.

    We found significant decrease in blood loss and blood transfusion requirements in MIMVS group. As a result of decreasing the demands for blood transfusion, the hazards of blood transfusion are lessened, and the patient’s costs are decreased. Wang et al. (2009) and Ward et al. (2013) showed that MIMVS is associated with less blood loss and decreased blood transfusion requirements postoperative.

     Evaluation of pain by visual analogue pain scale in the study revealed high statistically significant change with low pain sensation in MIMVS groupSantana et al. (2011)reported less pain in hospital land, after discharge, less analgesic usage, greater patient satisfaction, and a return to normal activity.  A statistically significant difference in length of incision was found between the two groups and the same result was found in similar studies (Modi et al., 2008; Gao et al., 2012 and Shah et al., 2013).

    In group “A”, postoperative spirometric study revealed that all mechanical pulmonary function tests had no significant reduction one month after surgery denoting better postoperative pulmonary functions than sternotomy group. Pulmonary functions deteriorated more in group “B”. This was highly statistically significant. Similar results found in(Modi et al., 2008; Gao et al., 2012 and Shah et al., 2013)

     There was no significant difference in EF%, LV dimensions, LA diameter or PAP between both groups 1 month post operatively. TTE showed well-functioning mitral prosthesis with no paravalvular leak and mild decrease in pulmonary artery pressure in both groups.

      Holzhey et al. (2011)showed that MIMVS is feasible for mitral valve surgery without affecting the core of surgery or compromising the surgical target. In group A, no patient had superficial wound infection. While in group B three patient had superficial wound infection. 

     Aybek et al. (2006); Iribarne et al. (2010) and Shah et al. (2013)reported that MIMVS were less prone to infection while sternal wounds were more vulnerable to infection. 

     In our study, the total hospital stay significantly decreased in MIMVS group. Most patients in MIMVS group can be discharged on the third or fourth postoperative day, and the only reason for staying in the hospital was to manage anticoagulation protocols as most of the patients were living outside of Cairo. 

     Galloway et al. (2009) and Suri et al. (2009)reported that MIMVS patients had a shorter length of stay than sternotomy patients.

     In this study, MIMVS has more cost than conventional group as it is a starting program in our institute.  Iribarne et al. (2011) and Ritwick et al. (2013)reported that MIMVS was associated with a significant reduction in costs. The cost savings associated with MIMVS could potentially be an underestimate in our analysis because we only included costs associated with the surgical admission. Further cost savings associated with MIMVS could be realized if the time horizon of our economic analysis was expanded to one year.

CONCLUSION

     In patients with mitral valve disease, minimally invasive surgery can be an alternative to conventional mitral valve surgery. Right anterolateral mini-thoracotomy provided excellent exposure of the mitral valve and offers a better cosmetic scar.

There was comparable short-term mortality and in-hospital morbidity between both groups. Pain perception, transfusions, postoperative blood loss, duration of ventilation, ICU, hospital length of stay and early return to normal life activity were reduced in mini-thoracotomy group than conventional sternotomy group.

REFERENCES

1. Ailawadi G, Agnihotri AK, Mehall JR, Wolfe JA, Hummel BW, Fayers TM and Barnhart GR (2016): Minimally Invasive Mitral Valve Surgery I Patient Selection, Evaluation and Planning. Innovations (Philadelphia, Pa.), 11(4): 243–250.

2. Antunes MJ (2015): Challenges in rheumatic valvular disease: Surgical strategies for mitral valve preservation. Global Cardiology Science and Practice, 2015(1): 9-11.

3. Atluri P, Woo YJ, Goldstone AB, Fox J, Acker MA, Szeto WY and Hargrove WC (2013): Minimally invasive mitral valve surgery can be performed with optimal outcomes in the presence of left ventricular dysfunction. Annals of Thoracic Surgery, 96(5): 1596–1602.

4. Aybek T, Dogan S, Risteski PS, Zierer A, Wittlinger T, Wimmer-Greinecker G and Moritz A (2006): Two hundred forty minimally invasive mitral operations through right minithoracotomy. The Annals of Thoracic Surgery, 81(5): 1618–24.

5. De Praetere H, Verbrugghe P, Rega F, Meuris B and Herijgers P (2015): Starting minimally invasive valve surgery using endoclamp technology: Safety and results of a starting surgeon. Interactive Cardiovascular and Thoracic Surgery, 20(3): 351–358.

6. Galloway AC, Schwartz CF, Ribakove GH, Crooke GA, Gogoladze G, Ursomanno P and Grossi EA (2009): A Decade of Minimally Invasive Mitral Repair: Long-Term Outcomes. Annals of Thoracic Surgery, 88: 1180–1184.

7. Gao C, Yang M, Xiao C, Wang G, Wu Y, Wang J and Li J (2012): Robotically assisted mitral valve replacement. The Journal of Thoracic and Cardiovascular Surgery, 143(4 Suppl): S64-7.

8. Glauber M, Miceli A, Canarutto D, Lio A, Murzi M, Gilmanov D and Solinas M (2015): Early and long-term outcomes of minimally invasive mitral valve surgery through right minithoracotomy: a 10-year experience in 1604 patients. Journal of Cardiothoracic Surgery, 10(1): 181-190.

9. Holzhey DM, Shi W, Borger MA, Seeburger J, Garbade J, Pfannmller B and Mohr FW (2011): Minimally invasive versus sternotomy approach for mitral valve surgery in patients greater than 70 years old: A propensity-matched comparison. Annals of Thoracic Surgery, 91(2): 401–405.

10. Iribarne A, Easterwood R, Russo MJ, Wang YC, Yang J, Hong KN and Argenziano M (2011): A minimally invasive approach is more cost-effective than a traditional sternotomy approach for mitral valve surgery. Journal of Thoracic and Cardiovascular Surgery, 142: 1507–1514.

11. Iribarne A, Russo MJ, Easterwood R, Hong KN, Yang J, Cheema FH and Argenziano M (2010): Minimally invasive versus sternotomy approach for mitral valve surgery: a propensity analysis. The Annals of Thoracic Surgery, 90(5): 1471-7-8.

12. Mariscalco G and Musumeci F (2014): The minithoracotomy approach: a safe and effective alternative for heart valve surgery. The Annals of Thoracic Surgery, 97(1): 356–64.

13. Modi P, Hassan A and Chitwood WR (2008): Minimally invasive mitral valve surgery: a systematic review and meta-analysis. European Journal of Cardio-Thoracic Surgery: Official Journal of the European Association for Cardio-Thoracic Surgery, 34: 943–952.

14. Moscarelli M, Cerillo A, Athanasiou T, Farneti P, Bianchi G, Margaryan R and Solinas M (2016): Minimally invasive mitral valve surgery in high-risk patients: operating outside the boxplot. Interactive CardioVascular and Thoracic Surgery, 22(6): 756–761.

15. Ritwick B, Chaudhuri K, Crouch G, Edwards JR, Worthington M and Stuklis RG (2013): Minimally invasive mitral valve procedures: the current state. Minimally Invasive Surgery, 2013(3): 25-37.

16. Santana O, Reyna J, Grana R, Buendia M, Lamas GA and Lamelas J (2011): Outcomes of minimally invasive valve surgery versus standard sternotomy in obese patients undergoing isolated valve surgery. Annals of Thoracic Surgery, 91(2): 406–410.

17. Schmitto JD, Mokashi SA and Cohn LH (2010): Minimally-invasive valve surgery. Journal of the American College of Cardiology, 56(6): 455–62.

18. Shah ZA, Ahangar AG, Ganie FA, Wani ML, Lone H, Wani SN and Gani M (2013): Comparison of Right Anterolateral Thorocotomy with Standard Median Steronotomy for Mitral Valve Replacement, 7(1): 15–20.

19. Suri RM, Schaff HV, Meyer SR and Hargrove WC (2009): Thoracoscopic versus open mitral valve repair: a propensity score analysis of early outcomes. The Annals of Thoracic Surgery, 88(4): 1185–90.

20. Wang D, Wang Q, Yang X, Wu Q and Li Q (2009): Mitral Valve Replacement Through a Minimal Right Vertical Infra-axillary Thoracotomy Versus Standard Median Sternotomy. Annals of Thoracic Surgery, 87(3): 704–708.

21. Ward AF, Grossi EA and Galloway AC (2013): Minimally invasive mitral surgery through right mini-thoracotomy under direct vision. Journal of Thoracic Disease, 5(6): S673-9.


النتائج المبکرة للجراحات محدودة التداخل باستخدام منظار تجویف الصدر مقارنة بالجراحات التقلیدیة فی أمراض الصمام المیترالی

 

أحمدمحمدمحجوب(1)، تامرصبریالبنا(1)، عبد الرحمنمحمدعبد الرحمن(2)،

 محمدشفیقحسن(2)،  محمدعز الدین عبد الرؤوف(2)

 

(1) قسم جراحة القلب والصدر، معهد القلب القومی

(2) قسم جراحة القلب والصدر، کلیة طب الأزهر، جامعة الأزهر

 

خلفیة البحث : جراحات الصمام المتیرالی محدودة التداخل بإستخدام منظار تجویف الصدر تتمیز بأن لها مظهر تجمیلی بدیلاً  للطریقة التقلیدیة التی ینتج عنها ندبه سیئة، والتی هی أکثر عرضة لحدوث الإلتهابات وتلوث الجرح.

الغرضمنالبحث: المقارنة بین النتائج المبکرة للجراحات محدودة التداخل بإستخدام منظار تجویف الصدر مقارنة بالجراحات التقلیدیة فی أمراض الصمام المیترالی

المرضیوطرقالبحث: أجریت هذه الدراسة على 50 مریضا.

تم تصنیف المرضى إلى مجموعتین متساویتین:

المجموعة (أ): (مجموعة التداخل المحدود) الذین یحتاجون إلى جراحات الصمام المیترالی بإستخدام منظار تجویف الصدر.

• المجموعة (ب): (مجموعة التدخل التقلیدی) الذین یحتاجون إلى جراحة الصمام المیترالی عن طریق شق عظمة القص.

النتائج: لم یکن هناک فروق ذات دلالة إحصائیة فیما یتعلق بالعمر، والجنس، وأعراض المرض ودرجة شدته، کما کشفت نتائج الموجات الصوتیة على القلب قبل الجراحة ودراسة وظائف الرئة قبل الجراحة عن عدم وجود دلالة إحصائیة.

               وفیما یتعلق بالمقارنة أثناء العملیة، لم یکن هناک فروق ذات دلالة إحصائیة فی وقت إیقاف عضلة القلب ووقت ماکینة القلب الصناعی، ولکن هناک فرق فی مجموع وقت الجراحة الکامل داخل غرفة العملیات وقد یکون هذا الإختلاف بسبب حداثة الطریقة الجدیدة بإستخدام منظار تجویف الصدر.

               وقد کان طول الجرح أقل بشکل ملحوظ فی المجموعة "أ" عما کان فی المجموعة "ب"، کما کان هناک اختلافاً کبیراً فی وقت الرعایة المرکزة. وکان وقت استمرار المریض على جهاز التفس الصناعی أقصر فی مجموعة "أ"، وکان فقدان الدم ونقل الدم أقل فی مجموعة "أ".

               وکانت مدة إستمرار المریض فی  وحدة العنایة المرکزة أقصر فی مجموعة "أ". وتم إنخفاض الوظائف الرئویة بعد الجراحة بشکل ملحوظ فی المجموعة "ب"، عنها فی المجموعة "أ"، وکان هناک ألم أقل بکثیر بعد العملیة الجراحیة فی المجموعة (أ) عنها فی المجموعة (ب) کما کانت مدة الإقامة فی المستشفى أقل فی المجموعة (أ) منها فی مجموعة (ب).

الخلاصة: جراحات التدخل المحدود بإستخدام منظار تجویف الصدر لعلاج أمراض الصمام المیترالی الصحیح لیست متمیزة فقط بصغر شکل الجرح  الأفضل من حیث المظهر التجمیلی، ولکنها تتمیز أیضاً بقصر مدة الإقامة فی الرعایة المرکزة وقصر فترة التواجد فی المستشفى، وسرعة العودة لممارسة الحیاة بصورة طبیعیة بعد الجراحة، کما تتیح التدخل بطریقة أسهل فی حالة الإحتیاج إلی جراحة قلب مفتوح مرة أخرى.

 

REFERENCES
1. Ailawadi G, Agnihotri AK, Mehall JR, Wolfe JA, Hummel BW, Fayers TM and Barnhart GR (2016): Minimally Invasive Mitral Valve Surgery I Patient Selection, Evaluation and Planning. Innovations (Philadelphia, Pa.), 11(4): 243–250.
2. Antunes MJ (2015): Challenges in rheumatic valvular disease: Surgical strategies for mitral valve preservation. Global Cardiology Science and Practice, 2015(1): 9-11.
3. Atluri P, Woo YJ, Goldstone AB, Fox J, Acker MA, Szeto WY and Hargrove WC (2013): Minimally invasive mitral valve surgery can be performed with optimal outcomes in the presence of left ventricular dysfunction. Annals of Thoracic Surgery, 96(5): 1596–1602.
4. Aybek T, Dogan S, Risteski PS, Zierer A, Wittlinger T, Wimmer-Greinecker G and Moritz A (2006): Two hundred forty minimally invasive mitral operations through right minithoracotomy. The Annals of Thoracic Surgery, 81(5): 1618–24.
5. De Praetere H, Verbrugghe P, Rega F, Meuris B and Herijgers P (2015): Starting minimally invasive valve surgery using endoclamp technology: Safety and results of a starting surgeon. Interactive Cardiovascular and Thoracic Surgery, 20(3): 351–358.
6. Galloway AC, Schwartz CF, Ribakove GH, Crooke GA, Gogoladze G, Ursomanno P and Grossi EA (2009): A Decade of Minimally Invasive Mitral Repair: Long-Term Outcomes. Annals of Thoracic Surgery, 88: 1180–1184.
7. Gao C, Yang M, Xiao C, Wang G, Wu Y, Wang J and Li J (2012): Robotically assisted mitral valve replacement. The Journal of Thoracic and Cardiovascular Surgery, 143(4 Suppl): S64-7.
8. Glauber M, Miceli A, Canarutto D, Lio A, Murzi M, Gilmanov D and Solinas M (2015): Early and long-term outcomes of minimally invasive mitral valve surgery through right minithoracotomy: a 10-year experience in 1604 patients. Journal of Cardiothoracic Surgery, 10(1): 181-190.
9. Holzhey DM, Shi W, Borger MA, Seeburger J, Garbade J, Pfannmller B and Mohr FW (2011): Minimally invasive versus sternotomy approach for mitral valve surgery in patients greater than 70 years old: A propensity-matched comparison. Annals of Thoracic Surgery, 91(2): 401–405.
10. Iribarne A, Easterwood R, Russo MJ, Wang YC, Yang J, Hong KN and Argenziano M (2011): A minimally invasive approach is more cost-effective than a traditional sternotomy approach for mitral valve surgery. Journal of Thoracic and Cardiovascular Surgery, 142: 1507–1514.
11. Iribarne A, Russo MJ, Easterwood R, Hong KN, Yang J, Cheema FH and Argenziano M (2010): Minimally invasive versus sternotomy approach for mitral valve surgery: a propensity analysis. The Annals of Thoracic Surgery, 90(5): 1471-7-8.
12. Mariscalco G and Musumeci F (2014): The minithoracotomy approach: a safe and effective alternative for heart valve surgery. The Annals of Thoracic Surgery, 97(1): 356–64.
13. Modi P, Hassan A and Chitwood WR (2008): Minimally invasive mitral valve surgery: a systematic review and meta-analysis. European Journal of Cardio-Thoracic Surgery: Official Journal of the European Association for Cardio-Thoracic Surgery, 34: 943–952.
14. Moscarelli M, Cerillo A, Athanasiou T, Farneti P, Bianchi G, Margaryan R and Solinas M (2016): Minimally invasive mitral valve surgery in high-risk patients: operating outside the boxplot. Interactive CardioVascular and Thoracic Surgery, 22(6): 756–761.
15. Ritwick B, Chaudhuri K, Crouch G, Edwards JR, Worthington M and Stuklis RG (2013): Minimally invasive mitral valve procedures: the current state. Minimally Invasive Surgery, 2013(3): 25-37.
16. Santana O, Reyna J, Grana R, Buendia M, Lamas GA and Lamelas J (2011): Outcomes of minimally invasive valve surgery versus standard sternotomy in obese patients undergoing isolated valve surgery. Annals of Thoracic Surgery, 91(2): 406–410.
17. Schmitto JD, Mokashi SA and Cohn LH (2010): Minimally-invasive valve surgery. Journal of the American College of Cardiology, 56(6): 455–62.
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