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ORIGINAL ARTICLE
Year : 2022  |  Volume : 10  |  Issue : 2  |  Page : 87-93

Clinical significance and postoperative outcomes after pulmonary vein isolation for atrial fibrillation in mitral valve surgery


Department of Cardio Vascular and Thoracic Surgery, U. N. Mehta Institute of Cardiology and Research Center, Ahmadabad, Gujarat, India

Date of Submission10-Mar-2022
Date of Decision28-Mar-2022
Date of Acceptance24-May-2022
Date of Web Publication12-Aug-2022

Correspondence Address:
Dr. Deepti Kakkar
Department of Cardio Vascular and Thoracic Surgery, U. N. Mehta Institute of Cardiology and Research Center, Ahmadabad, Gujarat
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/heartindia.heartindia_17_22

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  Abstract 


Atrial fibrillation is the most common tachyarrhythmia associated with mitral valve disease, resulting in significant morbidity and mortality. Atrial fibrillation is a marker of advanced cardiovascular disease and an independent predictor of death. As a large number of patients undergoing mitral valve operations are associated with chronic atrial fibrillation, pulmonary vein isolation procedure with cut and sew method can be concomitantly performed with a mitral valve operation and it is enough to improve the quality of life after operation by eliminating the morbidity associated with chronic atrial fibrillation. The aim of this study is to find out the immediate postoperative outcomes of the patients with known mitral valve disease with atrial fibrillation who are undergoing mitral valve surgery with concomitant pulmonary vein isolation at our institution. The perioperative risk factors such as older age, duration of atrial fibrillation, the size of the left atrium, and the mitral valve pathology were evaluated for their clinical significance. Preoperative, intraoperative, and postoperative variables were retrieved and analyzed retrospectively. The outcomes were compared between these subgroups using various statistical tools. Conversion to normal sinus rhythm was more significant in the younger age group (<45 years) as compared to the older age group. Seventy-eight percent patients (n = 117) were free from atrial fibrillation at the time of discharge. The overall mortality was 4% (n = 6). There was no procedure-related death.

Keywords: Atrial fibrillation, atrial fibrosis, combined procedure, cox-maze procedure, cryoablation, cut and sew method, mitral valve operation, pulmonary vein isolation, radiofrequency ablation, thromboembolism


How to cite this article:
Desai D, Kakkar D. Clinical significance and postoperative outcomes after pulmonary vein isolation for atrial fibrillation in mitral valve surgery. Heart India 2022;10:87-93

How to cite this URL:
Desai D, Kakkar D. Clinical significance and postoperative outcomes after pulmonary vein isolation for atrial fibrillation in mitral valve surgery. Heart India [serial online] 2022 [cited 2022 Sep 29];10:87-93. Available from: https://www.heartindia.net/text.asp?2022/10/2/87/353732




  Introduction Top


Atrial fibrillation is the most prevalent arrhythmia associated with mitral valve disease,[1] resulting in significant morbidity and mortality. Atrial fibrillation is a marker of advanced cardiovascular disease. It represents the progression of the disease and stage of remodeling in the atria. A large number of patients undergoing mitral valve operations are associated with chronic atrial fibrillation.[2],[3] In this group of patients, pulmonary vein isolation procedures with cut and sew method can be concomitantly performed with a mitral valve operation. This can greatly improve the quality of life and eliminate the associated morbidities.

There have been some reports describing experience with the combined procedures. This study is going to update experience with the pulmonary vein isolation procedure with the cut and sew method combined with mitral valve operation at our institution.


  Materials and methods Top


From 2012 to 2015, 150 patients with chronic atrial fibrillation and mitral valve disease underwent combined mitral valve surgery and pulmonary vein isolation surgery. Patients were identified from the Cardiovascular Information Registry, The Medical Records Department of our institute. Preoperative, intraoperative, and postoperative variables were retrieved. The patients with known rheumatic mitral valve disease with mitral regurgitation or mitral stenosis undergoing the mitral valve surgery concomitantly with pulmonary vein isolation procedure for atrial fibrillation were included. Patients with other than rheumatic etiology for mitral valve disease requiring the surgery, patients with lone atrial fibrillation,[4] or atrial fibrillation due to reasons other than mitral valve disease were excluded.

The findings of electrocardiograms and transthoracic echocardiography were noted. Trans-esophageal echocardiography was performed intraoperatively for all the patients.

Surgical method

All patients had a mid-line sternotomy approach. All surgical procedures were performed after the establishment of moderate hypothermic cardiopulmonary bypass with standardized protocols using the aortic and bicaval cannulation technique. The aorta was cross-clamped. Cold blood cardioplegic solution was administered to the heart through an antegrade cardioplegia cannula. After going on complete cardiopulmonary bypass, the left atriotomy was performed via an incision just posterior to the interatrial groove near the orifices of the right pulmonary veins. The incision was extended superiorly and inferiorly onto the left atrium around the right pulmonary veins [Figure 1].
Figure 1: Complete cardiopulmonary bypass established after snaring cavae. Aorta was cross clamped. Cold cardioplegic solution was administered to achieve total electromechanical arrest

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The left atrial incision was continued across the left atrium toward the left pulmonary veins to isolate and encircle them [Figure 2]. The heart was retracted to the right to expose the left atrial appendage. The left atrial appendage was ligated for all patients. Two orientation sutures of 4-0 polypropylene were placed through the left pulmonary vein encircling incision at the level of the left superior and left inferior pulmonary veins. Encircling incision was completed between orientation sutures [Figure 3]. Orientation sutures were tied, then used to close the left atrium between them. Exposure returned to the interior of the left atrium. Orientation sutures were passed inside the left atrium. The same sutures were used to close encircling incision which was made for left pulmonary vein isolation inferiorly for about 2 cm of posterior wall of the left atrium and superiorly to midpoint [Figure 4]. The left atrial appendage was closed from inside. The encircling incision was closed completely on the right side near to right pulmonary veins.
Figure 2: Left encircling incision was developed from left atrium via extending it across posterior wall of left atrium till left superior and inferior pulmonary veins

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Figure 3: Heart was retracted to right and inferior to expose left atrial appendage. The orientation sutures were used for closure

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Figure 4: Closure of the left encircling incision using the same orientation sutures which was brought from behind

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Mitral valve replacement was performed at this point of operation using standard surgical techniques. All patients were given warfarin after surgery, with a target international normalized ratio from 2.5 to 3.5.

Statistical methods and tools

All the variables were analyzed with described statistical methods. Chi-square test or Fisher exact test used for the analysis of variables. The postoperative outcomes were compared between perioperative risk factors such as older age, female sex, prolonged duration of atrial fibrillation, the size of the left atrium, and the mitral valve pathology. All of them were evaluated for their clinical significance. An independent t-test was used to compare the means between two unrelated groups. P < 0.05 was considered statistically significant.


  Results Top


Out of total 150 patients of the study population, 46.7% patients were male (n = 70) The mean age of the sample population was 45.66 ± 10.57 (n = 150). The mean age of presentation for atrial fibrillation was found earlier in the female population (44.90 ± 10.21 vs. 46.53 ± 10.97). There was no statistically significant difference between the mean age for male population and mean age for female population (P = 0.35).

The mean duration of atrial fibrillation was 22.36 ± 12.41 months. The cardiothoracic ratio (0.65 ± 0.09) was higher for all patients. On echocardiographic evaluation, the patients with mitral valve regurgitation (n = 100, 66.66%) had more incidence of atrial fibrillation than mitral stenosis (n = 50, 33.33%).

Most of the patients had undergone mitral valve replacement (n = 143, 95.33%) with standard intraoperative techniques. Bi-leaflet mechanical mitral valve prosthesis was used. The overall mean cardiopulmonary bypass time was 188.107 ± 66.87 min and aorta cross-clamp time was 148.22 ± 55.65 min.

Postoperative outcomes

The overall mean duration of postoperative mechanical ventilation was 24.43 ± 23.47 h with the mean postoperative intensive care stay was 151.99 ± 120.94 h. The mean total postoperative hospital stay was 12.91 ± 9.32 days. During the immediate postoperative period, complication like postoperative bleeding which required the re-exploration was found in 10 patients (6.7%). The immediate postoperative morbidity like low cardiac output requiring the intra-aortic balloon pump insertion was noted in 10% of the study population.(n = 15) Some of the patients had experienced multi-organ dysfunction (n = 12, 8%) which included the acute kidney injury requiring dialysis support. A total of 11 patients had to be re-intubated (7.4%) in the immediate postoperative stay. The major morbidity such as postoperative cerebrovascular accidents were found in 4% (n = 6) of the study population. Sepsis was found in 8% of total patients (n = 12). The wound-related problems mainly surgical site infections requiring minor interventions were found in 6% of patients (n = 9). The in-hospital mortality was 4% (n = 6). At the time of discharge from hospitals, 78% of patients (n = 117) were free from atrial fibrillation or any other atrial tachyarrhythmia requiring anti-arrhythmic drugs [Table 1].
Table 1: Postoperative variable and Outcomes

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Independent predictors for postoperative outcomes

Older age of the patient

The sample population was divided into two subgroup of patients: age more than 45 years (n = 76, 50.7%) and age < 45 years (n = 74, 49.3%). The mean age (54.24 ± 5.47 vs. 36.85 ± 6.47) of this two groups was found significant (P < 0.05). The history of cerebrovascular accident was higher in group with age more than 45 years (n = 6, 7.9% vs n = 2, 2.7%; P = 0.027). The cardiothoracic ratio on chest X-ray was found significant (0.63 ± 0.09 vs. 0.67 ± 0.09; P = 0.009). The postoperative ventilation duration was higher in older age group (27.97 ± 27.66 vs. 20.79 ± 17.66). The immediate postoperative morbidities such as low cardiac output and related complication were found more in older age group (n = 11, 14.5% vs. n = 4, 5.4%; P = 0.06). Other morbidities were found not significant. The procedural success in terms of conversion to normal sinus rhythm was found significantly higher in younger age group (n = 53, 69.7% vs. n = 64, 86.5%; P = 0.02). In other words, more number of patients of higher age group remained in atrial fibrillation (n = 23, 30.3% vs. n = 10, 13.5%; P = 0.01). The in-hospital mortality was higher with older age group of patients (n = 4, 5.3% vs. n = 2, 2.7%) [Table 2].
Table 2: Comparisons of Outcomes in older age subgroup

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Left atrial enlargement

The perioperative variable and outcomes were compared between the subgroups of patients: those with left atrial size more than 55 mm and those with < 55 mm. The difference between the mean age of these subgroups was found significant (42.23 ± 10.05 vs. 49 ± 10.02; P < 0.005). The large atrial size was significantly associated with atrial fibrillation duration. The mean cardiothoracic ratio was compared (0.73 ± 0.07 vs. 0.58 ± 0.04; P < 0.005). More number of patients were found with vegetation on mitral valve with larger left atrium (n = 4, 5.4% vs. n = 2, 2.6%; P = 0.43). That explains the need for the reduction for atrial size by doing pulmonary vein isolation [Table 3].
Table 3: Outcomes in left atrial enlargement

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In the study population with known rheumatic mitral valve disease, one-third of sample patients had mitral stenosis (n = 50, 33.3%) and remaining with mitral regurgitation (n = 100, 66.7%) as dominant pathology along with atrial fibrillation. The stenotic and regurgitant subgroups were compared for immediate post-operative outcomes. The postoperative comorbidities were higher in stenotic group but not statistically significant [Table 4]. The number of patients with conversion to normal sinus rhythm was found more in group with regurgitant lesion of the mitral valve (n = 35, 70% vs. n = 82, 82%; P = 0.09) The in-hospital mortality was found higher with stenotic group.(n = 4, 8% vs. n = 2, 2%; P = 0.09).
Table 4: Outcomes associated with mitral valve pathology

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Echocardiographic indices

On comparison, there was a significant reduction of the left atrial size was noted post operatively (56.26 ± 9.50 vs. 46.53 ± 5.02; P < 0.005). The postoperative left ventricular diastolic function was improved significantly in terms of reduction of end diastolic volume (116.66 ± 41.44 vs. 107.46 ± 36.13; P = 0.003). There was a significant improvement in pulmonary hypertension also noted (55.16 ± 20.03 vs. 41.16 ± 11.45; P < 0.005) [Table 5].
Table 5: Comparison of Echocardiographic Indices

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  Discussion Top


All 150 patients of the sample were known cases of rheumatic mitral valve disease with variable duration of atrial fibrillation. All the enrolled patients had anti-arrhythmic agents in the past, but the atrial fibrillation could not be controlled with pharmacological measures.

The preoperative variables were analyzed with various statistical methods. There were no clinically significant differences on immediate postoperative outcomes due to anthropometric variables but in deciding intraoperative strategies and decision-making like selection of valve prosthesis (size and type); these variable were found very important. The demographic variables such as age and sex of the patients were analyzed. 143 In our study population, 80 patients were female (53.33%). There was no significant difference noted in the age of presentation, but female population presented little earlier. This was explained by the higher prevalence of rheumatic mitral valve disease in the young female population in India.[5] In our study, past history of systemic hypertension (n = 11, 7.3%), diabetes mellitus (n = 20, 13.3%), any episode of cerebrovascular accident (n = 8, 5.3%), and smoking (n = 15, 10%) were found in the study population.

The older age group had significant differences in immediate postoperative outcomes. We divided the sample population into two subgroups with criteria more than 45 years and < 45 years. We could compare the perioperative risk factors for these two groups. On analysis of the outcome, we found the conversion to normal sinus rhythm was more significant in younger age group compared to older age group (n = 53, 69.7% vs. n = 64, 86.5%; P = 0.02). In other words, atrial fibrillation remained persistent postoperatively in patients with older age (n = 23, 30.3% vs. n = 10, 13.5%; P = 0.01) This is explained by theory of atrial fibrosis.[6] The long-standing mitral pathology is the cause for persistent wall stress on left atrial wall. This persistent wall stress leads to the development of chronic persistent inflammation which is one of the triggers for the atrial fibrosis and ultimately atrial fibrillation.

Disintegrin and matrix metalloproteinase levels are increased in atrial fibrillation which is responsible for cell-cell and cell-matrix interactions leading to dilatation of atria as a long-term complication.[7] The patients with severe fibrosis of atrial wall do not respond well with DC cardioversion compared to mild and moderate fibrosis.[8] Hence, surgical intervention like pulmonary vein isolation helps to reduced the left atrial size and disrupt the accessory triggering pathways.[9] We found immediate morbidities more in the older patients. The incidence of low cardiac output (n = 11, 14.5% vs. n = 4, 5.4%; P = 0.06) and multi-organ failure (n = 8, 10.5% vs. n = 4, 5.4%; P = 0.36) were higher with older age group of the patients. The in-hospital mortality was also higher with older age group of patients (n = 4, 5.3% vs. n = 2, 2.7%, P = 0.68). Hence, older age group is associated with more postoperative morbidities and mortality though we couldn't prove it statistically significant.

Large left atrial size is also considered as an individual predictor for risk. In our study, all 150 patients had dilated left atrium. The mean size of the left atrium was 56.26 ± 9.50 mm. We could not compare the outcomes with the control group in which left atrium is normal. This was one of the confounding factor of the study.

We have compared the outcomes between the two different subgroups with left atrium size more than 55 mm and < 55 mm. In both the subgroups the immediate postoperative morbidities and other outcomes did not show any comparable significant differences including the mortality. We could explain this with reduction in postoperative left atrial size in both the subgroups. The mean left atrial size postoperatively on echocardiography was 46.53 ± 5.02. It was significant reduction with P < 0.005. Hence, overall outcomes were improved with improvement with left atrial size. Thus, the need for combining the pulmonary vein isolation procedure in atrial fibrillation with dilated atria is justified probably due to improving the immediate postoperative outcome.

We compared the outcomes in different mitral valve pathology. We divided the study population into stenotic and regurgitant lesions. We observed that patients with regurgitant lesion had better results compared to stenotic lesion. The number of patients with conversion to normal sinus rhythm were found more in the group with regurgitant lesion of mitral valve (n = 35, 70% vs. n = 82, 82%; P = 0.09) The in-hospital mortality was found higher with stenotic group (n = 4, 8% vs. n = 2, 2%; P = 0.09). The higher pressure and volume overload is found as a causative factor for left atrial remodeling. In mitral stenosis with dilated left atrium, the left atrial biopsies taken during mitral valve surgeries have proven more atrial fibrosis and more chronic persistent inflammatory component compared to regurgitant lesions. Paroxysmal atrial fibrillation mostly initiates in the pulmonary veins. A great deal of emphasis has been given on the role of the pulmonary veins in triggering of atrial fibrillation. The anatomy of the pulmonary veins is variable in humans. Electrically excitable cardiac muscle extends 1–4 cm beyond the ostium of the veins.[10] Developmental biological studies[11] suggest that pacemaker tissue may be present in the pulmonary veins. Many intraoperative mapping studies[12] have shown ectopic foci for developing atrial beats found in the region of pulmonary veins. Schmitt, et al.[13] have shown that in bi-atrial mapping studies the premature beats that trigger atrial fibrillation were located in the pulmonary veins 53% of the time and in the posterior atrium in another 29% of cases.

Pulmonary vein isolation has shown good success in achieving normal sinus rhythm in patients with sustained atrial fibrillation. In some patients, the normal sinus rhythm is not achieved even after pulmonary vein isolation which explains another complex mechanism for the development of atrial fibrillation or other anatomical triggers may be involved. Usually in the setting of mitral valve, disease-associated atrial fibrillation the mechanism for atrial fibrillation is the concurrent focal atrial activation.[14] Pulmonary vein isolation surgery usually involves more than just the pulmonary veins. It usually extends into oblique sinus of left atria and left atrial muscles adjacent to origins of pulmonary veins. Hence, it incorporates the large cardiac mass in isolation surgery compared to catheter-based ablation techniques. Thus, this large cardiac mass ablation or isolation typically reduces the critical mass needed to sustain atrial fibrillation.

In spite of being controversial, the pulmonary vein isolation done in atrial fibrillation along with mitral valve surgeries has shown acceptable outcomes overall. 78% patients (n = 117) were free from atrial fibrillation or any other atrial tachyarrhythmia requiring anti-arrhythmic drugs at the time of discharge from the hospital. Therefore, it is likely that isolating the pulmonary vein alone is sufficient treatment for persistent and long-standing chronic atrial fibrillation. These results have prove the theory that atrial fibrillation might have right-sided or bi-atrial triggers in some instances. Hence, further extensive lesion is required to convert in the normal sinus rhythm. The overall mortality was 4% (n = 6). There was no procedure-related death. The cause for the mortality during the study was persistent atrial fibrillation and low cardiac output state refractory to the treatment.

Limitations of the study

The study was conducted in a single center in a retrospective manner. As being retrospective, this study offers a follow-up for the early postoperative period. For better understanding, the long-term follow-up is important. Doing pulmonary vein isolation procedures in patients with multi-valvular surgery still remains controversial. A multi-center prospective study is required for a better understanding of clinical significance of the associated risk factors and postoperative outcomes.


  Conclusion Top


Atrial fibrillation is the most prevalent arrhythmia frequently associated with mitral valve disease. Due to atrial fibrillation, risk of thromboembolism increases, resulting in significant morbidity and mortality. Atrial fibrillation is a predictor for risk and associated with advanced cardiovascular disease. Atrial fibrillation is an independent predictor of death. Pulmonary vein isolation procedure with cut and sew method can be concomitantly performed with a mitral valve operation. This can be enough to improve the quality of life after operation by eliminating the morbidity associated with chronic atrial fibrillation.

Ethical approval

Institutional Ethics Committee approval was taken for this study.

Authors' contributions

Both the authors have contributed equally in designing the analysis, data collection, data analysis, manuscript writing.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Cox JL. Intraoperative options for treating atrial fibrillation associated with mitral valve disease. J Thorac Cardiovasc Surg 2001;122:212-5.  Back to cited text no. 1
    
2.
Feinberg WM, Blackshear JL, Laupacis A, Kronmal R, Hart RG. Prevalence, age distribution, and gender of patients with atrial fibrillation. Analysis and implications. Arch Intern Med 1995;155:469-73.  Back to cited text no. 2
    
3.
Fuster V, Rydén LE, Asinger RW, Cannom DS, Crijns HJ, Frye RL, et al. ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines and Policy Conferences (Committee to develop guidelines for the management of patients with atrial fibrillation) developed in collaboration with the North American Society of Pacing and Electrophysiology. Eur Heart J 2001;22:1852-923.  Back to cited text no. 3
    
4.
Kopecky SL, Gersh BJ, McGoon MD, Whisnant JP, Holmes DR Jr., Ilstrup DM, et al. The natural history of lone atrial fibrillation. A population-based study over three decades. N Engl J Med 1987;317:669-74.  Back to cited text no. 4
    
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Padmavati S. Rheumatic heart disease: prevalence and preventive measures in the Indian subcontinent. Keywords: Rheumatic heart disease; rheumatic fever. Heart 2001;86:127.  Back to cited text no. 5
    
6.
Allessie M, Ausma J, Schotten U. Electrical, contractile and structural remodeling during atrial fibrillation. Cardiovasc Res 2002;54:230-46.  Back to cited text no. 6
    
7.
Mary-Rabine L, Albert A, Pham TD, Hordof A, Fenoglio JJ Jr., Malm JR, et al. The relationship of human atrial cellular electrophysiology to clinical function and ultrastructure. Circ Res 1983;52:188-99.  Back to cited text no. 7
    
8.
Bailey GW, Braniff BA, Hancock EW, Cohn KE. Relation of left atrial pathology to atrial fibrillation in mitral valvular disease. Ann Intern Med 1968;69:13-20.  Back to cited text no. 8
    
9.
Schwartzman D, Bazaz R, Nosbisch J. Common left pulmonary vein. J Cardiovasc Electrophysiol 2004;15:560-6.  Back to cited text no. 9
    
10.
Spach MS, Barr RC, Jewett PH. Spread of excitation from the atrium into thoracic veins in human beings and dogs. Am J Cardiol 1972;30:844-54.  Back to cited text no. 10
    
11.
Blom NA, Gittenberger-de Groot AC, DeRuiter MC, Poelmann RE, Mentink MM, Ottenkamp J. Development of the cardiac conduction tissue in human embryos using HNK-1 antigen expression: Possible relevance for understanding of abnormal atrial automaticity. Circulation 1999;99:800-6.  Back to cited text no. 11
    
12.
Chen YJ, Chen SA, Chang MS, Lin CI. Arrhythmogenic activity of cardiac muscle in pulmonary veins of the dog: Implication for the genesis of atrial fibrillation. Cardiovasc Res 2000;48:265-73.  Back to cited text no. 12
    
13.
Schmitt C, Ndrepepa G, Weber S, Schmieder S, Weyerbrock S, Schneider M, et al. Biatrial multisite mapping of atrial premature complexes triggering onset of atrial fibrillation. Am J Cardiol 2002;89:1381-7.  Back to cited text no. 13
    
14.
Nitta T, Ishii Y, Miyagi Y, Ohmori H, Sakamoto S, Tanaka S. Concurrent multiple left atrial focal activations with fibrillatory conduction and right atrial focal or re-entrant activation as the mechanism in atrial fibrillation. J Thorac Cardiovasc Surg 2004;127:770-8.  Back to cited text no. 14
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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