A combined cellular and surgical ventricular reconstruction therapeutic approach produces attenuation of remodeling in infarcted rats Academic research paper on "Veterinary science"

Accepted Manuscript

A combined cellular and surgical ventricular reconstruction therapeutic approach produces attenuation of remodeling in infarcted rats

Michael J. Bonios, MD, Maria Anastasiou-Nana, MD, Despina N. Perrea, MD, Konstantinos Malliaras, MD

PII: S1109-9666(16)30117-8

DOI: 10.1016/j.hjc.2016.11.036

Reference: HJC 98

To appear in: Hellenic Journal of Cardiology

Received Date: 19 July 2016 Revised Date: 18 November 2016 Accepted Date: 22 November 2016

Please cite this article as: Bonios MJ, Anastasiou-Nana M, Perrea DN, Malliaras K, A combined cellular and surgical ventricular reconstruction therapeutic approach produces attenuation of remodeling in infarcted rats, Hellenic Journal of Cardiology (2017), doi: 10.1016/j.hjc.2016.11.036.

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

A combined cellular and surgical ventricular reconstruction therapeutic approach produces attenuation of remodeling in infarcted rats

1 12 Michael J. Bonios1 MD, Maria Anastasiou-Nana1 MD, Despina N. Perrea2 MD,

Konstantinos Malliaras1 MD

3 Department of Cardiology, University of Athens School of Medicine, Athens, Greece

2 Laboratory for Experimental Surgery and Surgical Research "N.S. Christeas", University of Athens School of Medicine, Athens, Greece

Short title: Left ventricle reconstruction surgery combined with stem cells

Address for correspondence:

Konstantinos Malliaras, MD

3rd Department of Cardiology, University of Athens School of Medicine 67 Mikras Asias Street, 11 527, Athens, Greece

Tel: +30 210 8236877; Fax: +30 210 7789901; e-mail: malliaras@gmail.com

Background: Left ventricular reconstruction (LVR) has been shown to provide transient benefits in LV structure and function of infarcted hearts; however long-term results have been disappointing, as LVR-induced benefits are typically not sustained. We hypothesized that administration of cardiosphere-derived cells (CDCs), which promote myocardial repair and regeneration, may result in long-term preservation of the beneficial effects of LVR in ischemic cardiomyopathy.

Methods: Wistar Kyoto rats underwent myocardial infarction (MI) and two weeks later were randomized into 3 groups: in Group 1 (n=9) LVR was performed by plication of the infarcted apex and CDCs were injected in the infarct border zone (IBZ); group 2 animals (n=9) underwent LVR and received vehicle solution in the IBZ. Group 3 animals (n=10) were injected with vehicle solution in IBZ, without undergoing LVR. Echocardiograms were performed at baseline, 4 days post-apex plication, and 3 months post-MI.

Results: At baseline, all animal groups had comparable LVEF, LV end-diastolic volume (EDV) and LV end-systolic volume (ESV). Four days post-LV apex plication, Group 1 and Group 2 animals exhibited comparable significant improvement in EF and comparable significant reduction in LVEDV and LVESV. Three months post-MI, Group 1 animals had decreased LVEDV, decreased LVESV, less impaired CS, increased peak systolic torsion and increased EF compared to animals in Groups 2 and 3.

Conclusion: In infarcted rat hearts, intramyocardial delivery of CDCs in conjunction with LVR resulted in significant and sustained amelioration of LV remodeling and improvement in LV function, compared to LVR alone.

Key words: Remodeling, reconstruction, cardiosphere-derived cells

Introduction

Left ventricular reconstruction surgery (LVR) aims at surgical restoration of a spherical dilated infarcted LV to its normal elliptical shape through exclusion of scarred myocardium and application of an endoventricular patch.1,2 While LVR has been shown to produce acute reduction in LV volumes and improvement in LV systolic function, long-term effects have been underwhelming; LVR-induced benefits are often not sustained 3-7 most likely due to progression of adverse remodeling in the non-infarcted myocardium despite surgical exclusion of the scar.

Cell therapy with cardiosphere-derived cells (CDCs) has emerged as a potential therapeutic strategy for ischemic cardiomyopathy, yielding promising results in the first-in man CADUCEUS trial. 8,9 Mechanistic animal studies have demonstrated that CDCs promote heart repair and attenuate remodeling post-myocardial infarction by exerting regenerative, angiogenic and antifibrotic effects.10-12 Here, we hypothesized that that application of a combined surgical and biological therapeutic approach comprising LVR and cell therapy with CDCs may result in sustained structural and functional improvements post-LVR.

Methods Ethical Approval

Animal care, surgical operations and postoperative care were approved by the Athens University Medical School Ethics Committee and by the Veterinary Directorate of the Ministry of Agriculture in agreement with the European Union directive 86/609.

Tissue Culture

CDCs were expanded from hearts of 3-month-old male Wistar Kyoto rats (Charles

Rivers Laboratories, Italy), as described previously. Briefly, small pieces of myocardial

tissue (explants) were partially digested with trypsin and placed on fibronectin-coated dishes. In the following days, a layer of stromal-like cells emerged from the cardiac explant over which phase bright cells proliferated. These outgrowth cells were harvested using mild enzymatic digestion and were seeded on D-poly-lysine-coated dishes, where they formed three-dimensional cardiospheres. Cardiospheres were subsequently harvested and plated on fibronectin-coated flasks to generate CDCs. CDCs were cultured in Iscove's modified Dulbecco's medium (containing 4.5 g/L glucose, 20% fetal bovine serum, 10% glutamine, 10% penicillin/streptomycin, and 0.1 mmol/L mercaptoethanol) and expanded for three passages prior to transplantation.

Surgical procedures

Syngeneic Wistar Kyoto rats were used in this study. Animals were intubated; anesthesia was induced with 4% isoflurane inhalation and maintained with 1.5% inhalation. The heart was exposed through a right lateral thoracotomy and myocardial infarction (MI) was induced by permanent ligation of the middle portion of the left anterior descending coronary artery (LAD) using a 5.0-mm silk suture. The chest was then closed, and animals were allowed to recover. Two weeks later, after a second thoracotomy, animals were randomly assigned into 3 groups: a) in group 1 (LVR+c) LVR was performed by plication of the infarcted apex using a 2-0 silk suture (excluding the infarcted myocardial tissue), and 3*106 CDCs were injected in the border zone of the LV plication; b) in group 2 (LVR+p) LVR was performed and vehicle solution (Phosphate Buffered Saline-PBS) was injected in the border zone of the LV plication; c) in group 3 (control group) no LVR was performed and vehicle solution was injected in the border zone of the infarcted area. Three months post-MI, animals were euthanized and hearts were excised and weighed immediately following excision. All animals used in the study received humane care, in compliance with the 1996 "Guide for the Care and the Use of Laboratory Animals" published by the US National Institutes of Health.

Echocardiography

Conventional echocardiographicparameters

Cardiac echocardiography was performed using a 10-MHz transducer coupled to a Vivid Q machine (GE Medical Systems, Horten, Norway). Echocardiography was performed in 10 non-infarcted rats (to obtain baseline echocardiographic parameters) and in infarcted rats at three timepoints: prior to the second thoracotomy (2 weeks post-MI, groups 1,2&3), 4 days post-apex plication (groups 1&2), and 3 months post-MI (groups 1,2&3). Rats were intubated and anesthesia was maintained with 1.5% isoflurane during imaging; heart rate was monitored, and body temperature was maintained at 37°C during image acquisition. Two-dimensional long-axis images were used for measurement of LV end-diastolic volume (LVEDV), LV end-systolic volume (LVESV), LV end-diastolic diameter (LVEDD) and left ventricular ejection fraction (LVEF). To ensure uniformity of the studied population, animals were included in the study if their LVEF was >40% and <55% 2 weeks post-LAD ligation.

Deformational echocardiographic parameter analysis

Three LV short-axis planes were obtained at basal (at the level of the mitral valve), mid-LV (at the level of papillary muscles) and apical (distally to the papillary muscles) levels. For speckle tracking analysis the endocardial border was traced in each image and the ROI was adjusted to fit the myocardium. Each short-axis image was automatically divided into 6 standard segments (septal, anteroseptal, anterior, lateral, posterior, inferior) and the LV rotation from the apical and basal short-axis images was calculated as the average angular displacement of the 6 standard segments by referring to the ventricular centroid, frame by frame. Counter-clockwise rotation was marked as a positive value and clockwise rotation as a negative value when viewed from the apex. The LV twist curve was generated by calculating the difference between apical and basal rotations at each corresponding timepoint. LV torsion was then calculated as the ratio between LV twist (in degrees) and the LV diastolic longitudinal length (in cm) between the LV apex and the mitral plane.

Circumferential strain (CS) of the mid-LV was calculated using the mid-LV short axis images. Mean circumferential strain was defined as the average strain of all 6 segments in a particular short-axis view. The peak longitudinal strain (LS) in all 6 segments from a

long-axis image was averaged to calculate the LS. The adjustments of the sector width for this transducer resulted in a maximum frame rate of 90 to 100 frames/sec. We measured circumferential strain only, since its reproducibility is superior to that of radial strain in rat

studies. 14

Statistics

Values are reported as mean ± SEM. Comparisons of echocardiographic data among groups were performed by 2-way repeated measures analysis of variance. P values < 0.05 were considered statistically significant.

Results

Adverse events and mortality

A total of 124 rats were used in the study. Fifty four animals died during surgery or in the follow-up period and 31 animals were excluded due to EF <40% or >55% 2 weeks post-LAD ligation (to ensure a relatively uniform degree of MI-induced deterioration of LV function at baseline). One animal was excluded when signs of loose suture were revealed during echocardiography. Nine animals assigned to group 1 (LVR+c), 9 animals assigned to group 2 (LVR+p) and 10 animals assigned to group 3 (control) successfully completed the follow-up and were included in the analysis.

LV structural deformation and functional deterioration post-MI

The echocardiographic parameters of non-infarcted animals are provided in table 1. As shown in figures 1&2, induction of MI resulted in significant deformation of cardiac structure and deterioration of cardiac function. Compared to non-infarcted animals, infarcted animals (Groups 1,2&3), exhibited a significant increase in LVEDV (+77%, p<0.001), LVESV (+212%) and LVEDD (+35%, p<0.001), and a significant reduction in EF (-34%, p<0.001), CS (-22%, p<0.001), peak LV torsion (-65%, p<0.001), LS (-56%, p<0.001) and

sphericity index (SI) (-21%, p<0.001) 2 weeks post-MI. All aforementioned echocardiography parameters were comparable among groups 1,2&3at two weeks post-MI.

Acute effects of LVR on left on LV structure and function

LVR resulted in acute improvement of LV structure and function. As shown in Figs 1&2, four days post-LV plication Group 1&2 animals exhibited significant reductions in LVEDV (-41%, p<0.001), LVESV (-67%, p<0.001) and LVEDD (-15%, p<0.001), and significant improvements in LVEF (+52%, p<0.001) and CS (+22%, p<0.001) compared to baseline (2 weeks post-MI, prior to LV plication). LVR had no significant beneficial effect on peak LV torsion (+9%, p=0.7), LS (+9%, p=0.7) and SI (-8%, p=0.1). All aforementioned echocardiographic parameters were comparable between groups 1&2 at four days post-LVR.

Long-term effects of LVR and cell therapy on LV structure and function

As shown in Fig 1, LVR in conjunction with cell therapy with CDCs produced sustained attenuation of remodeling and improvement in function; 3 months post-MI Group 1 animals had decreased LVEDV (274±9 uL vs 357±29 uL vs 369±19 uL,p=0.003, in Groups 1, 2 and 3 respectively, p<0.003), decreased LVESV (149±8 uL vs 216±26 uL vs 232±13 uL, p=0.002), decreased LVEDD (6.5±0.2 mm vs 7.7±0.4 mm vs7.8±0.2 mm, p=0.002,) and increased EF (48±4% vs 36±4 vs 35±3%, p=0.005) compared to animals in groups 2&3. Representative serial M-mode echocardiography images showing sustained improvement of cardiac structure and function following a combined therapeutic approach of cell therapy and surgical LVR are provided in Fig 3. In addition, group 1 animals exhibited less impaired CS (-14.2± 0.4% vs -10.9±0.6% vs -10.9±0.7%, p=0.001) (Fig 2,4), increased peak systolic torsion (7.8±0.6 °/cm vs 4.7±0.7 °/cm vs 4.4±0.8 °/cm, p=0.006) (Fig 2,4) and decreased heart weight (Fig 5) compared to animals in groups 2&3.

Discussion

The salient finding of our study is that a combined biological and surgical therapeutic approach comprising cell therapy with CDCs in conjunction with LVR produces sustained attenuation of remodeling and improvement in function in infarcted rats. This finding is in concordance with previous experimental studies 5-7 reporting beneficial effects of combined biological and surgical therapeutic approaches on cardiac structure and function post-MI. The novelty of our study lies in the utilization of heart-derived cells and the in-depth echocardiographic evaluation of cardiac function (with assessment of LV strain and torsion) post-cell therapy and LVR.

Post-infarction LV remodeling comprises changes in LV size (dilatation) and geometry (increased sphericity). This maladaptive process produces a transverse orientation of the normally obliquely-orientated myocardial fibers, resulting in reduction of ejection

fraction and impairment of LV torsion, even in the setting of preserved fiber shortening. 15-17

The concept of reducing LV volume by surgical exclusion of the scarred myocardial tissue

was introduced by Dor. While many early non-randomized trials reported beneficial effects post-LVR 1,19,2°, the randomized STICH trial challenged the role of SVR in ischemic heart failure 21; in STICH, LVR produced only modest reductions in LV volumes and failed to decrease morbidity or mortality. In our study, LVR resulted in acute reduction of LV

volumes and improvement in systolic function, in accordance with previous experimental

22,23 24,25

studies in small 22,23 and large animals. 24,25 However, the acute beneficial effects of LVR on

cardiac structure and function were not sustained over the long-term follow up. This finding

is consistent with studies in human subjects, showing that (at least in a subset of patients)

LVR only produces transient benefits. 3,4 In the study by Dor et al 4 left ventricular end-

systolic volume increased by up to 20% within 1 year post-LVR in patients with large

akinetic or dyskinetic scars. In the study by Di Donato et al, the LVR-induced benefits in

cardiac structure and function observed acutely post-LVR were completely abrogated within

11 months in a substantial portion of patients undergoing LVR.3 While the reasons for this

are unclear, potential explanations include failure of complete surgical scar exclusion,

additional myocardial damage induced by LVR itself and progression of the remodeling

process in the non-infarcted myocardium despite exclusion of the scar (due to relative

volume overload). We hypothesized that a combined approach comprising LVR and cell

therapy with heart-derived cells (which have been shown to exert regenerative and anti-remodeling effects) could result in sustained structural and functional improvements post-LVR.

In our study, infarcted animals that received cell therapy with CDCs in conjunction with LVR exhibited sustained attenuation of remodeling (decreased LV volumes) and improved systolic function over the long-term follow-up compared to infarcted animals that underwent LVR only or no LVR (control group). Importantly, the combined biological and surgical therapeutic approach employed in our study produced sustained improvement in cardiac deformational and rotational parameters (CS and torsion), which have been shown to be independent predictors of remodeling post-MI. 26-30

CDCs have been shown to induce therapeutic regeneration of infarcted myocardium in both animal 13,14,31,32 and clinical studies.8,9 The vast majority of newly-generated myocardium arises from endogenous sources (proliferation of resident myocytes and activation of endogenous progenitors.10-12 In addition, heart-derived cells have been shown

to exert significant angiogenic and anti-fibrotic effects. We postulate that the aforementioned regenerative, angiogenic and antifibrotic effects of heart-derived cells underlie the sustained attenuation of adverse remodeling and improvement in systolic function observed post-LVR in our study. The encouraging results of our study justify further assessment of the combined therapeutic approach comprising LVR and cell therapy with CDCs in large animal models of ischemic heart failure and possibly in humans.

Study limitations

Our study has important limitations. First, our study design did not include a group receiving cell therapy only (without LVR). However, our study primarily aimed to determine whether the transient benefits observed post-LVR could be preserved after concurrent administration of cell therapy. Thus, inclusion of a group receiving cell therapy only (without LVR), was deemed unnecessary. Second, no histological analysis was performed in the explanted hearts. Third, our study does not offer any mechanistic insights

into the anti-remodeling effects of CDCs. However, several previous studies in CDCs have investigated the regenerative, antifibrotic and angiogenic effects of heart-derived cells. 10-12

Conclusion

A combined biological and surgical therapeutic approach comprising cell therapy with CDCs in conjunction with LVR produces sustained attenuation of remodeling and improvement in function (including improvement in cardiac deformational and rotational parameters) in infarcted rats.

Figures

End-diastolic volume

Normal 2 weeks 4 days 3 months animals post-MI post-LVR post-MI

B) 250 200

150 100 50 0

End-systolic volume

Normal 2 weeks 4 days 3 months animals post-MI post-LVR post-MI

• LVR + p

-LVR + c ----Control

C) 80 60

Ejection fraction

Normal 2 weeks 4 days 3 months animals post-MI post-LVR post-MI

End-diastolic diameter

Normal 2 weeks 4 days 3 months animals post-MI post-LVR post-MI

Figure 1. Serial echocardiographic assessment of left ventricular end-diastolic volume (A), end-systolic volume (B), ejection fraction (C) and end-diastolic diameter (D). Surgical left ventricular reconstruction (LVR) in conjunction with cell therapy with CDCs (LVR + C) produced sustained attenuation of remodeling (decreased end-diastolic volume, decreased end-systolic volume, decreased end-diastolic diameter) and improvement in function (increased ejection fraction) post-MI, compared to surgical LVR alone (LVR + P) or no LVR. * p<0.05

Peak left ventricle torsion

Circumferential strain

'/cm 5 .

B) -20

(%) -15 ■

Normal 2 weeks 4 days 3 months animals post-MI post-LVR post-MI

.......LVR + p

Longitudinal strain

Normal 2 weeks 4 days 3 months animals post-MI post-LVR post-MI

■LVR+c ----Control

Sphericity index

Normal 2 weeks 4 days 3 months animals post-MI post-LVR post-MI

Normal 2 weeks 4 days 3 months animals post-MI post-LVR post-MI

Figure 2. Serial echocardiography assessment of peak left ventricular torsion (A), circumferential strain (B), longitudinal strain (C) and sphericity index (D). Surgical left ventricular reconstruction (LVR) in conjunction with cell therapy with CDCs (LVR + C)

produced sustained improvement in left ventricular torsion and circumferential strain post-MI, compared to surgical LVR alone (LVR + P) or no LVR. * p<0.05

2 weeks 4 days 3 months

post-MI post-LVR post-MI

Figure 3. Representative serial M-mode echocardiographic images from an animal undergoing surgical left ventricular reconstruction (LVR) in conjunction with cell therapy with CDCs (LVR + C, bottom row) and an animal undergoing surgical LVR alone (LVR + P, top row). Note the decreased end-diastolic diameter and the improved fractional shortening observed in the animal undergoing LVR and cell therapy compared to the animal undergoing LVR alone 3 months post-MI.

Left ventricular rotation (white). Apical rotation (blue). Basal rotation (purple)

Left ventricular circumferential strain (mid-portion)

2 weeks 4 days 3 months 2 weeks post-MI post SVR Post-MI post-MI

4 days 3 months post R post-MI

Figure 4. Representative serial 2d-speckle tracking left ventricle rotational mechanics curves from an animal undergoing surgical left ventricular reconstruction (LVR) in conjunction with cell therapy with CDCs (LVR + C, right side) and an animal undergoing surgical LVR alone (LVR + P, left side). Three months post-myocardial infarction, the LVR-c animal exhibited superior left ventricular rotational mechanics.

Heart weight

LVR+p iLVR+c I Control

Figure 5. Animals undergoing surgical left ventricular reconstruction (LVR) in conjunction with cell therapy with CDCs (LVR + C) exhibited reduced heart weight at 3 months post-MI, compared to animals undergoing surgical LVR alone (LVR + P) or no LVR.

Table 1. Conventional and 2d- speckle tracking deformational and rotational left ventricle echocardiographic parameters of normal animals (without infarction)

Left ventricle end-diastolic volume (uL)

Left ventricle end-systolic volume (uL)

Left ventricle ejection fraction (%)

Left ventricle end diastolic diameter (mm)

Left ventricle circumferential strain (%)

(mid-portion)

Peak left ventricle torsion (°/cm)

137 ± 7 41 ± 5 70 ± 4 4.2 ± 1.5

-18.3 ± 0.2

20.5 ± 1.5

Left ventricle longitudinal strain (%) Left ventricle sphericity index

12.2 ± 0.3 2.8 ± 0.1

Competing Interests

Authors report no conflicts of interest

Author contributions

All authors: approved the final version of the manuscript and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Finally, it is confirmed that all persons designated as authors qualify for authorship, and all those who qualify for authorship are listed

References

1. Athanasuleas CL, Buckberg GD, Stanley AW, et al. Surgical ventricular restoration in the treatment of congestive heart failure due to post-infarction ventricular dilation. J Am Coll Cardiol 2004;44:1439-45.

2. Athanasuleas CL, Buckberg GD, Stanley AW, et al. Surgical ventricular restoration: the RESTORE Group experience. Heart Fail Rev 2004;9:287-97.

3. Di Donato M, Castelvecchio S, Burkhoff D, Frigiola A, Raweh A, Menicanti L. Baseline left ventricular volume and shape as determinants of reverse remodeling induced by surgical ventricular reconstruction. Ann Thorac Surg 2011;92:1565-71.

4. Dor V, Sabatier M, Di Donato M, Montiglio F, Toso A, Maioli M. Efficacy of endoventricular patch plasty in large postinfarction akinetic scar and severe left ventricular dysfunction: comparison with a series of large dyskinetic scars. J Thorac Cardiovasc Surg 1998;116:50-9.

5. Kang K, Sun L, Xiao Y, et al. Aged human cells rejuvenated by cytokine enhancement of biomaterials for surgical ventricular restoration. J Am Coll Cardiol 2012;60:2237-49.

6. Saito S, Miyagawa S, Sakaguchi T, et al. Myoblast sheet can prevent the impairment of cardiac diastolic function and late remodeling after left ventricular restoration in ischemic cardiomyopathy. Transplantation 2012;93:1108-15.

7. Sakakibara Y, Tambara K, Lu F, et al. Combined procedure of surgical repair and cell transplantation for left ventricular aneurysm: an experimental study. Circulation 2002;106:I193-7.

8. Makkar RR, Smith RR, Cheng K, et al. Intracoronary cardiosphere-derived cells for heart regeneration after myocardial infarction (CADUCEUS): a prospective, randomised phase 1 trial. Lancet 2012;379:895-904.

9. Malliaras K, Makkar RR, Smith RR, et al. Intracoronary cardiosphere-derived cells after myocardial infarction: evidence of therapeutic regeneration in the final 1-year results of the CADUCEUS trial (CArdiosphere-Derived aUtologous stem CElls to reverse ventricUlar dySfunction). J Am Coll Cardiol 2014;63:110-22.

10. Chimenti I, Smith RR, Li TS, et al. Relative roles of direct regeneration versus paracrine effects of human cardiosphere-derived cells transplanted into infarcted mice. Circ Res 2010;106:971-80.

11. Malliaras K, Ibrahim A, Tseliou E, et al. Stimulation of endogenous cardioblasts by exogenous cell therapy after myocardial infarction. EMBO Mol Med 2014;6:760-77.

12. Malliaras K, Zhang Y, Seinfeld J, et al. Cardiomyocyte proliferation and progenitor cell recruitment underlie therapeutic regeneration after myocardial infarction in the adult mouse heart. EMBO Mol Med 2013;5:191-209.

13. Smith RR, Barile L, Cho HC, et al. Regenerative potential of cardiosphere-derived cells expanded from percutaneous endomyocardial biopsy specimens. Circulation 2007;115:896-908.

14. Bonios M, Chang CY, Pinheiro A, et al. Cardiac resynchronization by cardiosphere-derived stem cell transplantation in an experimental model of myocardial infarction. J Am Soc Echocardiogr 2011;24:808-14.

15. Ingels NB, Jr. Myocardial fiber architecture and left ventricular function. Technol Health Care 1997;5:45-52.

16. Sallin EA. Fiber orientation and ejection fraction in the human left ventricle. Biophys J 1969;9:954-64.

17. Pasipoularides A. Fluid dynamics of ventricular filling in heart failure: overlooked problems of RV/LV chamber dilatation. Hellenic J Cardiol 2015;56:85-95.

18. Dor V, Kreitmann P, Jourdan J. Interest of physiological closure (circumferential plasty on contractile areas) of left ventricle after resection and endocardiectomy for aneurysm or akinetic zone: Comparison with classical technique about a series of 209 left ventricular resections. J Cardiovasc Surg 1985;26:73.

19. Dor V, Di Donato M, Sabatier M, Montiglio F, Civaia F. Left ventricular reconstruction by endoventricular circular patch plasty repair: a 17-year experience. Semin Thorac Cardiovasc Surg 2001;13:435-47.

20. Dor V, Sabatier M, Montiglio F, Civaia F, DiDonato M. Endoventricular patch reconstruction of ischemic failing ventricle. a single center with 20 years experience. advantages of magnetic resonance imaging assessment. Heart Fail Rev 2004;9:269-86.

21. Jones RH, Velazquez EJ, Michler RE, et al. Coronary bypass surgery with or without surgical ventricular reconstruction. N Engl J Med 2009;360:1705-17.

22. Nishina T, Nishimura K, Yuasa S, et al. Initial effects of the left ventricular repair by plication may not last long in a rat ischemic cardiomyopathy model. Circulation 2001;104:I241-5.

23. Schwarz ER, Speakman MT, Kloner RA. A new model of ventricular plication: a suturing technique to decrease left ventricular dimensions, improve contractility, and attenuate ventricular remodeling after myocardial infarction in the rat heart. J Cardiovasc Pharmacol Ther 2000;5:41-9.

24. Cheng Y, Aboodi MS, Annest LS, et al. Off-pump epicardial ventricular reconstruction restores left ventricular twist and reverses remodeling in an ovine anteroapical aneurysm model. J Thorac Cardiovasc Surg 2014;148:225-31.

25. Zhang P, Guccione JM, Nicholas SI, et al. Endoventricular patch plasty for dyskinetic anteroapical left ventricular aneurysm increases systolic circumferential shortening in sheep. J Thorac Cardiovasc Surg 2007;134:1017-24.

26. Beyar R, Sideman S. Left ventricular mechanics related to the local distribution of oxygen demand throughout the wall. Circ Res 1986;58:664-77.

27. Bonios MJ, Kaladaridou A, Tasoulis A, et al. Value of apical circumferential strain in the early post-myocardial infarction period for prediction of left ventricular remodeling. Hellenic J Cardiol 2014;55:305-12.

28. Hung CL, Verma A, Uno H, et al. Longitudinal and circumferential strain rate, left ventricular remodeling, and prognosis after myocardial infarction. J Am Coll Cardiol 2010;56:1812-22.

29. Nucifora G, Marsan NA, Bertini M, et al. Reduced left ventricular torsion early after myocardial infarction is related to left ventricular remodeling. Circ Cardiovasc Imaging 2011;3:433-42.

30. Toumanidis S, Kaladaridou A, Bramos D, et al. Effect of left ventricular pacing mode and site on hemodynamic, torsional and strain indices. Hellenic J Cardiol 2016;57:169-77.

31. Malliaras K, Li TS, Luthringer D, et al. Safety and efficacy of allogeneic cell therapy in infarcted rats transplanted with mismatched cardiosphere-derived cells. Circulation 2012;125:100-12.

32. Terrovitis J, Lautamaki R, Bonios M, et al. Noninvasive quantification and optimization of acute cell retention by in vivo positron emission tomography after intramyocardial cardiac-derived stem cell delivery. J Am Coll Cardiol 2009;54:1619-26.

33. Tseliou E, de Couto G, Terrovitis J, et al. Angiogenesis, cardiomyocyte proliferation and anti-fibrotic effects underlie structural preservation post-infarction by intramyocardially-injected cardiospheres. PLoS One 2014;9:e88590.