Restoration of optimal ellipsoid left ventricular geometry: lessons learnt from in silico surgical modelling Srilakshmi M. Adhyapaka,†*, Prahlad G. Menonb,c,† and V. Rao Parachurid a b c d
Department of Cardiology, St. John's Medical College Hospital, Bangalore, India Sun Yat Sen University-Carnegie Mellon University (SYSU-CMU) Joint Institute of Engineering, Pittsburgh, PA, USA Shunde International Joint Institute, Guangdong China and QuantMD, LLC, Pittsburgh, PA, USA Senior Cardiac Surgeon and Head, Heart Lung Transplantation Program, Narayana Hrudayalaya Institute of Medical Sciences, India
* Corresponding author. Narayana Hrudayalaya Institute of Medical Sciences 258/A, Bommasandra Industrial Area, Anekal Taluk, Bangalore 560099, India. Tel: +91-80-27835000; fax: +91-80-27832648; e-mail: [email protected] (S.M. Adhyapak). Received 28 June 2013; received in revised form 16 September 2013; accepted 20 September 2013
Abstract OBJECTIVES: Several issues that are inherent in the surgical techniques of surgical ventricular restoration (SVR) need specialized devices or techniques to overcome them, which may not always result in optimal outcomes. We used a non-invasive novel in silico modelling technique to study left ventricular (LV) morphology and function before and after SVR. The cardiac magnetic resonance imaging derived actual pre- and postoperative endocardial morphology and function was compared with the in silico analysis of the same. METHODS: Cardiac magnetic resonance steady state free precession (SSFP) cine images were employed to segment endocardial surface contours over the cardiac cycle. Using the principle of Hausdorff distance to examine phase-to-phase regional endocardial displacement, dyskinetic/akinetic areas were identified at the instant of peak basal contraction velocity. Using a three-dimensional (3D) surface clipping tool, the maximally scarred, dyskinetic or akinetic LV antero-apical areas were virtually resected and a new apex was created. A virtual rectangular patch was created upon the clipped surface LV model by 3D Delaunay triangulation. Presurgical endocardial mechanical function quantified from cine cardiac magnetic resonance, using a technique of spherical harmonics (SPHARM) surface parameterization, was applied onto the virtually clipped and patched LV surface model. Finally, the in silico model of post-SVR LV shape was analysed for quantification of regional left ventricular volumes (RLVVs) and function. This was tested in 2 patients with post-myocardial infarction antero-apical LV aneuryms. Left ventricular mechanical dysynchrony was evaluated by RLVV analysis of pre-SVR, in silico post-SVR and actual post-SVR LV endocardial surface data. RESULTS: Following exclusion of the scarred areas, the virtual resected LV model demonstrated significantly lesser areas of akinesia. The decreases in regional LV volumes in the in silico modelling were significant and comparable with the actual decreases following SVR. Both the regional end diastolic volume (EDV) and end systolic volume (ESV) at the apex decreased significantly corresponding to greater reductions in apical volumes by the technique of rectangular patch plasty (apical EDV 2.1607 ± 0.20577 to 0.4774 ± 0.1775 ml, P = 0.007; apical ESV 1.9708 ± 0.36451 to 0.442 ± 0.047 ml, P = 0.013). CONCLUSIONS: This pilot study was done using novel in silico techniques for virtual surgical modelling, which helped in accurate estimation and planning of optimal LV restoration by SVR. Keywords: Surgical ventricular restoration • Left ventricular aneurysms • Cardiac magnetic resonance imaging
INTRODUCTION Unavailability of donor hearts due to increasingly difficult logistics has made palliative measures mandatory to improve quality of life in patients with ischaemic cardiomyopathy. The use of assist devices has gained acceptance for this indication [1]. Although refuted in randomized trials, the procedure of surgical ventricular restoration (SVR) for left ventricular (LV) aneurysms results in definitive improvements in quality of life for non-transplant candidates [2]. Results from the STICH analysis have shown mortality benefit in addition to clinical improvements when SVR was added to coronary artery bypass graft (CABG) if the ESV is 1 h Coronary artery bypass Mitral valve repair
Mortality
Low output
≥0.05 ≥0.05 0.03 0.027 0.029 0.03 0.04 0.04 0.02 ≥0.05 ≥0.05
0.003 0.04 0.032 0.04 ≥0.05 0.02 ≥0.05 ≥0.05 0.01 0.02 0.03
Adapted with permission from Asian Cardiovasc Thorac Ann 2008;16:401–6. ESVI: end-systolic volume index; NYHA: New York Heart Association.
estimated patch dimensions were marginally larger—59.5 ± 10.6 mm length and 41 ± 11.3 mm breadth—in contrast with the real post-SVR patches (52.8 ± 12.2 mm length and 38 ± 9.98 mm breadth). The angle of the patch with the LV base was 50.5 ± 2.12°.
DISCUSSION
Supplementary Video 2: Pre- (semi-transparent) and post in silico SVR LV endocardial function, coloured by consecutive phase-to-phase Hausdorff distance, highlighting dark territories occupied by the aneruysm which are excluded by virtue of the virtual resection. The post-SVR apex lies on the septal wall while the remainder of the LV (after virtual resection) has good phase-to-phase wall-motion function (white on the Hausdorff-distance colorbar).
end-diastole and end-systole with improvements in the LVEF. Cardiac magnetic resonance studies were repeated at 6 weeks following surgery to document LV remodelling and its effect on LV mechanics. A decrease in LV EDV, LV ESV and increase in LV EF were observed in both patients. The LV mass decreased significantly from 157 ± 16.9 to 94 ± 2.82 g (P = 0.03). The current risk factors affecting mid-term survival in our centre are highlighted in Table 1 [8]. In order to define the changes in LV geometry with surgical decreases in LV EDV, we studied the post-SVR RLVV at end-diastole and end-systole. The decreases in regional ESV at the base from baseline were significant (2.578 ± 0.232 to 1.652 ± 0.036 ml, P = 0.015), with insignificant decreases in basal EDV from 3.324 ± 0.439 to 2.9217 ± 0.1451 (P = 0.128). The basal EF increased significantly from 23.37 ± 1.654 to 43.38 ± 1.576%, P = 0.003. However, both the regional EDV and ESV at the apex decreased significantly (apical EDV 2.1607 ± 0.20577 to 0.4774 ± 0.1775 ml, P = 0.007; apical ESV 1.9708 ± 0.36451 to 0.442 ± 0.047 ml, P = 0.013), conforming to greater reductions in apical volumes (Fig. 4). The in silico post-SVR model also demonstrated similar reductions in LV volumes at end-diastole and end-systole. The in silico
Although SVR has proven benefits in terms of restoration of ventricular geometry and function reflecting in better clinical outcomes, long-term results have shown worsening due to adverse LV remodelling reflected by re-dilatation of the LV with increasing sphericity attributed to the surgical technique and preoperative LV volumes [9]. Several studies have demonstrated better results with optimal LV shape restoration than volume restoration alone [10, 11]. We aimed at optimal LV geometry restoration through the use of in silico presurgical planning. The principle of non-invasive in silico surgery capitalizes on estimates of the scarred area quantified from preoperative cardiac magnetic resonance images. The residual contractile LV can be visualized accurately and exclusion of scarred areas of the anterior wall, apex and scarred portions of the septum can be accomplished virtually. This eliminates the need for residual LV volume measuring devices intraoperatively. Further, the angulation and geometry of the intraventricular patch can be virtually morphed onto the clipped virtual LV, wherein the scarred areas have been optimally clipped. The crux of this technique was that the in silico-determined optimal exclusion site of scarred tissue or plane of dissection conformed to the appropriate actual post-SVR location of the intraventricular patch. By optimizing the intraventricular patch geometry and its intraventricular alignment, the intraoperative residual LV volume estimation was not necessary. The restored LV morphology in our patients was more ellipsoid than the baseline LV morphology as evidenced by a more conical apex with significant decreases in apical EDV and ESV. Although at the base the decrease in EDV was not significant, the EF increased significantly indicating improved basal function. Thus, this modelling technique avoided a restrictive postoperative
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NEW IDEAS
S.M. Adhyapak et al. / Interactive CardioVascular and Thoracic Surgery
Figure 4: Polar plot of phase-to-peak systole computed RLVV analysis, from presurgical (left), in silico post-SVR (middle) and actual post-SVR (right) LV endocardial function. The in silico model’s expectation for improvement in mechanical dysynchrony is exceeded in the true post-SVR LV on account of the unaccounted elastic nature of the SVR patch. Representative data presented for Patient 1 only.
LV with a box-like distorted geometry responsible for diastolic dysfunction. In addition, it helps visualize the function of the restored LV for persistence of areas of mechanical dysynchrony. This model also helps in patient selection for SVR by exclusion of patients without a significant residual LV volume. The in silico model has certain minor drawbacks. The sphericity of the modelled LV was greater than that of the real life post-SVR LV, as the modelled intraventricular patch was larger. This was due to the lack of radial shrinkage of the patch and border zone being factored into the model after suturing within the LV cavity and the lack of material properties in the modelled patch. The presented methodology is quick to implement on a patient-specific basis and may be routinely employed for preoperative planning of SVR and device therapies, such as the myosplint device which requires accurate surgical positioning [12]. This technique has the potential to optimize the novel percutaneous or off-pump LV aneurysm exclusion techniques by estimating infarct extent and presurgical planning of accurate positioning of the device components [13]. In the use of epicardial device placement without ventriculotomy, the guidance of the device placement sites on the ventricular epicardium can be mapped preoperatively. The extent of scar and the border zone which needs to be plicated by the device placement and estimation of optimal residual LV volume can be defined. In device-based therapies targeting the ventricular equator like the myosplint device [14], preoperative assessment of the ventricular radius at the base, mid-cavity and apex can be made. The device placement can be simulated. The post-device placement splinting of the ventricle should lead to an ellipsoid shape which can be assessed preoperatively. The post-device contraction and relaxation patterns of the LV can be assessed preoperatively to aid patient selection and optimal placement of the devices within the LV cavity.
LIMITATIONS OF THE STUDY This constitutes a pilot study in 2 patients which has demonstrated significant beneficial outcomes and requires validation of this technique in larger patient cohorts. The major limitations of this technique are that the modelled LV volumes and patch sizes are marginally larger, due to the lack of factoring radial shrinkage of
the border zone and the patch after suturing within the LV cavity and the absence of material properties in the patch.
CONCLUSIONS This pilot study demonstrates that virtual surgical modelling can help in estimating the postoperative LV geometry accurately in terms of residual LV volume, angulation of the intraventricular patch, optimal scar exclusion and postoperative LV function. This technique can be employed in larger patient cohorts for patientspecific individualization of the surgical techniques of SVR.
SUPPLEMENTARY MATERIAL Supplementary material is available at ICVTS online. Conflict of interest: none declared.
REFERENCES [1] Burkhoff D. New heart failure therapy: the shape of things to come? J Thorac Cardiovasc Surg 2001;122:421–23. [2] Velazquez EJ, Lee KL, Deja MA, Jain A, Sopko G, Marchenko A et al. for the STICH Investigators. Coronary bypass surgery with or without surgical ventricular reconstruction. N Engl J Med 2009;360:1705–17. [3] Michler RE, Rouleau JL, Al-Khalidi HR, Bonow RO, Pellikka PA, Pohost GM et al. Insights from the STICH trial: change in left ventricular size after coronary artery bypass grafting with and without surgical ventricular reconstruction. J Thorac Cardiovasc Surg 2013;146:1139–45. [4] Hausdorff F. Dimension und außeres maß. Math Ann 1918;79:157–79. [5] Chung MK. Tensor-based cortical surface morphometry via weighted spherical harmonic representation. IEEE Trans Med Imaging 2008;27:1143–51. [6] Shors SM, Cotts WG, Pavlovic-Surjancev B. Heart failure: evaluation of cardiopulmonary transit times with time-resolved MR angiography. Radiology 2003;229:743–8. [7] Heiberg E, Sjogren J, Ugander M. Design and validation of Segment–freely available software for cardiovascular image analysis. BMC Med Imaging 2010;10:1. [8] Parachuri VR, Adhyapak SM, Kumar P, Setty R, Rathod R, Shetty DP. Ventricular restoration by linear endoventricular patchplasty and linear repair. Asian Cardiovasc Thorac Ann 2008;16:401–6. [9] Pocar M, Di Mauro A, Passolunghi D, Moneta A, Alsheraei AM, Bregasi A et al. Predictors of adverse events after surgical ventricular restoration for advanced ischemic cardiomyopathy. Eur J Cardiothorac Surg 2010;37: 1093–2100.
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[10] Calafiore AM, Iacò AL, Amata D, Castello C, Varone E, Fabio F et al. Left ventricular surgical restoration for anteroseptal scars: volume versus shape. J Thorac Cardiovasc Surg 2010;139:1123–30. [11] Adhyapak SM, Parachuri VR. Lessons from a mathematical hypothesis— modification of the endoventricular circular patch plasty. Eur J Cardiothorac Surg 2011;39:945–51. [12] Guccione JM, Salahieh A, Moonly SM, Kortsmit J, Wallace AW, Ratcliffe MB. Myosplint decreases wall stress without depressing function in the
failing heart: a finite element model study. Ann Thorac Surg 2003;76: 1171–80. [13] Wechsler AS, Sadowski J, Kapelak B, Bartus K, Kalinauskas G, Rucinskas K et al. Durability of epicardial ventricular restoration without ventriculotomy. Eur J Cardiothorac Surg 2013;44:e189–92. [14] Sabbah HN. The cardiac support device and the myosplint: treating heart failure by targeting left ventricular size and shape. Ann Thorac Surg 2003; 75:S13–9.
Department of Cardiology, St. John's Medical College Hospital, Bangalore, India Sun Yat Sen University-Carnegie Mellon University (SYSU-CMU) Joint Institute of Engineering, Pittsburgh, PA, USA Shunde International Joint Institute, Guangdong China and QuantMD, LLC, Pittsburgh, PA, USA Senior Cardiac Surgeon and Head, Heart Lung Transplantation Program, Narayana Hrudayalaya Institute of Medical Sciences, India
* Corresponding author. Narayana Hrudayalaya Institute of Medical Sciences 258/A, Bommasandra Industrial Area, Anekal Taluk, Bangalore 560099, India. Tel: +91-80-27835000; fax: +91-80-27832648; e-mail: [email protected] (S.M. Adhyapak). Received 28 June 2013; received in revised form 16 September 2013; accepted 20 September 2013
Abstract OBJECTIVES: Several issues that are inherent in the surgical techniques of surgical ventricular restoration (SVR) need specialized devices or techniques to overcome them, which may not always result in optimal outcomes. We used a non-invasive novel in silico modelling technique to study left ventricular (LV) morphology and function before and after SVR. The cardiac magnetic resonance imaging derived actual pre- and postoperative endocardial morphology and function was compared with the in silico analysis of the same. METHODS: Cardiac magnetic resonance steady state free precession (SSFP) cine images were employed to segment endocardial surface contours over the cardiac cycle. Using the principle of Hausdorff distance to examine phase-to-phase regional endocardial displacement, dyskinetic/akinetic areas were identified at the instant of peak basal contraction velocity. Using a three-dimensional (3D) surface clipping tool, the maximally scarred, dyskinetic or akinetic LV antero-apical areas were virtually resected and a new apex was created. A virtual rectangular patch was created upon the clipped surface LV model by 3D Delaunay triangulation. Presurgical endocardial mechanical function quantified from cine cardiac magnetic resonance, using a technique of spherical harmonics (SPHARM) surface parameterization, was applied onto the virtually clipped and patched LV surface model. Finally, the in silico model of post-SVR LV shape was analysed for quantification of regional left ventricular volumes (RLVVs) and function. This was tested in 2 patients with post-myocardial infarction antero-apical LV aneuryms. Left ventricular mechanical dysynchrony was evaluated by RLVV analysis of pre-SVR, in silico post-SVR and actual post-SVR LV endocardial surface data. RESULTS: Following exclusion of the scarred areas, the virtual resected LV model demonstrated significantly lesser areas of akinesia. The decreases in regional LV volumes in the in silico modelling were significant and comparable with the actual decreases following SVR. Both the regional end diastolic volume (EDV) and end systolic volume (ESV) at the apex decreased significantly corresponding to greater reductions in apical volumes by the technique of rectangular patch plasty (apical EDV 2.1607 ± 0.20577 to 0.4774 ± 0.1775 ml, P = 0.007; apical ESV 1.9708 ± 0.36451 to 0.442 ± 0.047 ml, P = 0.013). CONCLUSIONS: This pilot study was done using novel in silico techniques for virtual surgical modelling, which helped in accurate estimation and planning of optimal LV restoration by SVR. Keywords: Surgical ventricular restoration • Left ventricular aneurysms • Cardiac magnetic resonance imaging
INTRODUCTION Unavailability of donor hearts due to increasingly difficult logistics has made palliative measures mandatory to improve quality of life in patients with ischaemic cardiomyopathy. The use of assist devices has gained acceptance for this indication [1]. Although refuted in randomized trials, the procedure of surgical ventricular restoration (SVR) for left ventricular (LV) aneurysms results in definitive improvements in quality of life for non-transplant candidates [2]. Results from the STICH analysis have shown mortality benefit in addition to clinical improvements when SVR was added to coronary artery bypass graft (CABG) if the ESV is 1 h Coronary artery bypass Mitral valve repair
Mortality
Low output
≥0.05 ≥0.05 0.03 0.027 0.029 0.03 0.04 0.04 0.02 ≥0.05 ≥0.05
0.003 0.04 0.032 0.04 ≥0.05 0.02 ≥0.05 ≥0.05 0.01 0.02 0.03
Adapted with permission from Asian Cardiovasc Thorac Ann 2008;16:401–6. ESVI: end-systolic volume index; NYHA: New York Heart Association.
estimated patch dimensions were marginally larger—59.5 ± 10.6 mm length and 41 ± 11.3 mm breadth—in contrast with the real post-SVR patches (52.8 ± 12.2 mm length and 38 ± 9.98 mm breadth). The angle of the patch with the LV base was 50.5 ± 2.12°.
DISCUSSION
Supplementary Video 2: Pre- (semi-transparent) and post in silico SVR LV endocardial function, coloured by consecutive phase-to-phase Hausdorff distance, highlighting dark territories occupied by the aneruysm which are excluded by virtue of the virtual resection. The post-SVR apex lies on the septal wall while the remainder of the LV (after virtual resection) has good phase-to-phase wall-motion function (white on the Hausdorff-distance colorbar).
end-diastole and end-systole with improvements in the LVEF. Cardiac magnetic resonance studies were repeated at 6 weeks following surgery to document LV remodelling and its effect on LV mechanics. A decrease in LV EDV, LV ESV and increase in LV EF were observed in both patients. The LV mass decreased significantly from 157 ± 16.9 to 94 ± 2.82 g (P = 0.03). The current risk factors affecting mid-term survival in our centre are highlighted in Table 1 [8]. In order to define the changes in LV geometry with surgical decreases in LV EDV, we studied the post-SVR RLVV at end-diastole and end-systole. The decreases in regional ESV at the base from baseline were significant (2.578 ± 0.232 to 1.652 ± 0.036 ml, P = 0.015), with insignificant decreases in basal EDV from 3.324 ± 0.439 to 2.9217 ± 0.1451 (P = 0.128). The basal EF increased significantly from 23.37 ± 1.654 to 43.38 ± 1.576%, P = 0.003. However, both the regional EDV and ESV at the apex decreased significantly (apical EDV 2.1607 ± 0.20577 to 0.4774 ± 0.1775 ml, P = 0.007; apical ESV 1.9708 ± 0.36451 to 0.442 ± 0.047 ml, P = 0.013), conforming to greater reductions in apical volumes (Fig. 4). The in silico post-SVR model also demonstrated similar reductions in LV volumes at end-diastole and end-systole. The in silico
Although SVR has proven benefits in terms of restoration of ventricular geometry and function reflecting in better clinical outcomes, long-term results have shown worsening due to adverse LV remodelling reflected by re-dilatation of the LV with increasing sphericity attributed to the surgical technique and preoperative LV volumes [9]. Several studies have demonstrated better results with optimal LV shape restoration than volume restoration alone [10, 11]. We aimed at optimal LV geometry restoration through the use of in silico presurgical planning. The principle of non-invasive in silico surgery capitalizes on estimates of the scarred area quantified from preoperative cardiac magnetic resonance images. The residual contractile LV can be visualized accurately and exclusion of scarred areas of the anterior wall, apex and scarred portions of the septum can be accomplished virtually. This eliminates the need for residual LV volume measuring devices intraoperatively. Further, the angulation and geometry of the intraventricular patch can be virtually morphed onto the clipped virtual LV, wherein the scarred areas have been optimally clipped. The crux of this technique was that the in silico-determined optimal exclusion site of scarred tissue or plane of dissection conformed to the appropriate actual post-SVR location of the intraventricular patch. By optimizing the intraventricular patch geometry and its intraventricular alignment, the intraoperative residual LV volume estimation was not necessary. The restored LV morphology in our patients was more ellipsoid than the baseline LV morphology as evidenced by a more conical apex with significant decreases in apical EDV and ESV. Although at the base the decrease in EDV was not significant, the EF increased significantly indicating improved basal function. Thus, this modelling technique avoided a restrictive postoperative
157
NEW IDEAS
S.M. Adhyapak et al. / Interactive CardioVascular and Thoracic Surgery
Figure 4: Polar plot of phase-to-peak systole computed RLVV analysis, from presurgical (left), in silico post-SVR (middle) and actual post-SVR (right) LV endocardial function. The in silico model’s expectation for improvement in mechanical dysynchrony is exceeded in the true post-SVR LV on account of the unaccounted elastic nature of the SVR patch. Representative data presented for Patient 1 only.
LV with a box-like distorted geometry responsible for diastolic dysfunction. In addition, it helps visualize the function of the restored LV for persistence of areas of mechanical dysynchrony. This model also helps in patient selection for SVR by exclusion of patients without a significant residual LV volume. The in silico model has certain minor drawbacks. The sphericity of the modelled LV was greater than that of the real life post-SVR LV, as the modelled intraventricular patch was larger. This was due to the lack of radial shrinkage of the patch and border zone being factored into the model after suturing within the LV cavity and the lack of material properties in the modelled patch. The presented methodology is quick to implement on a patient-specific basis and may be routinely employed for preoperative planning of SVR and device therapies, such as the myosplint device which requires accurate surgical positioning [12]. This technique has the potential to optimize the novel percutaneous or off-pump LV aneurysm exclusion techniques by estimating infarct extent and presurgical planning of accurate positioning of the device components [13]. In the use of epicardial device placement without ventriculotomy, the guidance of the device placement sites on the ventricular epicardium can be mapped preoperatively. The extent of scar and the border zone which needs to be plicated by the device placement and estimation of optimal residual LV volume can be defined. In device-based therapies targeting the ventricular equator like the myosplint device [14], preoperative assessment of the ventricular radius at the base, mid-cavity and apex can be made. The device placement can be simulated. The post-device placement splinting of the ventricle should lead to an ellipsoid shape which can be assessed preoperatively. The post-device contraction and relaxation patterns of the LV can be assessed preoperatively to aid patient selection and optimal placement of the devices within the LV cavity.
LIMITATIONS OF THE STUDY This constitutes a pilot study in 2 patients which has demonstrated significant beneficial outcomes and requires validation of this technique in larger patient cohorts. The major limitations of this technique are that the modelled LV volumes and patch sizes are marginally larger, due to the lack of factoring radial shrinkage of
the border zone and the patch after suturing within the LV cavity and the absence of material properties in the patch.
CONCLUSIONS This pilot study demonstrates that virtual surgical modelling can help in estimating the postoperative LV geometry accurately in terms of residual LV volume, angulation of the intraventricular patch, optimal scar exclusion and postoperative LV function. This technique can be employed in larger patient cohorts for patientspecific individualization of the surgical techniques of SVR.
SUPPLEMENTARY MATERIAL Supplementary material is available at ICVTS online. Conflict of interest: none declared.
REFERENCES [1] Burkhoff D. New heart failure therapy: the shape of things to come? J Thorac Cardiovasc Surg 2001;122:421–23. [2] Velazquez EJ, Lee KL, Deja MA, Jain A, Sopko G, Marchenko A et al. for the STICH Investigators. Coronary bypass surgery with or without surgical ventricular reconstruction. N Engl J Med 2009;360:1705–17. [3] Michler RE, Rouleau JL, Al-Khalidi HR, Bonow RO, Pellikka PA, Pohost GM et al. Insights from the STICH trial: change in left ventricular size after coronary artery bypass grafting with and without surgical ventricular reconstruction. J Thorac Cardiovasc Surg 2013;146:1139–45. [4] Hausdorff F. Dimension und außeres maß. Math Ann 1918;79:157–79. [5] Chung MK. Tensor-based cortical surface morphometry via weighted spherical harmonic representation. IEEE Trans Med Imaging 2008;27:1143–51. [6] Shors SM, Cotts WG, Pavlovic-Surjancev B. Heart failure: evaluation of cardiopulmonary transit times with time-resolved MR angiography. Radiology 2003;229:743–8. [7] Heiberg E, Sjogren J, Ugander M. Design and validation of Segment–freely available software for cardiovascular image analysis. BMC Med Imaging 2010;10:1. [8] Parachuri VR, Adhyapak SM, Kumar P, Setty R, Rathod R, Shetty DP. Ventricular restoration by linear endoventricular patchplasty and linear repair. Asian Cardiovasc Thorac Ann 2008;16:401–6. [9] Pocar M, Di Mauro A, Passolunghi D, Moneta A, Alsheraei AM, Bregasi A et al. Predictors of adverse events after surgical ventricular restoration for advanced ischemic cardiomyopathy. Eur J Cardiothorac Surg 2010;37: 1093–2100.
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S.M. Adhyapak et al. / Interactive CardioVascular and Thoracic Surgery
[10] Calafiore AM, Iacò AL, Amata D, Castello C, Varone E, Fabio F et al. Left ventricular surgical restoration for anteroseptal scars: volume versus shape. J Thorac Cardiovasc Surg 2010;139:1123–30. [11] Adhyapak SM, Parachuri VR. Lessons from a mathematical hypothesis— modification of the endoventricular circular patch plasty. Eur J Cardiothorac Surg 2011;39:945–51. [12] Guccione JM, Salahieh A, Moonly SM, Kortsmit J, Wallace AW, Ratcliffe MB. Myosplint decreases wall stress without depressing function in the
failing heart: a finite element model study. Ann Thorac Surg 2003;76: 1171–80. [13] Wechsler AS, Sadowski J, Kapelak B, Bartus K, Kalinauskas G, Rucinskas K et al. Durability of epicardial ventricular restoration without ventriculotomy. Eur J Cardiothorac Surg 2013;44:e189–92. [14] Sabbah HN. The cardiac support device and the myosplint: treating heart failure by targeting left ventricular size and shape. Ann Thorac Surg 2003; 75:S13–9.
