Publications by authors named "Sinan Tolga Coskun"

6 Publications

  • Page 1 of 1

Computer-Aided Patient-Specific Coronary Artery Graft Design Improvements Using CFD Coupled Shape Optimizer.

Cardiovasc Eng Technol 2011 Mar 18;2(1):35-47. Epub 2010 Nov 18.

This study aims to (i) demonstrate the efficacy of a new surgical planning framework for complex cardiovascular reconstructions, (ii) develop a computational fluid dynamics (CFD) coupled multi-dimensional shape optimization method to aid patient-specific coronary artery by-pass graft (CABG) design and, (iii) compare the hemodynamic efficiency of the sequential CABG, i.e., raising a daughter parallel branch from the parent CABG in patient-specific 3D settings. Hemodynamic efficiency of patient-specific complete revascularization scenarios for right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex artery (LCX) bypasses were investigated in comparison to the stenosis condition. Multivariate 2D constraint optimization was applied on the left internal mammary artery (LIMA) graft, which was parameterized based on actual surgical settings extracted from 2D CT slices. The objective function was set to minimize the local variation of wall shear stress (WSS) and other hemodynamic indices (energy dissipation, flow deviation angle, average WSS, and vorticity) that correlate with performance of the graft and risk of re-stenosis at the anastomosis zone. Once the optimized 2D graft shape was obtained, it was translated to 3D using an in-house "sketch-based" interactive anatomical editing tool. The final graft design was evaluated using an experimentally validated second-order non-Newtonian CFD solver incorporating resistance based outlet boundary conditions. 3D patient-specific simulations for the healthy coronary anatomy produced realistic coronary flows. All revascularization techniques restored coronary perfusions to the healthy baseline. Multi-scale evaluation of the optimized LIMA graft enabled significant wall shear stress gradient (WSSG) relief (~34%). In comparison to original LIMA graft, sequential graft also lowered the WSSG by 15% proximal to LAD and diagonal bifurcation. The proposed sketch-based surgical planning paradigm evaluated the selected coronary bypass surgery procedures based on acute hemodynamic readjustments of aorta-CA flow. This methodology may provide a rational to aid surgical decision making in time-critical, patient-specific CA bypass operations before in vivo execution.
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http://dx.doi.org/10.1007/s13239-010-0029-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3291828PMC
March 2011

Feasibility of implantable cardioverter defibrillator treatment in five patients with familial Friedreich's ataxia--a case series.

Artif Organs 2010 Nov;34(11):1061-5

Department of Thoracic Cardiovascular Surgery, University of Göttingen, Germany.

Friedreich's ataxia (FRA) is an autosomal recessive disease of the central nervous system that is associated with familial cardiomyopathy. Cardiac involvement is seen in more than 90% of the patients and is the most common cause of death in these patients. We present a case series and discuss the indications for implantable cardioverter defibrillator (ICD) implantation in FRA with review of the literature. Five pediatric patients who suffer from FRA (four female and one male, mean age 17.4 years) underwent ICD implantation between 2007 and 2008 in the University Hospital of Goettingen. The diagnosis of FRA was established by standard clinical criteria and proven in each case by genotyping at the frataxin locus. The time from diagnosis to ICD implantation was 10.4±1.73 years (range 8-15 years). All patients received transvenous lead systems. There were no intraoperative and postoperative complications. At the latest follow-up, the neuromuscular symptoms exhibited no further progress and no ICD activations were noticed. Only minor repolarization changes were seen on electrocardiogram. All patients had normal echocardiographic findings and no angina has been reported. Coronary angiographies were normal. It is evident that many FRA patients develop ventricular dysfunction. In the absence of a definitive surgical cure an ICD is generally indicated in young patients with hemodynamically significant sustained ventricular tachyarrhythmias for prevention of sudden cardiac death. Our experience implies the safe use of ICD in children with FRA.
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http://dx.doi.org/10.1111/j.1525-1594.2010.01140.xDOI Listing
November 2010

Aortic valve surgery in congenital heart disease: a single-center experience.

Artif Organs 2010 Mar;34(3):E85-90

Department of Thoracic and Cardiovascular Surgery, University of Göttingen, Göttingen, Germany.

The optimal treatment of congenital aortic valve lesions is a controversial issue. This study was performed to evaluate the outcome after surgical treatment of aortic valve lesions in congenital aortic valve disease. Between the years of 2000 and 2008, 61 patients (mean age: 12.6 +/- 9.6 years, range: 1 day to 40 years) underwent aortic valve surgery for congenital aortic valve disease. Twenty-four patients had undergone previous cardiovascular operations. Indications for surgery were aortic regurgitation in 14.7% (n = 9), aortic stenoses in 26.2% (n = 16), and mixed disease in 59.1% (n = 36). The Ross procedure was performed in 37.7% (n = 23), aortic valve replacement with biological or mechanical prostheses in 29.5% (n = 18). Concomitant procedures were performed in 91.8% (n = 56) due to associated congenital cardiac defects. The overall mortality rate was 5%. Six patients needed reoperation. Implantation of permanent pacemakers occurred in six patients for permanent atrioventricular block. At the latest clinical evaluation, all survivors are in New York Heart Association class I-II and are living normal lives. Aortic valve surgeries in patients with congenital heart disease have had low mortality and morbidity rates in our series. Surgical technique as well as timing should be tailored for each patient. Aortic valve replacement should be delayed until the implantation of an adult-sized prosthesis is possible.
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http://dx.doi.org/10.1111/j.1525-1594.2009.00958.xDOI Listing
March 2010

Surgical treatment of left ventricular aneurysm.

Asian Cardiovasc Thorac Ann 2009 Oct;17(5):490-3

Department of Cardiovascular Surgery, Heart and Diabetes Center North-Rhine Westphalia, University of Bochum, Georg Strasse 11, 32545 Bad Oeynhausen, Germany.

When a left ventricular aneurysm leads to pulmonary congestive symptoms, aneurysmectomy may provide relief. This retrospective study included 269 patients who underwent aneurysmectomy between 1993 and 2002, by the classic Cooley operation in 164 and by Dor ventriculoplasty in 105. There were no significant differences in early and late survival between groups, although the frequency of extended anteroseptal infarction was higher in patients undergoing the Dor procedure. Postoperative echocardiographic findings showed significant improvements in left ventricular function in both groups, in terms of end-diastolic and end-systolic dimensions and ejection fraction. Left ventricular aneurysmectomy significantly improved the clinical status and hemodynamic parameters of symptomatic patients. The choice of surgical technique depends on the extent of the scar segment, especially the presence of an anteroseptal scarred area. The Dor procedure is more suitable for restoring normal left ventricular geometry in patients with extensive septal infarction.
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http://dx.doi.org/10.1177/0218492309348636DOI Listing
October 2009

Hemodynamic changes in a model of chronic heart failure induced by multiple sequential coronary microembolization in sheep.

Artif Organs 2009 Nov 10;33(11):947-52. Epub 2009 Oct 10.

Department of Thoracic, Cardiac and Vascular Surgery, University of Goettingen, Goettingen, Germany.

Although a large variety of animal models for acute ischemia and acute heart failure exist, valuable models for studies on the effect of ventricular assist devices in chronic heart failure are scarce. We established a stable and reproducible animal model of chronic heart failure in sheep and aimed to investigate the hemodynamic changes of this animal model of chronic heart failure in sheep. In five sheep (n = 5, 77 +/- 2 kg), chronic heart failure was induced under fluoroscopic guidance by multiple sequential microembolization through bolus injection of polysterol microspheres (90 microm, n = 25.000) into the left main coronary artery. Coronary microembolization (CME) was repeated up to three times in 2 to 3-week intervals until animals started to develop stable signs of heart failure. During each operation, hemodynamic monitoring was performed through implantation of central venous catheter (central venous pressure [CVP]), arterial pressure line (mean arterial pressure [MAP]), implantation of a right heart catheter {Swan-Ganz catheter (mean pulmonary arterial pressure [PAP mean])}, pulmonary capillary wedge pressure (PCWP), and cardiac output [CO]) as well as pre- and postoperative clinical investigations. All animals were followed for 3 months after first microembolization and then sacrificed for histological examination. All animals developed clinical signs of heart failure as indicated by increased heart rate (HR) at rest (68 +/- 4 bpm [base] to 93 +/- 5 bpm [3 mo][P < 0.05]), increased respiratory rate (RR) at rest (28 +/- 5 [base] to 38 +/- 7 [3 mo][P < 0.05]), and increased body weight 77 +/- 2 kg to 81 +/- 2 kg (P < 0.05) due to pleural effusion, peripheral edema, and ascites. Hemodynamic signs of heart failure were revealed as indicated by increase of HR, RR, CVP, PAP, and PCWP as well as a decrease of CO, stroke volume, and MAP 3 months after the first CME. Multiple sequential intracoronary microembolization can effectively induce myocardial dysfunction with clinical and hemodynamic signs of chronic ischemic cardiomyopathy. The present model may be suitable in experimental work on heart failure and left ventricular assist devices, for example, for studying the impact of mechanical unloading, mechanisms of recovery, and reverse remodeling.
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http://dx.doi.org/10.1111/j.1525-1594.2009.00921.xDOI Listing
November 2009

Experiences with surgical treatment of ventricle septal defect as a post infarction complication.

J Cardiothorac Surg 2009 Jan 6;4. Epub 2009 Jan 6.

Department of Thoracic Cardiovascular Surgery, University of Göttingen, Göttingen, Germany.

Background: Complications of acute myocardial infarction (AMI) with mechanical defects are associated with poor prognosis. Surgical intervention is indicated for a majority of these patients. The goal of surgical intervention is to improve the systolic cardiac function and to achieve a hemodynamic stability. In this present study we reviewed the outcome of patients with post infarction ventricular septal defect (PVSD) who underwent cardiac surgery.

Methods: We analysed retrospectively the hospital records of 41 patients, whose ages range from 48 to 81, and underwent a surgical treatment between 1990 and 2005 because of PVSD.

Results: In 22 patients concomitant coronary artery bypass grafting (CAGB) was performed. In 15 patients a residual shunt was found, this required re-op in seven of them. The time interval from infarct to rupture was 8.7 days and from rupture to surgery was 23.1 days. Hospital mortality in PVSD group was 32%. The mortality of urgent repair within 3 days of intractable cardiogenic shock was 100%. The mortality of patients with an anterior VSD and a posterior VSD was 29.6% vs 42.8%, respectively. All patients who underwent the surgical repair later than day 36 survived.

Conclusion: Surgical intervention is indicated for a majority of patients with mechanical complications. Cardiogenic shock remains the most important factor that affects the early results. The surgical repair of PVSD should be performed 4-5 weeks after AMI. To improve surgical outcome and hemodynamics the choice of surgical technique and surgical timing as well as preoperative management should be tailored for each patient individually.
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http://dx.doi.org/10.1186/1749-8090-4-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2631454PMC
January 2009