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ORIGINAL ARTICLE Finite element analysis regarding patch size, stiffness, and contact condition to the endocardium in surgery for post infarction ventricular septal rupture Toshiaki ItoHiroaki HagiwaraAtsuo Maekawa Takenori Yamazaki Received: 17 February 2013/Accepted: 15 April 2013/Published online: 23 April 2013 ? The Japanese Association for Thoracic Surgery 2013 Abstract BackgroundThe purpose of this study is to establish a rational surgical design to minimize suture line stress of the patch and thus prevent residual leakage in surgery for post infarction ventricular septal rupture (VSR). MethodsA computer model that simulates surgery for VSR was developed. Stress force on the suture line of the patch was calculated at varying size, stiffness, and contact condition of the endocardial patch to the inner surface of the heart using a fi nite element analysis. Clinical results and echo fi ndings of 34 consecutive patients with a mean age of 72.6 9.5 (range 5589) who underwent emer- gency surgery for VSR from 1995 to 2012 were reviewed. ResultsSuture line stress decreased by two-thirds as the size or stiffness of the patch increased in comparison with the basic conditions that mimic a pericardial patch fi tted to the septal plane. On the other hand, suture line stress increased sixfold when there was a dead space beneath the patch. 30-day mortality was 12 %, and in-hospital mor- tality 18 %. On echocardiography, all three patients who had dead space beneath the patch had residual leak. Another patient who had huge posterior defect also showed residual leak. Clinical results were well matched to model results. 5-year survival rate of all patients who received operation was 68.7 9.3 %. ConclusionIn endocardial patch type surgery for VSR, proper sizing of the patch to suffi ciently fi t to endocardial surface in a tension-free condition is the most important to avoid residual leak. KeywordsMyocardial infarction ? Ventricular septal rupture ? Computer applications Introduction Postoperative residual leak after patch closure for post- infarction ventricular septal rupture (VSR) is a strong factor of poor outcome 1, 2. Dehiscence of the patch is caused by fragility of myocardium acutely after myocardial infarction. Therefore, some investigators have proposed delaying operation until the tissues surrounding the septal defect have become durable owing to scar formation 3. However, critically ill patients cannot always wait until the chronic stage due to ongoing multiple organ failure. Maltais et al. 2 recently reported that time delay between VSR diagnosis and surgery was a signifi cant predictor of poor outcome. To avoid detachment of the patch in emergency surgery for VSR, several operative techniques have been proposed. David et al. 4 focused on enlargement of the patch that excludes all infarcted areas. Others concentrated on rein- forcement of the suture line using transmural interrupted sutures1,5,6.Regardingpatchmaterial,xenopericardium, Tefl on felt, a combination of both 7, and further rein- forcement using biological glues 7, 8 have been reported. The purpose of this study is to estimate the change in suture line stress, which may lead to patch dehiscence in T. Ito (11: 3841. 2. Maltais S, Ibrahim R, Basmadjian AJ, Carrier M, Bouchard D, Cartier R, et al. Postinfarction ventricular septal defects: towards a new treatment algorithm? Ann Thorac Surg. 2009;87:68793. 3. Miyajima M, Kawashima T, Saito T, Yokoyama H, Ohori K, Kuwaki K, et al. Delayed closure of postinfarction ventricular septal rupture. Ann Thorac Cardiovasc Surg. 2010;16:12830. 4. David TE, Dale L, Sun Z. Postinfarction ventricular septal rup- ture: repair by endocardial patch with infarct exclusion. J Thorac Cardiovasc Surg. 1995;110:131522. 5. Ito T, Hagiwara H, Maekawa A. Entire septal patch technique for postinfarction ventricular septal rupture. Ann Thorac Surg. 2000;70:2735. 6. Ito T, Hagiwara H, Maekawa A. Early and late results of entire septal patch technique for post infarction ventricular septal rup- ture. Gen Thorac Cardiovasc Surg. 2012;60:4759. 7. Tabuchi N, Tanaka H, Arai H, Mizuno T, Nakahara H, Oshima N, et al. Double-patch technique for postinfarction ventricular septal perforation. Ann Thorac Surg. 2004;77:3423. 8. Musumeci F, Shukla V, Mignosa C, Casali G, Ikram S. Early repair of postinfarction septal defect with geratin-resorcin-formol biological glue. Ann Thorac Surg. 1996;62:4868. 9. Shibata T, Suehiro S, Ishikawa T, Hattori K, Kinoshita H. Repair of postinfarction ventricular septal defect with joined endocardial patches. Ann Thorac Surg. 1997;63:11657. 638Gen Thorac Cardiovasc Surg (2013) 61:632639 123 10. Kobayashi T, Mikamo A, Suzuki R, Murakami M, Shirasawa B, Hamano K. Simple geometrical infarct exclusion technique with a single patch for postinfarction ventricular septal perforation. Ann Thorac Surg. 2010;89:204952. 11. Sugimoto T, Yoshii S, Yamamoto K, Sakakibara K, Iida Y, Ueahra A, et al. A modifi ed infarct exclusion technique: triple- patch technique for postinfarction ventricular septal perforation. J Thorac Cardiovasc Surg. 2008;135:7023. 12. Daggett WM, Guyton RA, Mundth ED, Buckley MJ, McEnany MT, Gold HK, et al. Surgery for post-myocardial infarct ven- tricular septa