Finite element analysis regarding patch size, stiffness, and contact condition to the endocardium in surgery for post infarction ventricular septal rupture

Background: The 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). Methods: A 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 finite element analysis. Clinical results and echo findings of 34 consecutive patients with a mean age of 72.6 ± 9.5 (range 55-89) who underwent emergency surgery for VSR from 1995 to 2012 were reviewed. Results: Suture 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 fitted 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 mortality 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 %. Conclusion: In endocardial patch type surgery for VSR, proper sizing of the patch to sufficiently fit to endocardial surface in a tension-free condition is the most important to avoid residual leak.