Residual Stress Impairs Pump Function After Surgical Ventricular Remodeling: A Finite Element Analysis

Abstract

Objectives Surgical ventricular restoration (Dor procedure) is generally thought to reduce left ventricular (LV) myofiber stress (FS) but to adversely affect pump function. However, the underlying mechanism is unclear. The goal of this study was to determine the effect of residual stress (RS) on LV FS and pump function after the Dor procedure. Methods Previously described finite element models of the LV based on MRI data obtained in five sheep 16 weeks after antero-apical myocardial infarction were used. Simulated Dacron patches that were elliptical and 25% of the infarct opening area were implanted using a virtual suture technique (VIRTUAL-DOR). In each case, diastole and systole were simulated and RS, FS, LV volumes, systolic and diastolic function, and pump (Starling) function were calculated. Results VIRTUAL-DOR was associated with significant RS that was tensile (2.89±1.31 kPa) in the remote myocardium and compressive (234.15±65.53 kPa) in the borderzone (BZ). VIRTUAL-DOR+RS (compared to VIRTUAL-DOR-NO-RS) was associated with further reduction in regional diastolic and systolic FS with the greatest change in the BZ (43.5-fold and 7.1-fold respectively, p<0.0001). VIRTUAL-DOR+RS was also associated with further reduction in systolic and diastolic volumes (7.9%, p=0.0606 and 10.6%, p=0.0630, respectively). The resultant effect was a further reduction in pump function after VIRTUAL-DOR+RS. Conclusion Residual stress that occurs after the Dor procedure is positive (tensile) in the remote myocardium and negative (compressive) in the BZ and associated with reductions in fiber stress and LV volumes. The resultant effect is a further reduction in LV pump (Starling) function.

Optimizing Epicardial Restraint and Reinforcement Following Myocardial Infarction: Moving Towards Localized, Biomimetic, and Multitherapeutic Options

“…The biventricular FEA model investigating the Acorn CorCap CSD also showed similar results [52]. Although it is outside the scope of this work, it is worth noting that FEA models of endocardial patch placement, and their effect on myofiber stress have also been described [53,54].…”

Clinical and hemodynamic outcomes of the Dor procedure in adults with ischemic cardiomyopathy

“…It is possible that these patterns of stress–strain relationships may be partially responsible for the decreased diastolic functioning post‐SVR. It has been suggested that different patch sizes or shapes can help regulate the tensile and compressive forces to give the best diastolic result while still achieving other surgical goals 111 . However, this theory needs to consider other patient factors relevant to diastolic functioning mentioned earlier in this review.…”

“…In animal studies examining residual stress, the stress remaining after the Dor procedure was associated with a greater reduction in myofiber stress and was found to be tensile in remote myocardium but compressive in the borderzone 111,112 . It is possible that these patterns of stress–strain relationships may be partially responsible for the decreased diastolic functioning post‐SVR.…”

“…In animal studies examining residual stress, the stress remaining after the Dor procedure was associated with a greater reduction in myofiber stress and was found to be tensile in remote myocardium but compressive in the borderzone. 111,112 It is possible that these patterns of stress-strain relationships may be partially responsible for the de- There is also evidence to suggest that it may be a viable option for eligible cardiac transplant patients. The use of mathematical modeling and MRI technology is starting to allow for better analysis into the clinical efficacy of SVR as well as possible areas of focus as techniques evolve.…”

“…A study by Ratcliffe and colleagues 112 posits that diastolic dysfunction after SVR is directly related to the steep end-diastolic pressure-volume relationship (EDVPR) slope and that this measurement should be used to evaluate postsurgical function. It has also been proposed that contractility of the excluded ventricular wall in SVR can play a role in the postoperative Starling relationship 111. Although more research needs to be done to understand the diastolic effects of SVR, such animal studies offer promising opportunities for future exploration and surgical advancement.11 | CONCLUSION Surgical ventricular restoration is an important advancement in the surgical management of HF.…”