Contribution of computational model for assessment of heart tissue local stress caused by suture in LVAD implantation.

STUDY: Implantation of a Left Ventricular Assist Device (LVAD) may produce both excessive local tissue stress and resulting strain-induced tissue rupture that are potential iatrogenic factors influencing the success of the surgical attachment of the LVAD into the myocardium. By using a computational simulation compared to mechanical tests, we sought to investigate the characteristics of stress-induced suture material on porcine myocardium. METHODS: Tensile strength experiments (n = 8) were performed on bulk left myocardium to establish a hyperelastic reduced polynomial constitutive law. Simultaneously, suture strength tests on left myocardium (n = 6) were performed with a standard tensile test setup. Experiments were made on bulk ventricular wall with a single U-suture (polypropylene 3-0) and a PTFE pledget. Then, a Finite Element simulation of a LVAD suture case was performed. Strength versus displacement behavior was compared between mechanical and numerical experiments. Local stress fields in the model were thus analyzed. RESULTS: A strong correlation between the experimental and the numerical responses was observed, validating the relevance of the numerical model. A secure damage limit of 100 kPa on heart tissue was defined from mechanical suture testing and used to describe numerical results. The impact of suture on heart tissue could be accurately determined through new parameters of numerical data (stress diffusion, triaxiality stress). Finally, an ideal spacing between sutures of 2 mm was proposed. CONCLUSION: Our computational model showed a reliable ability to provide and predict various local tissue stresses created by suture penetration into the myocardium. In addition, this model contributed to providing valuable information useful to design less traumatic sutures for LVAD implantation. Therefore, our computational model is a promising tool to predict and optimize LVAD myocardial suture.

Effects of the self-myocardial retroperfusion with aortic-coronary sinus shunt on cardiac output and ischemic events in high-risk patients undergoing OPCAB surgery.

AIM: Despite controversies, off-pump coronary artery bypass (OPCAB) surgery has become a routine procedure. Obvious advantages have been demonstrated in high-risk patients. However, OPCAB surgery has limitations in specific high-risk situations with hazards of operative deleterious events. We describe an innovative procedure of self-myocardial retroperfusion (SMR) with an aortic-coronary sinus shunt (ACSS). We prospectively evaluated the protective effects and benefits of SMR in high-risk coronary patients with impaired LVEF. METHODS: Eighteen consecutive high-risk (ES>10) coronary patients (mean age: 65.94 years; range: 34-85; mean ES: 26.97%) with LVEF≤35% who were not eligible for IABP were assigned for OPCAB surgery. Following sternotomy, the cardiac indexes (CI) were measured before, during SMR and after completion of coronary artery bypasses. Operative events with and without SMR were accurately collected, and postoperative cardiac Troponin T release was measured. RESULTS: OPCAB procedures were performed in all patients. Intraoperative use of SMR significantly increased CI (P=3.1041810.10-8) and reversed deleterious operative events (ECG changes/low cardiac output). Hospital mortality was 0%. Incidence of transient atrial fibrillation was 33.33%. Neither stroke nor renal insufficiency was observed. The mean graft number/patient was 2.05. Mean postoperative cardiac Troponin T value was 0.79 µg/L. Beating heart preservation optimized by SMR contributed to reduce ischemia-reperfusion injury, as validated by an immediate increase of CI after completion of coronary bypasses (P=3.35009.10-9). CONCLUSION: The concept of SMR with an ACSS during OPCAB procedures definitely improved CI and reversed ischemic features in high-risk patients and should be considered as an operative temporary myocardial assistance.

Efficacy of TachoSil® as a sutureless hemostatic patch to repair a perforation of the interventricular groove during endocardial radiofrequency ablation.

Catheter ablation is a well-established therapeutic option for management of recurrent ventricular tachycardia in patients with ischemic/non-ischemic heart disease and procedural complications include a mortality rate of up to 3% and a risk of major complications up to 10%. Cardiac perforation following a catheter ablation is rare but serious complication and occurs in 1% of ventricular ablation procedures. The appropriate surgical repair may be challenging and need cardiopulmonary bypass support according to the location of the lesion and the hemodynamic status of the patient. We report the case of a free wall right ventricular perforation of the interventricular groove with cardiac tamponade following catheter ablation for recurrent ventricular tachycardia. Due to the proximity of the left anterior descending artery and the extreme fragility of tissues, the patient was treated successfully by a sutureless patch technique using a fibrin tissue-adhesive collagen fleece (TachoSil®). This technique is a safe and effective surgical option to repair a ventricular perforation especially when the ventricular tissues are fragile. It is simple and enable to realize surgical repair also if the localization of tear is difficult to access and without the need for cardiopulmonary bypass support if hemodynamic conditions are stable.