Finite Element Analysis Investigate Pulmonary Autograft Root and Leaflet Stresses to Understand Late Durability of Ross Operation

Ross operation might be a valid option for congenital and acquired left ventricular outflow tract disease in selected cases. As the pulmonary autograft is a living substitute for the aortic root that bioinspired the Ross operation, we have created an experimental animal model in which the vital capacity of the pulmonary autograft (PA) has been studied during physiological growth. The present study aims to determine any increased stresses in PA root and leaflet compared to the similar components of the native aorta. An animal model and a mathematical analysis using finite element analysis have been used for the purpose of this manuscript. The results of this study advance our understanding of the relative benefits of pulmonary autograft for the management of severe aortic valve disease. However, it launches a warning about the importance of the choice of the length of the conduits as mechanical deformation, and, therefore, potential failure, increases with the length of the segment subjected to stress. Understanding PA root and leaflet stresses is the first step toward understanding PA durability and the regions prone to dilatation, ultimately to refine the best implant technique.

Role of autophagy in aneurysm and dissection of the ascending aorta

Maintenance of physiologically balanced levels of autophagy is crucial for cellular homeostasis and in the normal vessel wall, balanced autophagy can be considered a cytoprotective mechanism that preserves endothelial function and prevents cardiovascular disease. Recent studies pointed out the importance of the modulation of the autophagic flux in the pathogenesis of aortic dissection and aneurysms of the ascending aorta. Notably, shear stress (and its receptor p62), IL-6, Rab7 and Atg5/IRE1α pathways of autophagy may be considered the novel super-selective therapeutic target for the preventive and postoperative treatment of aortic aneurysm and aortic dissection. This review intends to summarize current evidences in this field trying to enlighten new avenues for future researches.

Deep Sternal Wound Infection (DSWI) and Mediastinitis After Cardiac Surgery: Current Approaches and Future Trends in Prevention and Management

Median sternotomy is the most common access for cardiac surgery. Deep surgical wound infection (DSWI) and mediastinitis after median sternotomy remain significant clinical problems after cardiac surgery in terms of mortality, morbidity and healthcare-associated costs. Despite recent advances in medical management and consensus papers, their incidence ranges from 1% to 5%, and the associated mortality ranges from 20% to 50%. Recent studies in this field are providing excellent outcomes with promising results for the near future. The choice of sternal closure technique plays a crucial role in the prevention of DSWI and mediastinitis and should be tailored to the patient's characteristics, as clinical judgement and experience play a pivotal role. Early aggressive surgical debridement, vacuum-assisted closure (VAC) therapy, muscle flap and newer technologies are revolutionizing the paradigm of treatment of DSWI. Also, recent advances in tissue engineering have been refining potential approaches to tissue regeneration or substitution for enhanced wound repair. This editorial aims to briefly summarize the current and future techniques in DSWI prevention and treatment after cardiac surgery.

Lights and Shadows on the Ross Procedure: Biological Solutions for Biological Problems

The Ross procedure represents a valid option for aortic valve replacement in young adults and was repeatedly shown to restore survival to that of the age- and sex-matched general population. However, its major drawback relies in the risk of pulmonary autograft (PA) dilation, negative histological remodeling and need for reoperation. Several techniques and materials to reinforce the PA have been proposed. They mainly include Dacron, personalized external aortic root support with a polyethylene terephthalate mesh system, autologous aortic tissue and bioresorbable materials. Synthetic materials, despite widely used in cardiac surgery, have significant biocompatibility issues with the PA and their interaction with this living structure translates into negative remodeling phenomena and disadvantageous biomechanical behaviors. Conversely, biomaterials with tailored degradable profiles might be able to reinforce while integrating with the PA and enhance its remodeling capabilities. The recent advancement in this field are here discussed.

Inflammatory Response and Endothelial Dysfunction Following Cardiopulmonary Bypass: Pathophysiology and Pharmacological Targets

BACKGROUND

Endothelial injury occurring during cardiopulmonary bypass is a major contributing factor in the development of organ dysfunction, which leads to many of the postoperative complications occurring during cardiac surgery.

OBJECTIVE

This narrative review aims to summarize the main mechanisms of cardiopulmonary bypass - related disease, evaluating the unfavorable events leading to tissue injury, with a description of current pharmacologic and non-pharmacologic mechanisms to reduce CPB-related injury.

METHODS

A Medline/Pubmed/Scopus search was conducted using clinical queries with the key terms "cardiac surgery", "cardiopulmonary bypass", "inflammation" and "endothelial injury", and related MeSH terms, until July 2019. The search strategy included meta-analyses, randomized controlled trials, clinical trials, reviews and pertinent references. Patents were searched using the same key terms from https://patents.google.com/, www.uspto.gov, and www.freepatentsonline.com.

RESULTS

In this review, we discuss the current knowledge of the mechanisms of vascular endothelial cell injury, the acute inflammatory response, and the regulatory factors that control the extent of vascular injury during extracorporeal circulation, summarizing the main target of anti-inflammatory pharmacologic and non-pharmacologic strategies.

CONCLUSION

Inflammatory response and endothelial dysfunction following cardiopulmonary bypass are the prices to pay for the benefits offered during cardiac surgery procedures. Counteracting the detrimental effect of extracorporeal circulation appears to be crucial to improve clinical outcomes in pediatric and adult cardiac surgery. The intrinsic complexity and the tight interplay of the factors involved might require a holistic approach against inflammation and endothelial response.

Are the dynamic changes of the aortic root determinant for thrombosis or leaflet degeneration after transcatheter aortic valve replacement?

The role of the aortic root is to convert the accumulated elastic energy during systole into kinetic flow energy during diastole, in order to improve blood distribution in the coronary tree. Therefore, the sinuses of Valsalva of the aortic root are not predisposed to accept any bulky material, especially in case of uncrushed solid calcific agglomerates. This concept underlines the differences between surgical aortic valve replacement, in which decalcification is a main part of the procedure, and transcatheter aortic valve replacement (TAVR). Cyclic changes in shape and size of the aortic root influence blood flow in the Valsalva sinuses. Recent papers have been investigating the dynamic changes of the aortic root and whether those differences might be correlated with clinical effects, and this paper aims to summarize part of this flourishing literature. Post-TAVR aortic root remodeling, dynamic flow and TAVR complications might have a fluidodynamic background, and clinically observed side effects such as thrombosis or leaflet degeneration should be further investigated in basic researches. Also, aortic root changes could impact valve type and size selection, affecting the decision of over-sizing or under-sizing in order to prevent valve embolization or coronary ostia obstruction.

Mitral regurgitation after transcatheter aortic valve replacement

Patients undergoing transcatheter aortic valve replacement (TAVR) might have an associated significant MR that can potentially lead to left ventricular (LV) failure after procedure. Considering the specific alterations in the mitral valve in TAVR scenario and the widespread use of TAVR in recent years, it appears important to know and understand the anatomical, functional and clinical implications to develop adequate strategies for the future. Patients with severe mitral regurgitation (MR) have been generally excluded from randomized clinical trials, making poor the impact that associated MR can have on clinical outcomes after TAVR. Several factors must be considered whose presence influences the severity of MR. For example, the elevated prevalence of coronary disease with consequent ischemic MR may account for LV dilation observed at the end stage of aortic stenosis. Evidence randomized studies and registries suggests that the rate of concomitant moderate-to-severe MR in patients undergoing TAVR oscillates between 2% and 33%, and patients with moderate to severe MR may have hemodynamic frailty with clinical deterioration during mechanical intervention. Short- and long-term outcomes, including cardiac mortality, appear to be influenced by the existence of preoperative moderate-to-severe MR or by the postprocedural worsening of mild MR, generally due to adverse LV remodeling. The incidence and the prognostic effect of concomitant MR in patients undergoing TAVR requires specific attention as might trigger adjunctive strategy treatment which should be carefully evaluated in clinical trials.

Structural heart disease: the year in valvular and complex coronary intervention trials

The need for treatment strategies targeting complex structural heart and obstructive epicardial coronary artery disease (CAD) is rapidly growing. The demographics in referral centers has shifted to an older population with greater co-morbidities and higher risk. Indeed, nearly one quarter of patients in tertiary-care settings have moderate or severe valvular heart disease, and despite a decrease in overall CAD burden in the United States over the past two decades the prevalence of myocardial infarction remains high. The 2019 societal scientific sessions included novel research and landmark presentations on less invasive valvular and safer complex coronary interventions in the aforementioned populations, in hopes of improving patient outcomes and expanding treatment indications. Transcatheter aortic valve replacement (TAVR), percutaneous mitral and tricuspid valve therapy, and complex coronary interventions, were the focus of important clinical trials and registry data. Herein, we provide a select and concise review of the most pivotal studies presented.

Mitral regurgitation: lessons learned from COAPT and MITRA-Fr

Recent studies about percutaneous treatment of secondary mitral regurgitation (MR) underlined the importance of left ventricular geometry and features of mitral valve as determinants of procedural and long-term success. Guideline-directed medical therapy (GDMT), transcatheter mitral valve treatment (TMVT) and surgical procedures (mitral valve replacement, mitral valve repair at level of the annulus or subvalvular apparatus) have been extensively evaluated but not adequately compared in current clinical studies. A detailed analysis of the results of the study about transcatheter mitral valve repair would allow to evaluate the safety and effectiveness of such procedure and would provide potential indications for improving the quality of percutaneous and surgical repair in patients with moderate-to-severe secondary MR. Patients with proportionate MR (i.e., MR severity is proportional to the amount of left ventricular dilatation) are prone to respond to the optimization of medical therapy, while patients with disproportionate MR (i.e., MR severity is disproportionately higher than predicted by left ventricular dilatation, with high EROA and small left ventricle) are likely to benefit from additional repair. The identification of specific subpopulation of "high responders", based on the anatomic characteristics of the mitral valve and the relative dimensions of the annulus, the regurgitation and the left ventricle, can also apply to medical therapy. However, some pivotal component of MR (such as the symmetry of tethering and the differences in biomechanical features of leaflets) are not adequately investigated in current studies and warrant further evaluation.

Transthoracic versus intra-operative transesophageal echocardiography in right heart assessment

Methods

Fifty-four patients who had combined mitral and tricuspid valve surgery were included. Right heart measurements were performed in the TTE apical 4-chamber (A4C) and RV inflow views, and TEE mid-esophageal 4-chamber (ME4C) and transgastric RV inflow views at end-diastole. Spearman correlation coefficients (r) were applied to test for associations between the imaging modalities.

Results

The mean age was 65 years and 39% were male. All patients had ≥ moderate tricuspid regurgitation (TR), and a secondary/functional etiology was present in 89%. The median TAd and RV basal (RVd) diameters in the TTE-A4C view measured 37 mm [interquartile range (IQR), 34–44] and 43 mm (IQR, 40–51), respectively. The TTE-A4C TAd strongly correlated with the TEE-ME4C measurement (r=0.72), with an overestimation of 1 mm (IQR, −2 to 4) by TEE (P<0.01). For RVd, the TTE-A4C measurement correlated moderately with the TEE-ME4C view (r=0.61), underestimating the RVd by −1 mm (IQR, −4 to 3.3) (P<0.01). No correlation was observed between TAPSE measured by TTE and TEE (r=0.22, P=0.13).

Conclusions

Intra-operative TEE may reliably quantitate TA and RV size and geometry. The current findings are best interpreted as hypothesis-generating for future validative studies.

Biomechanical future of the growing pulmonary autograft in Ross operation

It has been few years since the preliminary translational research study on mechanics performance of autologous pulmonary tissue were published to circumvent complication relies to SVD. Several studies reported the modification of pulmonary native autograft root subjected to dynamic stress strain in long-term outcomes of aortic valve replacement. Our multidisciplinary research team firstly describe the weave relationship between stress-strain, growth and remodelling in an experimental model of Ross Operation. From a biomechanical point of view, the rapid absorption of polydioxanone constituting the internal part of the device may limit the potential negative effect of excessive stretching and improvement of steeper curve in the circumferential response. Improvement of longitudinal stretching of pulmonary autograft by external component of device are indicative of auxetic effect of e-PTFE. Successful reinforcement with semiresorbable device can also be favourable to pulmonary autograft function in growing patients needing to match somatic growth. The attendant decrease in PA expansion and the preserved features of the valve leaflets enhances durability of Ross operation. Strengthening of the distal pulmonary root anastomosis using external reinforcement, modifying the ascending phase of the circumferential stress curve, might be advisable as previously described. PA is an ideal substitute for aortic valve replacement not only in Mr. Ross's dreams but also from the biomechanical point of view.

A Finite Element Analysis Study from 3D CT to Predict Transcatheter Heart Valve Thrombosis

Background: Transcatheter aortic valve replacement has proved its safety and effectiveness in intermediate- to high-risk and inoperable patients with severe aortic stenosis. However, despite current guideline recommendations, the use of transcatheter aortic valve replacement (TAVR) to treat severe aortic valve stenosis caused by degenerative leaflet thickening and calcification has not been widely adopted in low-risk patients. This reluctance among both cardiac surgeons and cardiologists could be due to concerns regarding clinical and subclinical valve thrombosis. Stent performance alongside increased aortic root and leaflet stresses in surgical bioprostheses has been correlated with complications such as thrombosis, migration and structural valve degeneration. Materials and Methods: Self-expandable catheter-based aortic valve replacement (Medtronic, Minneapolis, MN, USA), which was received by patients who developed transcatheter heart valve thrombosis, was investigated using high-resolution biomodelling from computed tomography scanning. Calcific blocks were extracted from a 250 CT multi-slice image for precise three-dimensional geometry image reconstruction of the root and leaflets. Results: Distortion of the stent was observed with incomplete cranial and caudal expansion of the device. The incomplete deployment of the stent was evident in the presence of uncrushed refractory bulky calcifications. This resulted in incomplete alignment of the device within the aortic root and potential dislodgment. Conclusion: A Finite Element Analysis (FEA) investigation can anticipate the presence of calcified refractory blocks, the deformation of the prosthetic stent and the development of paravalvular orifice, and it may prevent subclinical and clinical TAVR thrombosis. Here we clearly demonstrate that using exact geometry from high-resolution CT scans in association with FEA allows detection of persistent bulky calcifications that may contribute to thrombus formation after TAVR procedure.

Ross operation 23 years after surgery: It should not be a "forgotten" option

INTRODUCTION

The Ross procedure plays a pivotal part in both congenital and acquired diseases of the aortic valve, especially in young patients. The advantages of this procedure are widely known; however, long-term studies have shown dilation of the pulmonary autograft (PA) in up to 20% of patients in the second decade postoperatively.

METHODS

Three cases (ages 38, 51, and 53) who underwent the Ross procedure 23 years ago for bicuspid valves and endocarditis. Cases were followed-up with echocardiogram and computed tomography scan with three-dimensional reconstructions.

RESULTS

The PA showed normal function with favorable geometry alongside the thoracic aorta, while the pulmonary homograft preserved its function with a low degree of calcification. The mean annual expansion of the autograft was only 0.15, 0.30, and 0.40 mm with no pathological dilation after 20 years DISCUSSION: Ross operation provides excellent hemodynamic results while avoiding long-term anticoagulation and might constitute a valid adjunct in selected categories such as young or endocarditis patients.

Preoperative atorvastatin reduces bleeding and blood transfusions in patients undergoing elective isolated aortic valve replacement

OBJECTIVES

Minimization of bleeding to reduce the use of blood products is of utmost importance in cardiac surgery. Statins are known for their pleiotropic effects beyond lipid-lowering properties, and the use of atorvastatin preoperatively is associated with reduced risk of bleeding and blood product use after coronary surgery. However, no studies have investigated if this beneficial effect also extends to aortic valve surgery.

METHODS

In this retrospective cohort study, 1145 consecutive patients undergoing elective primary isolated aortic valve replacement meeting the inclusion and exclusion criteria were selected from January 2009 to December 2017 (547 in the atorvastatin group, 598 in the control group). Postoperative bleeding, blood product use, and complications were monitored during hospitalization.

RESULTS

Postoperative bleeding was significantly lower in the atorvastatin group compared with the controls in the first 12 h after surgery (372 ± 137 vs 561 ± 219 ml; P = 0.001) and considering overall bleeding (678 ± 387 vs 981 ± 345 ml, P = 0.001). A total of 32.3% of controls and 26.3% of atorvastatin users received packed red blood cells (P = 0.027), and major surgical complications were similar between the groups. Postoperative length of stay was shorter in the atorvastatin group with an average reduction of 1 day of hospitalization (6.0 ± 1.4 vs 6.9 ± 2.1 days; P = 0.001). Postoperative bleeding among the atorvastatin-treated patients was significantly greater in those taking lower doses compared to those taking higher doses of atorvastatin with a 20% between-group difference (P = 0.001).

CONCLUSIONS

Preoperative treatment with atorvastatin might reduce postoperative bleeding and transfusion of packed red blood cells in patients undergoing elective isolated aortic valve replacement. This result might translate into faster recovery after surgery and reduced hospitalization costs.

The Radial Artery for Coronary Bypass Grafting: The Fifth Decade

BACKGROUND

In 1989, we reported the use of the radial artery as a second target conduit for coronary artery bypass grafting. However, underpowered randomized trials have reported differences in clinical outcomes between the radial artery and other grafts. As we approach 50 years of experience with radial artery grafting, we reviewed the literature to determine the second-best target vessel for coronary operations.

METHODS

An electronic review of the literature with an emphasis on randomized controlled trials, propensity-matched observational series, and meta-analyses identified a large population of patients who received arterial conduit and saphenous vein grafts.

RESULTS

The radial artery has been proven to be reliable as a second target conduit for coronary artery bypass grafting, with outcomes and patency rates superior to those for saphenous vein graft. It has also been proven to be both safe and effective as a third conduit in the territory of the right coronary artery. A paucity of evidence with few comparable series limits the use of the gastroepiploic artery.

CONCLUSION

In its fifth decade of use, we can definitively conclude that the aorto-to-coronary radial bypass graft is the conduit of choice for coronary operations after the left internal thoracic artery to the left anterior descending artery.

Changes of the coronary arteries and cardiac microvasculature with aging: Implications for translational research and clinical practice

Aging results in functional and structural changes in the cardiovascular system, translating into a progressive increase of mechanical vessel stiffness, due to a combination of changes in micro-RNA expression patterns, autophagy, arterial calcification, smooth muscle cell migration and proliferation. The two pivotal mechanisms of aging-related endothelial dysfunction are oxidative stress and inflammation, even in the absence of clinical disease. A comprehensive understanding of the aging process is emerging as a primary concern in literature, as vascular aging has recently become a target for prevention and treatment of cardiovascular disease. Change of life-style, diet, antioxidant regimens, anti-inflammatory treatments, senolytic drugs counteract the pro-aging pathways or target senescent cells modulating their detrimental effects. Such therapies aim to reduce the ineluctable burden of age and contrast aging-associated cardiovascular dysfunction. This narrative review intends to summarize the macrovascular and microvascular changes related with aging, as a better understanding of the pathways leading to arterial aging may contribute to design new mechanism-based therapeutic approaches to attenuate the features of vascular senescence and its clinical impact on the cardiovascular system.

Sternal wound closure in the current era: the need of a tailored approach

OBJECTIVE

Median sternotomy remains the most common access to perform cardiac surgery procedures. However, the experience of the operating surgeon remains a crucial factor during sternal closure to avoid potential complications related to poor sternal healing, such as mediastinitis. Considering the lack of major randomized controlled trials and the heterogeneity of the current literature, this narrative review aims to summarize the different techniques and approaches to sternal closure with the aim to investigate their reflections into clinical outcomes and to inform the choice on the most effective closure method after median sternotomy.

METHODS

A literature search through PubMed, Embase, EBSCO, Cochrane database of systematic reviews, and Web of Science from its inception up to April 2019 using the following search keywords in various combinations: sternal, sternotomy, mediastinitis, deep sternal wound infection, cardiac surgery, closure.

RESULTS

Single wire fixation methods, at present, seems the most useful method to perform sternal closure in routine patients, although patients with a fragile sternum might benefit more from a figure-of-eight technique. In high-risk patients (e.g. chronic pulmonary disease, obesity, bilateral internal mammary artery harvesting, diabetes, off-midline sternotomy), rigid plate fixation is currently the most effective method, if available; alternatively, weave techniques could be used.

CONCLUSION

The choice among the sternal closure techniques should be mainly inspired and tailored on the patient's characteristics, and correct judgement and experience play a pivotal role. A decisional algorithm has been proposed as an attempt to overcome the absence of specific guidelines and to guide the operative approach. This operative approach might be used also in non-cardiac procedure in which median sternotomy is required, such as in case of thoracic surgery.