Resistance to infection of long-term cryopreserved human aortic valve allografts

Valved Conduits for Right Ventricular Outflow Tract Reconstruction: A Review of Current Technologies and Future Directions

The need for right ventricular outflow tract reconstruction is common and growing in congenital heart surgery given expanding indications for the repair of congenital as well as acquired heart disease. Various valved conduit options currently exist including homografts, xenograft pulmonary valved conduits (Contegra™), and porcine valved conduits. The major limitation for all conduits is implant durability, which requires reoperation. Currently, cryopreserved homografts are often used given their superiority shown in long-term data. Significant limitations remain in the cost and availability of the graft, particularly for smaller sizes. Contegra conduits are available in a variety of sizes. Nonetheless, the data regarding long-term durability are less robust and studies comparing durability with homografts have been conflicting. Additionally, there is concern for increased rates of late endocarditis in this conduit. Porcine valved conduits offer a reliable option but are limited by structural valve degeneration associated with all types of bioprosthetic heart valve replacements. New developments in the field of tissue engineering have produced promising bio-restorative valved conduits that may overcome many of the limitations of previous conduit technologies. These remain in the early stages of clinical testing. This review summarizes the clinical data surrounding the conduits used most commonly in clinical practice today and explores emerging technologies that may bring us closer to developing the ideal conduit.

Advancements and Challenges in the Management of Prosthetic Valve Endocarditis: A Review

Prosthetic valve endocarditis (PVE) is the medical term used to describe a focus of infection involving a valvular substitute within the heart. It is a significant concern in the field of cardiology, and the epidemiology of PVE has seen notable developments over the last five decades. The disease currently affects an older demographic and is becoming increasingly prevalent in patients with transcatheter-implanted valves. It is imperative that we urgently address the significant challenges posed by PVE. It is a disease that has a wide range of potential aetiologies, clinical presentations, and courses. In developed countries, Staphylococcus aureus is now the predominant causative organism, resulting in an aggressive form of disease that frequently afflicts vulnerable or elderly populations. However, it is clear that Enterococcus species present a significant challenge in the context of PVE following TAVR procedures, given their elevated prevalence. The 2023 Duke/International Society for Cardiovascular Infectious Diseases infective endocarditis diagnostic criteria now include significant developments in microbiological and image-based techniques for diagnostic purposes, specifically the incorporation of fluorine-18 fluorodeoxyglucose positron emission tomography and computed tomography. These developments unequivocally enhance the diagnostic sensitivity for PVE, while maintaining the specificity. They do so in accordance with the results of studies conducted specifically for the purpose of validation. The lack of rigorous scientific studies and a shortage of funding and resources for research have led to a significant gap in our understanding. Randomized controlled trials could provide invaluable insight and guidance for clinical practice, but they are missing, which represents a major gap. It is clear that there is an urgent need for more research. PVE is a life-threatening condition that must be handled by a multidisciplinary endocarditis team at a cardiac centre in order to improve outcomes. The emergence of innovative surgical techniques has empowered clinicians to steer more patients away from surgical procedures, despite the presence of clear indications for them. A select group of patients can now complete parenteral or oral antimicrobial treatment at home. Additionally, antibiotic prophylaxis is the best option for individuals with prosthetic valves who are going to have invasive dental procedures. These individuals should be given antibiotics beforehand.

The Surgical Treatment of Infective Endocarditis: A Comprehensive Review

Infective endocarditis (IE) is a severe cardiac complication with high mortality rates, especially when surgical intervention is delayed or absent. This review addresses the expanding role of surgery in managing IE, focusing on the variation in surgical treatment rates, the impact of patient demographics, and the effectiveness of different surgical approaches. Despite varying global data, a notable increase in surgical interventions for IE is evident, with over 50% of patients undergoing surgery in tertiary centres. This review synthesizes information from focused literature searches up to July 2023, covering preoperative to postoperative considerations and surgical strategies for IE. Key preoperative concerns include accurate diagnosis, appropriate antimicrobial treatment, and the timing of surgery, which is particularly crucial for patients with heart failure or at risk of embolism. Surgical approaches vary based on valve involvement, with mitral valve repair showing promising outcomes compared to replacement. Aortic valve surgery, traditionally favouring replacement, now includes repair as a viable option. Emerging techniques such as sutureless valves and aortic homografts are explored, highlighting their potential advantages in specific IE cases. The review also delves into high-risk groups like intravenous drug users and the elderly, emphasizing the need for tailored surgical strategies. With an increasing number of patients presenting with prosthetic valve endocarditis and device-related IE, the review underscores the importance of comprehensive management strategies encompassing surgical and medical interventions. Overall, this review provides a comprehensive overview of current evidence in the surgical management of IE, highlighting the necessity of a multidisciplinary approach and ongoing research to optimize patient outcomes.

Early and late outcomes of surgical repair of mycotic aortic aneurysms: A 30-year experience

OBJECTIVE

Mycotic aortic aneurysm and its associated complications are often catastrophic. In this study, we examined the early and late outcomes of surgical repair of mycotic aortic aneurysm at our center over the last 3 decades.

METHODS

We retrospectively reviewed our prospectively maintained aortic surgery database with supplemental adjudication of medical records. Aortic infection was confirmed through clinical, radiological, intraoperative, pathological, and treatment evidence.

RESULTS

Seventy-five patients (median age, 68 years; interquartile range, 62-74) who underwent surgical repair of a mycotic aortic aneurysm between 1992 and 2021 were included. Almost all patients (n = 72; 96%) presented with symptoms, including 26 patients (35%) with rupture, and many underwent urgent or emergency repair (n = 64; 85%). Sixty-one patients underwent open repair, and 14 patients underwent hybrid or endovascular repair. Infection-specific adjunct techniques included rifampin-soaked grafts (n = 16), omental pedicle flaps (n = 21), and antibiotic irrigation catheters (n = 8). There were 15 early deaths (20%), including 10 of the 26 patients (38%) who presented with rupture; however, persistent stroke, paraplegia or paraparesis, and renal failure necessitating dialysis were uncommon (each <5%). Almost all early survivors (52/60; 87%) were discharged with long-term antibiotic therapy. Estimated survival at 2, 6, and 10 years was 55.7% ± 5.8%, 39.0% ± 5.7%, and 26.9% ± 5.5%, respectively.

CONCLUSIONS

A substantial proportion of patients with mycotic aortic aneurysm present with rupture and generally require urgent or emergency repair. Operative mortality and complications are common, especially for patients who present with rupture, and late survival is poor.

Bridging Molecular and Clinical Sciences to Achieve the Best Treatment of Enterococcus faecalis Endocarditis

Enterococcus faecalis (E. faecalis) is a commensal bacterium that causes various infections in surgical sites, the urinary tract, and blood. The bacterium is becoming a significant concern because it tends to affect the elderly population, which has a high prevalence of undiagnosed degenerative valvular disease and is often subjected to invasive procedures and implanted medical devices. The bacterium's actions are influenced by specific characteristics like pili activity and biofilm formation. This resistance significantly impedes the effectiveness of numerous antibiotic therapies, particularly in cases of endocarditis. While current guidelines recommend antimicrobial therapy, the emergence of resistant strains has introduced complexity in managing these patients, especially with the increasing use of transcatheter therapies for those who are not suitable for surgery. Presentations of the condition are often varied and associated with generalised symptoms, which may pose a diagnostic challenge. We share our encounter with a case study that concerns an octogenarian who had a TAVI valve and developed endocarditis. We also conducted a literature review to identify the essential treatment algorithms for such cases.

A Literature Review on the Use of Aortic Allografts in Modern Cardiac Surgery for the Treatment of Infective Endocarditis: Is There Clear Evidence or Is It Merely a Perception?

Infective valve endocarditis is caused by different pathogens and 60% of those involve the aortic valve with valve failure. Although S. aureus is recognized as the most frequently isolated causative bacterium associated with IE in high-income countries, Gram-positive cocci nevertheless play a crucial role in promoting infection in relation to their adhesive matrix molecules. The presence of pili on the surface of Gram-positive bacteria such as in different strains of Enterococcus faecalis and Streptococcus spp., grants these causative pathogens a great offensive capacity due to the formation of biofilms and resistance to antibiotics. The indications and timing of surgery in endocarditis are debated as well as the choice of the ideal valve substitute to replace the diseased valve(s) when repair is not possible. We reviewed the literature and elaborated a systematic approach to endocarditis management based on clinical, microbiological, and anatomopathological variables known to affect postoperative outcomes with the aim to stratify the patients and orient decision making. From this review emerges significant findings on the risk of infection in the allograft used in patients with endocarditis and no endocarditis etiology suggesting that the use of allografts has proved safety and effectiveness in patients with both pathologies.

Host-Bacterium Interaction Mechanisms in Staphylococcus aureus Endocarditis: A Systematic Review

Staphylococci sp. are the most commonly associated pathogens in infective endocarditis, especially within high-income nations. This along with the increasing burden of healthcare, aging populations, and the protracted infection courses, contribute to a significant challenge for healthcare systems. A systematic review was conducted using relevant search criteria from PubMed, Ovid's version of MEDLINE, and EMBASE, and data were tabulated from randomized controlled trials (RCT), observational cohort studies, meta-analysis, and basic research articles. The review was registered with the OSF register of systematic reviews and followed the PRISMA reporting guidelines. Thirty-five studies met the inclusion criteria and were included in the final systematic review. The role of Staphylococcus aureus and its interaction with the protective shield and host protection functions was identified and highlighted in several studies. The interaction between infective endocarditis pathogens, vascular endothelium, and blood constituents was also explored, giving rise to the potential use of antiplatelets as preventative and/or curative agents. Several factors allow Staphylococcus aureus infections to proliferate within the host with numerous promoting and perpetuating agents. The complex interaction with the hosts' innate immunity also potentiates its virulence. The goal of this study is to attain a better understanding on the molecular pathways involved in infective endocarditis supported by S. aureus and whether therapeutic avenues for the prevention and treatment of IE can be obtained. The use of antibiotic-treated allogeneic tissues have marked antibacterial action, thereby becoming the ideal substitute in native and prosthetic valvular infections. However, the development of effective vaccines against S. aureus still requires in-depth studies.

The New Challenge for Heart Endocarditis: From Conventional Prosthesis to New Devices and Platforms for the Treatment of Structural Heart Disease

Infective endocarditis is a sinister condition with considerable morbidity and mortality. Its relevance in the current era is compounded by the increased use of implanted devices such as replacement valves or cardiac implantable electronic devices. These infections are caused by multiple different bacteria with different virulence, pathogenicity, and antimicrobial resistance. Unlike in native endocarditis, the presence of foreign tissue permits sustenance by inflammatory and thrombotic processes as the artificial surfaces promote inflammatory responses and hypercoagulability. Prevention of these infections has been suggested with the use of homografts in combination with antibiotics. Others have attempted to use "low fouling coats" with little clinical success thus far. The use of antibiotic prophylaxis plays a pivotal part in reducing the incidence of prosthesis-related endocarditis. This remains especially crucial with the increasing use of transcatheter heart valve therapies. The widespread use of cardiac implantable electronic devices such as permanent pacemakers, implantable cardioverter defibrillators, and cardiac resynchronization therapy devices has also heralded a noticeable increase in cases of infectious endocarditis affecting complex equipment which can be difficult to treat. Multimodality strategies are needed with input from surgeons and cardiologists to ensure treatment is both prompt and successful, tailored to the individual needs of the patients.

Trends in Managing Cardiac and Orthopaedic Device-Associated Infections by Using Therapeutic Biomaterials

Over the years, there has been an increasing number of cardiac and orthopaedic implanted medical devices, which has caused an increased incidence of device-associated infections. The surfaces of these indwelling devices are preferred sites for the development of biofilms that are potentially lethal for patients. Device-related infections form a large proportion of hospital-acquired infections and have a bearing on both morbidity and mortality. Treatment of these infections is limited to the use of systemic antibiotics with invasive revision surgeries, which had implications on healthcare burdens. The purpose of this review is to describe the main causes that lead to the onset of infection, highlighting both the biological and clinical pathophysiology. Both passive and active surface treatments have been used in the field of biomaterials to reduce the impact of these infections. This includes the use of antimicrobial peptides and ionic liquids in the preventive treatment of antibiotic-resistant biofilms. Thus far, multiple in vivo studies have shown efficacious effects against the antibiotic-resistant biofilm. However, this has yet to materialize in clinical medicine.

Sharing of decision-making for infective endocarditis surgery: a narrative review of clinical and ethical implications

Infective endocarditis (IE) is nowadays one of the most challenging disease in cardiac surgery because of its multifaceted clinical and anatomical presentation. Despite the many clinical and surgical advances achieved in the past 60 years, there is a lack of evidence regarding the ideal strategy. The present review aims to investigate and highlight two main novel concepts for the decision-making of the best substitute. Firstly, the concept of an "endocarditis team": a coordinated multidisciplinary effort in the diagnostic work-up, especially in conditions of high risk of embolization or clinical deterioration. A good "endocarditis team" has the role to overcome such problem, in order to ensure a prompt and balanced strategy. Secondly, which ethical considerations are required to drive the choice of valvular substitute. The choice of best valve substitute is a relevant issue of debate, not only with operative but also prognostic and accordingly ethical aftermaths. Many different solutions have been developed to substitute the infected valve. Among these: mechanical prosthesis (MP), biological stented prosthesis (BP), sutureless bioprosthesis and cryopreserved homografts (CHs). Patients need to be informed in detail about the technical issues pertaining the use of these valve substitute. We will discuss the evidences regarding the risk of recurrent infections or future potentially severe calcification of aortic homograft valve and wall (in other words, the failure of the homograft) and the difficulties in managing the reoperation.

Learning From Controversy: Contemporary Surgical Management of Aortic Valve Endocarditis

Aortic valve replacement is the commonest cardiac surgical operation performed worldwide for infective endocarditis (IE). Long-term durability and avoidance of infection relapse are goals of the procedure. However, no detailed guidelines on prosthesis selection and surgical strategies guided by the comprehensive evaluation of the extension of the infection and its microbiological characteristics, clinical profile of the patient, and risk of infection recurrence are currently available. Conventional mechanical or stented xenografts are the preferred choice for localized aortic infection. However, in cases of complex IE with the involvement of the root or the aortomitral continuity, the use of homograft is suggested according to the surgeon and center experience. Homograft use should be counterbalanced against the risk of structural degeneration. Prosthetic bioroot or prosthetic valved conduit (mechanical and bioprosthetic) are also potentially suitable alternatives. Further development of preservation techniques enabling longer durability of allogenic substitutes is required. We evaluate the current evidence for the use of valve substitutes in aortic valve endocarditis and propose an evidence-based algorithm to guide the choice of therapy. We performed a systemic review to clarify the contemporary surgical management of aortic valve endocarditis.

Revisiting the guidelines and choice the ideal substitute for aortic valve endocarditis

Aortic valve replacement is the most commonly performed cardiac surgical operation worldwide for infective endocarditis (IE). Long-term durability and avoidance of infection relapse are the treatment goals. However, no detailed guidelines on prosthesis selection and surgical strategy are available. Management should be guided by a comprehensive evaluation of infection extension and its microbiological characteristics, the clinical profile of the patient and the risk of infection recurrence. We conducted a literature search of the PubMed database, EMBASE and Cochrane Library (through November 2019) for studies reporting to the use of biological substitutes in aortic valve endocarditis (AVE). Studies comparing long-term outcomes in the use of allogenic and autologous with conventional prostheses were investigated. Conventional mechanical or stented xenografts are the preferred choice for localized aortic infection. In cases of complex IE with the involvement of the root or the aorto-mitral continuity, the use of homografts are recommended, according to surgeon's and center experience. Homograft use needs to be balanced against the risk of structural degeneration. Prosthetic bioroot or prosthetic valved conduit with a mechanical or bioprosthetic valve are acceptable alternatives. The choice of aortic valves substitute and surgical strategy in IE is multifaceted. Principles guiding the selection of prosthesis and surgical approach rely on the long-term durability and the avoidance of infection relapse. A decisional algorithm considering the extension of the infection and its microbiological characteristics, the clinical profile of the patient and the risk of infection recurrence is provided. A multidisciplinary effort is required to achieve consistent outcomes.

The use of allogenic and autologous tissue to treat aortic valve endocarditis

The surgical treatment of aortic valve endocarditis (AVE) is generally performed using conventional mechanical or biological xenograft prosthesis, with limited use of aortic homograft (Ao-Homo) or pulmonary autograft (PA). Clinical evidence has demonstrated a clear contradiction between the proven benefits of Ao-Homo and PA in the context of infection and the very limited use of allogenic or autologous tissue in everyday clinical practice. This review aims to summarize the most recent and relevant literature in order to foster the scientific debate on the use of the use of allogenic and autologous tissue to treat AVE. The decisional process of the Heart Team should also include the preferences of the patient, his/her family, the general cardiologist or primary care physician. The use of allogenic or autologous valve substitute is beneficial if there is a high risk of recurrence of infection, avoiding extensive adhesiolysis and debridement of synthetic material. In any case, those procedures should be performed by highly trained centers to optimize outcomes.

Assessment of cytocompatibility and mechanical properties of detergent-decellularized ovine pericardial tissue

Background:

Autologous pericardium is widely used for the repair of different sized cardiovascular defects. However, its use is limited especially in redo cardiac surgery. We developed an engineered tissue based on decellularized pericardium reseeded with blood-derived endothelial cells.

Materials and Methods:

Decellularization of ovine pericardium was performed using detergent treatment. Ovine outgrowth blood-derived and green fluorescent protein–labeled endothelial cells were used to reseed the decellularized ovine pericardium on the mesothelial side. The cell adhesion was assessed using fluorescent microscopy up to 15 days of in vitro cultivation. The mechanical properties of the pericardium were evaluated using suturability, burst pressure, and suture retention strength tests.

Results:

After decellularization the pericardial sheets appeared cell-free and repopulation using ovine blood-derived endothelial cells was successful by forming a robust monolayer. Detergent treatment did not affect the extracellular matrix. The thickness of decellularized tissue was similar to native ovine pericardium (285.3 ± 28.2 µm, respective 276.9 ± 23.8 µm, p = 0.48). Decellularized patch showed similar suturability comparable to the native ovine pericardium. Resulted burst pressure was not significantly different (native/decellularized: 312.5 ± 13.6/304.2 ± 16, p = 0.35). The suture retention strength of native pericardium was 638.33 ± 90.2 gr and comparable to decellularized tissue (622.2 ± 89.9 gr, p = 0.76). No differences were observed concerning elongation of native and decellularized pericardium (8.33 ± 1.5 and 8.5 ± 0.84 mm, respectively; p = 0.82).

Conclusion:

Mesothelial surface of decellularized ovine pericardium is suitable for reseeding with ovine blood-derived endothelial cells. The mechanical properties of detergent-treated pericardium were comparable to native tissue.

Evaluation of allograft contamination and decontamination at the Treviso Tissue Bank Foundation: A retrospective study of 11,129 tissues

Microbiological contamination of retrieved tissues has become a very important topic and a critical aspect in the safety of allografts. We have analysed contamination in 11,129 tissues with a longitudinal contamination profile for each individual tissue. More specifically, 10,035 musculoskeletal tissues and 1,094 cardiovascular tissues were retrieved from a total of 763 multi-tissue donors, of whom 105 were heart-beating donors as well as organ donors, while the remaining 658 were non-heart beating donors and tissue donors only. All tissues were decontaminated twice, the first time immediately after retrieval and the second time after processing. Each tissue was submitted to microbiological culture three times, i.e., upon retrieval (Time 1), after the first decontamination (Time 2) and after the second decontamination (Time 3). The contamination rate for musculoskeletal tissues was 52%, 16.2% and 0.5% at Time 1, 2 and 3, respectively. The contamination rate for cardiovascular tissues was 84%, 42% and 6%. More than one strain was simultaneously present in 10.8% of musculoskeletal tissues and 44.6% of cardiovascular tissues. Out of 8,560 non-heart-beating donor musculoskeletal tissues, 4,689 (54.8%), 1,383 (16.2%) and 42 (0.5%) were contaminated at Time 1, Time 2 and Time 3, respectively. Out of 1,475 heart-beating donor musculoskeletal tissues, 522 (35.4%) 113 (7.7%) and 2 (0.1%) tissues were found to be contaminated at Time 1, 2 and 3, respectively. Out of 984 non-heart beating donor cardiovascular tissues, 869 (88.3%), 449 (45.6%) and 69 (7%) proved positive at Time 1, 2 and 3 respectively, while 50 (45.5%) and 10 (9.1%) heart-beating donor cardiovascular tissues were contaminated at Time 1 and 2. No tissue was contaminated at Time 3. Based on our methods, the two-step decontamination approach is mandatory in order to drastically reduce the number of tissues found to be positive at the end of the process.

Evaluation of new antibiotic cocktails against contaminating bacteria found in allograft tissues

Contamination of retrieved tissues is a major problem for allograft safety. Consequently, tissue banks have implemented decontamination protocols to eliminate microorganisms from tissues. Despite the widespread adoption of these protocols, few comprehensive studies validating such methods have been published. In this manuscript we compare the bactericidal activity of different antibiotic cocktails at different temperatures against a panel of bacterial species frequently isolated in allograft tissues collected at the Treviso Tissue Bank Foundation, a reference organization of the Veneto Region in Italy that was instituted to select, recover, process, store and distribute human tissues. We were able to identify at least two different formulations capable of killing most of the bacteria during prolonged incubation at 4 °C.