Recent advancements in the minimally invasive management of esophageal perforation, leaks, and fistulae

INTRODUCTION

Historically, the gold standard management of esophageal perforations, leaks, and fistulae has been traditional open surgery, but it is associated with significant morbidity and mortality. Minimally invasive approaches offer alternatives to surgery in treating hemodynamically stable patients with such defects. In this review article, we will discuss the recent advancements in the minimally invasive management of esophageal perforations, leaks, and fistulas.

AREAS COVERED

This review includes information from case reports, case series, and clinical trials on minimally invasive management of esophageal perforations, leaks, and fistulas. The focus is on the devices, outcomes, and application of the technology.

EXPERT COMMENTARY

Minimally invasive treatment represents significant progress in the management of esophageal perforations, leaks, and fistulas. Based on current evidence, it seems safe and effective but it is evolving and more studies are needed to help draw definitive conclusions.

Cytomegalovirus immunoglobulin G titers do not predict reactivation risk in immunocompetent hosts

Cytomegalovirus (CMV) reactivation occurs in roughly one-third of immunocompetent patients during critical illness, and is associated with worse outcomes. These outcomes have prompted consideration of early antiviral prophylaxis, but two-third of patients would receive unnecessary treatment. Tissue viral load has been associated with risk of reactivation in murine models, and recent work has suggested a relationship between immune responses to CMV and underlying viral load. We, therefore, sought to confirm the hypothesis that serum CMV-specific immunoglobulin G (IgG) correlates with tissue viral load, and might be used to predict the risk of reactivation during critical illness. We confirm that there is a good correlation between tissue viral load and serum CMV-specific IgG after laboratory infection of inbred mice. Further, we show that naturally infected outbred hosts have variable tissue viral DNA loads that do not correlate well with serum IgG. Perhaps as a consequence, CMV-specific IgG was not predictive of reactivation events in immunocompetent humans. When reactivation did occur, those with the lowest IgG levels had longer durations of reactivation, but IgG quartiles were not associated with differing peak DNAemia. Together our data suggest that CMV-specific IgG titers diverge from tissue viral loads in outbred immunocompetent hosts, and their importance for the control of reactivation events remains unclear.

Devices for ex vivo heart and lung perfusion

INTRODUCTION

The number of organs available for heart and lung transplantation is far short of the number that is needed to meet demand. Perfusion and ventilation of donor organs after procurement has led to exciting advances in the field of cardiothoracic transplantation. The clinical implications of this technology allows for techniques to evaluate the quality of an organ, active rehabilitation of organs after procurement and prior to implantation, and increased time between organ procurement and implantation. This ex-vivo perfusion technique has also been referred to in the lay press as the 'heart in a box' or 'lung in a box.'

AREAS COVERED

This review includes information from case reports, case series, and clinical trials on ex vivo heart and lung perfusion. The focus is on the devices, ventilation and perfusion techniques, outcomes, and application of the technology.

EXPERT COMMENTARY

Ex vivo perfusion of donor hearts and lungs prior to transplantation has proven to be a viable alternative to standard cold-preservation strategies. Its use has allowed for ongoing expansion of the donor pool. The biggest barriers to expansion of this technology are access, cost, and lack of evidence which clearly supports superior outcomes.

Transcatheter Tricuspid Valve Implantation of NaviGate Bioprosthesis in a Preclinical Model

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Surgery for isolated tricuspid regurgitation carries a high mortality risk, especially in the setting of right ventricular dysfunction and reoperation.

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Transcatheter valve therapy is as promising alternative for treatment of isolated tricuspid valve disease associated with right heart failure.

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The NaviGate bioprosthesis is a novel self-expanding valved stent designed to treat functional tricuspid regurgitation.

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The preclinical evaluation shows that transcatheter tricuspid valve implantation using the NaviGate device is safe, is feasible through 2 different approaches, and results in a secure and stable engagement of the native annulus, with excellent hemodynamic and valve performance.

Patients with isolated functional or recurrent tricuspid regurgitation are often denied surgery because they are considered to be at high risk. Transcatheter valve therapy provides a less invasive alternative for tricuspid regurgitation associated with right heart failure. We have evaluated the feasibility of transcatheter tricuspid valve implantation of the NaviGate valved stent in a long-term swine model. The valved stent was successfully implanted through transjugular and transatrial approaches on the beating heart with excellent hemodynamic and valve performance. No conduction disturbance or coronary obstruction was observed. This technology could provide an alternative treatment for patients who are at high surgical risk with severe tricuspid regurgitation and compromised right ventricular function.

Transcatheter mitral valve replacement with the NaviGate stent in a preclinical model

AIMS

The aim of this study was to test the feasibility of transcatheter mitral valve implantation of the NaviGate device in acute and chronic preclinical models.

METHODS AND RESULTS

We evaluated NaviGate valved stent implantation in the mitral position in an acute swine model (n=24, ≤5 days) through three different approaches - transatrial, transapical, and transseptal - and in a chronic swine model (n=12, >10 days) through a transatrial approach. The NaviGate implantation procedures were successful in 83% of the acute model studies (n=20) and 83% of the chronic model studies (n=10). Echocardiographic assessment showed low gradient across the valved stent (mean gradient <3 mmHg) and the left ventricular outflow tract (mean gradient <6 mmHg). Post implantation, there was no mitral regurgitation (MR) in 75% (n=15) of the acute studies and mild MR in 25% (n=5). In the chronic model, there was no MR in 60% (n=6) and mild MR in 40% (n=4). The implantation procedure was aborted in four acute studies due to inferior vena cava injury and in two chronic studies due to prosthesis-annulus mismatch.

CONCLUSIONS

In preparation for clinical application, transcatheter mitral implantation of the NaviGate valved stent was proved feasible in acute and chronic preclinical models. The three featured delivery approaches are of particular value for high-risk patients with functional MR and challenging vascular access.

Repair of left ventricular pseudoaneurysm with the triple patch technique (Empanada Patch)

Left ventricular pseudoaneurysm is a rare but serious complication of myocardial infarction that requires urgent intervention to avoid unpredictable fatal rupture. Surgical repair aims at excluding the aneurysmal area with a patch to preserve the left ventricular geometry. Here, we present a case of successful repair of inferobasal left ventricular pseudoaneurysm using a modified triple patch technique ('Empanada Patch').

A modified collagen gel dressing promotes angiogenesis in a preclinical swine model of chronic ischemic wounds

We recently performed proteomic characterization of a modified collagen gel (MCG) dressing and reported promising effects of the gel in healing full-thickness excisional wounds. In this work, we test the translational relevance of our aforesaid findings by testing the dressing in a swine model of chronic ischemic wounds recently reported by our laboratory. Full-thickness excisional wounds were established in the center of bipedicle ischemic skin flaps on the backs of animals. Ischemia was verified by laser Doppler imaging, and MCG was applied to the test group of wounds. Seven days post wounding, macrophage recruitment to the wound was significantly higher in MCG-treated ischemic wounds. In vitro, MCG up-regulated expression of Mrc-1 (a reparative M2 macrophage marker) and induced the expression of anti-inflammatory cytokine interleukin (IL)-10 and of fibroblast growth factor-basic (β-FGF). An increased expression of CCR2, an M2 macrophage marker, was noted in the macrophages from MCG treated wounds. Furthermore, analyses of wound tissues 7 days post wounding showed up-regulation of transforming growth factor-β, vascular endothelial growth factor, von Willebrand's factor, and collagen type I expression in MCG-treated ischemic wounds. At 21 days post wounding, MCG-treated ischemic wounds displayed higher abundance of proliferating endothelial cells that formed mature vascular structures and increased blood flow to the wound. Fibroblast count was markedly higher in MCG-treated ischemic wound-edge tissue. In addition, MCG-treated wound-edge tissues displayed higher abundance of mature collagen with increased collagen type I : III deposition. Taken together, MCG helped mount a more robust inflammatory response that resolved in a timely manner, followed by an enhanced proliferative phase, angiogenic outcome, and postwound tissue remodeling. Findings of the current study warrant clinical testing of MCG in a setting of ischemic chronic wounds.

Mediastinal mass presented 36 years after coronary bypass grafting: is vein graft pseudoaneurysm a differential diagnosis?

Saphenous vein graft aneurysm is a relatively rare but serious complication of coronary artery bypass grafting (CABG). The diagnosis of such cases is clinically challenging and requires a high index of suspicion, especially if presented atypically or very late after CABG. Herein, we report a case of a saphenous vein graft pseudoaneurysm that presented 36 years after CABG and was masquerading as a right atrial myxoma on serial echocardiograms over a 2-year follow-up period.

Reversal of paralysis and visceral ischemia after thoracic aortic ligation for infection via extra anatomic ascending aorta to infarenal aorta bypass graft

Surgical management of acute aortic infection is challenging, including excision of the infected segment and reconstruction either through extra-anatomical bypass or in situ graft replacement with higher risk of re-infection. Here in, we present a case of delayed paralysis developed after an extra-anatomic (axillary-bifemoral) bypass of infected thoracic aorta in a 51 year old Caucasian male. Reversal of paralysis was successfully achieved via larger extra-anatomical ascending aorta to infra-renal aorta bypass and cerebrospinal fluid (CSF) drainage.

Mixed-species biofilm compromises wound healing by disrupting epidermal barrier function

In chronic wounds, biofilm infects host tissue for extended periods of time. This work establishes the first chronic preclinical model of wound biofilm infection aimed at addressing the long-term host response. Although biofilm-infected wounds did not show marked differences in wound closure, the repaired skin demonstrated compromised barrier function. This observation is clinically significant, because it leads to the notion that even if a biofilm infected wound is closed, as observed visually, it may be complicated by the presence of failed skin, which is likely to be infected and/or further complicated postclosure. Study of the underlying mechanisms recognized for the first time biofilm-inducible miR-146a and miR-106b in the host skin wound-edge tissue. These miRs silenced ZO-1 and ZO-2 to compromise tight junction function, resulting in leaky skin as measured by transepidermal water loss (TEWL). Intervention strategies aimed at inhibiting biofilm-inducible miRNAs may be productive in restoring the barrier function of host skin.

A modified collagen gel enhances healing outcome in a preclinical swine model of excisional wounds

Collagen-based dressings are of great interest in wound care. However, evidence supporting their mechanism of action is scanty. This work provides first results from a preclinical swine model of excisional wounds, elucidating the mechanism of action of a modified collagen gel (MCG) dressing. Following wounding, wound-edge tissue was collected at specific time intervals (3, 7, 14, and 21 days postwounding). On day 7, histological analysis showed significant increase in the length of rete ridges, suggesting improved biomechanical properties of the healing wound tissue. Rapid and transient mounting of inflammation is necessary for efficient healing. MCG significantly accelerated neutrophil and macrophage recruitment to the wound site on day 3 and day 7 with successful resolution of inflammation on day 21. MCG induced monocyte chemotactic protein-1 expression in neutrophil-like human promyelocytic leukemia-60 cells in vitro. In vivo, MCG-treated wound tissue displayed elevated vascular endothelial growth factor expression. Consistently, MCG-treated wounds displayed significantly higher abundance of endothelial cells with increased blood flow to the wound area indicating improved vascularization. This observation was explained by the finding that MCG enhanced proliferation of wound-site endothelial cells. In MCG-treated wound tissue, Masson's trichrome and picrosirius red staining showed higher abundance of collagen and increased collagen type I:III ratio. This work presents first evidence from a preclinical setting explaining how a collagen-based dressing may improve wound closure by targeting multiple key mechanisms. The current findings warrant additional studies to determine whether the responses to the MCG are different from other collagen-based products used in clinical setting.

Role of induced hypothermia in thoracoabdominal aortic aneurysm surgery

For more than 50 years, hypothermia has been used in aortic surgery as a tool for neuroprotection. Hypothermia has been introduced into thoracoabdominal aortic aneurysm (TAAA) surgery by many cardiovascular centers to protect the body's organs, including the spinal cord. Numerous publications have shown that hypothermia can prevent immediate and delayed motor dysfunction after aortic cross-clamping. Here, we reviewed the historical application of hypothermia in aortic surgery, role of hypothermia in preclinical studies, cellular and molecular mechanisms by which hypothermia confers neuroprotection, and the role of systemic and regional hypothermia in clinical protocols to reduce and/or eliminate the devastating consequences of ischemic spinal cord injury after TAAA repair.

Developing digital tissue phantoms for hyperspectral imaging of ischemic wounds

Hyperspectral imaging has the potential to achieve high spatial resolution and high functional sensitivity for non-invasive assessment of tissue oxygenation. However, clinical acceptance of hyperspectral imaging in ischemic wound assessment is hampered by its poor reproducibility, low accuracy, and misinterpreted biology. These limitations are partially caused by the lack of a traceable calibration standard. We proposed a digital tissue phantom (DTP) platform for quantitative calibration and performance evaluation of spectral wound imaging devices. The technical feasibility of such a DTP platform was demonstrated by both in vitro and in vivo experiments. The in vitro DTPs were developed based on a liquid blood phantom model. The in vivo DTPs were developed based on a porcine ischemic skin flap model. The DTPs were projected by a Hyperspectral Image Projector (HIP) with high fidelity. A wide-gap 2nd derivative oxygenation algorithm was developed to reconstruct tissue functional parameters from hyperspectral measurements. In this study, we have demonstrated not only the technical feasibility of using DTPs for quantitative calibration, evaluation, and optimization of spectral imaging devices but also its potential for ischemic wound assessment in clinical practice.

Platelet-rich fibrin matrix improves wound angiogenesis via inducing endothelial cell proliferation

The economic, social, and public health burden of chronic ulcers and other compromised wounds is enormous and rapidly increasing with the aging population. The growth factors derived from platelets play an important role in tissue remodeling including neovascularization. Platelet-rich plasma (PRP) has been utilized and studied for the last four decades. Platelet gel and fibrin sealant, derived from PRP mixed with thrombin and calcium chloride, have been exogenously applied to tissues to promote wound healing, bone growth, hemostasis, and tissue sealing. In this study, we first characterized recovery and viability of as well as growth factor release from platelets in a novel preparation of platelet gel and fibrin matrix, namely platelet-rich fibrin matrix (PRFM). Next, the effect of PRFM application in a delayed model of ischemic wound angiogenesis was investigated. The study, for the first time, shows the kinetics of the viability of platelet-embedded fibrin matrix. A slow and steady release of growth factors from PRFM was observed. The vascular endothelial growth factor released from PRFM was primarily responsible for endothelial mitogenic response via extracellular signal-regulated protein kinase activation pathway. Finally, this preparation of PRFM effectively induced endothelial cell proliferation and improved wound angiogenesis in chronic wounds, providing evidence of probable mechanisms of action of PRFM in healing of chronic ulcers.