Blood-brain barrier disruption after cardiac surgery

BACKGROUND AND PURPOSE

CNS complications are often seen after heart surgery, and postsurgical disruption of the BBB may play an etiologic role. The objective of this study was to determine the prevalence of MR imaging-detected BBB disruption (HARM) and DWI lesions after cardiac surgery.

MATERIALS AND METHODS

All patients had an MRI after cardiac surgery. For half the patients (group 1), we administered gadolinium 24 hours after surgery and obtained high-resolution DWI and FLAIR images 24-48 hours later. We administered gadolinium to the other half (group 2) at the time of the postoperative scan, 2-4 days after surgery. Two stroke neurologists evaluated the images.

RESULTS

Of the 19 patients we studied, none had clinical evidence of a stroke or delirium at the time of the gadolinium administration or the scan, but 9 patients (47%) had HARM (67% in group 1; 30% in group 2; P = .18) and 14 patients (74%) had DWI lesions (70% in group 1; 78% in group 2; P = 1.0). Not all patients with DWI lesions had HARM, and not all patients with HARM had DWI lesions (P = .56).

CONCLUSIONS

Almost half the patients undergoing cardiac surgery have evidence of HARM, and three-quarters have acute lesions on DWI after surgery. BBB disruption is more prevalent in the first 24 hours after surgery. These findings suggest that MR imaging can be used as an imaging biomarker to assess therapies that may protect the BBB in patients undergoing heart surgery.

Ex-vivo expanded baboon CD4+ CD25 Hi Treg cells suppress baboon anti-pig T and B cell immune response

BACKGROUND

CD4(+) CD25(+) FoxP3(+) regulatory T (Treg) cells play an important role in regulating immune responses. A very small number of Treg cells are present in peripheral blood and lymphoid organs, but due to their ability to suppress the immune response, they have a high potential for immunotherapy in clinics. Successful ex-vivo expansion of naturally occurring CD4(+) CD25(+) T cells has been achieved after TCR stimulation in the presence of T cell growth factors. In this study, we evaluated the role of these Treg cells in suppressing proliferative response of baboon T and B cells to pig xenoantigens.

METHODS

Naturally occurring baboon CD4(+) CD25(+) regulatory T cells (nTreg) were sorted from peripheral blood and expanded in the presence of either anti-CD3/CD28 beads or irradiated pig peripheral blood mononuclear cells with IL-2. Treg cells were also enriched directly from CD4(+) T cells cultured in the presence of rapamycin (0.1-10 nm). Mixed lymphocyte culture and polyclonal B cell stimulation with ex-vivo Treg cells were performed to assess the function of ex-vivo expanded Treg cells.

RESULTS

The nTreg cells were expanded to more than 200-fold in 4 weeks and retained all the nTreg cell phenotypic characteristics, including high levels of FoxP3 expression. 2-fold increase in enrichment of CD4(+) CD25(+) FoxP3(+) Treg cells from CD4(+) cells was observed with rapamycin compared to cultures without rapamycin. The ex-vivo expanded Treg cells obtained from both methods were able to suppress the baboon anti-porcine xenogeneic T and B cell immune response in-vitro efficiently (more than 90% suppression at 1:1 ratio of T regulatory cells: T effector cells), and their suppression potential was retained even at 1:256 ratio. However, freshly isolated nTreg cells had only 70% suppression at 1:1 ratio, and their suppressive ability was reduced to ≤ 50% at 1:16 ratio. Furthermore, we have found that ex-vivo expanded Treg can also suppress the proliferation of B cells after polyclonal stimulation. Forty to 50 percent reduction in B cell proliferation was observed when ex-vivo expanded Treg cells were added to the culture at a 1:1 ratio. The addition of CD4(+) CD25(Neg) cells however induced vigorous proliferation.

CONCLUSION

Ex-vivo expanded CD4(+) CD25(+) FoxP3(+) Treg cells can be used to efficiently suppress xenogeneic immune responses by inhibiting T and B cell proliferation. These ex-vivo expanded Treg cells may also be used with other immunosuppressive agents to overcome xenograft rejection in preclinical xenotransplantation models.

B-cell depletion extends the survival of GTKO.hCD46Tg pig heart xenografts in baboons for up to 8 months

Xenotransplantation of genetically modified pig organs offers great potential to address the shortage of human organs for allotransplantation. Rejection in Gal knockout (GTKO) pigs due to elicited non-Gal antibody response required further genetic modifications of donor pigs and better control of the B-cell response to xenoantigens. We report significant prolongation of heterotopic alpha Galactosyl transferase "knock-out" and human CD46 transgenic (GTKO.hCD46Tg) pig cardiac xenografts survival in specific pathogen free baboons. Peritransplant B-cell depletion using 4 weekly doses of anti-CD20 antibody in the context of an established ATG, anti-CD154 and MMF-based immunosuppressive regimen prolonged GTKO.hCD46Tg graft survival for up to 236 days (n = 9, median survival 71 days and mean survival 94 days). B-cell depletion persisted for over 2 months, and elicited anti-non-Gal antibody production remained suppressed for the duration of graft follow-up. This result identifies a critical role for B cells in the mechanisms of elicited anti-non-Gal antibody and delayed xenograft rejection. Model-related morbidity due to variety of causes was seen in these experiments, suggesting that further therapeutic interventions, including candidate genetic modifications of donor pigs, may be necessary to reduce late morbidity in this model to a clinically manageable level.

Optimal surgical management of severe ischemic mitral regurgitation: to repair or to replace?

BACKGROUND

Ischemic mitral regurgitation, a complication of myocardial infarction and coronary artery disease more generally, is associated with a high mortality rate and is estimated to affect 2.8 million Americans. With 1-year mortality rates as high as 40%, recent practice guidelines of professional societies recommend repair or replacement, but there remains a lack of conclusive evidence supporting either intervention. The choice between therapeutic options is characterized by the trade-off between reduced operative morbidity and mortality with repair versus a better long-term correction of mitral insufficiency with replacement. The long-term benefits of repair versus replacement remain unknown, which has led to significant variation in surgical practice.

METHODS AND RESULTS

This article describes the design of a prospective randomized clinical trial to evaluate the safety and effectiveness of mitral valve repair and replacement in patients with severe ischemic mitral regurgitation. This trial is being conducted as part of the Cardiothoracic Surgical Trials Network. This article addresses challenges in selecting a feasible primary end point, characterizing the target population (including the degree of mitral regurgitation) and analytical challenges in this high mortality disease.

CONCLUSIONS

The article concludes by discussing the importance of information on functional status, survival, neurocognition, quality of life, and cardiac physiology in therapeutic decision making.

Off-pump surgery for giant right coronary artery aneurysms

Coronary artery aneurysms larger than 5 cm are exceedingly rare, and a standard treatment for them is lacking. We report two cases of giant right coronary artery aneurysms successfully treated by off-pump resection of the aneurysm and bypass grafting. The controversy surrounding the proper management of such cases is discussed.

Case study and review: treatment of tricuspid prosthetic valve thrombosis

Prosthetic valve thrombosis (PVT) is a severe and life-threatening complication of heart valve replacement. Conventional therapy is surgical thrombectomy or valve replacement. Medical thrombolysis is another emerging option. We report the case of a 57 year old woman with a history of Ebstein anomaly who underwent successful treatment of tricuspid prosthetic valve thrombosis with intra-atrial infusion of very low dose recombinant tissue plasminogen activator (tPA). We review the presentation, etiology, diagnosis, and treatment of tricuspid PVT emphasizing a modified medical option as a safe, minimally invasive alternative to surgical intervention or conventional medical therapy for tricuspid valve thrombosis.

Does laser type impact myocardial function following transmyocardial laser revascularization?

BACKGROUND

Transmyocardial laser revascularization (TMR) is currently clinically performed with either a CO(2) or Ho:YAG laser for the treatment of severe angina. While both lasers provide symptomatic relief, there are significant differences in the laser-tissue interactions specific to each device that may impact their ability to enhance the perfusion of myocardium and thereby improve contractile function of the ischemic heart.

METHODS

A porcine model of chronic myocardial ischemia was employed. After collecting baseline functional data with cine magnetic resonance imaging (MRI) and dobutamine stress echo (DSE), 14 animals underwent TMR with either a CO(2) or Ho:YAG laser. Transmural channels were created with each laser in a distribution of 1/cm(2) in the ischemic zone. Six weeks post-treatment repeat MRI as well as DSE were obtained after which the animals were sacrificed. Histology was preformed to characterize the laser-tissue interaction.

RESULTS

CO(2) TMR led to improvement in wall thickening in the ischemic area as seen with cine MRI (40.3% vs. baseline, P < 0.05) and DSE (20.2% increase vs. baseline, P < 0.05). Ho:YAG treated animals had no improvement in wall thickening by MRI (-11.6% vs. baseline, P = .67) and DSE (-16.7% vs. baseline, P = 0.08). Correlative semi-quantitative histology revealed a significantly higher fibrosis index in Ho:YAG treated myocardium versus CO(2) (1.81 vs. 0.083, P < 0.05).

CONCLUSIONS

In a side-by-side comparison CO(2) TMR resulted in improved function of ischemic myocardium as assessed by MRI and echocardiography. Ho:YAG TMR led to no improvement in regional function likely due to concomitant increase in fibrosis in the lasered area.

Marrow stromal cells differentiate into vasculature after allogeneic transplantation into ischemic myocardium

BACKGROUND

Marrow stromal cells (MSCs) are reportedly able to improve ventricular function after myocardial infarction through the paracrine effect or regenerating myocytes. However, the evidence to prove that is scant. In this animal study, we employed MSCs isolated from transgenic pigs designed to express enhanced green fluorescent proteins as the donor to study the fate of the cells after allogeneic transplantation.

METHODS

Green MSCs prepared from transgenic pigs were allogeneically transplanted into chronic ischemic myocardium of 8 Yorkshire pigs by direct intramyocardial injection (total 1.2 × 10(8) cells in 2.5 mL saline, with 25 injection sites). Cohorts of 2 animals were sacrificed at 1, 2, 4, and 6 weeks, and 3 months after injection to study the fate of the injected cells.

RESULTS

Allogeneic injection of the green MSCs is safe; no observable side effects or signs of graft versus host disease were observed. By 4',6-diamidino-2-phenylindole (DAPI) counterstained frozen sections, the green cells were found migrating from the injected area into deeper layers of myocardium over the course of 1 to 6 weeks. By immunofluorescent staining, the green cells were associated with smooth muscle actin or von Willebrand factor positive cells, suggesting that the transplanted cells were contributing to the formation of new vessels. We found no evidence that these cells were associated with the new generation of cardiac myocytes. Three months after injection, clusters of MSCs still can be found in the middle layer of ischemic myocardium; however, no unlimited cell growth was found.

CONCLUSIONS

Allogeneic transplantation of green MSCs can be safely used to elucidate the mechanisms of cell-based therapy. The benefits of this therapy appear mainly due to the angiogenesis, not the regeneration, of cardiac myocytes.

Surgical and nonsurgical complications of a pig to baboon heterotopic heart transplantation model

A modified immunosuppressive regimen, developed at the National Institutes of Health, has been employed in a large animal model of heterotopic cardiac xenotransplantation. Graft survival has been prolonged, but despite this, our recipients have succumbed to various surgical or nonsurgical complications. Herein, we have described different complications and management strategies. The most common complication was hypercoagulability (HC) after transplantation, causing thrombosis of both small and large vasculature, ultimately leading to graft loss. While managing this complication we discovered that there was a delicate balance between HC and consumptive coagulopathy (CC). CC encountered in some recipient baboons was not able to be reversed by stopping anticoagulation and administering multiple blood transfusions. Some complications had iatrogenic components. To monitor the animals, a solid state left ventricular telemetry probe was placed directly into the transplanted heart via the apex. Induction of hypocoagulable states by continuous heparin infusion led to uncontrollable intra-abdominal bleeding in 1 baboon from this apical site. This occurrence necessitated securing the probe more tightly with multiple purse strings and 4-quadrant pledgeted stay sutures. One instance of cardiac rupture originated from a lateral wall infarction site. Earlier studies have shown infections to be uniformly fatal in this transplant model. However, owing to the telemetry placement, infections were identified early by temperature spikes that were treated promptly with antibiotics. We had several cases of wound dehiscence due to recipients disrupting the suture line. These complications were promptly resolved by either re-approximating the wound or finding distractions for the baboon. A few of the most common problems we faced in our earlier experiments were related to the jacket, tether, and infusion pumps. It was difficult to keep the jackets on some baboons and the tether had to be modified several times before we assured long-term success. Infusion catheter replacement resulted in transplant heart venous obstruction and thrombosis from a right common femoral venous line. Homeostatic perturbations such as HC and CC and baboon-induced wound complications comprised most complications. Major bleeding and death due to telemetry implantation and infarct rupture occurred in 2 baboons. Despite the variety of complications, we achieved significant graft prolongation in this model.

Pneumatic actuated robotic assistant system for aortic valve replacement under MRI guidance

We present a pneumatic actuated robotic assistant system for transapical aortic valve replacement under MRI guidance in a beating heart. This is a minimally invasive procedure that is currently performed manually inside the MRI bore. A robotic assistance system that integrates an interactive real-time MRI system, a robotic arm with a newly developed robotic valve delivery module, as well as user interfaces for the physician to plan the procedure and manipulate the robot, would be advantageous for the procedure. An Innomotion arm with hands-on cooperative interface was used as a device holder. A compact MRI compatible robotic delivery module was developed for delivering both balloon-expandable and self-expanding prostheses. A compact fiducial that can be placed close to the volume of interest and requires a single image plane was used for image-based robot registration. The system provides different user interfaces at various stages of the procedure. We present the development and evaluation of the components and the system in ex-vivo experiments.

Transapical aortic valve replacement under real-time magnetic resonance imaging guidance: experimental results with balloon-expandable and self-expanding stents

OBJECTIVE

Aortic valves have been implanted on self-expanding (SE) and balloon-expandable (BE) stents minimally invasively. We have demonstrated the advantages of transapical aortic valve implantation (tAVI) under real-time magnetic resonance imaging (rtMRI) guidance. Whether there are different advantages to SE or BE stents is unknown. We report rtMRI-guided tAVI in a porcine model using both SE and BE stents, and compare the differences between the stents.

METHODS

A total of 22 Yucatan pigs (45-57 kg) underwent tAVI. Commercially available stentless bioprostheses (21-25 mm) were mounted on either BE platinum-iridium stents or SE-nitinol stents. rtMRI guidance was employed as the intraoperative imaging. Markers on both types of stents were used to enhance visualization in rtMRI. Pigs were allowed to survive and had follow-up MRI scans and echocardiography at 1, 3, and 6 months postoperatively.

RESULTS

rtMRI provided excellent visualization of the aortic valve implantation mounted on both stent types. The implantation times were shorter with the SE stents (60 ± 14s) than with the BE stents (74 ± 18s), (p=0.027). The total procedure time was 31 and 37 min, respectively (p=0.12). It was considerably easier to manipulate the SE stent during deployment, without hemodynamic compromise. This was not always the case with the BE stent, and its placement occasionally resulted in coronary obstruction and death. Long-term results demonstrated stability of the implants with preservation of myocardial perfusion and function over time for both stents.

CONCLUSIONS

SE stents were easier to position and deploy, thus leading to fewer complications during tAVI. Future optimization of SE stent design should improve clinical results.

Computer aided minimally invasive cardiac procedures

Minimally invasive cardiac procedures have been investigated to reduce the risks associated with open heart surgery. With the assistance of improvements in engineering technologies such as medical imaging, surgical navigation, and robotic devices, more cardiac surgeries can be performed in a minimally invasive fashion. We have surveyed these state-of-the-art engineering technologies and the minimally invasive cardiac procedures that are benefited from these technologies.

Midterm results of transapical aortic valve replacement via real-time magnetic resonance imaging guidance

OBJECTIVE

Percutaneous valve replacements are presently being evaluated in clinical trials. As delivery of the valve is catheter based, the safety and efficacy of these procedures may be influenced by the imaging used. To assist the surgeon and improve the success of the operation, we have performed transapical aortic valve replacements using real-time magnetic resonance imaging guidance.

METHODS

Twenty-eight swine underwent aortic valve replacement by real-time magnetic resonance imaging on the beating heart. Stentless bioprostheses mounted on balloon-expandable stents were used. Magnetic resonance imaging (1.5 T) was used to identify the critical anatomic landmarks. In addition to anatomic confirmation of adequate placement of the prosthesis, functional assessment of the valve and left ventricle and perfusion were also obtained with magnetic resonance imaging. A series of short-term feasibility experiments were conducted (n = 18) in which the animals were humanely killed after valve placement and assessment by magnetic resonance imaging. Ten additional animals were allowed to survive and had follow-up magnetic resonance imaging scans and confirmatory echocardiography at 1, 3, and 6 months postoperatively.

RESULTS

Real-time magnetic resonance imaging provided superior visualization of the landmarks needed. The time to implantation after apical access was 74 +/- 18 seconds. Perfusion scanning demonstrated adequate coronary flow and functional imaging documented preservation of ventricular contractility in all animals after successful deployment. Phase contrast imaging revealed minimal intravalvular or paravalvular leaks. Longer term results demonstrated stability of the implants with preservation of myocardial perfusion and function over time.

CONCLUSIONS

Real-time magnetic resonance imaging provides excellent visualization for intraoperative guidance of aortic valve replacement on the beating heart. Additionally, it allows assessment of tissue perfusion and organ function that is not obtainable by conventional imaging alone.

Rapid and dynamic alterations of gene expression profiles of adult porcine bone marrow-derived stem cell in response to hypoxia

This study sought to identify the gene expression patterns of porcine bone marrow-derived MSC in response to hypoxia and to investigate novel specific hypoxic targets that may have a role in determining MSC proliferation/survival and differentiation. MSC from 15 animals were incubated in 1% oxygen and 8% carbon dioxide for 6, 12, and 24 h. RNA samples were isolated and assayed with Affymetrix porcine arrays and quantitative reverse-transcription PCR. Significant gene expression levels among the four groups of normoxia, 6-, 12-, and 24-h hypoxia were identified. The pattern in the 12-h hypoxia group was similar to that of the 24-h group. Of 23,924 probes, 377 and 210 genes were regulated in the 6- and 24-h hypoxia groups, respectively. Functional classification of the hypoxic regulated genes was mainly clustered in cell proliferation and response to stress. However, the major upregulated genes in the 6-h group were activated in cell cycle phases; the genes in the 24-h hypoxia were evenly separated into cell differentiation, apoptosis, and cellular metabolic processes. Twenty-eight genes were upregulated in all hypoxia groups; these genes are considered as hypoxic targets. Our results identified a genome-wide hypoxia-induced gene expression pattern in porcine MSC. This study provides a global view of molecular events in the cells during exposure to hypoxia and revealed a set of novel candidate hypoxic targets.

Direct injection of autologous mesenchymal stromal cells improves myocardial function

Cell-based therapies have been employed with conflicting results. Whether direct injection of ex-vivo expanded autologous marrow stromal cells (MSCs) would improve the function of ischemic myocardium and enhance angiogenesis is not well defined. In a porcine model of chronic ischemia, MSCs were isolated and cultured for 4 weeks. Sixteen animals were random divided into two groups to receive either direct intramyocardial injection of autologous MSCs, or equal volumes and injections sites of saline. Cine MRI and epicardial echocardiography were performed just prior to the injections and again 6 weeks later at the time of sacrifice at which point tissue was also analyzed. Myocardial function as assessed by regional wall thickening (as measured by dobutamine stress echocardiograms) demonstrated a 40.9% improvement after cell treatment of the ischemic zone (p=0.016) whereas the saline treated animals only had a 3.7% change (p=0.82) compared to baseline. The left ventricular ejection fractions of MSC group showed 19.5% improvement from baseline 35.9+/-3.8% to 42.9+/-5.8% (p=0.049). Increased vascularity was found in the MSC group compared to controls (0.80+/-0.30 vs 0.50+/-0.19 capillary/myocyte ratio, p=0.018). Direct injection of autologous MSCs promotes angiogenesis and enhances the functional improvements following chronic myocardial ischemia. This suggests that the angiogenesis engendered by cell treatment may be physiologically meaningful by improving the contractility of ischemic myocardium.

MRI-compatible Hands-on Cooperative Control of a Pneumatically Actuated Robot

MRI compatible robots are emerging as useful tools for image guided interventions. A shared control between a user and the MRI compatible robot makes it more intuitive instrument especially during setup phases of interventions. We present a MRI compatible, hands-on cooperative system using Innomotion robotic arm. An economic MRI compatible user input sensor was developed and its functionality was tested under typical application conditions. Performance improvement in phantom tasks shows promise of adding hands-on interface in MRI compatible robots.

Rapamycin promotes the enrichment of CD4(+)CD25(hi)FoxP3(+) T regulatory cells from naïve CD4(+) T cells of baboon that suppress antiporcine xenogenic response in vitro

The CD4(+)CD25(+)FoxP3(+) regulatory T (Treg) cells play an important role in regulating the immune response. These Treg cells are present in peripheral blood and lymphoid organs and have a high potential for immunotherapy in clinics. Adoptive cell transfer therapy using CD4(+)CD25(+) cells has been shown to prevent autoimmune diseases and has also induced transplant tolerance in mice. Treg cells low frequency in peripheral blood will necessitate its ex vivo expansion to enable adaptive immunotherapy. Recently, it has been reported that rapamycin, an immunosuppressive agent, inhibits T-cell proliferation while selectively increasing the number of Treg cells. Based on this additional mode of action, rapamycin can be used to expand Treg cells for ex vivo cellular therapy in T-cell-mediated diseases and in transplantation. We have reported the ex vivo expansion of baboon Treg cells, using irradiated pig peripheral blood mononuclear cell (PBMC) and interleukin (IL)-2, and have demonstrated the suppression of autologus CD4(+)CD25(neg) T-cell proliferation in response to pig PBMCs. In the present study, we have expanded baboon CD4(+) T cells in the presence or absence of rapamycin (0.1-10 nmol/L) using irradiated pig PBMCs and IL-2 to enrich the regulatory T cells. CD4(+)CD25(+)FoxP3(+) Treg cells were increased up to 2 times in the presence of rapamycin versus without rapamycin in vitro. However, a higher dose of rapamycin (> or = 10 nmol/L) considerably decreases the number of Treg cells. Furthermore, purified CD4(+)CD25(+) Treg cells enriched from CD4(+) cells in the presence of rapamycin were able to suppress the baboon anti-porcine xenogeneic immune responses in vitro up to 93% at a 1:1 ratio (Treg cells:T effector cells) and suppression ability exists even at a 1:256 ratio, whereas freshly isolated natural Treg cells suppress only 70% at 1:1 and lose their suppressive ability (>50%) at 1:16. Our results demonstrate that the addition of rapamycin to the culture enriches the Treg phenotype and induces functional regulatory T cells. This method may allow the production of large numbers of regulatory cells for the preclinical testing of Treg cell therapy in a non-human primate model.

Postoperative troponin I values: insult or injury?

BACKGROUND

Troponin I (TnI) is increasingly employed as a highly specific marker of acute myocardial ischemia. The value of this marker after cardiac surgery is unclear.

HYPOTHESIS

The purpose of this study was to measure serum TnI levels prospectively at 1, 6, and 72 h after elective cardiac operations. In addition, TnI levels were measured from the shed mediastinal blood at 1 and 6 h postoperatively. Serum values were correlated with cross clamp time, type of operation, incidence of perioperative myocardial infarction, as assessed by postoperative electrocardiograms (ECG) and regional wall motion, as documented by intraoperative transesophageal echocardiography (TEE).

METHODS

Sixty patients underwent the following types of surgery: coronary artery bypass graft (CABG) (n = 45), valve repair/replacement (n = 10), and combination valve and coronary surgery (n = 5). Myocardial protection consisted of moderate systemic hypothermia (30-32 degrees C), cold blood cardioplegia, and topical cooling for all patients.

RESULTS

Of 60 patients, 57 (95%) had elevated TnI levels, consistent with myocardial injury, 1 h postoperatively. This incidence increased to 98% (59/60) at 6 h postoperatively. There was a positive correlation between the length of cross clamp time and initial postoperative serum TnI (r = 0.70). There was no difference in the serum TnI values whether or not surgery was for ischemic heart disease (CABG or CABG + valve versus valve). There were no postoperative myocardial infarctions as assessed by serial ECGs. There was no evidence of diminished regional wall motion by TEE. Levels of TnI in the mediastinal shed blood were greater than assay in 58% (35/60) of the patients at 1 h and in 88% (53/60) at 6 h postoperatively. Patients who received an autotransfusion of mediastinal shed blood (n = 22) had on average a 10-fold postoperative increase in serum TnI levels between 1 and 6 h. Patients who did not receive autotransfusion average less than doubled their TnI levels over the same interval. At 72 h, TnI levels were below the initial postoperative levels but still indicative of myocardial injury.

CONCLUSION

Postoperative TnI levels are elevated after all types of cardiac surgery. There is a strong correlation between intraoperative ischemic time and postoperative TnI level. Further elevation of TnI is significantly enhanced by reinfusion of mediastinal shed blood. Despite these postoperative increases in TnI, there was no evidence of myocardial infarction by ECG or TEE. The postoperative TnI value is even less meaningful after autotransfusion of shed mediastinal blood.

Role of negative pressure wound therapy in treating peripheral vascular graft infections

Wound complications involving large subcutaneous vessels can cause significant challenges for surgeons. Negative pressure wound therapy (NPWT) has been increasingly used for treating complex wounds in vascular surgery, including groin infections, either as a bridge to surgical closure or as a primary wound treatment modality. Although a growing body of evidence exists for managing various problematic wounds, such as diabetic foot ulcers and open abdominal wounds, the role of NPWT in wounds involving large blood vessels or wounds complicating infected vascular grafts has not been well defined. A multidisciplinary advisory panel reviewed the literature relevant to wounds related to vascular surgical procedures and complications, focusing on large subcutaneous or infected vascular conduits. The results supported by the literature and the clinical practice of the consensus panel suggested that NPWT can be a useful adjunct to the management of vascular groin infections and dehiscences but must be used with caution.

Real-time magnetic resonance imaging guidance for cardiovascular procedures

Magnetic resonance imaging (MRI) of the cardiovascular system has proven to be an invaluable diagnostic tool. Given the ability to allow for real-time imaging, MRI guidance of intraoperative procedures can provide superb visualization, which can facilitate a variety of interventions and minimize the trauma of the operations as well. In addition to the anatomic detail, MRI can provide intraoperative assessment of organ and device function. Instruments and devices can be marked to enhance visualization and tracking, all of which is an advance over standard X-ray or ultrasonic imaging.

Transmyocardial laser revascularization

It has been almost a decade since transmyocardial laser revascularization (TMR) was approved for clinical use in the United States. The safety of TMR was demonstrated initially with nonrandomized studies in which TMR was used as the only treatment for patients with severe angina. TMR efficacy was proven after multiple randomized controlled trials. These revealed significant angina relief compared to maximum medical therapy in patients with diffuse coronary disease not amenable to conventional revascularization. In light of these results, TMR has been used as an adjunct to coronary artery bypass grafting (CABG). By definition, patients treated with this combined therapy have more severe coronary disease and comorbidities that are associated with end-stage atherosclerosis. Combination CABG + TMR has resulted in symptomatic improvement without additional risk. The likely mechanism whereby TMR has provided benefit is the angiogenesis engendered by the laser-tissue interaction. Improved perfusion and concomitant improvement in myocardial function have been observed post-TMR. Additional therapies to enhance the angiogenic response include combining TMR with stem cell-based treatments, which appear to be promising future endeavors.