You Su Sun

Transformation of nonvascular acellular tissue matrices into durable vascular conduits.

BACKGROUND Prosthetic grafts commonly used for vascular reconstruction are limited to synthetics and cross-linked tissue grafts. Within these devices, graft infections are common, compliance mismatch is significant, and handling qualities are poor. Natural biological tissues that are unfixed have been shown to resist infections and be durable and compliant. A natural biological matrix that could be remodeled appropriately after implantation would be a desirable graft for vascular reconstruction. METHODS SynerGraft tissue engineering strategies have been used to minimize antigenicity and produce stable unfixed vascular grafts from nonvascular bovine tissues. These grafts have replaced the abdominal aortas of 8 dogs that have been followed for up to 10 months. RESULTS Early evaluation indicates rapid recellularization by recipient smooth muscle actin positive cells, which become arranged circumferentially, into the media. Arterioles were present in the adventitial areas and endothelial cells were seen to cover lumenal surfaces. After 10 months, grafts were patent and not aneurysmal. CONCLUSIONS These data indicate that SynerGraft processing of animal tissues is capable of producing stable vascular conduits that exhibit long-term functionality in other species.

Effect of chronic native flow competition on internal thoracic artery grafts

Residual competitive flow from the native coronary artery has been proposed as a mechanism that reduces flow in an internal thoracic artery graft (ITA), resulting in narrowing and ultimately failure of the graft. Results from acute experiments have indicated that competitive flow from a fully patent native artery did not abolish ITA graft flow. The present study was designed to examine the consequences of dynamic flow competition between the native vessel and the ITA graft in a chronic model. Fifteen mongrel dogs underwent coronary artery bypass grafting using the pedicled left ITA anastomosed to the normal, fully patent circumflex (CFX) coronary artery. The procedure was performed through a sterile thoracotomy, without systemic cardiopulmonary bypass, using a brief local occlusion to construct the anastomosis. Intraoperatively, ITA flow was measured in situ on the chest wall, before the pedicle was mobilized. Internal thoracic artery graft and distal CFX flow were measured after the anastomosis was completed, with and without brief occlusion of the proximal CFX. Angiography was performed 72 hours, 4 weeks, and 8 weeks later; graft patency and diameter were evaluated. After 8 weeks, open-chest direct flow measurements comparable with the intraoperative assessment were obtained. Two grafts (13%) occluded early, the technical result of poor anastomotic construction. In the 13 remaining animals, all grafts were widely patent at all time points. Internal thoracic artery flow in situ averaged 10.9 +/- 7.8 mL/min (mean +/- standard deviation), and was maintained after grafting (11.5 +/- 4.4 mL/min; p = not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Competitive flow from a fully patent coronary artery does not limit acute mammary graft flow

The shriveled, stenotic mammary graft sometimes observed after internal mammary artery (IMA) to coronary artery bypass grafting has been attributed to competitive flow from the insufficiently stenosed native coronary vessel. To study further the effects of native coronary artery competing flow on IMA graft flow, 10 dogs (mean weight, 23.5 +/- 3.69 kg) underwent coronary artery bypass grafting using the pedicled left IMA anastomosed to a normal, fully patent proximal circumflex (CFX) coronary artery. The procedure was performed through a left thoracotomy, off pump, using a brief local occlusion to perform the anastomosis. Native in situ IMA flow, CFX flow distal to the anastomosis, and IMA graft flow were measured using calibrated electromagnetic flow probes. When the CFX proximal to the anastomosis was occluded transiently, IMA flow increased to supply 100% of the previously measured distal CFX flow (60.2 +/- 7.9 mL/min). When both the IMA graft and CFX proximal to the anastomosis were patent, total distal perfusion was maintained (58.9 +/- 7.8 mL/min) and relative IMA graft flow (26.5 +/- 3.3 mL/min) was proportional to the relative diameter of the IMA graft to the native coronary artery (r = 0.96). The mean flow in the IMA in situ on the chest wall before its division was 23.8 +/- 8.1 mL/min. These results suggest that, at least acutely in a canine model, IMA graft flow is maintained above in situ levels even when grafted to a completely patent coronary artery and that acute competitive flow probably does not cause mammary artery shriveling.

Hemodynamic effects of the vacuum-assisted closure device on open mediastinal wounds1

BACKGROUND Application of the Vacuum-Assisted Closure device (VAC) to open sternal wounds has negative hemodynamic effects. We hypothesized that the interposition of a muscle flap attenuates these negative hemodynamic effects. MATERIALS AND METHODS After institutional approval, monitoring lines were placed in anesthetized, ventilated pigs. Through a median sternotomy, sonometric crystals were strategically positioned around the left ventricle. A rectus flap was rotated over the mediastinal wound, and the VAC was placed over the flap. After baseline measurements, a vacuum of 125 mmHg [Group (GP) 1, n = 5] or 50 mmHg (GP2, n = 6) was initiated. Hemodynamics were recorded every 15 min for 1.5 h, and 15 min after cessation of the vacuum therapy. GP3 (n = 6) underwent intermittent VAC cycling (on 5 min/off 2 min). Significance determined by t test. RESULTS While non-flapped animals had significant detriment in both left ventricular filling volume and cardiac output, flapped animals had insignificant depression of both parameters. CONCLUSION Application of muscle flaps to sternal wounds prior to VAC therapy significantly attenuates the negative hemodynamic effects seen when the VAC is used alone.

Transfemoral balloon aortic occlusion during open cardiopulmonary resuscitation improves myocardial and cerebral blood flow

These experiments were designed to determine whether the limited cardiac output during open cardiac massage could be preferentially directed to the coronary and cerebral vessels by balloon occlusion of the descending thoracic aorta. Sixteen dogs were instrumented to monitor cardiac output and left atrial, right atrial, right ventricular, left ventricular, and arterial blood pressures. Measurements of myocardial and cerebral blood flow distribution during massage were made using the radioactive microsphere technique. Each animal underwent two episodes of fibrillation and resuscitation. In one episode the arrest was managed by open massage alone, and in the other, open massage was accompanied by balloon occlusion, with the order randomized. When compared to control, open cardiac massage was associated with a significant decrease in mean arterial pressure; however, the addition of balloon occlusion produced a 130% increase in the mean arterial pressure that was obtained during open CPR (control, 93 +/- 5 mm Hg; massage alone, 35 +/- 2 mm Hg; massage + balloon, 76 +/- 2 mm Hg, P less than 0.01). In a similar fashion, although the absolute blood flow was reduced by 50% when compared to control, the blood flow (ml/min/g) to the brain and heart during massage was 100% better when balloon occlusion was employed (brain: control, 0.41 +/- 0.03; massage only, 0.05 +/- 0.01; massage + balloon, 0.25 +/- 0.02, P less than 0.01; heart: control, 1.46 +/- 0.11; massage alone, 0.35 +/- 0.05; massage + balloon, 0.71 +/- 0.05, P less than 0.01). These results suggest that aortic occlusion significantly increased myocardial and cerebral perfusion patterns during ventricular fibrillation and open cardiac massage.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Vacuum Assisted Closure Therapy on early systemic cytokine levels in a swine model.

Vacuum Assisted Closure® (V.A.C.®) Therapy has previously been shown to facilitate healing of wounds. However, the physiological mechanism(s) of this treatment modality and its systemic effects require further investigations. The goal of this porcine study was to investigate the effect of V.A.C.® Therapy on the systemic distribution of the inflammatory cytokines interleukin (IL)‐6, IL‐8, IL‐10, and transforming growth factor‐β1. Twelve pigs were each given one full‐thickness excisional wound, using electrocautery. Six of the pigs were treated with V.A.C.® Therapy and six with saline‐moistened gauze. Serum samples were collected immediately after wound creation, and hourly for 4 hours. Samples were analyzed using commercially available enzyme‐linked immunosorbent assay kits. During the initial 4 hours of treatment, V.A.C.® Therapy resulted in earlier and greater peaking of IL‐10 and maintenance of IL‐6 levels compared with saline‐moistened gauze controls, which showed decreased IL‐6 values over the first hour (both at p<0.05). No other treatment‐based differences were detected.

Differences in myocardial and peripheral VEGF and KDR levels after acute ischemia

BACKGROUND Recent clinical use of vascular endothelial growth factor (VEGF) in the treatment of both myocardial and peripheral ischemia has suggested the possibility of tissue specific coregulation of VEGF and its receptors (eg, kinase domain region [KDR]). The present study was performed to detect the relationship between VEGF and KDR protein levels after acute myocardial and peripheral ischemia. METHODS Eleven dogs were divided into two groups: peripheral ischemia (n = 6, ligation of major limb arteries) and myocardial ischemia (n = 5, circumflex artery ligation). Muscle biopsy specimens were taken from the perfusion territories of the occluded circumflex artery and limb arteries 3 hours and 6 hours after ligation. Protein levels were determined using Western blot analysis. RESULTS In myocardium, VEGF levels increased on average eightfold from baseline (p < 0.05) both 3 hours and 6 hours after occlusion, whereas myocardial KDR levels dropped by about 60% at 3 hours and 80% at 6 hours (p < 0.05). With limb ischemia, both VEGF and KDR levels were significantly elevated at 3 hours. CONCLUSIONS In acute ischemia, regulation of VEGF and KDR may be controlled differently in cardiac and skeletal muscle. Myocardial KDR levels showed a significant decrease from baseline compared with a significant rise with peripheral ischemia.

Thoracoscopic robot-assisted bronchoplasty

BackgroundIn robotic surgery, the ideal position of the system, as well as the optimal working angles and the proper positioning of the thoraco ports position is very important. No robot-assisted bronchoplasty has been reported. Our study describes use of the da VinciTM surgical system (Intuitive Surgical, Inc.) for robotic sleeve upper lobectomy in a human fresh cadaver.MethodsA male cadaver was placed in the left lateral decubitus position. After thoracoscopic upper lobectomy was performed through the working port and the two ports, the robotic system was then set up behind the cadaver. The working port allowed introduction of the optical scope and the robotic surgical arms were inserted into the thoraco ports. The right bronchus was dissected and wedge was cut out with the robotic scissors. After standard lymph node dissection, end-to-end bronchial anastomosis was performed with robotic instruments. Once the anastomosis was complete, air leakage was checked with saline solution placed in the pleural cavity.ResultsThoracoscopic robot-assisted bronchoplasty was performed successfully.ConclusionsIn evaluating various positions of the system we demonstrated that our technique is sufficient approaches to robotic bronchoplasty. This procedure offers specific advantages over conventional bronchoplasty with accuracy and safety.

Experimental supplemental vein grafting and hypoperfusion syndrome

An additional saphenous vein graft (SVG) sometimes is required to the same coronary system if acute internal thoracic artery (ITA) graft flow is inadequate. These experiments were conducted to determine the consequences produced by ITA-SVG dual grafting. Fourteen dogs each received two coronary grafts (without bypass, using local occlusion) to the proximal circumflex coronary artery, using the ITA and an SVG, and then the circumflex artery was ligated proximally. Simultaneous flow in both grafts was determined at rest and after pharmacologic (adenosine, phenylephrine) or physiologic (cardiac pacing) stimulation. Serial angiography was performed during the first 4 weeks after grafting to determine patency patterns of the ITAs and SVGs. In the resting heart, flow was 7.5 +/- 1.6 mL/min (17.5%) in the ITA graft and 35.3 +/- 5.2 mL/min (82.5%) in the SVG (mean +/- standard deviation [% total distal perfusion]), and the combined flow was not significantly different from the original native flow. Intravenous adenosine (0.2 mg.kg-1.min-1) preferentially increased both the total ITA flow and its fractional contribution to total distal perfusion (18.4 +/- 3.2 [31.1%]; p < 0.05 versus rest). Saphenous vein graft flow was not changed significantly (40.3 +/- 6.0 mL/min), in part due to a modest decrease in arterial pressure. In contrast, intravenous phenylephrine (0.003 mg.kg-1.min-1) decreased both absolute ITA flow and its relative contribution to distal perfusion (6.1 +/- 1.1 [10.9%]; p < 0.05 versus rest), despite an increased systemic perfusion pressure, which increased SVG flow significantly (50.1 +/- 4.8 [89.1%]; p < 0.05 versus rest).(ABSTRACT TRUNCATED AT 250 WORDS)

Thoracoscopic robot-assisted extended thymectomy in the human cadaver

MethodsThoracoscopic robot-assisted extended thymectomy was performed in a human cadaver. The technique utilized the da VinciTM surgical system inserted through the subxiphoid approach with the sternum lifted upward (anteriorly). A small subxiphoid incision and two additional thoracoports were made in the chest wall, and the sternum was lifted by a new lifting retractor system.ResultsThis method provided sufficient view and working space in the anterior mediastinum. A complete thymectomy was performed with facility. The robotic system provides superior optics and allows for enhanced dexterity.ConclusionsMinimally invasive robotic-assisted thymectomy is an effective procedure and may add benefits for both surgeon and patients.