Volkmar Falk

Influence of three-dimensional vision on surgical telemanipulator performance

Background: Different viewing conditions (two- and three-dimensional National Television Standard Committee [2D-NTSC and 3D-NTSC] and two-dimensional high-definition television [2D-HDTV]) on telemanipulator performance were evaluated. Methods: Six taskes were performed by 15 endoscopic surgeons using the daVinci telemanipulation system. Performance time and errors were measured. Encoder data from the system were used for kinematic analysis of motion. A self-evaluation questionnaire regarding performance under various viewing conditions was obtained. Results: Resolution was better with 2D-HDTV. The estimate of relative distance was not influenced by the different visualization systems. Motor skill tasks were performed faster with binocular vision (3D-NTSC) than with monocular vision (2D-NTSC, 2D-HDTV). For both 2D settings, the deceleration phase of motion was prolonged (p < 0.05 vs 3D). Peak velocity was reduced with 2D-HDTV as compared with 3D-NTSC (p = 0.01). The surgeons tended to favor the 3D system despite their use of 2D systems in their own practice. Conclusions: Three-dimensional vision enhances telemanipulator performance as compared with a 2D system at the same or higher level of resolution. Because it allows faster and more precise movement, future surgical systems should focus on 3D visualization.

Endoscopic computer-enhanced beating heart coronary artery bypass grafting

BACKGROUNDnTelemanipulation systems have enabled coronary revascularization on the arrested heart. The purpose of this study was to develop a technique for computer-enhanced endoscopic coronary artery bypass grafting on the beating heart.nnnMETHODSnThe operation was performed using the daVinci telemanipulation system. Through three ports, the left internal thoracic artery was harvested in 10 mongrel dogs (30 to 35 kg) using single right-lung ventilation and CO2 insufflation. Through a fourth port an articulating stabilizer, manipulated from a second surgical console, was inserted to stabilize the heart. The left anterior descending artery was snared using silicone elastomer slings anchored in the stabilizer cleats and the graft to coronary artery anastomosis was performed.nnnRESULTSnIn 7 of 10 dogs, total endoscopic beating heart bypass grafting, cardiac stabilization, arteriotomy, and arterial anastomosis were performed using computer-enhanced technology. Endoscopic stabilization and temporary left anterior descending artery occlusion were well tolerated. All grafts were patent although minor strictures were found in 2. In 3 dogs, the procedure could not be completed (1 ventricular arrhythmia, 1 left atrial laceration, and 1 right ventricular outflow tract compression).nnnCONCLUSIONSnEndoscopic beating heart coronary artery bypass grafting is possible in a canine model using a computer-enhanced instrumentation system and articulating stabilization.

Regulation of matrix metalloproteinases and effect of MMP-inhibition in heart transplant related reperfusion injury.

PURPOSEnMetalloproteinases (MMPs) regulate extracellular matrix turnover and degrade basal lamina. Aim of the study was to examine the regulation of MMPs and the effect of an MMP inhibitor in transplant related ischemia/reperfusion injury.nnnMETHODSnHeterotopic cardiac transplantation was performed after 4 h of ischemia in three groups of six rats: allografts (black hooded inbred strain, PVG donor/August Copenhagen Irish inbred strain recipient); allografts treated with a competitive MMP-inhibitor (Batimastat) 15 mg/kg every 24 h; isografts (PVG donor and recipient). Normal PVG hearts served as a control. Hearts were explanted after 72 h of reperfusion. Expression of MMP-2 and -9 was measured using gelatin zymography. Proteolytic activity was measured using a gelatinase activity assay. Myeloperoxidase activity and tumor necrosis factor-alpha (TNF-alpha) were measured as markers of inflammatory response. Immunostaining for collagen IV and laminin was used to study degradation of basal lamina.nnnRESULTSnThere was a significant increase of MMP-2 expression in allografts (2271+/-571 microg/ml) as compared to normal (683+/-139 microg/ml) and the Batimastat-treated (259+/-140 microg/ml, P<0.05) groups. Although pro-MMP-2 expression was equally high in the untreated iso- and allograft group (75+/-23 versus 62+/-30 microg/ml) MMP-2 expression in the isograft hearts was significantly lower (359+/-267 microg/ml) suggesting activation of the pro-form by an immunologic mechanism. Pro-MMP-9 levels were significantly higher in the untreated iso- and allograft groups as opposed to normal hearts and MMP-inhibited hearts. MMP-9 was completely inhibited by Batimastat treatment. Collagenolytic activity was lower in the treated group as compared to untreated allografts (538+/-140 versus 384+/-97 microg/ml, P<0.05), demonstrating effective inhibition of MMPs by Batimastat. In the treated group a lesser extent of basement membrane component alterations could be demonstrated by laminin and collagen IV staining. There was a significant reduction in myeloperoxidase activity (P=0.027) as well as lower TNF-alpha levels (ns) in the in the Batimastat treated group.nnnCONCLUSIONnIschemia leads to an increase in MMP expression and degradation of basal lamina. This process is enhanced in allografts as compared to isografts suggesting additional activation of MMPs by immunologic mechanisms. MMP-inhibition is effective in preventing the proteolytic activity of MMPs and may alter the host rejection response by preserving extracellular matrix components and basement membranes.

Up-regulation of Bcl-2 through hyperbaric pressure transfection of TGF-β1 ameliorates ischemia-reperfusion injury in rat cardiac allografts

BACKGROUNDnOxidative stress after ischemia-reperfusion of cardiac allografts leads to activation of cardiomyocytes and production of cytokines. Bcl-2, an inhibitor of the apoptotic pathway, also has strong antioxidant properties. Ischemia-reperfusion injury after transplantation leads to decreased bcl-2 and increased tumor necrosis factor (TNF)-alpha levels. Transforming growth factor (TGF)-beta1 is known to attenuate ischemia-reperfusion injury and inhibits apoptosis of myofibroblasts. We hypothesize that TGF-beta1, prevents bcl-2 cleavage and increased TNF-alpha production.nnnMETHODSnRat PVG donor hearts were heterotopically transplanted into ACI recipients. Donor hearts were procured and assigned to groups: (1) intracoronary TGF-beta1 (200 ng/ml) perfusion and pressure at 78 psi for 45 minutes (n = 4); (2) intracoronary TGF-beta1 perfusion and incubation for 45 minutes without pressure (n = 4), (3) saline perfusion and incubation for 45 minutes without pressure (n = 4). Hearts were procured 4 hours after transplantation and analyzed by reverse transcriptase-polymerase chain reaction for bcl-2 mRNA expression, ELISA for TNF-alpha, and for myeloperoxidase activity (MPO).nnnRESULTSnBcl-2 decreased in untreated animals (bcl-2:G3PDH ratio = 0.85 +/- 0.73 vs 1.16 +/- 0.11, not significant [NS]), whereas TNF-alpha increased to 669.99 +/- 127.09 vs 276.84 +/- 73.65 pg/mg total protein in controls (p < 0.003). In TGF-beta(1) pressure-treated hearts, bcl-2 was up-regulated (2.49 +/- 0.6 vs 1.16 +/- 0.11, controls, p < 0.005), whereas TNF-alpha was unchanged (396.1 +/- 100.38 vs 276.84 +/- 73.65 pg/mg, NS). Hearts treated with TGF-beta1 and pressure showed significant up-regulation of bcl-2 compared with hearts treated with TGF-beta1 without pressure (2.49 +/- 0.6 vs 1.17 +/- 0.6, p < 0.02). MPO showed no differences.nnnCONCLUSIONSnBcl-2 is down-regulated and TNF-alpha up-regulated in this model of ischemia-reperfusion injury. Furthermore, TGF-beta1 is linked to this process and ameliorates reperfusion injury by up-regulating bcl-2 and inhibiting TNF-alpha. Therapeutic overexpression of myocardial TGF-beta1 may be clinically useful to control ischemia-reperfusion injury associated with cardiac transplantation.

Comparison of Three High-End Endoscopic Visualization Systems on Telesurgical Performance

Previous studies and surgeon interviews have shown that most surgeons prefer quality standard definition (SD)TV 2D scopes to first generation 3D endoscopes. The use of a telesurgical system has eased many of the design constraints on traditional endoscopes, enabling the design of a high quality SDTV 3D endoscope and an HDTV endoscopic system with outstanding resolution. The purpose of this study was to examine surgeon performance and preference given the choice between these. The study involved two perceptual tasks and four visual-motor tasks using a telesurgical system using the 2D HDTV endoscope and the SDTV endoscope in both 2D and 3D mode. The use of a telesurgical system enabled recording of all the subjects motions for later analysis. Contrary to experience with early 3D scopes and SDTV 2D scopes, this study showed that despite the superior resolution of the HDTV system surgeons performed better with and preferred the SDTV 3D scope.