Microvascular responses to (hyper-)gravitational stress by short-arm human centrifuge: arteriolar vasoconstriction and venous pooling.

PURPOSE: We hypothesized that lower body microvessels are particularly challenged during exposure to gravity and hypergravity leading to failure of resistance vessels to withstand excessive transmural pressure during hypergravitation and gravitation-dependent microvascular blood pooling. METHODS: Using a short-arm human centrifuge (SAHC), 12 subjects were exposed to +1Gz, +2Gz and +1Gz, all at foot level, for 4 min each. Laser Doppler imaging and near-infrared spectroscopy were used to measure skin perfusion and tissue haemoglobin concentrations, respectively. RESULTS: Pretibial skin perfusion decreased by 19% during +1Gz and remained at this level during +2Gz. In the dilated area, skin perfusion increased by 24 and 35% during +1Gz and +2Gz, respectively. In the upper arm, oxygenated haemoglobin (Hb) decreased, while deoxy Hb increased with little change in total Hb. In the calf muscle, O2Hb and deoxy Hb increased, resulting in total Hb increase by 7.5 ± 1.4 and 26.6 ± 2.6 µmol/L at +1Gz and +2Gz, respectively. The dynamics of Hb increase suggests a fast and a slow component. CONCLUSION: Despite transmural pressures well beyond the upper myogenic control limit, intact lower body resistance vessels withstand these pressures up to +2Gz, suggesting that myogenic control may contribute only little to increased vascular resistance. The fast component of increasing total Hb indicates microvascular blood pooling contributing to soft tissue capacitance. Future research will have to address possible alterations of these acute adaptations to gravity after deconditioning by exposure to micro-g.

Blood transfusion during versus after cardiopulmonary bypass is associated with postoperative morbidity in neonates undergoing cardiac surgery.

INTRODUCTION: Cardiac surgery on neonates for the correction of congenital heart defects is usually associated with the transfusion of packed red blood cells (PRBCs) into the cardiopulmonary bypass (CPB) circuit. We hypothesised that such transfusions of stored PRBCs directly into the arterial system may increase postoperative morbidity when compared to intravenous transfusion. PATIENTS AND METHODS: In this retrospective cohort study, data from 122 consecutive neonates who received transfusions of PRBCs in the course of corrective surgery for congenital heart defects were analysed. Group assignment was according to the timing of the first transfusion: during CPB (On-CPB) or after weaning from CPB (Post-CPB). Chi Square and rank sum tests were applied to compare clinical characteristics. Times until extubation and release from the intensive care unit were analysed by Kaplan-Meier curves and by multivariate Cox regression. RESULTS: Transfusion of PRBCs during CPB was associated with greater 48 hour blood loss (mean±standard deviation, 86±125 versus 32±16 mL/kg, p<0.001), longer duration of mechanical ventilation (214±268 versus 99±75 h, p<0.001) and longer stay on the intensive care unit (10.9±12.1 versus 5.3±3.5 days, p<0.001). However, the groups also differed in many characteristics, such as bodyweight, complexity of surgery or preoperative haemoglobin concentration, which may also affect outcome. Yet, multivariate analyses confirmed an independent association of transfusion On-CPB with an adverse clinical outcome. CONCLUSIONS: Our results are consistent with the hypothesis that the transfusion of PRBCs during CPB may increase postoperative morbidity. However, due to the limitations of this retrospective analysis, further studies are needed to confirm a causal relationship between the timing of the transfusion and the clinical outcome and to elucidate putative mechanisms of such an association.

The 2nd Berlin BedRest Study: protocol and implementation.

Long-term bed-rest is used to simulate the effect of spaceflight on the human body and test different kinds of countermeasures. The 2nd Berlin BedRest Study (BBR2-2) tested the efficacy of whole-body vibration in addition to high-load resisitance exercise in preventing bone loss during bed-rest. Here we present the protocol of the study and discuss its implementation. Twenty-four male subjects underwent 60-days of six-degree head down tilt bed-rest and were randomised to an inactive control group (CTR), a high-load resistive exercise group (RE) or a high-load resistive exercise with whole-body vibration group (RVE). Subsequent to events in the course of the study (e.g. subject withdrawal), 9 subjects participated in the CTR-group, 7 in the RVE-group and 8 (7 beyond bed-rest day-30) in the RE-group. Fluid intake, urine output and axiallary temperature increased during bed-rest (p < .0001), though similarly in all groups (p > or = .17). Body weight changes differed between groups (p < .0001) with decreases in the CTR-group, marginal decreases in the RE-group and the RVE-group displaying significant decreases in body-weight beyond bed-rest day-51 only. In light of events and experiences of the current study, recommendations on various aspects of bed-rest methodology are also discussed.

Evaluation of sympathetic blockade after intrathecal and epidural lidocaine in rats by laser Doppler perfusion imaging.

The widespread use of neuraxial anaesthesia increases the need for animal models to evaluate therapeutic prospects, mechanisms and risks of this technique. As a methodological prerequisite, we characterised the sympathetic blockade after different modes of neuraxial anaesthesia with regard to segments supplying the splanchnic region. Under haemodynamic monitoring, lidocaine 2% or saline were infused via intrathecal (10 microl), lumbar epidural (10 and 30 microl) or thoracic epidural (10 and 30 microl) catheters. Segmental spread of neuraxially infused local anaesthetic was assessed using methylene blue. Mean arterial blood pressure decreased more severely after neuraxial lidocaine in thoracic epidural (10 and 30 microl) compared to high-volume (30 microl anaesthesia animals. Determination of the sympathetic blockade by means of laser Doppler perfusion imaging was restricted to the paws due to a higher density of subcutaneous blood vessels as compared to the abdominal wall (mean +/- SD: 3.93 +/- 0.06 vs. 1.35 +/- 0.05/384 mm(2), p < 0.05). Only high-volume (30 microl) lumbar and thoracic epidural anaesthesia (10 and 30 microl) increased skin perfusion in both hind and front paws. This extensive sympathetic blockade was demonstrated to include splanchnic segments using thermography. Segmental spread of methylene blue did not closely correspond to laser Doppler findings and should be interpreted as minimum rather than exact epidural spread of local anaesthetic.

Estimation of the left ventricular relaxation time constant tau requires consideration of the pressure asymptote.

The left ventricular isovolumic pressure decay, obtained by cardiac catheterization, is widely characterized by the time constant tau of the exponential regression p(t)=Pomega+(P0-Pomega)exp(-t/tau). However, several authors prefer to prefix Pomega=0 instead of coestimating the pressure asymptote empirically; others present tau values estimated by both methods that often lead to discordant results and interpretation of lusitropic changes. The present study aims to clarify the relations between the tau estimates from both methods and to decide for the more reliable estimate. The effect of presetting a zero asymptote on the tau estimate was investigated mathematically and empirically, based on left ventricular pressure decay data from isolated ejecting rat and guinea pig hearts at different preload and during spontaneous decrease of cardiac function. Estimating tau with preset Pomega=0 always yields smaller values than the regression with empirically estimated asymptote if the latter is negative and vice versa. The sequences of tau estimates from both methods can therefore proceed in reverse direction if tau and Pomega change in opposite directions between the measurements. This is exemplified by data obtained during an increasing preload in spontaneously depressed isolated hearts. The estimation of the time constant of isovolumic pressure fall with a preset zero asymptote is heavily biased and cannot be used for comparing the lusitropic state of the heart in hemodynamic conditions with considerably altered pressure asymptotes.

In situ analysis of coronary terminal arteriole diameter responses: technical report of a new experimental model.

INTRODUCTION: To date, investigation of coronary arteriole vasomotor activity has been limited to arterioles >30- 40 microm. Here, we introduce a new experimental model to allow for in situ microscopy of terminal coronary arterioles. METHODS: Rat hearts were perfused in a closed loop system (priming volume 20 ml) which was placed on a computer-controlled microscope stage. FITC-dextran and tetrodotoxin (TTX, 50 microM) were added. Tilting of the microscope by 90 degrees allowed for visual access to the ventricular surface. Arterioles were identified by the flow direction of fluorescent beads (1 microm). Images were recorded on video tape, and arteriole diameters were measured offline. Stability of the preparation and maintenance of coronary flow reserve were analyzed. Responses of coronary flow and arteriole diameters to the vasodilators papaverine and Na-nitroprusside were recorded. RESULTS: In TTX-arrested control hearts coronary flow and terminal arteriole diameters were stable for 2 h. Administration of papaverine and Na-nitroprusside increased coronary flow from 6.4 +/- 0.7 to 13.3 +/- 1.3 ml/min, decreasing coronary resistance by 52 +/- 3%. Terminal coronary arteriole diameters increased from 12.0 +/- 0.9 to 13.6 +/- 1.0 microm, decreasing hindrance of this vessel segment by 45 +/- 11%. CONCLUSION: Preservation of coronary terminal arteriolar tone and adequate responsiveness to vasodilators in the TTX-arrested isolated heart were demonstrated. Thus, this model may serve to complement our understanding of coronary microvascular control mechanisms by extending observations to the terminal arteriolar bed.

OPS imaging of human microcirculation: a short technical report.

Despite the pivotal role of microcirculation in numerous diseases, techniques for the direct assessment of human microcirculation are limited. A new approach based on orthogonal polarization spectral (OPS) imaging (Cytoscan microscope) allows noninvasive observation of human microcirculation in all accessible tissue surfaces. Limitations remain: application of pressure with the instrument affects blood flow, lateral movement of tissue precludes continuous investigation of a given microvascular region, and blood flow velocities above 1 mm/s cannot be measured. We addressed these problems by (a) constructing an attachment to the probe, preventing direct contact of the instrument with the observed tissue area and allowing fixation of the tissue, and (b) implementing a double-flash spatial correlation technique extending the measuring range for blood flow velocities up to approximately 40 mm/s. The modified approach was tested in vitro and in vivo. Velocity readings correlated well with velocities of an external standard (r(2) = 0.99, range 1.9-33.8 mm/s). Pulsatile flow patterns synchronous with heart rate with maximal velocities of about 10 mm/s could be detected in arterioles of the human sublingual mucosa. The modified instrument may prove useful to investigate the microcirculation in the context of research, diagnosis and therapy control.

Initial reperfusion with magnesium after cardioplegic arrest attenuates myocardial reperfusion injury.

BACKGROUND: Magnesium's effect on calcium ion concentrations may attenuate myocardial reperfusion injury. The aim of this study was therefore to investigate the effects on the recovery of myocardial function of initial reperfusion with varying Mg(2+) concentrations following cardioplegic arrest. METHODS: Isolated guinea pig hearts underwent 3.5 hours of cardioplegic arrest in St. Thomas Hospital II solution (STH) or Bretschneider HTK solution (HTK) at 24 degrees C. Control hearts were reperfused with normal Krebs-Henseleit solution (KHS). In the therapy groups, hearts were initially reperfused with 5, 10, or 20 mM Mg(2+) for 15 minutes, followed by 30 minutes of perfusion with KHS. RESULTS: During initial reperfusion, elevated Mg(2+) concentrations markedly reduced rate-pressure product, dP/dt and O 2 demand. Release of LDH and CK was reduced in the therapy groups pretreated with Bretschneider HTK. After Mg(2+) washout, left ventricular function recovery and compliance was improved after HTK but not after STH cardioplegia. Following both STH and HTK cardioplegia, Mg(2+) reperfusion reduced reperfusion arrhythmias. CONCLUSIONS: The combination of HTK cardioplegia with 15 min initial Mg(2+) (5 and 10 mM, but not 20 mM) reperfusion was clearly superior to HTK followed by immediate Krebs-Henseleit reperfusion as well as STH cardioplegia with or without initial Mg(2+) reperfusion. The high Mg(2+) concentrations in the STH solution might mask beneficial effects of Mg(2+) reperfusion.

Cariporide (HOE 642) attenuates leukocyte activation in ischemia and reperfusion.

UNLABELLED: Cariporide (HOE 642) ameliorates myocardial ischemia/reperfusion (I/R) injury, by the well established reduction of cytosolic [Ca(2+)] in cardiac myocytes through inhibition of Na(+)/H(+) exchange. However, postischemic inflammation also contributes to I/R injury. We tested the hypothesis that cariporide also modulates the inflammatory response. The effect of cariporide on L-selectin expression by human leukocytes in vitro and leukocyte adhesion and emigration in the reperfused rat cremaster muscle in vivo were studied. The rat cremaster muscle was exteriorized for intravital videomicroscopy, induction of ischemia (90 min), and reperfusion (90 min). Eleven rats were pretreated with cariporide (9 mg/kg body weight IV) whereas 11 rats received saline. Leukocyte adhesion was quantified offline. Human venous blood was incubated with cariporide (3 micromol/L) or saline, stimulated with formyl- methionine-leucine-phenylalanine (10(-10)-10(-6) mol/L), and granulocyte L-selectin expression was analyzed by flow cytometry. Cariporide reduced leukocyte rolling and adhesion by approximately 35% and 45%, respectively, after 30 min of reperfusion. Leukocyte extravasation was decreased by approximately 85% after 90 min. Cariporide increased L-selectin shedding at each formyl-methionine-leucine-phenylalanine concentration, reducing the 50% effective dose from 9.95 to 4.68 nmol/L. Thus, cariporide may ameliorate I/R injury not only by the known reduction of cytosolic [Ca(2+)] in cardiomyocytes, but also by attenuating leukocyte-dependent inflammatory responses. Promotion of L-selectin shedding from activated leukocytes may present a mechanism underlying this newly detected effect. IMPLICATIONS: This study provides evidence that inhibition of Na(+)/H(+) exchange by cariporide (HOE 642) attenuates the postischemic inflammatory response. Leukocyte adhesion and emigration, assessed by in vivo microscopy, were markedly reduced in rat cremaster muscle, possibly because of increased L-selectin shedding of activated leukocytes as demonstrated by flow cytometry.

c7E3Fab reduces postischemic leukocyte-thrombocyte interaction mediated by fibrinogen. Implications for myocardial reperfusion injury.

Reperfusion injury after coronary occlusion is in part mediated by leukocyte activation and adhesion. Platelets may interact with polymorphonuclear granulocytes (PMNs), causing aggravated reperfusion injury. We studied whether c7E3Fab, a chimeric Fab fragment blocking platelet glycoprotein (GP) IIb/IIIa, decreases PMN-platelet-dependent myocardial dysfunction after ischemia. Isolated guinea pig hearts (n=5 per group) perfused at a constant flow of 5 mL/min were subjected to ischemia (15 minutes, 37 degrees C) and reperfusion. Human PMNs (10x10(6) cells, 3 mL), platelets (400x10(6), 3 mL), and fibrinogen (1 mg/mL) were infused for 3 minutes after 2 minutes of reperfusion, with or without c7E3Fab. Flow cytometry detected GPIIb/IIIa (platelets) and MAC-1 (aMbeta2, PMNs) as well as coaggregates of both in the effluent, whereas double-fluorescence microscopy visualized intracoronary PMN-platelet coaggregates. Postischemic recovery of pressure-volume work (12-cm H(2)O preload and 60-mm Hg afterload) was defined as the ratio of postischemic to preischemic external heart work (mean+/-SEM). c7E3Fab reduced platelet GPIIb/IIIa detection to 10% of controls, blocked a transcoronary MAC-1 increase (+25% without versus -23% with c7E3Fab), and inhibited PMN-platelet coaggregation in the effluent (49+/-12% without versus 17+/-2% with c7E3Fab) as well as in the hearts themselves (5.0+/-0.7/cm(2) without versus 1.2+/-0.3/cm(2) surface area with c7E3Fab). Postischemic recovery of external heart work (83+/-5% in cell-free hearts) declined to 46+/-4% after postischemic PMN-platelet infusion, but not in the presence of c7E3Fab (74+/-11%) or LPM19c (71+/-6%). We conclude that c7E3Fab inhibits formation of PMN-platelet aggregates during myocardial reperfusion, an effect that protects against PMN-platelet-dependent stunning.

Involvement of CD95/Apo1/Fas in cell death after myocardial ischemia.

BACKGROUND: The death of cardiac cells during ischemia and reperfusion is partially mediated by apoptosis, as seen, eg, in autopsy material of patients after acute myocardial infarction. METHODS AND RESULTS: To study the role of CD95/Fas/Apo1 for induction of postischemic cell death, we used an ischemia/reperfusion model of isolated rat and mouse hearts in Langendorff perfusion. In this model, caspase-dependent apoptosis occurred during postischemic reperfusion. Moreover, soluble CD95 ligand/Fas ligand was released by the postischemic hearts early after the onset of reperfusion. In addition, this ligand was synthesized de novo under these circumstances. Similar findings were observed for other "death-inducing" ligands, such as tumor necrosis factor (TNF)-alpha and TNF-related apoptosis-inducing ligand. In primary adult rat myocyte culture, hypoxia and reoxygenation caused a marked increase in sensitivity to the apoptotic effects of CD95 ligand. Isolated hearts from mice lacking functional CD95 (lpr) display marked reduction in cell death after ischemia and reperfusion compared with wild-type controls. CONCLUSIONS: These data suggest that CD95/Apo1/Fas is directly involved in cell death after myocardial ischemia. The CD95 system might thus represent a novel target for therapeutic prevention of postischemic cell death in the heart.

Effects of endothelium/leukocytes/platelet interaction on myocardial ischemia--reperfusion injury.

Platelet fibrinogen receptor (GPIIb/IIIa) antagonists clinically improve the effectiveness of thrombolysis or PTCA in treatment of acute myocardial infarction. 7E3Fab, the chimeric Fab fragment of a monoclonal GPIIb/IIIa antibody, reduces the incidence of death, reinfarction or restenosis in patients and may improve blood flow and regional wall motion in reperfused myocardium. Besides inhibition of platelet aggregation, 7E3Fab may block fibrinogen bridging between the polymorphonuclear neutrophil (PMN) adhesion molecule MAC-1 and platelet GP IIb/IIIa, thus attenuating interaction of platelets with PMN. Experimentally, the interaction of platelets with PMN exacerbated postischemic myocardial stunning. In our own studies in isolated guinea pig hearts, human PMN, platelets and fibrinogen where simultaneously infused during the initial reperfusion period after 15 min of global ischemia. FACS analysis of cells in the coronary effluant revealed that 7E3Fab reduced platelet GP IIb/IIIa expression to 10% of baseline. PMN-platelet aggregate formation in the coronary effluate was markedly reduced by 7E3Fab, parallel to a decrease of PMN-platelet aggregates found by in situ double fluorescence microscopy in the postischemic coronary vasculature. The inhibition of PMN-platelet aggregate formation by 7E3Fab treatment coincided with a significant improvement of external heart work, which suffered a 50% reduction after ischemia, reperfusion, and exposure to PMN, platelets and fibrinogen. Obviously, application of 7E3Fab inhibits formation and coronary retention of PMN-platelet aggregates in the postischemic, reperfused myocardium. This effect may contribute to the clinically observed beneficial effects of this adjuvant treatment after myocardial ischemia.

Endothelial activation--a strategic event during postischemic myocardial inflammation.

Reperfusion after limited ischemia increases leukocyte adhesion, which may contribute to postischemic myocardial and endothelial stunning. Leukocyte adhesion is enhanced immediately after the onset of reperfusion, indicating rapid regulatory mechanisms. In addition, de novo synthesis of, e.g., adhesion molecules induced by reperfusion has been described, providing a prolonged postischemic inflammatory reaction. Enhanced transcription of adhesion molecules involves NF kappa B activation which appears as an essential transcription factor for reperfusion-induced subacute endothelial activation. Both, acute and subacute endothelial activation seem to contribute to the final extent of leukocyte-dependent reperfusion injury and successive treatment of both appears to be a promising therapeutic strategy for postischemic myocardial inflammation and its detrimental effects.

Time-dependent efficacy of initial reperfusion with 2,3 butanedione monoxime (BDM) on release of cytosolic enzymes and ultrastructural damage in isolated hearts.

BACKGROUND: Reperfusion injury after cardioplegia may not be sufficiently addressed by conventional cardioplegic techniques in open heart surgery. 2,3-butanedione monoxime (BDM) has the potential to reduce myocardial reperfusion injury by uncoupling myocyte contraction from the intracellular calcium concentration, thus reducing reperfusion contracture. The aim of this study was to investigate the effects of different application periods of BDM during initial reperfusion on myocardial tissue injury after cardioplegia. METHODS: Isolated guinea-pig hearts underwent 50 min of cardioplegic arrest in St. Thomas' Hospital II solution at 37 C. Control hearts (n = 8) were immediately reperfused with normal Krebs-Henseleit solution for 30 min. In the therapy groups BDM-5, BDM-20, and BDM-40 (n = 8, each), hearts were initially reperfused with BDM (20mmol/L) for either 5, 20, or 40 min, respectively, followed by 30 min of reperfusion with normal Krebs-Henseleit solution. Coronary venous effluent was collected to estimate myocardial tissue damage through release of cytosolic enzymes (LDH and CK) and cardiac troponin 1. Ultrastructural alterations were qualitatively assessed by electron microscopy. RESULTS: Initial reperfusion with BDM markedly reduced LDH and CK release, as long as BDM was present. After washout of the protective agent a rebound of enzyme release occurred in BDM-5 hearts which was effectively reduced in BDM-20 and BDM-40 hearts. Troponin I release was similarly increased in all groups at the onset of reperfusion and rapidly decreased thereafter. Myocardial ultrastructural damage was most pronounced in control hearts, intermediate in BDM-5 and BDM-40 hearts, but markedly attenuated in BDM-20 hearts. CONCLUSIONS: Both 20 and 40 min of initial reperfusion effectively protected the hearts from reperfusion damage as indicated by cytosolic enzyme release, while 5 min of treatment were clearly insufficient. Toxic effects of BDM during the longer treatment period of 40 min or induction of edema by the long-term perfusion of non-beating hearts in this group may account for the worse preservation of myocardial ultrastructure in BDM-40 hearts. Thus, contraction uncoupling during initial reperfusion by BDM or similarly acting drugs may prove a viable principle for reduction of myocardial reperfusion injury. However, the ideal duration of treatment for the best therapeutic effect must be carefully evaluated.

Selectins and beta 2-integrins mediate post-ischaemic venular adhesion of polymorphonuclear leukocytes, but not capillary plugging, in isolated hearts.

Leukocytes adhering to venular endothelium and emigrating into the tissue contribute to myocardial reperfusion injury. The aim of the present study was to characterize the contribution of two different families of adhesion molecules, selectins and integrins, to post-ischaemic capillary plugging and venular adhesion of leukocytes in an isolated heart model. Guinea-pig hearts were perfused using the Langendorff technique. After 20 min stabilization global ischaemia was induced for 15 min at 37 degrees C. With the onset of reperfusion 10(7) isolated polymorphonuclear leukocytes (PMN), prelabelled with rhodamine 6G, were infused within 1 min. Perfusion was continued for 2 min to wash out all cells not firmly adhering to the vascular endothelium. Hearts were then arrested, mounted on a microscope stage and perfused with a cardioplegic solution containing 0.01% fluorescein isothiocyanate (FITC)-dextran (MW 150,000). In situ videofluorescence microscopy was used to quantify PMN plugging and adherent PMN. Four groups were studied: control (no treatment or ischaemia, n = 6); ischaemia (no treatment and 15 min ischaemia, n = 5); fucoidin (pretreatment of hearts and PMN with 0.3 mg/ml selectin inhibitor fucoidin and 15 min ischaemia, n = 5) and CD18 (pretreatment of PMN with 0.1 mg monoclonal antibody against CD18 and 15 min ischaemia, n = 5). Capillary plugging by PMN was 25 +/- 5 PMN/mm2 epicardial surface area and increased moderately to 55 +/- 6 PMN/mm2 in reperfused hearts. This increase was not affected by fucoidin or CD18 antibody. In contrast, post-ischaemic adhesion of PMN in small venules increased ninefold from 21 +/- 5 to 196 +/- 23 PMN/mm2 endothelial surface area. The increase in PMN adhesion to venular endothelium was blocked completely by pretreatment with fucoidin (19 +/- 5 PMN/mm-2) or CD18 antibody (7 +/- 2 PMN/mm-2). We conclude that selectin interaction alone is not sufficient to account for post-ischaemic PMN adhesion in the small venules of the coronary vasculature, because blocking the integrin subunit CD18 also inhibited PMN adhesion completely. On the other hand, neither integrins nor selectins seem to be involved in post-ischaemic capillary plugging by PMN in our perfused heart model.

Early experience with robotic technology for coronary artery surgery.

BACKGROUND: To achieve an endoscopic coronary bypass anastomoses we performed a study with endoscopic robotic instrumentation and camera guidance using three-dimensional (3-D) visualization. METHODS: The surgical robotic system ZEUS (Computer Motion Inc, Goleta, CA) consists of three interactive robotic arms and a control unit allowing the surgeon to move the instrument arms in a scaled down mode. The third arm (AESOP, Computer Motion Inc, Goleta, CA) positions the endoscope via voice control. The study had three phases. Phase I: In a phantom model, end-to-side anastomoses between vein grafts and the left anterior descending coronary artery (LAD) of 109 pig hearts were performed. Phase II: In 6 dogs (FBI, 20-25 kg) the left internal mammary artery (LIMA) was harvested endoscopically. During Port-Access (Heartport Inc, Redwood City, CA) cardiopulmonary bypass (CPB), LIMA and LAD were then anastomosed endoscopically with the help of telemetric ZEUS instruments (Computer Motion Inc). Phase III: A total of seven patients were operated on with help of the ZEUS system (Computer Motion Inc). After endoscopic LIMA harvesting and CPB using the Port-Access (Heartport Inc) system, the bypass graft (LIMA to LAD) was anastomosed endoscopically through three thoracic ports in 2 patients. Another 3 patients were operated on off-pump with regional stabilization and 2 patients with sternotomy and routine CPB. RESULTS: The practice with the phantom model and the subsequent animal experiments allowed the surgeons to gain sufficient experience for the clinical setting. In the clinical cases, times for anastomoses ranged from 20 to 42 minutes. Median internal mammary artery flow rate was 74 mL per minute (range 36-110 mL per minute). One patient in the off-pump group was converted to CPB and routine anastomosis. All patients had an uneventful angiographic control and postoperative course. CONCLUSIONS: Using telemetic technology, a completely endoscopic anastomosis of LIMA to LAD is possible on the arrested heart, as well as on the beating heart.

Efficacy of contraction uncoupling by 2,3-butanedione monoxime during initial reperfusion versus cardioplegic arrest for protection of isolated hearts.

The efficacy of 2,3-butanedione monoxime (BDM) as additive to St. Thomas Hospital II solution (STH) as compared to initial BDM reperfusion with regard to myocardial ischaemia/reperfusion injury was investigated in isolated guinea pig hearts. Isolated guinea pig hearts were perfused with Krebs-Henseleit buffer in the Langendorff technique at constant pressure of 55 mmHg. After cardioplegic arrest with STH solution, global ischaemia was induced for 50 min and recovery of myocardial function was monitored during 30 min reperfusion. Control hearts (n = 8) received no further treatment. In BDMCP hearts (n = 8), 20 mM BDM were added to STH only. BDMREP hearts (n = 8) were treated with 20 mM BDM during the initial 20 min of reperfusion. BDMCP/REP hearts (n = 8) received BDM during cardioplegic arrest as well as during initial reperfusion. Left ventricular systolic function as assessed by developed pressure (LVDP) was depressed to 47 +/- 3% of pre-ischaemic baseline in control. Only initial BDM reperfusion (BDMREP) resulted in improved recovery of LVDP to 66 +/- 5%. Similar data were obtained for dP/dtmax and dP/dtmin. Reperfusion contracture was attenuated in both groups receiving initial BDM reperfusion (BDMREP and BDMCP/REP). BDM in STH did not protect hearts from cellular injury as assessed by release of lactate dehydrogenase (LDH) during reperfusion. In contrast, no increase in LDH release occurred during initial BDM reperfusion in BDMREP and BDMCP/REP hearts, followed by a mild rebound after washout of the drug. Addition of BDM to the cardioplegic STH solution did not protect isolated hearts from cellular injury or depression of post-ischaemic function. In contrast, initial BDM reperfusion alone attenuated reperfusion contracture, prevented LDH release, and improved recovery of systolic and diastolic myocardial function. The combination of BDM treatment during cardioplegic arrest with initial BDM reperfusion provides no additional protection from reperfusion injury.

Tumor necrosis factor-alpha contributes to ischemia- and reperfusion-induced endothelial activation in isolated hearts.

-During myocardial reperfusion, polymorphonuclear neutrophil (PMN) adhesion involving the intercellular adhesion molecule-1 (ICAM-1) may lead to aggravation and prolongation of reperfusion injury. We studied the role of early tumor necrosis factor-alpha (TNF-alpha) cleavage and nuclear factor-kappaB (NF-kappaB) activation on ICAM-1 expression and venular adhesion of PMN in isolated hearts after ischemia (15 minutes) and reperfusion (30 to 480 minutes). NF-kappaB activation (electromobility shift assay) was found after 30 minutes of reperfusion and up to 240 minutes. ICAM-1 mRNA, assessed by Northern blot, increased during the same interval. Functional effect of newly synthesized adhesion molecules was found by quantification (in situ fluorescence microscopy) of PMN, given as bolus after ischemia, which became adherent to small coronary venules (10 to 50 microm in diameter). After 480 minutes of reperfusion, ICAM-1-dependent PMN adhesion increased 2.5-fold compared with PMN adhesion obtained during acute reperfusion. To study the influence of NF-kappaB on PMN adhesion, we inhibited NF-kappaB activation by transfection of NF-kappaB decoy oligonucleotides into isolated hearts using HJV-liposomes. Decoy NF-kappaB but not control oligonucleotides blocked ICAM-1 upregulation and inhibited the subacute increase in PMN adhesion. Similar effects were obtained using BB 1101 (10 microg), an inhibitor of TNF-alpha cleavage enzyme. These data suggest that ischemia and reperfusion in isolated hearts cause liberation of TNF-alpha, activation of NF-kappaB, and upregulation of ICAM-1, an adhesion molecule involved in inflammatory response after ischemia and reperfusion.

Efficacy of myocardial initial reperfusion with 2,3 butanedione monoxime after cardioplegic arrest is time-dependent.

OBJECTIVE: In a previous study, initial reperfusion of isolated hearts after cardioplegic arrest with 2,3 butanedione monoxime (BDM) for 5 min was markedly superior to warm hyperkalemic reperfusion in improving the initial oxygen balance and reducing reperfusion arrhythmias. However, left ventricular contractility was only marginally enhanced. The goal of the present study was to test, wether the efficacy of BDM reperfusion can be enhanced by prolonging the application period. METHODS: 32 Langendorff perfused guinea pig hearts were subjected to 50 min of cardioplegic arrest in St. Thomas Hospital II solution at 37 degrees C for 50 min. Control hearts (n = 8) were immediately reperfused with normal Krebs solution for 30 min. In BDM-5, BDM-20, and BDM-40 hearts (n = 8, each), a 5, 20, or 40 min period of initial BDM reperfusion preceded perfusion with normal Krebs. RESULTS: BDM markedly improved the O2 balance during initial reperfusion by reducing O2 demand by over 50% (p < 0.01) in all treatment groups while coronary flow was maintained. Reperfusion contracture, estimated by the end-diastolic balloon pressure was inhibited by more than 50% in BDM-20 and BDM-40 hearts. Recovery of left ventricular developed pressure, dP/dtmax, and -dP/dtmax was significantly enhanced throughout the reperfusion period only in the BDM-20 group (p < 0.05). Myocardial ultrastructure was best preserved in BDM-20 hearts. CONCLUSIONS: 20 min of initial BDM reperfusion were clearly superior to immediate Krebs reperfusion or a shorter (5 min) or longer (40 min) BDM treatment period in attenuating reperfusion damage. Thus, contraction uncoupling during initial reperfusion by BDM or similarly acting drugs may prove a viable technique to reduce myocardial reperfusion damage in patients undergoing open heart surgery.

Optimizing the oxygen balance during initial reperfusion with 2,3-butanedione monoxime attenuates cardiac reperfusion injury.

The effect of 20 mmol/L butanedione monoxime on myocardial ischemia/reperfusion damage was studied in isolated guinea pig hearts. Three groups of hearts (n = 8) were perfused in the Langendorff mode and cardioplegic arrest was induced with St. Thomas Hospital II solution (STS) at 37 degrees C for 50 min. Myocardial oxygen demand, recovery of myocardial function, and creatine kinase release during 30 min of reperfusion were monitored. Preservation of myocardial ultrastructure was determined by electron microscopy. Control (C) hearts underwent cardioplegic arrest and reperfusion without treatment. BDM was added during cardioplegic arrest in BDMSTS hearts, or to the initial (20 min) reperfusate in BDMREP hearts. BDM during initial reperfusion markedly reduced O2 demand and prevented creatine kinase release from cardiac myocytes, resulting in improved recovery of myocardial function and attenuation of myocardial ultrastructural damage after washout of the drug. In contrast, addition of BDM to the cardioplegic solution provided no protection from ischemic or reperfusion injury.