Pneumatic antishock garment decreases hemorrhage and mortality from splenic injury

The effect of the pneumatic antishock garment (PASG) in controlling hemorrhage and death from splenic injury was studied in a canine model. Twelve (two groups of 6) anesthetized dogs had their spleens crushed. Carotid blood pressure, carotid blood flow, splenic artery flow and abdominal aortic flow, as well as the death rate and blood loss, were measured. Group 1 dogs did not have PASG inflation, but group 2 dogs had PASG inflation to an intraperitoneal pressure of 60 mm Hg. All group 1 dogs died within 27 to 58 minutes, but all group 2 dogs survived. Blood loss was 9.4 +/- 1.4 mL/min in group 1 and 1.6 +/- 0.9 mL/min in group 2. In group 1 carotid artery blood pressure, carotid artery flow, splenic artery flow and abdominal aortic flow fell from 120 +/- 10 mm Hg, 284 +/- 12 mL/min, 194 +/- 18 mL/min and 285 +/- 10 mL/min respectively to 0 with death of the animals. By 2 hours in group 2 dogs the carotid artery blood pressure had dropped from 116 +/- 12 to 99 +/- 12 mm Hg, and over the same period carotid artery flow, splenic artery flow and abdominal aortic flow fell from 296 +/- 8 mL/min, 190 +/- 26 mL/min and 279 +/- 16 mL/min respectively to 259 +/- 14 mL/min, 39.0 +/- 6 mL/min and 45 +/- 11 mL/min respectively. Thus, inflation of the PASG maintained carotid artery blood pressure wh ile decreasing splenic, abdominal and aortic flow as well as splenic hemorrhage, with a decrease in the death rate, over a 2-hour period.     

Effect of flow competition on internal thoracic artery graft: postoperative velocimetric and angiographic study

OBJECTIVES: To assess the effects of competitive blood flow on internal thoracic artery grafts, we investigated postoperative flow velocity characteristics and angiographic findings of the grafts with various grades of native coronary artery stenosis. METHODS: Fifty patients who had an internal thoracic artery graft to the left anterior descending artery underwent intravascular Doppler graft velocimetry during postoperative angiography. Patients were divided into 3 groups according to the grade of native coronary stenosis: group H (28 patients), 80% stenosis or greater; group M (16 patients), 60% to 79% stenosis; and group L (6 patients), 40% to 59% stenosis. Phasic flow velocity of the grafts was measured with an intravascular Doppler ultrasound-tipped guide wire during angiography. Graft flow volume was calculated from the diameter and the average peak velocity. RESULTS: Average peak velocity (group H, 27.1 +/- 8.6 cm/s; group M, 16.9 +/- 3.9 cm/s; group L, 7.2 +/- 3.7 cm/s), distal graft diameter (group H, 2.27 +/- 0.23 mm; group M, 2. 00 +/- 0.28 mm; group L, 1.07 +/- 0.27 mm), and calculated graft flow volume (group H, 33.1 +/- 12.0 mL/min; group M, 16.2 +/- 5.8 mL/min; group L, 2.3 +/- 2.0 mL/min) significantly differed among the 3 groups. Graft flow in diastole and systole also differed among the 3 groups. CONCLUSIONS: Competitive blood flow reduces internal thoracic artery graft flow and diameter according to the grade of the native coronary artery stenosis. These data suggest that grafting the internal thoracic artery to the coronary artery with stenosis of a low grade can cause graft atrophy and failure.     

Blood flow in composite arterial grafts and effect of native coronary flow

BACKGROUND: Total arterial coronary revascularization can be achieved by joining arteries together as a composite graft with the proximal left internal mammary artery as the only source of blood inflow. Proof of the capacity of this composite conduit to provide adequate blood flow to the coronary circulation is required. METHODS: The radial artery was anastomosed to the left internal mammary artery as a Y graft in 17 patients and all coronary arteries grafted. Intraoperative blood flow through the composite grafts was evaluated by the transit-time Doppler technique. RESULTS: Against no resistance, blood flow in the left internal mammary artery alone was 99 +/- 9 mL/min and rose to 173 +/- 16 mL/min when the radial artery was anastomosed as a Y graft. Composite-graft flow following grafting was 88 +/- 9 mL/min, 49 +/- 6 mL/min when the aortic clamp was removed and native coronary flow restored and 82 +/- 13 mL/min following weaning from cardiopulmonary bypass. The maximal potential flow through the composite graft was 2.3-fold (95% CI 1.6 to 3.2) greater than that after cardiopulmonary bypass. CONCLUSIONS: Total arterial revascularization, using a composite graft, provided a 2.3-fold reserve of blood flow to the coronary vascular bed through the grafts.     

PEG-hirudin/iloprost coating of small diameter ePTFE grafts effectively prevents pseudointima and intimal hyperplasia development.

OBJECTIVES: Small diameter PTFE grafts are prone to thrombosis and intimal hyperplasia development. Heparin graft coating has beneficial effects but also potential drawbacks. The purpose of this study was to evaluate the experimental efficacy of PEG-hirudin/iloprost coated small caliber PTFE grafts. METHODS: Thirty-six femoro-popliteal ePTFE grafts (expanded polytetrafluoroethylene, diameter 4 mm) were inserted into 18 pigs. Grafts were randomised individually for each leg and grouped for 3 groups. Group I consisted of native ePTFE grafts, group II were grafts coated with a polylactide polymer (PLA) without drugs and group III grafts were coated with PLA containing a polyethylene glycol (PEG)-hirudin/iloprost combination. The follow-up period was 6 weeks. Patency rates were calculated and development of pseudointima inside the grafts was noted. Thickness of intimal hyperplasia at the distal anastomoses was measured using light microscopy. RESULTS: Patency rates for group I were 6/9 (67%), for group II 9/10 (90%) and 12/12 (100%) for group III. In groups I and II there was a significant reduction of blood flow proximal to the graft at graft harvest, to 29+/-12 and 28+/-20 ml/min respectively (both p<0.01 versus preoperative value), whilst in group III blood flow, 99+/-21 ml/min, remained at the preoperative level. Subtotal stenosis due to development of pseudointima was noted in each of the native and PLA coated grafts but not in group III grafts. Intimal hyperplasia at the distal anastomosis was lowest in group III. CONCLUSIONS: The PEG-hirudin/iloprost coating of ePTFE prostheses effectively reduced pseudointima and intimal hyperplasia development and led to superior graft patency.     

Intraoperative hemodynamic assessment of gastroepiploic artery and saphenous vein bypass grafts: a comparative study.

OBJECTIVE: Blood flow characteristics of right gastroepiploic artery and saphenous vein conduits were compared during bypass surgery. METHODS: This study is based on a consecutive series of 97 patients undergoing a bypass graft to the right coronary artery, posterior descending artery, or posterolateral branch using either a pediculated right gastroepiploic artery (n = 52) or a saphenous vein (n = 45) bypass graft. Flows and velocity profiles were measured with an 8-MHz pulsed-wave Doppler ultrasound flowmeter. Thorough flow measurements were made (1) after cessation of cardiopulmonary bypass and (2) before chest closure. RESULTS: At the end of cardiopulmonary bypass, flow in the right gastroepiploic artery (59. 0 +/- 6.7 mL/min) did not differ (P =.08) from flow in the saphenous vein (46.1 +/- 2.7 mL/min). Mean trace velocity was 11.9 +/- 0.7 cm/s in the right gastroepiploic artery and 11.6 +/- 0.8 cm/s in the saphenous vein (P =.80), but peak systolic velocity was 29.4 +/- 1.2 cm/s for the right gastroepiploic artery and 23.1 +/- 1.3 cm/s for the saphenous vein (P <.001). Likewise, before chest closure, flow was 57.1 +/- 4.7 mL/min in the right gastroepiploic artery and 46.5 +/- 4.0 mL/min in the saphenous vein (P =.10), mean velocity was 12. 9 +/- 0.7 and 11.6 +/- 0.8 cm/s, respectively (P = .22), and systolic peak velocity was 30.0 +/- 1.2 and 22.3 +/- 1.2 cm/s, respectively (P < .001). CONCLUSIONS: There were no flow differences between right gastroepiploic artery and saphenous vein grafts implanted into the same coronary bed in comparable groups of patients. Waveform shape of the right gastroepiploic artery grafts was characterized by a wider spectral dispersion resulting in a higher maximal frequency.     

Portal hyperperfusion causes disturbance of microcirculation and increased rate of hepatocellular apoptosis: investigations in heterotopic rat liver transplantation with portal vein arterialization

Clinical results of portal vein arterialization (PVA) in liver transplantation are controversial. One reason for this is the lack of a standardized flow regulation. Our experiments in rats compared PVA with blood-flow regulation to PVA with hyperperfusion in heterotopic auxiliary liver transplantation (HALT). In group I (n = 19), the graft's portal vein was completely arterialized via the right renal artery in-stent technique, using a 0.3-mm stent, leading to a physiological average portal blood flow. In group II (n = 19), a 0.5-mm stent was used. In group II, the average portal blood flow after reperfusion was significantly elevated (group II: 6.4 +/- 1.5; group I: 1.7 +/- 0.4 mL/min/g of liver weight; P < .001). The sinusoidal diameter after reperfusion was significantly greater in group II (9.8 +/- 0.5 microm) than in group I (5.5 +/- 0.2 microm; P < .001). Red blood cell velocity in the dilated sinusoids was significantly lower in group II (171 +/- 18 microm/s) than in group I (252 +/- 13 microm/s). Stasis of erythrocytes occurred; consequently, the functional sinusoidal density was significantly reduced in group II (38 +/- 7%) compared with group I (50 +/- 3%; P < .01). Two hours after reperfusion of the portal vein, the number of apoptotic hepatocytes was significantly higher in group II than in group I (I: 0 +/- 0 vs II: 7 +/- 9 M30-positive hepatocytes/10 high-power fields). The 6-week survival rate was 9 of 11 in both groups. In group II, 6 of 9 grafts showed massive hepatocellular necroses after 6 weeks, whereas in group I, only 1 of 9 presented a slight hepatocellular necrosis. Finally, our results demonstrate negative effects of portal hyperperfusion in transplanted livers, which are correctable by adequate flow regulation.     

Sympathetic stimulation increases the blood flow through the in situ right gastroepiploic artery graft after off-pump coronary artery bypass graft surgery

Objective: The right gastroepiploic artery is gaining popularity as an in situ arterial graft for coronary artery bypass surgery. Unlike the internal thoracic artery, the right gastroepiploic artery is a visceral artery and has a vasoconstrictive tendency in response to sympathetic stimulation. We hypothesized that blood flow through the in situ right gastroepiploic arterial graft might be compromised after sympathetic stimulation. Methods: Thirty patients scheduled for off-pump coronary artery bypass surgery using the left internal thoracic artery and the right gastroepiploic artery as in situ arterial grafts were enrolled. Blood flow through both arteries was measured by transit time flow before (T1), during (T2), and after noradrenalinee infusion (T3). Results: After sympathetic stimulation, blood flow of both the right gastroepiploic artery (30.1 ± 13.9 mL/min at T1 vs 36.2 ± 17.5 mL/min at T2; P = 0.001) and left internal thoracic artery grafts (37.3 ± 19.1 mL/min at T1 vs 41.8 ± 18.2 mL/min at T2; P = 0.01) was increased significantly. However, blood flow in proportion to cardiac output increased only in the right gastroepiploic artery graft (P = 0.01). Conclusions: Sympathetic stimulation increases, rather than compromises, blood flow through the right gastroepiploic artery graft after coronary revascularization.     

重组蛇毒纤溶因子修饰聚氨酯人工血管的犬颈动脉置换实验

OBJECTIVE: To evaluate the implantation effect of artificial vascular grafts with recombinant fibrinolytic enzyme factor II (rF II)-immobilized lumina in animal test. METHODS: Four mm internal diameter (ID) polyurethane (PU) artificial vascular grafts were prepared by dipping and leaching method. The micro-pore size and morphology of the graft walls were observed by SEM. The graft lumina were immobilized with rF II. Twenty hybrid male dogs [weighing (20 +/- 1) kg] were used for animal model of carotid artery defect and were randomly divided into 3 groups: rF II -immobilized PU group, no rF II -immobilized PU group and expanded polytetrafluoroethylene (ePTFE) group. The vascular grafts were implanted for repairing injured segments of carotid artery in dogs. The general health state of animals was recorded. At 30 days and 60 days, the patency rate of every group was calculated. At 60 days IDs were measured, cell proliferation in neointima was inspected by light microscope, morphology on neointima was observed by SEM. RESULTS: The ID of the PU vascular grafts was (3.74 +/- 0.06) mm, wall thickness was 0.4-0.6 mm, the wall density was 0.25 g/cm3, the porosity was 79.8%, racical compliance was 8.57%/100 mmHg. In the wall, micropores were well distributed and opened-pores structure was observed. Pore size was (140 +/- 41) microm in the outside layer, pore size was (100 +/- 3) microm in the inside layer, thickness ratio of outside / inside layers was 2 : 1, the pore size was (40 +/- 16) microm on the lumina surface. After operation the wounds on neck healed, all the animals survived and had no complication. At 30 days and 60 days after implantation, the patency rate for rF II -immobilized PU group were 100% and 66.7%, for no rF II -immobilized PU group were 66.7% and 33.3%, and for ePTFE group were 67.7% and 0 respectively, but at 60 days there were thrombosis at anastamotic sites of some grafts occluded. Before operation the IDs for rF II-immobilized PU group, no rF II -immobilized PU group and ePTFE group were (3.74 +/- 0.06), (3.74 +/- 0.06) and (4.00 +/- 0.03) mm, at 60 days after operation the IDs were (4.51 +/- 0.05), (4.31 +/- 0.24) and (4.43 +/- 0.12) mm respectively, showing no statistically significant differences between 3 groups (P > 0.05). Histological inspection indicated that at 15 days a layer of plasma protein deposited on the lumina, at 30 days some cells adhered to the lumina, at 60 days neointima could be observed on the lumina. Thickness of the neointima became larger with implantation time. At 60 days neointima thickness at proximal end, middle site and distal end of graft were (560 +/- 22), (78 +/- 5) and (323 +/- 31) microm respectively for rF II -immobilized PU group. The results of SEM showed that neointima surface consisted of flat and long cells which long axes ranged with blood flow direction and was similar to lumina morphology of carotid artery of dog. CONCLUSION: Immobilization of rF II to lumina of grafts could enhance fibrinolytic activity and inhibited formation of thrombo-embolia which led to an increase in patency rate after implantation.     

Comparison of the flow capacity of free arterial grafts and saphenous vein grafts for coronary bypass surgery

There is controversy regarding the flow reserve and capacity of arterial conduits to meet the needs of the myocardium. This study compared flow in 22 free arterial bypasses to 15 saphenous vein grafts in procedures involving twenty patients. To assess the maximal flow possible, (flow capacity) graft flow was measured using a calibrated pump while perfusing blood cardioplegia through the conduit and distal anastomosis during cardiac arrest (no competitive flow). This assessment was subsequently confirmed with whole blood during myocardial contraction while on cardiopulmonary bypass. Twenty-two free arterial grafts were used; 15 right internal mammary artery grafts, 4 right gastroepiploic grafts, 3 inferior epigastric artery grafts, and 3 sequential bypasses. Free arterial conduit flow ranged from 50 to 180cc/ml, with an average flow of 102.5+/-28.5ml/min as compared to saphenous vein graft flow, 102+/-28 ml/min. No correlation of flow with the conduit size was found. Arterial graft flow demonstrated a mild correlation with the size of the native coronary artery bypassed (R=0.47, P相似文献   

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.     

Immediate flow reserve of Y thoracic artery grafts: an intraoperative flowmetric study

OBJECTIVES: Use of both internal thoracic arteries in a Y graft configuration can raise concerns about the possibility of the single left internal thoracic artery being able to meet the flow requirements of two or three distal territories. We evaluated intraoperatively the flow reserve of a Y thoracic artery graft distally anastomosed to the anterior and lateral territories. METHODS: In 21 patients who had Y thoracic artery grafts, the flow was measured in the main stem of the left internal thoracic artery, in the left internal thoracic artery branch, and in the right internal thoracic artery. A transit time Doppler flowmeter was used. Measurements were repeated after the injection of a bolus of 20 mug/kg dobutamine. RESULTS: At baseline condition, the mean blood flow was 44.8 +/- 24.2, 23.4 +/- 11.5, and 21.4 +/- 15.3 mL/min in the main stem of the left internal thoracic artery, in the left internal thoracic artery branch, and in the right internal thoracic artery, respectively. After dobutamine injection, these values increased to 93.2 +/- 49.8, 46.1 +/- 22.6, and 42.5 +/- 31.2 mL/min, respectively. Flow reserve was 2.1 +/- 0.6, 2.2 +/- 0.9, and 2.1 +/- 0.9 mL/min, respectively. CONCLUSIONS: Intraoperative injection of dobutamine increases the flow in the Y thoracic graft by more than two times, not only in the main stem but also in each branch. This finding attests to the safety of Y thoracic conduits in terms of hemodynamic potential.     

Arteriovenous fistulas as adjuncts to venous bypass grafts

A canine model of occlusive hindlimb venous hypertension was used to determine which of two different, clinically applicable, adjunctive arteriovenous fistulas (AVFs), sequential or peripheral, would augment flow in autogenous cross-femoral venous bypass grafts (CFBs) with the least alteration of hindlimb hemodynamics. Unilateral venous hypertension was produced by iliofemoral venous ligation in three groups of five dogs: group I, venous ligation only (controls); group II, venous ligation followed by CFB with a sequential AVF; and group III, venous ligation with CFB and peripheral AVF. Bilateral hindlimb venous and arterial pressures and flows, and graft flows, were measured preoperatively and for 4 h postoperatively. Insertion of a CFB eliminated the venous hypertension in all 10 bypass dogs. Graft flow was augmented by addition of the sequential AVF (to 1167 +/- 309 mL/min from 92 +/- 12.3 mL/min: p less than .0001). However, this was accompanied, both in the limb ipsilateral to the AVF and in the contralateral limb, by the return of significant venous hypertension (p less than .001) and significant reduction (even reversal) of femoral vein flow caudad to the CFB (p less than .005). In contrast, adding the peripheral AVF augmented graft flow (to 200 +/- 62 mL/min from 65 +/- 43.7 mL/min; p less than .0001), but did not elevate venous pressure or impair venous flow in either hindlimb. The data from this short-term canine model suggest that a peripheral adjunctive AVF may effectively augment CFB graft flow without the potential for detrimental effects on venous hemodynamics characteristic of the sequential AVF.     

Effects of the site of distal anastomosis on the branch flow of coronary arteries in an A-C bypass grafting

Hemodynamics of coronary branch with retrograde blood flow of the host artery was examined in seven mongrel dogs, when the distal side of the graft was anastomosed at distal site to branching point in A-C bypass grafting. A Y-shaped tube was interposed to reconstruct coronary blood flow between the right carotid artery and the left anterior descending coronary artery (LAD), its one arm of Y was connected to proximal site of the branching point of the first diagonal artery (proximal anastomosis), and the other arm was connected to distal site of the branching point (distal anastomosis). After the LAD was ligated just distal to the bifurcation from the left main coronary artery, each arm was clamped in turn, and blood flow of the first diagonal branch was evaluated. Heart rate, left ventricular pressure and cardiac output (cardiac function), and blood pressure, flow and resistance of the interposed tube (bypass function) were not changed significantly in each arm clamped. The diagonal branch flow decreased from 11.2 +/- 2.7 ml/min (mean +/- S.D.) in proximal anastomosis to 10.3 +/- 3.1 ml/min in distal anastomosis with significant difference (P less than 0.05). The diagonal branch/bypass graft flow ratio decreased from 0.422 +/- 0.159 in proximal anastomosis to 0.395 +/- 0.160 in distal anastomosis with significant difference (p less than 0.05). The blood flow in systolic phase of the diagonal branch tended to increase in distal anastomosis as compared with proximal anastomosis. However, diastolic flow of the branch significantly decreased from 8.3 +/- 2.1 ml/min in proximal anastomosis to 7.1 +/- 2.2 ml/min in distal anastomosis (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Biologic degeneration of vein grafts after thrombotic occlusion: thrombectomy within 3 days results in better indices of viability

OBJECTIVES: To clarify the mechanism for poor patency of vein grafts after thrombectomy and the time limit for successful salvage operation, we investigated the time course of biologic degenerative changes in thrombosed vein grafts.Materials and methods The right femoral artery was replaced with a femoral vein graft in 25 mongrel dogs. After 3 months, grafts were explanted in 5 dogs (control grafts), and the remaining 20 dogs underwent femoral artery ligation to create a thrombosed graft. Of the 20 grafts, 5 were explanted at 3 days after ligation (group I-3) and 5 were explanted at 5 days after ligation (group I-5). Of the remaining 10 grafts, 5 underwent thrombectomy at 3 days after ligation (group II-3) and 5 underwent thrombectomy at 5 days after ligation, and were reimplanted into the left femoral artery, then explanted 28 days after reimplantation. The grafts were assessed with immunohistochemistry and prostaglandin (PG) I(2) assay (6-keto-PGI(1alpha)). RESULTS: Of the 25 grafts, occlusion recurred in 3 in group II-5 within 28 days after reimplantation. There were significant differences between group I-5 and group I-3 or control grafts for percentage of areas positive for alpha-actin, total number of cells per field, and proliferating cell nuclear antigen (PCNA)-positive cells in layer of thickened intima and atrophied media (I/M), and for total cell and PCNA- positive cell numbers per field in the adventitia. Mean 6-ketoPGF(1alpha) was 40 +/- 14.1 pg/mg/min in control dogs, 84 +/- 18.9 pg/mg/min in group I-3, and 15.4 +/- 7.7 pg/mg/min in group I-5, demonstrating a significant reduction in group I-5 (P =.009). CONCLUSION: Graft wall cell viability and PGI(2) production in thrombosed vein grafts are well preserved for up to 3 days. Therefore graft salvage operations no later than 3 days after thrombotic occlusion may provide acceptable long-term patency of salvaged grafts.     

Vasoactive drug effects on blood flow in internal mammary artery and saphenous vein grafts

The internal mammary artery is a dynamic coronary graft, whereas the saphenous vein graft is passive. Therefore, potential exists not only for beneficial vasodilation but also for catastrophic spasm of the artery. The purpose of this study was to examine blood flow in the internal mammary and saphenous vein grafts during infusion of drugs that are commonly used after cardiac operations. A canine right heart bypass preparation allowed precise control of cardiac output, blood pressure, and heart rate, which were maintained constant during drug infusion. Both the internal mammary and saphenous vein grafts were constructed so that they perfused the same coronary bed: They were anastomosed in a Y fashion to a ligated anterior descending coronary artery. Electromagnetic flow probes measured graft flow (with the other graft occluded) before and after 15 minutes of drug infusion. The order of drug infusion was randomized and changes were compared by tests for paired differences. Phenylephrine (2 micrograms/kg/min) decreased flow in both the internal mammary and saphenous vein grafts, whereas norepinephrine (0.1 microgram/kg/min) increased flow in both grafts. Epinephrine (0.05 microgram/kg/min) increased mammary artery flow 16% +/- 6% but decreased saphenous vein graft flow 9% +/- 7%. Nitroglycerin (1 microgram/kg/min) significantly increased internal mammary flow (36% +/- 13%), from 47 +/- 7 to 59 +/- 7 ml/min (p less than 0.01), whereas flow decreased significantly in the saphenous vein graft 14% +/- 3%, from 64 +/- 9 to 59 +/- 8 ml/min (p less than 0.01). Nitroprusside (1 microgram/kg/min) decreased mammary artery flow 12% +/- 2%, from 50 +/- 7 to 44 +/- 7 ml/min (p less than 0.01), but increased saphenous vein graft flow 25% +/- 8%, from 64 +/- 9 to 77 +/- 7 ml/min (p less than 0.01). All hemodynamic variables were unchanged, except for norepinephrine, which significantly increased the first derivative of left ventricular pressure. The results suggest that flow through the canine internal mammary artery is changed by the drugs commonly used in perioperative management. Epinephrine and nitroglycerin increased internal mammary artery flow and decreased saphenous vein graft flow, whereas nitroprusside had the opposite effect. The vascular reactivity of the internal mammary artery must be considered when these drugs are used after coronary revascularization.     

Robotic skeletonizing of the internal thoracic artery: is it safe?

BACKGROUND: The advantages of internal thoracic artery skeletonization include early high blood flow, a longer conduit, and less bleeding than pedicle internal thoracic artery grafts. Longer conduits are needed for complete endoscopic arterial revascularization. Therefore this study was designed to determine the feasibility and safety of internal thoracic artery skeletonization using the da Vinci robotic system (Intuitive Surgical, Sunnyvale, CA). METHODS: Nine dogs underwent bilateral robotic internal thoracic artery harvesting through three ports placed in the left chest. One internal thoracic artery was harvested as a pedicle in each dog, and the other was skeletonized. Internal thoracic artery blood flow was measured in each graft, and comparative endothelial histologic studies were performed. Data are mean +/- the standard error of the mean. RESULTS: All 18 internal thoracic arteries were harvested successfully. Skeletonized internal thoracic artery harvests required more time (48.0 minutes +/- 1.8) than pedicle internal thoracic artery harvests (39.0 minutes +/- 1.4; p < 0.05). Internal thoracic artery flows during the final intervals were similar (skeletonized = 30.0 mL/min +/- 2.4 vs pedicle = 31.5 mL/min +/- 1.8; p = 0.9). Free internal thoracic artery bleeding flow was similar in both groups (skeletonized = 162.0 mL/min +/- 3.0 vs pedicle = 189.0 mL/min +/- 2.4; p = 0.4). Histologically, both groups were similar with minimal endothelial damage. CONCLUSIONS: Robotically skeletonized harvesting is safe, but it requires more time (48.0 minutes +/- 1.8) than pedicle internal thoracic artery harvesting. Despite muted tactile feedback with robotics, neither technique was associated with histologic or functional damage. These encouraging results may represent an advantage for complete arterial revascularization in robotic coronary bypass patients.     

T grafts with the right internal thoracic artery to left internal thoracic artery versus the left internal thoracic artery and radial artery: flow dynamics in the internal thoracic artery main stem.

OBJECTIVE: Complete arterial coronary artery bypass grafting with 2 grafts can be achieved even in triple vessel disease by use of a T configuration. There is still uncertainty whether the coronary flow reserve in the main stem of the left internal thoracic artery is sufficient to supply more than 1 anastomosed coronary vessel. METHODS: Between March 1996 and February 1999, 251 patients with multivessel coronary artery disease underwent complete arterial revascularization with T grafts, using either the left internal thoracic artery with the free right internal thoracic artery graft (n = 73, group I) or the left internal thoracic artery and radial artery (n = 178, group II). A mean of 4.0 (group I) versus 4.3 (group II) coronary vessels were anastomosed per patient. One week (n = 92) and 6 months (n = 28) after the operation, flow was measured in the proximal left internal thoracic artery with a Doppler guide wire. Maximum flow was determined after injection of adenosine (30 microg). RESULTS: The in-hospital mortality was 2.7% (group I) versus 2.3% (group II). At angiography (n = 142, 56.6%) the patency rate was 96.3% (group I) versus 98.2% (group II). There was no significant difference between baseline flow, maximum flow, and coronary flow reserve between the 2 groups. Coronary flow reserve increased in both groups within the first 6 postoperative months (group I, 1.85 +/- 0.31 vs 2.77 +/- 0.77, P =.0002; group II, 1.82 +/- 0.4 vs 2.53 +/- 0.73, P =.009). CONCLUSION: Both variants of T grafts allow for complete arterial revascularization with good perioperative results. The flow reserve of the proximal internal thoracic artery is adequate for multiple coronary anastomoses irrespective of the choice of the second arterial graft.     

Collateral blood flow between left coronary artery bypass grafts and chronically occluded right coronary circulation in patients with triple vessel disease. Observations during complete revascularisation of beating hearts.

OBJECTIVE: Preoperative measurements of collateral blood flow in patients with triple vessel disease and chronic occlusions of the right coronary artery do not, currently, ascertain the need to revascularise an occluded right coronary artery. We performed direct measurements of flow across left coronary bypass grafts to determine their contributions to collateral blood flow. METHODS: Collateral blood flow was scored preoperatively according to Rentrop in 13 patients with triple vessel disease and chronic occlusions of the right coronary artery who underwent complete, off-pump, surgical revascularisation. The transit-time flow through the left coronary grafts was measured before and after unclamping of the right coronary artery bypass graft. RESULTS: Unclamping of the right coronary artery bypass graft was associated with a 5.9+/-6.9ml/min (mean+/-SD) decrease in flow across the left circumflex territory (P=0.009), which was proportional to the preoperative Rentrop score (P=0.007). No significant change was observed in flow across the graft to the left anterior descending artery. CONCLUSIONS: Grafts to the left circumflex system are the only grafts that supply a significant, albeit modest amount of collateral blood flow to chronically occluded right coronary artery. These observations confirm that (1) most collateral flow after revascularisation is supplied by the native network, and (2) revascularisation of an occluded right coronary artery is fully justified.     

Inhibition of experimental neointimal hyperplasia by recombinant human thrombomodulin coated ePTFE stent grafts

OBJECTIVES: The goal of this study was to evaluate the ability of recombinant human thrombomodulin (rTM) to inhibit neointimal hyperplasia when bound to expanded polytetrafluoroethylene (ePTFE) stent grafts placed in a porcine balloon injured carotid artery model. METHODS: The left carotid artery of male pigs, weighing 25 to 30 Kg, was injured with an angioplasty balloon. Two weeks later either a non-coated standard ePTFE stent graft (Viabahn, 6 x 25 mm, W. L. Gore & Associates) or a rTM coated stent graft was implanted into the balloon-injured segment using an endovascular technique. Carotid angiography was performed at the time of the balloon injury, two weeks later and then at 4 weeks to assess the degree of luminal stenosis. One month after stent graft deployment, the grafts were explanted following in situ perfusion fixation for histological analysis. The specimens were then cross-sectioned into proximal, middle and distal segments, and the residual arterial lumen and intimal to media (I/M) ratios were calculated with computerized planimetry. RESULTS: rTM binding onto ePTFE-grafts was confirmed by functional activation of protein C and histopathology with immuno-scanning electron microscopy, backscatter electron emission imaging and x-ray microanalysis. All seven of the rTM coated stent grafts and six of the seven uncoated stent grafts were patent at the time of explantation. The mean luminal diameter of the rTM coated stents was 93% +/- 2.0% of the original diameter, compared with 67% +/- 23% (P = .006) in the control group. Histological analysis demonstrated that the area obliterated by intimal hyperplasia at the proximal portion of the rTM stent was -27% compared with the control group: (2.73 +/- 0.69 mm(2), vs 3.47 +/- 0.67 mm(2), P <.05). CONCLUSIONS: Neointimal hyperplasia is significantly inhibited in ePTFE stent grafts coated with rTM compared with uncoated grafts, as documented by improved luminal diameter by angiography and by computerized planimetry measurements of residual lumen area. These findings suggest that binding of recombinant human thrombomodulin onto ePTFE grafts may improve the long-term patency of covered stents grafts. CLINICAL RELEVANCE: Decrease of neointimal hyperplasia of the magnitude observed in this study could significantly improve blood flow and patency of small caliber prosthetic grafts. If the durability of these results can be confirmed by long-term studies, this technique may prove useful in preventing graft stenosis and arterial thrombosis following angioplasty or vascular bypass procedures.     

Modified polytetrafluoroethylene: indium 111-labeled platelet deposition on carbon-lined and high-porosity polytetrafluoroethylene grafts.

Platelet accumulation on carbon-lined (CL) and high-porosity (HP) polytetrafluoroethylene (PTFE) grafts was investigated in vivo. In experiment 1, 20 CL grafts and 20 control PTFE grafts, each 5 cm in length and 4 mm in diameter, were interposed into both carotid and femoral arteries of 10 dogs. In experiment 2, 12 HP grafts (90 microns mean internodal distance) and 12 control PTFE grafts were implanted in six dogs. Indium 111-labeled platelets were injected intravenously and the grafts were retrieved 48 hours later. Radioactivity of the grafts and a control segment of the carotid artery was counted. A graft platelet accumulation index (GPAI) was calculated as the ratio of emission from the graft compared to that from the control segment. The GPAI of the CL graft was significantly less than the GPAI of the control graft in both the carotid (control 29.7 +/- 5.46, CL 22.3 +/- 6.55; n = 9 [p < 0.05]) and the femoral arteries (control 30.7 +/- 9.65, CL 22.0 +/- 6.59; n = 9 [p < 0.05]). There was no significant difference in GPAI between the control and HP grafts in the carotid arteries (control 30.6 +/- 11.8, HP 31.5 +/- 9.71; n = 6) and in the femoral arteries (control 31.5 +/- 7.88, HP 34.0 +/- 4.97; n = 6). Carbon lining decreases platelet accumulation on PTFE grafts in the early postoperative period, and HP grafts do not exhibit increased platelet uptake.