Yasuhiro Kouchi

Effect of differential shear stress on platelet aggregation, surface thrombosis, and endothelialization of bilateral carotid-femoral grafts in the dog

PURPOSE The purpose of this study was to determine the effects of increased shear stress on the aggregability of platelets as they traverse a long, small-caliber (6 mm) Dacron graft in the dog and on the surface thrombosis and endothelialization of such a graft. METHODS Each of nine dogs received bilateral carotid-femoral artery grafts, approximately 75 cm long, for 3 months; one graft of each pair had a distal femoral arteriovenous fistula to produce a higher shear rate than the contralateral graft. Platelet aggregation scores were determined on blood withdrawn from the external jugular vein and from the proximal and distal ends of the grafts in each animal. Graft flow rates, which were used in the computation of shear stress, and luminal pressure gradients through grafts were measured during surgery and specimen retrieval. Specimens were studied with light microscopy after hematoxylin and eosin and immunocytochemical staining and by scanning electron and transmission electron microscopy to evaluate the nature, composition, and thickness of the flow surface lining, as well as the transmural healing. RESULTS Two high-shear stress and two low-shear stress grafts occluded unilaterally; five dogs had bilaterally patent grafts, allowing comparative analyses. All subjects had low platelet aggregability with aspirin. Platelet aggregation scores taken from proximal and distal ends of the grafts were not significantly different. The high-shear stress grafts had significantly more endothelial-like cell coverage (p < 0.0371) than the low-shear stress grafts, less flow-surface thrombus (p < 0.0056), and a thinner surface lining (p < 0.0029), on both the neointima and pseudointima. CONCLUSIONS In subjects with low platelet aggregation scores, long Dacron grafts do not elevate platelet aggregability of blood flowing through them. High-shear stress grafts have less flow surface thrombus, more endothelialization, and a thinner surface lining than do low-shear stress grafts.

Comparison of the effect of monopolar and bipolar cauterization on skeletonized, dissected internal thoracic arteries

The internal thoracic artery is preferable to the saphenous vein for use as a conduit for coronary artery bypass. More extensive use is possible if this artery is mobilized in a skeletonized form to provide greater length. Internal thoracic arteries are usually mobilized with cauterization. This study compared the effectiveness and effects on neighboring areas of division of the branches of the canine internal thoracic artery with bipolar cauterization and monopolar cauterization. Branch closure was significantly more secure in the bipolar cauterization group, with bleeding in 25 (9%) of 279 branches of 15 internal thoracic arteries treated with monopolar cauterization, in contrast to bleeding in 4 (1.3%) of 306 branches in the 15 internal thoracic arteries treated with bipolar cauterization, which were paired with the group treated with monopolar cauterization. The group of internal thoracic arteries treated with monopolar cauterization had a significantly higher prevalence of leakage when luminal pressure was increased from 120 to 160 mm Hg. Scanning electron microscopy demonstrated partial loss of endothelial cells on the flow surface of internal thoracic arteries treated with bipolar cauterization, compared with almost complete loss of endothelial cells around the orificial areas after monopolar cauterization. Secondary bipolar cauterization treatment caused only slightly more damage than primary treatment, but secondary monopolar cauterization was much more severe and extensive than primary treatment. These data suggest that bipolar cauterization is preferable to monopolar cauterization for skeletonized dissection of the internal thoracic artery.

Eicosapentanoic acid suppresses intimal hyperplasia after expanded polytetrafluoroethylene grafting in rabbits fed a high cholesterol diet

The effect of purified eicosapentanoic acid on intimal fibrous hyperplasia in expanded polytetrafluoroethylene grafts was examined in 18 rabbits undergoing infrarenal aorta reconstruction. Six rabbits received commercial rabbit chow (control group), six a regular diet supplemented with 1% cholesterol (cholesterol group), and six the cholesterol diet with 91.1% pure eicosapentanoic acid 500 mg/day (eicosapentanoic acid group). Grafts were harvested 3 months after surgery for histologic examination. The platelet count and serum beta-thromboglobulin and platelet factor 4 concentrations were not significantly different between groups. Serum arachidonic acid level in the cholesterol group was significantly higher than in the control group, and serum eicosapentanoic acid levels in the eicosapentanoic acid group were significantly higher than in the remaining two groups. Intergroup differences in serum 6-keto-prostaglandin F1 alpha and thromboxane B2 concentrations were not significant. Intimal thickness at midgraft was 5.2 +/- 6.2 microns in the control group, 67.6 +/- 46.9 microns in the cholesterol group, and 19.2 +/- 18.4 microns in the eicosapntanoic acid group. intimal thickness in the cholesterol group was greater than in either the control or licosapentanoic acid group (p less than 0.01 and p less than 0.05, respectively). These data suggest that eicosapentanoic acid reduces intimal fibrous proliferation in expanded polytetrafluoroethylene grafting as a result of hypercholesterolemia and that this effect is independent of the platelet count, activated platelet factors, and the prostacyclin/thromboxane A2 ratio.

Implant site influence on arterial prosthesis healing: A comparative study with a triple implantation model in the same dog

PURPOSE The purpose of this study was to develop a cost-effective canine graft healing model that gives information on various implant sites and controls for variable factors between graft locations and between animals and to compare the influence of implant site (retropleural, retroperitoneal, and subcutaneous areas) on arterial graft healing in the same subject under such controlled study conditions. METHODS Five mongrel dogs were studied for 8 weeks, and one was studied for 3 years. Each received three porous Dacron grafts during the same surgery: a carotid-femoral bypass (C-FB) and interposition grafts in the descending thoracic aorta and abdominal aorta. To produce comparable shear stress calibers of the C-FB and abdominal aorta grafts were 2 mm less than those of the descending thoracic aorta, and a distal arterio-venous fistula was created to further increase the C-FB flow. For comparable blood aggregation status platelet aggregation was preevaluated and adjusted with antiplatelet agents. Graft flow surfaces were assessed for thrombus-free surface and endothelial-like cell coverage scores. Tissue samples were studied with hematoxylin-eosin, factor VIII/ von Willebrand factor, smooth muscle alpha-actin staining, and scanning electron microscopy and transmission electron microscopy. RESULTS All grafts were patent. Shear stress for the three grafts and platelet aggregation among the study subjects were comparable. Healing of descending thoracic aorta and abdominal aorta grafts was similar, but C-FB healing was slow, incomplete, and uneven, with a high incidence of seroma. Eight-week and 3-year results were comparable. CONCLUSIONS This model gives broad healing information about the areas where grafts are often implanted in humans. Eight weeks appears to be a sufficient period to reflect basic and general healing characteristics. Grafts heal better in the retropleural and retroperitoneal areas than in the subcutaneous tissues.

Effect of altered blood flow on the caliber and morphology of the internal thoracic artery in the dog

OBJECTIVE The purpose of this study was to evaluate in dogs the effect of blood flow alteration on caliber and morphology of in situ internal thoracic arteries. METHODS Six dogs underwent creation of a unilateral distal arteriovenous fistula between the internal thoracic artery and vein at the sixth rib to create high flow, and in six others the internal thoracic artery was unilaterally skeletonized and dissected. For both groups the contralateral internal thoracic artery served as the control; sides were alternated among cases. Blood flow was measured for shear stress calculation before and after surgical alteration. After 2 months, internal thoracic arteries were harvested with the entire anterior chest plate, which was dynamically inflated and fixed with 10% formalin at a controlled pressure of 120 mm Hg after angiography had been done at the same pressure. The luminal diameters were then measured at eight levels on the angiograms. Arterial tissue samples were taken at three levels and embedded, sectioned, and treated with hematoxylin-eosin and Verhoeff-van Gieson stains. Digital imaging analysis was used for quantitative morphometric studies. RESULTS All fistulas remained patent. In comparison with control arteries, high-flow internal thoracic arteries dilated and low-flow internal thoracic arteries narrowed, which was associated with significant change in shear stress for both groups. There were no substantial structural changes in the walls of either group. CONCLUSION In the dog, the luminal diameter of the internal thoracic artery responds to altered blood flow without intimal thickening or other undesirable wall changes.

Klippel-Trenaunay syndrome associated with splenomegaly: report of a case.

We report herein the case of a 19-year-old woman, diagnosed as having Klippel-Trenaunay syndrome at the age of 3 years, who presented to our hospital with severe abdominal pain. Abdominal computed tomography revealed splenomegaly, ascites, and paracentesis confirming an intrabdominal hemorrhage. Thus, an emergency laparatomy was performed for a suspected splenic rupture, and 2.5L of blood was drained from the abdominal cavity. Splenomegaly was confirmed, and a splenectomy was performed. The patients postoperative course was complicated by disseminated intravascular coagulation, but she recovered and was discharged 3 weeks following surgery. Pathological examination of the spleen suggested that the splenomegaly was caused by high venous pressure due to splenic vein stenosis. To our knowledge, this is the first reported case of Klippel-Trenaunay syndrome associated with marked splenomegaly.

Effect of prostaglandin I2 analogue TRK-100 on the suppression of intimal fibrous proliferation

This study investigated the effect of prostaglandin I2 analogue (TRK-100) on the healing of arterial anastomoses. The infrarenal abdominal aorta was divided and reanastomosed immediately in rabbits. A control group of rabbits were fed commercial rabbit food (ORC 4); a cholesterol group of rabbits were fed a diet with 1% cholesterol added to ORC 4; and a TRK group of rabbits received the same diet as the cholesterol group, but TRK-100 was given subcutaneously at a dose of 0.3 mg (TRK-I group) or 1.0 mg (TRK-II group) every other day. After 3 months a blood sample was taken for biochemical analysis, and the abdominal aorta was harvested for histologic examination. The serum lipid and thromboxane B2 concentrations and the thromboxane B2/6-keto prostaglandin F1 alpha ratio in the TRK groups were significantly lower than in the cholesterol group. The proliferative connective tissue did not cover the anastomotic suture line in either the control or the TRK groups. However, the suture line was covered completely by connective tissue in the cholesterol group. Intimal thickness in the cholesterol group was greater than in either the control or the TRK-II group (p less than 0.01 and p less than 0.05, respectively). These data suggest that TRK-100 may suppress intimal fibrous proliferation at anastomotic suture lines by a mechanism affecting the thromboxane B2/6-keto prostaglandin F1 alpha ratio.

Assessment of Laser Doppler Flowmetry During Abdominal Aortic Aneurysmectomy

The purpose of the present study was to assess the diagnostic utility of blood flow measurements at the sigmoid colon by laser Doppler flowmetry. Methods: A laser-Doppler flow probe was placed in contact with the serosa of the sigmoid colon in 41 patients undergoing resection of infrarenal abdominal aortic aneurysms. Blood flows were measured before aortic clamping, after reconstruction, and after inferior mesenteric artery revascularization. Results: The authors observed a colonic blood flow greater than 18 mL/minute/100 g in all the patients who did not develop postoperative ischemic colitis. Conclusions: The colonic blood flow needed to prevent postoperative ischemic colitis is greater than 18 mL/minute/100 g. The assessment of blood flow at the sigmoid colon by laser Doppler flowmetry is useful for predicting postoperative ischemic colitis.