Estrogen inhibits the vascular injury response in estrogen receptor alpha-deficient mice.

The atheroprotective effects of estrogen in women are well recognized, but the underlying mechanisms responsible are not well understood. Blood vessel cells express the classic estrogen receptor, ER alpha (ref. 2-6), and are directly affected by estrogen, which inhibits the development of atherosclerotic and injury-induced vascular lesions. We have generated mice in which the ER alpha gene is disrupted and have used a mouse model of carotid arterial injury to compare the effects of estrogen on wild-type and estrogen receptor-deficient mice. Increases in vascular medial area and smooth muscle cell proliferation were quantified following vascular injury in ovariectomized mice treated with vehicle or with physiologic levels of 17 beta-estradiol. Surprisingly, in both wild-type and estrogen receptor-deficient mice, 17 beta-estradiol markedly inhibited to the same degree all measures of vascular injury. These data demonstrate that estrogen inhibits vascular by a novel mechanism that is independent of the classic estrogen receptor, ER alpha.

Estrogen inhibits the response-to-injury in a mouse carotid artery model.

The atheroprotective effects of estrogen are well documented, but the mechanisms responsible for these effects are not well understood. To study the role of physiologic (nanomolar) estrogen levels on the arterial response-to-injury, we applied a mouse carotid artery injury model to ovariectomized C57BL/6J mice. Mice were treated with vehicle (-E2, n = 10) or 17 beta-estradiol (+E2, n = 10) for 7 d, subjected to unilateral carotid injury, and 14 d later contralateral (normal = NL) and injured carotids from -E2 and +E2 animals were pressure fixed, harvested, and analyzed by quantitative morphometry. E2 levels in +E2 mice were consistently in the nanomolar range (2.1-2.5 nM) at days 0, 7, and 14. At 14 d, measures of both intimal and medial area were markedly increased in the -E2 group: (-E2 vs NL, P < 0.05 for both), but were unchanged from normal levels in the +E2 group (+E2 vs NL, P = NS and +E2 vs -E2, P < 0.05 for both). Cellular proliferation, as assessed by bromodeoxyuridine (BrdU) labeling, was significantly increased over NL in the -E2 mice, but this increase was markedly attenuated in the estrogen replacement group (total BrdU positive cells/section: NL = 6.4 +/- 4.5; -E2 = 113 +/- 26, +E2 = 40 +/- 3.7; -E2 vs NL, P < 0.05; +E2 vs NL, P = NS; -E2 vs +E2, P < 0.05). These data (a) demonstrate significant suppression of the mouse carotid response-to-injury by physiologic levels of estrogen replacement; (b) support the utility of this model in the study of the biologic effects of estrogen on the vascular-injury response; and (c) suggest a direct effect of estrogen on vascular smooth muscle cell proliferation in injured vessels.

Calf muscle adaptation to peripheral vascular disease.

130 muscle biopsies were taken from the gastrocnemius of 82 patients with different degrees of peripheral vascular disease (PVD) and 19 normal controls for histochemical analysis, and 30 patients and 7 controls for biochemical analysis of "aerobic" and "anaerobic" enzymes. The results showed that the gastrocnemius of patients with PVD did not adapt by increasing its "aerobic" potential as previously suggested. Histochemical studies showed that the cross-sectional area of both Type 1 and Type 2 muscle fibres became smaller than those from age-matched controls in the presence of PVD, and in some cases biopsies from both legs confirmed that this trend was greater in those limbs with increasing evidence of PVD. There is also some evidence to suggest a decrease in absolute capillary numbers per muscle fibre. The biochemical assays confirmed decreased levels of aerobic enzymes with increasing evidence of PVD as judged by ankle systolic pressure, and those patients with intermittent claudication showed some evidence of increased anaerobic enzyme levels in comparison to both the normal controls and those with rest pain. Patients with PVD do not adapt to ischaemia/anoxia by increasing their aerobic capability, but show signs of muscle atrophy probably due to reduced mobility. Training regimes may benefit patients with intermittent claudication by reversing these changes.

The hemodynamic and metabolic alterations associated with acute heat stress injury in marathon runners.

Studies of clinical, metabolic, and hemodynamic responses to heat stress in eight marathon runners have demonstrated several important differences from those observed in nonconditioned subjects. Three marathoners manifested a nonanhidrotic form of heat stroke, a phenomenon not observed in our Marine recruits. Five patients with heat exhaustion evidenced signs of severe mental confusion despite apparently adequate hemodynamic function. Heart rate was significantly lower in all eight marathoners in comparison to the 15 Marine recruits. This latter observation suggests that either selective regional shunting of blood or increased stroke volume index occurs in marathoners subject to heat stress.

Above-knee polytetrafluoroethylene femoropopliteal bypass graft: Is it a reasonable alternative to the below-knee reversed autogenous vein graft?

To determine whether an above-knee polytetrafluoroethylene (AK-PTFE) femoropopliteal bypass graft might be an acceptable alternative to a below-knee reversed autogenous saphenous vein (BK-ASV) bypass graft, we compared 51 AK-PTFE grafts to 39 concurrently performed BK-ASV grafts. All patients were staged by preoperative noninvasive vascular laboratory criteria into limiting claudication or limb salvage groups and by intraoperative arteriography according to degree of runoff. There was no significant difference in the primary graft patency at 36 months between the AK-PTFE group (63%) and the BK-ASV group (72%). Secondary graft patency among the AK-PTFE group was improved by minor distal graft revision to 88% at 36 months. The preoperative noninvasive hemodynamic evaluation status was an influential factor; the graft patency rate among the patients with limiting claudication was superior to that among the limb salvage group, but the degree of runoff as shown by intraoperative angiography did not appear to have an effect on cumulative patency. Resting Doppler ankle/brachial artery pressure ratios did not predict subsequent occlusion of AK-PTFE grafts. Atherosclerosis is a progressive and systemic disease that frequently involves both the coronary and tibial vessels. AK-PTFE spares autogenous saphenous vein so that it can be reserved for use in coronary artery bypass or in subsequent treatment of more distal tibial vessel disease.

Platelet function abnormalities in a family with recurrent arterial thrombosis.

Three young family members with recurrent arterial thrombosis underwent investigation for lipid or coagulation abnormalities. Lipoprotein electrophoresis, cholesterol, triglyceride levels, and routine coagulation studies were unremarkable. By contrast, testing of platelet function showed enhanced platelet aggregability to epinephrine and collagen in two of the subjects. In addition, release of 14C-serotonin by adenosine diphosphate and epinephrine was increased over control values in these same two patients. The third subject demonstrated decreased platelet aggregation and lowered 14C-serotonin release, but was symptomatic with rest pain at the time of testing. The ongoing in vivo thrombosis in the third subject may account for hypocoagulable platelets by in vitro testing. These abnormally sensitive platelets identified by platelet function testing may be associated with a familial "hypercoagulability" syndrome. Definition of the hemostatic abnormality in these individuals provided a rational basis for pharmacological therapy with antiplatelet drugs, which appeared to be successful.

The relative importance of incompetent communicating veins in the production of varicose veins and venous ulcers.

To investigate the possible anatomic and hemodynamic reasons for the variability in response to surgery for venous insufficiency (a 50% ulcer recurrence rate following ligation of incompetent perforating veins), we performed phlebography and venous pressure measurements in 109 legs of 77 patients and in 30 healthy volunteers. Patients were divided into five groups: saphenofemoral incompetence alone (group 1), saphenopopliteal incompetence (group 2), incompetent lower leg communicating veins alone (group 3), calf communicating veins and saphenous incompetence (group 4), and postthrombotic limbs (group 5). Patients in groups 1 through 4 had phlebographically normal deep veins. As compared to the normal controls (68%), preoperative pressure measurements revealed a significantly smaller pressure fall during exercise (deltaVPex) in all groups, which was the least marked in groups 3 (26%) and 5 (17%). These latter two groups failed to increase their pressure fall with thigh tourniquet. deltaVPex 3 months after operation demonstrated normalization in groups 1, 2, and 4 (52%, 57% and 59% respectively). Groups 3 and 5 improved little following surgical ligation. Whenever saphenous vein incompetence coexists with lower leg communicating vein incompetence, the former appears to be the dominant cause of the pressure abnormalities. Based on venous pressure measurements and phlebography, patients with normal deep veins and who increase their deltaVPex with a thigh tourniquet should respond favourably to orthodox surgical ligation of the saphenofemoral or saphenopopliteal junction. By contrast, if no change in deltaVPex is noted in patients with incompetent perforating veins and the deep veins look abnormal on the phlebogram, then ligation of the incompetent communicating veins would appear to be associated with a high recurrence rate.

The effect of flow on vascular endothelial cells grown in tissue culture on polytetrafluoroethylene grafts.

Vascular grafts lined with endothelial cells (EC) grown to confluence in culture before implantation may provide a thromboresistant flow surface. Growth of EC on and their adherence to currently available prosthetic materials under conditions of flow are two impediments remaining in the development of such a graft. To address these problems, 22 polytetrafluoroethylene grafts (PTFE) (5 cm by 4 mm inside diameter) were pretreated with collagen and fibronectin, seeded with 2 to 3 X 10(6) bovine aortic EC per graft, and placed in tissue culture (seeded grafts). Twenty-two grafts pretreated with collagen and fibronectin alone served as controls. After 2 weeks morphologic studies revealed that 20/22 seeded grafts were lined with a confluent endothelial layer. Indium 111-oxine was then used to label the EC-seeded grafts. After exposure to either low (25 ml/min) or high (200 ml/min) flow rates for 60 minutes in an in vitro circuit, examination of the luminal surface of the graft by light microscopy and scanning electron microscopy revealed minimal loss of EC. These findings were corroborated by radionuclide scans that showed an insignificant loss of the EC-associated indium label during exposure to flow (7% low flow, 11% high flow). Pretreatment of PTFE grafts with collagen and fibronectin thus promotes both attachment and adherence of EC even under flow conditions.

The economic impact of acute variceal bleeding: cost-effectiveness implications for medical and surgical therapy.

The hospital costs and its respective components for 32 patients with acute variceal bleeding were determined. The average total cost for treating the 32 patients was $35,000. The cost for those patients who underwent elective surgery ($53,000) was approximately twofold that of the elective medical group. Nutritional and metabolic rehabilitation that prolonged hospitalization, reutilization of the intensive care unit, and perioperative blood requirements were the significant factors that increased the cost of treating the surgically treated patients. Derivation of the cost/benefit ratio, however, showed that the decreased rehospitalization rate of the surgically treated group and the apparent better "quality of life" almost offset the increased initial hospital costs for this group.

A prospective study of Doppler pressures and segmental plethysmography before and following aortofemoral bypass. Implications for predicting success and for adopting a uniform method of classifying arterial disease.

To determine the clinical and hemodynamic changes associated with aortofemoral bypass, 44 limbs of 31 patients underwent segmental plethysmography (PVR) and Doppler pressures (DSP) before operation, immediately after operation, and again at 6 months. Prior to operation patients were separated by angiographic criteria into two groups: aortoiliac segment disease alone (AI) (n = 22), and aortoiliac and femoropopliteal segment disease (AIFP) (n = 22). At 6 months the two groups were subdivided into four groups based on relief (oSx) or lack of relief (+Sx) of symptoms. Before operation the only significant difference between the four groups was a higher thigh PVR and calf DSP in the AI + Sx group. Six month PVR values in AIoSx were improved nearly twofold over preoperative measurements at the thigh and calf, but at the thigh level only for AIFPxSx. DSP was increased at all three levels in both AI and AIFPoSx groups. No hemodynamic improvement occurred in either the AI or the AIFP + Sx groups. A derivative index of PVR (thigh-ankle/15 mm) or the FPomega was significantly lower in AIFOsSx before operation. There was a significant disparity between classification by hemodynamics and by symptoms prior to operation which lessened somewhat after operation. These studies suggest that success or failure can be predicted before operation in AIFP by FPomega, and arterial disease should be classified by a combination of symptoms, angiography, and hemodynamics.

Liver metabolism and glucogenesis in trauma and sepsis.

The relationship of glucogenesis and other energy-requiring functions of the liver to the proteolysis which is characteristic of trauma and sepsis was studied in conscious pigs following laporotomy and after the induction of intraperitoneal sepsis. By means of appropriately placed thermal dilution catheters, portal and hepatic arterial blood flows, hepatic oxygen consumption, glucogenesis, and uptake of the fuel, substrates were measured. No animal was in shock. Despite significant increases of lactate and aminoacids delivered to the liver, the blood concentrations were maintained in the normal range. The rate of glucogenesis was proportional (r equals 0.71) to the sum of the glucogenic precursors (lactate, pyruvate, glycerol, and alanine) taken up by the liver. Higher rates of glucose production were accompanied by elevated blood insulin values. Hepatic oxygen consumption and the uptake of free fatty acids also were related directly to the glucogenic rate, the correlation coefficients being 0.69 and 0.74, respectively. In the absence of shock, the liver function and hepatic energy production remained normal in post-traumatic and septic states. Under the conditions insulin-resistant muscle in the presence of reduced free fatty acid availability mobilize protein to satisfy local energy requirements. Skeletal muscle can oxidize only branch chain aminoacids; other aminoacids, including alanine, are transported to the liver for glucogenesis or other purposed. This concept accounted for failure of glucose infusion to eliminate post-traumatic and septic proteolysis, since alanine is cleared only from blood by conversion in the liver to glucose. Thus it is concluded that in sepsis the release of glucogenic substrates because of altered metabolism in peripheral tissues determines the rate of hepatic glucogenesis. This relationship constitutes an important metabolic homeostatic mechanism.

Ultrastructural and capillary adaptation of gastrocnemius muscle to occlusive peripheral vascular disease.

The effect of chronic occlusive peripheral vascular disease (PVD) on the histochemistry and capillarity of the gastrocnemius muscle was studied in 129 biopsies taken from 93 subjects. Sixty-three patients underwent biopsy during surgical procedures, and data related to walking distance and ankle systolic pressure. Thirty biopsies taken from normal subjects post mortem served as a control group, and data were analyzed for fiber type distribution, fiber area, fiber type grouping, and fiber capillarity. Fiber type distribution did not alter significantly between the patients with PVD and the control group, but the mean fiber area of the type 1 fiber in male patients with intermittent claudication (IC) was reduced when compared to that in age-matched controls (4608 +/- 1181 mu 2, IC +/- 1 SD; 5795 +/- 1771 mu 2, controls +/- 1 SD) (P less than 0.05). When bilateral biopsies were taken from the gastrocnemii of patients with unilateral occlusions, the type 2 fibers in the diseased leg were significantly smaller than fibers of the control group (2821 +/- 953 mu 2, IC +/- 1 SD; 4318 +/- 1504 mu 2, controls +/- 1 SD) (P less than 0.02). Fiber type grouping, evidence of denervation and reinnervation of muscle, appeared to be more common in patients with more severe limb ischemia. Overall capillary numbers did not appear to alter with degree of ischemia, but fiber shrinkage appeared to compensate for any loss of capillaries in the more ischemic muscle. These data suggest that the limb of the untrained patient with IC does not adapt to ischemia by adjusting its exercise capacity but merely shows evidence of disuse. These adaptations suggest that there may be much to be gained by nonsurgical methods of treating IC.

The relative value of carotid noninvasive testing as determined by receiver operator characteristic curves.

To determine the relative value of carotid phonoangiography (CPA), oculoplethysmography-Kartchner (OPG-K), and Doppler ultrasonic arteriography (UA), 90 vessels undergoing carotid endarterectomy were prospectively examined. By analyzing the data on receiver operator characteristic curves, the dynamic relationship between sensitivity and specificity for each of the three noninvasive tests was assessed. Disease was defined by either the percentage of angiographic stenosis or the mean pressure gradient across the carotid (deltaP). All three tests were shown to be relatively insensitive, but quite specific, if disease was defined by 50% and 60% angiographic stenosis or deltaP of greater than 10 and 20 mm Hg. By employing a more rigid definition of disease, 70% stenosis or deltaP of greater than 30 mm Hg, sensitivity was increased for all examinations and was highest in OPG-K and UA for a given specificity. The sensitivity for UA was enhanced to 80% with a comparable specificity, if those 23 UA exams with plaque were treated as positive studies. The combination of CPA, OPG-K, and UA was superior to any one of these tests alone, but the best value balancing maximum sensitivity and specificity still was associated with a 23% false negative rate. This study would suggest that these three tests should be limited to screening patients at risk for carotid stenosis and not for symptomatic patients. To achieve the best balance between sensitivity and specificity, lax threshold criteria for calling the test positive should be employed, and the tests should be used in combination.

The costs of surgery for limb-threatening ischemia.

The clinical courses of 106 patients with limb-threatening ischemia were traced for as long as 5 years to determine the cost of their care. Seventy-eight patients initially treated with vascular reconstruction accrued an average of $40,769 +/- $3726 in costs over a mean follow-up period of 805 +/- 57 days, during which they had an average of 2.4 +/- 0.2 hospitalizations or 67 +/- 6 inpatient days. Twenty-eight high-risk patients treated with primary amputation accrued $40,563 +/- $4729 in costs over a mean follow-up period of 663 +/- 97 days, during which they had an average of 2.2 +/- 0.3 hospitalizations or 85 +/- 10 inpatient days. Successful revascularization resulted in lower costs ($28,374) than did primary amputation ($40,563) or failed reconstruction ($56,809). Patients with ischemic tissue loss accrued costs more rapidly than did patients with rest pain only. The high cost of providing care for these patients and the advent of diagnosis related group reimbursement mandate that proposed treatment protocols be evaluated not only for their effectiveness but also for their cost-effectiveness.

Altered thyroid hormone levels in bacterial sepsis: the role of nutritional adequacy.

Depressed triiodothyronine and elevated reverse triiodothyronine levels are commonly seen in patients with acute and chronic illness and in patients receiving markedly hypocaloric diets. To investigate the role of nutritional adequacy in causing the altered thyroid hormone levels found in severe illness, we studied patients with bacterial sepsis who were receiving a variety of nutritional regimens. Thirteen patients received only 5% dextrose in water (600-1000 kcal/day), 7 of whom were in shock. Seven patients received total parenteral nutrition (2500-3500 kcal/day). Analysis of thyroid hormone levels in these groups and in controls shows that a large component of the alteration in thyroid hormone levels found in patients with severe illness is due to the caloric deprivation associated with such severe illness.

Investigation of factors determining the optimal glucose infusion rate in total parenteral nutrition.

We have used the primed constant infusion of U-13C-glucose to study glucose metabolism during conventional total parenteral nutrition (TPN) in five postoperative surgical patients. Glucose production from nonrecycled carbon sources was suppressed to 17% of the basal level at the lowest rate of glucose infusion tested (4 mg/kg x min). Subsequent increases in glucose infusion rate had minimal effect in further suppressing glucose production. Additional nitrogen-sparing effects of glucose when glucose is infused at rates in excess of 4 mg/kg x min must therefore be derived from oxidation of the infused glucose. An increase in the infusion rate from 4 mg/kg x min to 7 mg/kg x min was associated with an increased rate of glucose oxidation, but a further increase in glucose infusion rate (9 mg/kg x min) was without significant effect on glucose oxidation. As the rate of TPN administration (glucose and amino acids) increased, both metabolic rate and RQ rose significantly. Our calculations indicate that the high RQ's observed during the highest glucose infusion rate (X = 1.13) could be attributed to the synthesis of fat from infused glucose, and that about 30% of the increase in VO2 above the basal level could also be attributed to fat synthesis. The progressive increase in the ability to clear glucose from the blood that occurred as TPN progressed was not due to an increase in the rate of oxidation of glucose; we found no correlation between glucose clearance and glucose oxidation.

Relationship of muscle surface pH to noninvasive hemodynamic studies in arterial occlusive diseases.

To examine the possible relationship between Doppler pressures (DP) and pulse volume amplitude (PVR) with muscle surface pH (pHm), we studied 20 patients before, during, and after arterial reconstruction. The mean pHm for the claudication, rest pain, and ischemic gangrene groups differed from a control group and from each other. The pHm varied directly with DP and PVR for the 20 patients as a whole. After reconstructive surgery, improvement in pHm seemed to precede changes in DP and PVR in six patients with combined segment disease. Although pHm correlates generally with DP and PVR, it is invasive. Therefore, pHm should not be used as a routine screening test. Whereas DP and PVR may reflect the anaerobic activity of peripheral tissue, they may be less prompt than pHm in responding to acute changes in blood flow.

Is 80 years too old for aneurysmectomy?

The records of 111 patients, 80 years of age or older, with a primary diagnosis of abdominal aortic aneurysm(AAA) showed that 86 patients underwent aneurysm resection and grafting. Ruptured AAAs (n=30) were associated with an operative mortality of 74%. By contrast, AAA resection in the expanding aneurysm group (n=19) and in the elective surgery group (n=44) was associated with a 10% and 2% mortality, respectively. Thus, resection of a nonruptured AAA in 63 octogenarians was carried out with an overall mortality of 4.7%. While nearly half of the patients had cardiac disease detected preoperatively, the elective group demonstrated a low incidence of previous myocardial infarction (7%) and congestive heart failure (8%). Concomitantly, the incidence of myocardial infarction (6%) and congestive heart failure was relatively low after AAA resection. Significant postoperative oliguric azotemia was observed in only 5% of the nonruptured patients. Long-term survival was comparable to that of the general population over the age of 80 years. The quality of life enjoyed by these patients was not adversely affected by AAA resection. By contrast, 50% of patients treated conservatively died of ruptured AAA. Physiologic rather than chronologic age should determine selection for AAA resection in the octogenarian.

Sequential pneumatic compression for lymphedema. A controlled trial.

We examined prospectively the effect of a new compression device for lymphedema, which utilizes a short duration and high-pressure cycle, that provides a sequential milking pattern to the limb through multiple compartments. Twenty-five patients (seven patients for upper-extremity and 18 for lower-extremity problems) underwent 24 hours of treatment. All extremities showed a decrease in circumferential measurements with the maximal reduction occurring at the wrist (45%) for the upper extremities and at the mid-calf (47%) for the lower extremities. Lower-extremity leg volume was reduced by 45%. Despite the high pressures no elevation in serum muscle enzyme levels was noted. This device reduced lymphedematous limbs rapidly and safely.