Relationship between 'on-treatment platelet reactivity', shear stress, and micro-embolic signals in asymptomatic and symptomatic carotid stenosis

BACKGROUND

Assessment of 'high on-treatment platelet reactivity (HTPR)' could enhance understanding of the pathophysiology of first or recurrent vascular events in carotid stenosis patients on antiplatelet therapy.

METHODS

This prospective, multi-centre study assessed antiplatelet-HTPR status and its relationship with micro-emboli signals (MES) in asymptomatic vs. symptomatic ≥ 50-99% carotid stenosis. Platelet function/reactivity was assessed under 'moderately high shear stress' with the PFA-100^® and 'low shear stress' with VerifyNow^® and Multiplate^® analysers. Bilateral 1-h transcranial Doppler ultrasound of the middle cerebral arteries classified patients as MES + ve or MES - ve.

RESULTS

Data from 34 asymptomatic patients were compared with 43 symptomatic patients in the 'early phase' (≤ 4 weeks) and 37 patients in the 'late phase' (≥ 3 months) after TIA/ischaemic stroke. Median daily aspirin doses were higher in early symptomatic (225 mg; P < 0.001), but not late symptomatic (75 mg; P = 0.62) vs. asymptomatic patients (75 mg). There was a lower prevalence of aspirin-HTPR in early (28.6%; P = 0.028), but not late symptomatic (38.9%; P = 0.22) compared with asymptomatic patients (56.7%) on the PFA-100^®, but not on the VerifyNow^® or Multiplate^® (P ≤ 0.53). Early symptomatic patients had a higher prevalence of aspirin-HTPR on the PFA-100^® (28.6%) vs. VerifyNow^® (9.5%; P = 0.049), but not Multiplate^® assays (11.9%, P = 0.10). There was no difference in aspirin-HTPR prevalence between any symptomatic vs. asymptomatic MES + ve or MES - ve subgroup.

DISCUSSION

Recently symptomatic moderate-severe carotid stenosis patients had a lower prevalence of aspirin-HTPR than their asymptomatic counterparts on the PFA-100^®, likely related to higher aspirin doses. The prevalence of antiplatelet-HTPR was positively influenced by higher shear stress levels, but not MES status.

Increased Leucocyte-Platelet Complex Formation in Recently Symptomatic versus Asymptomatic Carotid Stenosis Patients and in Micro-emboli Negative Subgroups

INTRODUCTION

 Cerebral micro-embolic signals (MES) predict risk of stroke in carotid stenosis patients. However, MES-negative 'recently symptomatic patients' also have a higher stroke risk than 'asymptomatic patients'. Differences in platelet activation status may contribute to this disparity in risk.

METHODS

 This prospective, observational study assessed platelet biomarkers and their relationship with MES in asymptomatic versus symptomatic moderate (≥50-69%) or severe (≥70-99%) carotid stenosis patients. Full blood count parameters were measured and whole-blood flow cytometry was used to quantify platelet surface CD62P and CD63 expression and leucocyte-platelet complex formation. Bilateral simultaneous transcranial Doppler ultrasound of the middle cerebral arteries classified patients as 'MES positive' or 'MES negative'.

RESULTS

 Data from 34 asymptomatic patients were compared with those from 43 symptomatic patients in the 'early phase' (≤ 4 weeks) and 37 of these symptomatic patients in the 'late phase' (≥ 3 months) after transient ischaemic attack/ischaemic stroke. There were no differences in %CD62P or %CD63 expression between early or late symptomatic and asymptomatic patients overall (p > 0.05). The percentage of lymphocyte-platelet complexes was higher in early symptomatic than in asymptomatic patients (2.8 vs. 2.16%; p < 0.001). MES were more commonly observed in early symptomatic (31.4%; p = 0.027) but not in late symptomatic (6.7%; p = 0.996) versus asymptomatic patients (7.1%). The percentage of lymphocyte-platelet complexes was higher in early symptomatic than in asymptomatic MES-negative patients (2.7 vs. 2.17%; p = 0.02).

CONCLUSION

These data add to the evidence that leucocyte-platelet complex formation/platelet activation is increased in recently symptomatic versus asymptomatic patients, and may contribute to the pathogenesis of first and subsequent strokes in carotid stenosis patients, including those who are MES negative.

Profile of von Willebrand factor antigen and von Willebrand factor propeptide in an overall TIA and ischaemic stroke population and amongst subtypes

INTRODUCTION

Von Willebrand factor propeptide (VWF:Ag II) is proposed to be a more sensitive marker of acute endothelial activation than von Willebrand factor antigen (VWF:Ag). Simultaneous data on VWF:Ag and VWF:Ag II profiles are very limited following TIA and ischaemic stroke.

METHODS

In this prospective, observational, case-control study, plasma VWF:Ag and VWF:Ag II levels were quantified in 164 patients≤4weeks of TIA or ischaemic stroke (baseline), and then ≥14days (14d) and ≥90days (90d) later, and compared with those from 27 healthy controls. TIA and stroke subtyping was performed according to the TOAST classification. The relationship between VWF:Ag and VWF:Ag II levels and platelet activation status was assessed.

RESULTS

'Unadjusted' VWF:Ag and VWF:Ag II levels were higher in patients at baseline, 14d and 90d than in controls (p≤0.03). VWF:Ag levels remained higher in patients than controls at baseline (p≤0.03), but not at 14d or 90d after controlling for differences in age or hypertension, and were higher in patients at baseline and 90d after controlling for smoking status (p≤0.04). 'Adjusted' VWF:Ag II levels were not higher in patients than controls after controlling for age, hypertension or smoking (p≥0.1). Patients with symptomatic carotid stenosis (N=46) had higher VWF:Ag and VWF:Ag II levels than controls at all time-points (p≤0.002). There was no significant correlation between platelet activation status and VWF:Ag or VWF:Ag II levels.

CONCLUSIONS

VWF:Ag and VWF:Ag II levels are increased in an overall TIA and ischaemic stroke population, especially in patients with recently symptomatic carotid stenosis. VWF:Ag II was not superior to VWF:Ag at detecting acute endothelial activation in this cohort and might reflect timing of blood sampling in our study.

Increased thrombin generation potential in symptomatic versus asymptomatic moderate or severe carotid stenosis and relationship with cerebral microemboli

INTRODUCTION

The importance of thrombin generation in the pathogenesis of TIA or stroke and its relationship with cerebral microembolic signals (MES) in asymptomatic and symptomatic carotid stenosis has not been comprehensively assessed.

METHODS

Plasma thrombin generation parameters from patients with moderate or severe (≥ 50%) asymptomatic carotid stenosis were compared with those from patients with symptomatic carotid stenosis in the early (≤ 4 weeks) and late phases (≥ 3 months) after TIA or stroke in this prospective, pilot observational study. Thrombin generation profile was longitudinally assessed in symptomatic patients with data at each time point. Bilateral transcranial Doppler ultrasound monitoring of the middle cerebral arteries was performed whenever possible to classify patients as MES-positive or MES-negative.

RESULTS

Data from 31 asymptomatic, 46 'early symptomatic' and 35 'late symptomatic' patients were analysed. Peak thrombin (344.2 nM vs 305.3 nM; p = 0.01) and endogenous thrombin potential (1772.4 vs 1589.7; p = 0.047) were higher in early symptomatic than asymptomatic patients. Peak thrombin production decreased in symptomatic patients followed up from the early to late phase after TIA or stroke (339.7 nM vs 308.6 nM; p = 0.02). Transcranial Doppler ultrasound data were available in 25 asymptomatic, 31 early symptomatic and 27 late symptomatic patients. Early symptomatic MES-positive patients had a shorter 'time-to-peak thrombin' than asymptomatic MES-positive patients (p=0.04), suggesting a more procoagulant state in this early symptomatic subgroup.

DISCUSSION

Thrombin generation potential is greater in patients with recently symptomatic than asymptomatic carotid stenosis, and decreases over time following TIA or stroke associated with carotid stenosis. These data improve our understanding of the haemostatic/thrombotic biomarker profile in moderate-severe carotid stenosis.

Longitudinal assessment of von Willebrand factor antigen and von Willebrand factor propeptide in response to alteration of antiplatelet therapy after TIA or ischaemic stroke

The impact of commencing or changing antiplatelet therapy on von Willebrand factor antigen (VWF:Ag) and von Willebrand factor propeptide (VWF:Ag II) levels has not been comprehensively assessed following TIA or ischaemic stroke. In this pilot, longitudinal, observational analytical study, VWF:Ag and VWF:Ag II levels were simultaneously quantified in platelet poor plasma by ELISA in patients within 4 weeks of TIA or ischaemic stroke (baseline), and then 14 days (14d) and >90 days (90d) after altering antiplatelet therapy. Ninety-one patients were recruited. Eighteen were initially assessed on no antiplatelet therapy, and then after 14d (N = 17) and 90d (N = 8) on aspirin monotherapy; 21 patients were assessed on aspirin and after 14d and 90d on clopidogrel; 52 were assessed on aspirin monotherapy, and after 14d and 90d on aspirin and dipyridamole combination therapy. VWF:Ag, VWF:Ag II levels and VWF:Ag/VWF:Ag II ratio were unchanged at 14d and 90d in the overall study population (p ≥ 0.1). VWF:Ag and VWF:Ag II levels remained stable at 14d and 90d after commencing aspirin (p ≥ 0.054), and after changing from aspirin to clopidogrel (p ≥ 0.2). Following the addition of dipyridamole MR to aspirin, there was a significant reduction in VWF:Ag levels at 14d (p = 0.03) and 90d (p = 0.005), but not in VWF:Ag II levels (p ≥ 0.3). The addition of dipyridamole to aspirin led to a persistent reduction in VWF:Ag but not in VWF:Ag II levels, suggesting that dipyridamole may inhibit release of platelet-derived VWF:Ag following TIA or ischaemic stroke.

Increased endothelial activation in recently symptomatic versus asymptomatic carotid artery stenosis and in cerebral microembolic-signal-negative patient subgroups

BACKGROUND AND PURPOSE

von Willebrand factor propeptide (VWF:Ag II) is potentially a more sensitive marker of acute endothelial activation than von Willebrand factor antigen (VWF:Ag). These biomarkers have not been simultaneously assessed in asymptomatic versus symptomatic carotid stenosis patients. The relationship between endothelial activation and cerebral microembolic signals (MESs) detected on transcranial Doppler ultrasound is unknown.

METHODS

In this multicentre observational analytical study, plasma VWF:Ag and VWF:Ag II levels in patients with ≥50% asymptomatic carotid stenosis were compared with those from patients with ≥50% symptomatic carotid stenosis in the 'early' (≤4 weeks) and 'late' (≥3 months) phases after transient ischaemic attack or ischaemic stroke. Endothelial activation was also longitudinally assessed in symptomatic patients during follow-up. Transcranial Doppler ultrasound monitoring classified patients as MES-positive or MES-negative.

RESULTS

Data from 31 asymptomatic patients were compared with those from 46 early symptomatic and 35 late phase symptomatic carotid stenosis patients, 23 of whom had undergone carotid intervention. VWF:Ag II levels were higher in early (12.8 μg/ml; P < 0.001), late (10.6 μg/ml; P = 0.01) and late post-intervention (10.6 μg/ml; P = 0.038) symptomatic patients than asymptomatic patients (8.9 μg/ml). VWF:Ag levels decreased in symptomatic patients followed up from the early to late phase after symptom onset (P = 0.048). Early symptomatic MES-negative patients had higher VWF: Ag II levels (13.3 vs. 9.0 μg/ml; P < 0.001) than asymptomatic MES-negative patients.

CONCLUSIONS

Endothelial activation is enhanced in symptomatic versus asymptomatic carotid stenosis patients, in early symptomatic versus asymptomatic MES-negative patients, and decreases over time in symptomatic patients. VWF:Ag II levels are a more sensitive marker of endothelial activation than VWF:Ag levels in carotid stenosis. The potential value of endothelial biomarkers and concurrent cerebral MES detection at predicting stroke risk in carotid stenosis warrants further study.

Increased platelet activation in early symptomatic vs. asymptomatic carotid stenosis and relationship with microembolic status: results from the Platelets and Carotid Stenosis Study

BACKGROUND

Cerebral microembolic signals (MES) may predict increased stroke risk in carotid stenosis. However, the relationship between platelet counts or platelet activation status and MES in symptomatic vs. asymptomatic carotid stenosis has not been comprehensively assessed.

SETTING

University teaching hospitals.

METHODS

This prospective, pilot observational study assessed platelet counts and platelet activation status, and the relationship between platelet activation and MES in asymptomatic vs. early (≤ 4 weeks after TIA/stroke) and late phase (≥ 3 months) symptomatic moderate or severe (≥ 50%) carotid stenosis patients. Full blood count measurements were performed, and whole blood flow cytometry was used to quantify platelet surface activation marker expression (CD62P and CD63) and circulating leucocyte-platelet complexes. Bilateral simultaneous transcranial Doppler ultrasound monitoring of the middle cerebral arteries was performed for 1 h to classify patients as MES positive or MES negative.

RESULTS

Data from 31 asymptomatic patients were compared with 46 symptomatic patients in the early phase, and 35 of these patients were followed up to the late phase after symptom onset. The median platelet count (211 vs. 200 × 10(9)  L(-1) ; P = 0.03) and the median percentage of lymphocyte-platelet complexes was higher in early symptomatic than asymptomatic patients (2.8 vs. 2.4%; P = 0.001). The percentage of lymphocyte-platelet complexes was higher in early symptomatic than in asymptomatic patients with ≥ 70% carotid stenosis (P = 0.0005) and symptomatic patients recruited within 7 days of symptom onset (P = 0.028). Complete TCD data were available in 25 asymptomatic, 31 early phase symptomatic and 27 late phase symptomatic patients. Twelve per cent of asymptomatic vs. 32% of early phase symptomatic (P = 0.02) and 19% of late phase symptomatic patients (P = 0.2) were MES positive. Early symptomatic MES-negative patients had a higher percentage of lymphocyte-platelet complexes than asymptomatic MES-negative patients (2.8 vs. 2.3%; P = 0.0085).

DISCUSSION

Recently, symptomatic carotid stenosis patients have had higher platelet counts (potentially reflecting increased platelet production, mobilization or reduced clearance) and platelet activation status than asymptomatic patients. MES were more frequently detected in early symptomatic than asymptomatic patients, but the differences between late symptomatic and asymptomatic groups were not significant. Increased lymphocyte-platelet complex formation in recently symptomatic vs. asymptomatic MES-negative patients indicates enhanced platelet activation in this early symptomatic subgroup. Platelet biomarkers, in combination with TCD, have the potential to aid risk-stratification in asymptomatic and symptomatic carotid stenosis patients.

Longitudinal assessment of thrombin generation potential in response to alteration of antiplatelet therapy after TIA or ischaemic stroke

The impact of changing antiplatelet therapy on thrombin generation potential in patients with ischaemic cerebrovascular disease (CVD) is unclear. We assessed patients within 4 weeks of TIA or ischaemic stroke (baseline), and then 14 days (14d) and >90 days (90d) after altering antiplatelet therapy. Thrombin generation was assessed in platelet poor plasma. Ninety-one patients were recruited. Twenty-four were initially assessed on no antiplatelet therapy, and then after 14d (N = 23) and 90d (N = 8) on aspirin monotherapy; 52 were assessed on aspirin monotherapy, and after 14 and 90 days on aspirin and dipyridamole combination therapy; 21 patients were assessed on aspirin and after 14 days (N = 21) and 90 days (N = 19) on clopidogrel. Peak thrombin generation and endogenous thrombin potential were reduced at 14 and 90 days (p ≤ 0.04) in the overall cohort. We assessed the impact of individual antiplatelet regimens on thrombin generation parameters to investigate the cause of this effect. Lag time and time-to-peak thrombin generation were unchanged at 14 days, but reduced 90 days after commencing aspirin (p ≤ 0.009). Lag time, peak thrombin generation and endogenous thrombin potential were reduced at both 14 and 90 days after adding dipyridamole to aspirin (p ≤ 0.01). Lag time was reduced 14 days after changing from aspirin to clopidogrel (p = 0.045), but this effect was not maintained at 90 days (p = 0.2). This pilot study did not show any consistent effects of commencing aspirin, or of changing from aspirin to clopidogrel on thrombin generation potential during follow-up. The addition of dipyridamole to aspirin led to a persistent reduction in peak and total thrombin generation ex vivo, and illustrates the diverse, potentially beneficial, newly recognised 'anti-coagulant' effects of dipyridamole in ischaemic CVD.

The cost utility of a multi-disciplinary foot protection clinic (MDFPC) in an Irish hospital setting

BACKGROUND

Foot ulceration which may result in lower limb amputation is one of the most feared complications among patients with diabetes and the prevention of both ulceration and amputation is a major challenge facing the health service. Many studies have proposed dedicated diabetic foot teams as the future of diabetic foot care.

AIMS

We aimed to quantify the cost benefit and sustainability of a multi-disciplinary foot protection clinic (MDFPC) in an Irish university hospital setting.

METHODS

A dedicated bi-weekly consultant-led MDFPC including Vascular Surgery, Endocrinology, Orthopaedic Surgery, Podiatry, Orthotics and Tissue Viability was established in June 2008.

RESULTS

Between 2006 and 2010, a total of 221 lower limb procedures (major/minor amputations and debridement) were performed. The number of major amputations decreased from 12 during the control period (2 years before the clinic) to 7 in the study period (2 years after the clinic). After costing all activity associated with the clinic, there was an overall saving of €114,063 per year associated with the introduction of the MDFPC.

CONCLUSION

This is the first study in an Irish context, and one of few international studies, to demonstrate that an aggressive-coordinated approach to diabetic foot care is both cost effective and clinically efficient in reducing the burden of foot-related complications in a diabetic population.

Changing trends in surgical treatment of carotid disease in Ireland (1996-2003)

BACKGROUND

Carotid endarterectomy (CEA) is a well-established method of stroke prevention in patients with symptomatic, high-grade internal carotid artery stenosis.

AIMS

To assess the change in carotid surgery practice in health board regions in Ireland over two different time periods in the past 11 years (1996-1998/2001-2003).

METHODS

Numbers of discharges of patients with a procedure code CEA (38.12) between 1996-1998 and 2001-2003 were obtained from the Hospital In-Patient Enquiry (HIPE) database maintained by the Economic and Social Research Institute (ESRI). Population data was obtained from national censuses.

RESULTS

There has been considerable change in the level of carotid surgery activity in specific health board regions between the two periods.

CONCLUSIONS

Still no region comes close to achieving levels of CEA recommended by population studies. This is important in the context of the MRC asymptomatic carotid surgery trial (ACST), as the numbers suitable for CEA will probably increase further in the future.

Topical local anaesthetic (tetracaine) reduces pain from botulinum toxin injections for axillary hyperhidrosis

A helpful tip

Anatomical variation at the saphenofemoral junction

Background

This study was designed to document the surgical anatomy of the saphenofemoral junction (SFJ).

Methods

The anatomy of the SFJ was recorded diagrammatically in 2089 consecutive groin dissections performed to treat primary varicose veins. The number of primary tributaries, bifid systems, junctional tributaries and the relationship of the external pudendal artery (EPA) to the long saphenous vein (LSV) were recorded.

Results

The LSV was bifid in 18·1 per cent of legs. The number of tributaries at the SFJ varied from one to ten. In 33·4 per cent one or more (junctional) tributaries joined the LSV or common femoral vein deep to the deep fascia. The EPA crossed anterior to 16·8 per cent of LSVs. In 4·6 per cent it passed posterior to one large tributary or trunk of a bifid LSV and anterior to the second trunk, making identification of the second trunk particularly difficult.

Conclusion

A thorough understanding of the anatomical variations of the SFJ is important in ensuring that the junction is managed safely and adequately in patients with varicose veins. Failure to appreciate these variations may account for a significant proportion of inadequate primary varicose vein surgery.

Current treatments for axillary hyperhidrosis

Primary hyperhidrosis affects up to 1% of the population and has a significant negative impact on quality of life. It affects the axillae in approximately 80% of cases. Hyperhidrosis results from excessive sympathetic stimulation of the eccrine sweat glands: the various treatment modalities available target points along the pathway between the central nervous system and the peripheral gland. The first line of treatment is topical aluminium chloride, which is effective in the majority of cases. Alternative treatments such as systemic anti-cholinergics and iontophoresis have significant disadvantages, while surgical sympathectomy has been regarded as the gold-standard in treatment of this condition. Recently, attention has focused on the use of intradermal botulinum toxin for the treatment of axillary hyperhidrosis. This is a highly effective, minimally-invasive treatment with few side effects, and is now recommended as the treatment of choice in isolated axillary hyperhidrosis

Staged resection or primary anastomosis for obstructing lesions to the left colon

The management of obstructing left-sided colonic and rectal lesions has traditionally been by a staged procedure. The introduction of 'on-table lavage', has made primary resection and anastomosis of the large bowel feasible for patients presenting as emergencies. We have studied the perioperative course of 28 patients who presented with left colonic obstruction to determine whether primary anastomosis conferred additional morbidity. The patients ranged in age from 29 to 89 years (mean 66 years) at presentation. The ASA status of patients was comparable in both groups (Table 1). Fourteen patients underwent resection, on-table lavage, and primary anastomosis (PA) and 14 a Hartmann's procedure (HP). The mean operative time for the PA procedure was 200 minutes compared to 110 minutes for the HP group. There was no significant difference in the postoperative complication rate nor mean hospital stay rate for the primary procedures between the two groups. There was no clinical anastomotic leak in patients undergoing primary anastomosis. However secondary surgery for patients undergoing colorectal reconnection conferred added morbidity for patients who had a HP. We conclude that resection, on-table lavage, and primary anastomosis is safe in the management of left-sided colonic obstruction and in most cases is the treatment of choice.

Endothelium derived relaxing factor is absent in experimental in situ vein grafts

Endothelium derived relaxing factor (EDRF) is a local modulator of vasomotor tone in most blood vessels. Reversed vein grafts in several animal models do not produce EDRF when stimulated, and have been shown to have altered responses to several vasoconstrictors. The preservation of EDRF production and vasomotor function in in situ vein grafts was examined in this study. In situ vein grafts of the right carotid artery were performed in five mongrel dogs using external jugular vein. The contralateral jugular vein was used as a control. The vessels were harvested after 6 weeks and rings from the central portion of each vessel studied in vitro in an organ bath. Following cumulative dose response curves to noradrenaline, the rings were precontracted with the estimated ED50 (50% effective dose) dose of noradrenaline, and cumulative doses of acetylcholine added to induce EDRF release. The vein grafts were hypersensitive to noradrenaline, the ED50 being reduced from 8.7 +/- 2.7 x 10(-7) M in the jugular veins to 1.7 +/- 0.7 x 10(-7) M in the vein grafts (p < 0.05). All of the jugular vein segments relaxed in response to acetylcholine with a mean maximal relaxation of 42 +/- 6% of precontraction. None of the vein graft segments relaxed in response to acetylcholine despite the presence of an intact endothelium on scanning electron microscopy, but did relax in response to calcium ionophore. The results indicate that in situ vein grafts, like reversed grafts, fail to produce EDRF in response to acetylcholine. The grafts are also hypersensitive to noradrenaline.(ABSTRACT TRUNCATED AT 250 WORDS)

Colorectal carcinoma over 30 years at one hospital: no evidence for a shift to the right

Many recent reports in the North American literature have documented an increase in the ratio of proximal to distal colorectal cancers with an increase in right-sided lesions. In order to assess trends in the distribution of large bowel carcinoma at our hospital we reviewed the files of 1553 patients who presented with primary colorectal carcinoma over a 30-year period. Thirty-nine percent of patients were over 70 years old and 51% were in the 50-69 year age group. Seventy five percent of the carcinomas were left-sided, 22% right-sided and caecal carcinomas accounted for 18%. This distribution varied only slightly over the study period. Left-sided lesions were more common in males (55%: p less than 0.005), and right-sided lesions were more common in females (57%: p less than 0.005). Caecal carcinoma was more common in patients over 69 years old than in younger patients (p less than 0.001). In elderly females (greater than 69 years) 30% of colorectal carcinomas occurred in the caecum. These findings may have important implications for the investigation of patients with suspected colorectal disease or for screening programmes.

Infrainguinal polytetrafluoroethylene grafts: saved limbs or wasted effort? A report on ten years' experience

Two-hundred and twenty-four infrainguinal polytetrafluoroethylene reconstructions were performed for critical ischemia over a 10 year period: 48 to the above-knee popliteal artery, 113 to the below-knee popliteal artery, and 63 to the tibial vessels. The cumulative patency rates were 84 +/- 6% and 63 +/- 9% for above-knee popliteal, 53 +/- 5% and 35 +/- 7% for below-knee popliteal, 45 +/- 6% and 30 +/- 9% for tibial vessels at one and five years respectively. Limb salvage rates were 81 +/- 6% and 73 +/- 9% (above-knee popliteal), 69 +/- 5% and 57 +/- 9% (below-knee popliteal), 64 +/- 7% and 32 +/- 10% (tibial vessels) at one and five years respectively. Graft occlusion did not result in limb loss in 32 cases. Preoperatively, 54% of the patients had limited mobility while 43% were regarded as severely restricted. At follow-up, 57% of the patients were considered to be independent, 26% had limited mobility, and 17% were still severely restricted. Polytetrafluoroethylene provides good short-term limb salvage and improved mobility in patients with critical ischemia and poor life expectancy. Its use is well worth the effort.

Histologic characteristics of carotid artery plaque

Carotid plaque characteristics associated with the production of symptoms were identified with quantification of carotid plaque constituents in high-grade stenotic asymptomatic (n = 8) and symptomatic (n = 44) plaques. Asymptomatic plaques contained significantly more fibrous/collagen material (88%) than symptomatic plaques (66%) (p less than 0.05). Hemorrhage constituted 2% and 1% of asymptomatic and symptomatic plaques, respectively. The predominant nonfibrous material was a pink amorphous material mixed with cholesterol, which composed 7% of asymptomatic and 27% of symptomatic plaques (p less than 0.05). No relationship was found between plaque composition and the number of ipsilateral ischemic neurologic events, nor was there evidence of a healing process. B-mode ultrasound scanning had a sensitivity of 94% in identifying plaque with greater than 80% fibrous content. We believe that plaque composition may be a useful discriminating factor in selecting asymptomatic patients for carotid endarterectomy.

Home parenteral nutrition using a totally implanted subcutaneous venous access device

Despite advances in the design and care of in-dwelling catheters, sepsis remains a significant problem in patients on long-term parenteral nutrition. In recent years there have been a number of reports concerning the successful use of totally implanted subcutaneous venous access devices in the management of patients requiring long-term intermittent intravenous administration of cytotoxic therapy and frequent blood sampling. The use of such a system for the administration of supplementary home parenteral nutrition in a patient with short-bowel syndrome is reported.

A new technique for bilateral iliac vein and inferior vena cava reconstruction using reinforced polytetrafluoroethylene

We report on the management of a patient with intractable venous claudication and ulceration due to bilateral iliac vein and inferior vena cava occlusion. An inverted V graft was constructed from two 8 mm diameter reinforced PTFE grafts. The upper end was anastomosed to the inferior infrarenal vena cava and the lower ends anastomosed to the common femoral veins. Bilateral arteriovenous fistulas were fashioned. Nine months later the graft is patent and the patient's only symptom is mild ankle edema. The theoretical advantage of this type of graft is that occlusion of one limb will not compromise the other, thus leaving a number of secondary options open if this should happen.

"Haemorrhagic" carotid plaque does not contain haemorrhage

The presence of haemorrhage in carotid bifurcation atheromatous plaques is widely believed to be associated with the production of ischaemic neurological events. This study set out to characterise plaque composition in symptomatic (SYM) and asymptomatic (ASYM) patients and to identify, if possible, the origin of intra-plaque haemorrhage. Fifty-nine plaques (50 SYM and 9 ASYM) were serially sectioned and examined for haemorrhage, haemosiderin, fibrin, cholesterol and collagen. Immunoperoxidase and electron microscopy studies were carried out on sections from five plaques in order to identify blood breakdown products. Intra-plaque haemorrhage was identified in 40 (68%) plaques and was similar in SYM and ASYM plaques. In only one did it constitute more than 15% of plaque content, and in the remainder it consisted of small collections of erythrocytes constituting greater than 1% of plaque content in only 21 (35%) plaques. The predominant non-fibrous component was a pink amorphous material mixed with cholesterol. Apart from traces of platelet breakdown products there was no evidence of haemorrhage in this pink material. Plaque roof rupture or ulceration was seen in 39 (66%) and in almost all cases overlay the amorphous/cholesterol material. Blood vessels were identified in 51 87%) plaques but were in close proximity to haemorrhage in only nine (15%).

The use of infrared laser therapy in the treatment of venous ulceration

Management of intractable venous ulceration remains an unrewarding task which is increasingly delegated to the realm of the vascular surgeon. The purpose of this pilot study was to assess the ulcer-healing effects of the newest form of biostimulation--the low power laser. Twelve patients with chronic venous ulcers unresponsive to conservative measures were treated with infrared laser irradiation for twelve weeks. Two ulcers healed completely and there was a 27% (p less than 0.01) reduction in size of the remaining ulcers. Treatment resulted in a 44% (p less than 0.01) increase in ulcer floor area occupied by healthy granulation tissue. The most dramatic effect of laser treatment was the reduction in ulcer pain, from 7.5 to 3.5 (linear analogue scale) (p less than 0.001). Laser irradiation had no effect on TcPO2, number of skin capillaries or pericapillary fibrin deposition in the lipodermatosclerotic area around the ulcer. The results of this pilot study are encouraging and a carefully controlled randomized study is indicated to compare low power laser irradiation to conventional treatment in the management of venous ulcers.

Duplex ultrasonography and selection of patients for carotid endarterectomy: plaque morphology or luminal narrowing?

Percentage of carotid stenosis and plaque morphology as determined by duplex scanning were correlated with symptoms and CT evidence of infarction in 108 patients. Severity of carotid stenosis less than 49% or greater than 50% narrowing was not associated with an increased risk of ipsilateral symptoms or CT infarction. However, a heterogeneous plaque appearance, suggesting intraplaque hemorrhage, did correlate with ipsilateral cerebral symptoms. Heterogeneous plaque appearance may be a more reliable indication for carotid endarterectomy than a hemodynamically significant stenosis.

Contractility of human gallbladder muscle in vitro

This study examined the effects of transmural nerve stimulation, acetylcholine, adrenoceptor agonists and several peptides on the contractility of strips of human gallbladder in vitro. Acetylcholine caused concentration-related contractions of the tissues and the sensitivity to acetylcholine was similar in gallbladders with mild and severe chronic cholecystitis. Noradrenaline and adrenaline relaxed gallbladder strips, probably via beta 2-adrenoceptor stimulation. Transmural nerve stimulation always caused contractions, but in the presence of atropine inhibitory responses were demonstrable and these were antagonized by propranolol. There was no evidence of non-adrenergic inhibitory neural responses. Of the peptides tested, only cholecystokinin octapeptide (CCK-OP), gastrin, pentagastrin, substance P and caerulein caused contractions. Responses to CCK-OP, gastrin and pentagastrin were antagonized by dibutyryl cyclic GMP. Hormones which had no effect upon human gallbladder strips included motilin, secretin, bombesin, neurotensin, glucagon, vasopressin, VIP and somatostatin. Considerable differences therefore exist between human tissues and those from experimental animals with respect to the direct actions of neural and hormonal stimuli on gallbladder contractility.

Effects of histamine receptor stimulation on diseased gallbladder and cystic duct

The effects of histamine receptor stimulation on the motility of diseased human gallbladder and cystic duct were studied on tissue strips in vitro. Histamine produced concentration-dependent contractions in normal tissues and in tissues from each disease group, but the sensitivity of the strips to histamine as measured by the median effective dose was dependent upon the grade of disease: normal, 90.0 microM; mild chronic cholecystitis, 32.4 microM; advanced chronic cholecystitis, 12.5 microM; and acute cholecystitis, 3.0 microM. There were no differences in histamine sensitivity among different regions (body, neck, and cystic duct) of the biliary system. Studies with receptor-selective agonists and antagonists indicated that the contractile effects were mediated via histamine H1 receptors. Histamine H2 receptor agonists caused only small relaxant responses in about 30% of strips from gallbladder body, but were without effect in gallbladder neck and cystic duct. We conclude that the effects of histamine on the motility of diseased human gallbladder may depend upon the severity of the cholecystitis.

The effects of vasoactive intestinal polypeptide on the motility of human and guinea pig gallbladder

The effects of several preparations of vasoactive intestinal polypeptide (VIP) on the motility of strips of human and guinea pig gallbladder were investigated in vitro. VIP (10(-12) to 10(-6) M) had no measurable effects on the spontaneous activity, resting tone or cholecystokinin-octapeptide induced tone of human gallbladder strips. However, VIP (10(-12) to 10(-6) M) caused biphasic effects on the tone of guinea pig gallbladder strips. At low concentrations (10(-12) to 10(-10) M) contractions were observed that became smaller at higher concentrations (10(-9) to 10(-8) M). At still higher concentrations (10(-7) to 10(-6) M) relaxations were elicited. It appears that VIP is not as potent a relaxant of gallbladder muscle as first described. Human gallbladder tissue was totally unresponsive to the VIP preparations tested.