James McCaslin

Lower-limb revascularization and major amputation rates in England†

The aim was to establish national data for lower‐limb revascularization and major amputation procedures performed in England.

Oral antiplatelet agents and bleeding risk in relation to major cardiovascular surgery.

INTRODUCTION Patients requiring major cardiovascular surgery are likely to be prescribed antiplatelet agents either alone or in combination. By virtue of antiplatelet agent effect, they can potentially increase bleeding complications, especially if used in combination. This article aims to review the evidence and make appropriate recommendations regarding these agents. ASPIRIN 16 papers are reviewed which concern surgery whilst taking aspirin. The bulk of the evidence is from the coronary bypass setting. CLOPIDOGREL: 14 papers are reviewed which concern surgery whilst taking clopidogrel. DIPYRIDAMOLE 2 papers are reviewed concerning dipyridamole. CILOSTAZOL: No trials are available concerning surgery and cilostazol. Several relevant publications are reviewed. CONCLUSION It is the recommendation of the authors that aspirin should usually be continued perioperatively, whilst clopidogrel should be stopped for seven days prior to surgery if at all possible.

Duplex ultrasound for the diagnosis of symptomatic deep vein thrombosis in the lower limb

This is the protocol for a review and there is no abstract. The objectives are as follows: To estimate the sensitivity and specificity of duplex ultrasound for the detection of distal and proximal DVT in symptomatic patients with prior testing by a clinical prediction rule (with or without additional D-dimer testing). The accuracy of ultrasound for DVT may be affected by body mass index and whether the patient has had a previous DVT. If possible, we shall investigate both previous DVT and body mass index as possible sources of heterogeneity, but recognise that these are patient-specific rather than study-specific characteristics. This means that results reported at the study level, for example average body mass index, may not be informative in an analysis and are more appropriately investigated with individual patient data. However, such an analysis may be possible if studies report results stratified by previous DVT status or body mass index. Two study-specific characteristics we shall investigate are the generation of the technology of the ultrasound scanner and type of reference standard: ascending venography, CT venography, or MR venography. Moreover, as the accuracy of duplex ultrasound depends on whether the DVT is distal or proximal, we shall perform separate meta-analyses according to site.

Design of a Pulsatile Fresh Frozen Human Cadaver Circulation Model for Endovascular Training

BACKGROUND The objective of this project was to create a model capable of training endovascular skills using a freshly frozen human cadaver (HC). We present the results of our experience creating a cadaveric model for endovascular skills training. We undertook a unique cadaver laboratory-based research project. METHODS We favor a minimally invasive surgical technique with inflow into the right common carotid artery and outflow through the left common femoral and right superficial femoral arteries. Endovascular access was through the right common femoral artery. RESULTS Through this technique, the arch, thoracic, abdominal, and iliac vessels are all accessible. We perfuse the model through an open pulsatile flow circuit at varying rates to maximize angiographic image capture while minimizing cadaveric edema thus expanding the models longevity. CONCLUSIONS A fresh frozen pulsatile human cadaver training model is a feasible and credible training model that has exciting potential for endovascular skills training.

Increased Platelet-monocyte Aggregation in Male Claudicants with the PlA1/A2 Polymorphism of Gp IIb/IIIa

OBJECTIVES To investigate the relationship between the Pl(A1/A2) polymorphism and platelet activation and aggregation in patients with Peripheral Arterial Disease (PAD). DESIGN A prospective single-centre cohort study. METHODS 45 patients with PAD on aspirin 75mg were recruited and phenotyped/genotyped for the Gp IIb/IIIa Pl(A1/A2) polymorphism. Platelet-Monocyte Aggregation (PMAs) was evaluated using flow-cytometry. RESULTS The formation of PMAs in the Pl(A2) group was higher but not statistically significant (p=0.17). However, when males were analysed separately, the formation of PMAs was significantly higher in the Pl(A2) group (p=0.0192). No difference was seen in the females. CONCLUSIONS In this study we show that the Pl(A1/A2) polymorphism primarily affects the aggregation of platelets to monocytes in males. The effect is not observed in females and understanding the mechanism behind this may help elucidate the way the polymorphism alters platelet function in the presence of aspirin.

Physician-Modified Fenestrated Endografts for Managing the Ruptured or Symptomatic Aortic Aneurysm: Technique Overview and Clinical Outcomes

Purpose: Fenestrated endovascular aneurysm repair (FEVAR) grafts have a 10- to 12-week manufacturing time and are generally not available for emergency cases of symptomatic or ruptured aortic aneurysm. In the absence of other alternatives, conventional off-the-shelf stent grafts can be modified by trained operators to treat these complex cases. The aim of this study is to present a single-center experience of physician-modified FEVAR. Methods: A retrospective review was performed of all physician-modified FEVAR identified from the hospital endovascular database at a single tertiary referral center between September 1996 and September 2017. Results: Eight cases of urgent or emergency endovascular aneurysm repair (EVAR) with physician-modified grafts were identified. Mean follow-up was 44 weeks (range: 5-106 weeks). Outcomes for all implanted grafts (7/8 cases) included 100% technical success, 14% rate of endoleak, no procedure-related complications, no adverse visceral events, 0% 30-day mortality and 100% 1-year target vessel patency, and freedom from aneurysm-related death. There was a 14% (1/7 cases) per patient reintervention rate. Conclusion: Modifying EVAR grafts is a highly technical process requiring meticulous planning and extensive elective experience with FEVAR. The current series demonstrates that physician modification of endografts for urgent or emergency abdominal aortic aneurysm repair is feasible and a safe alternative to open surgical aneurysm repair.

Validation of a flow cytometric technique to identify the HPA-1 polymorphism of platelet receptor Gp IIB/IIIA

We have previously used high resolution scanning laser Doppler imaging [LDI] to quantify spatial and temporal changes in vascular perfusion following dermal provocation with vasoactive mediators [Clough et al., B J Dermatol 1998;138:806-814]. We used the LDI in repeat mode with scans of 30 sec duration and ?4000 pixel density, giving a spatial resolution of ?0.6 mm² per pixel over an area of 5 x 5 cm². Peak responses were seen within 2-3 min of agonist administration. These studies also reveal heterogeneity of perfusion response that was suggestive of selective recruitment of vessels in relation to the underlying dermal vasculature architecture. We have now explored this further using FLPI: this imaging technique was used at frame rates between 5 Hz and 0.2 Hz and spatial resolutions between 0.017 and 0.52 mm² per pixel over areas of 2 x 2.7 cm² and 6.7 x 9 cm², respectively. Preliminary results suggest that the rate of the linear phase of the increase in blood flux adjacent to the site of provocation is of the order of 1.8 PU [laser Doppler perfusion units]/sec. At more distant sites [17 mm] blood flux appears to rise more slowly [0.6 PU/sec at] with a latency of between 20 – 40 sec. Peak responses were seen within 3 minutes of provocation. The propagation of the dilatation response away from the site of provocation was of the order of 0.5 mm/sec. The FLPI imager is now being used to explore further the development of the vasodilator response in healthy skin in order to study both normal physiological mechanisms and the mechanisms underlying pathological skin disorders in which the microvasculature plays a predominant role.We have used laser Doppler fluximetry [LDF] and signal processing to investigate the effects of smoking on microvascular function. Skin blood flux was measured using a pin-head probe [Moor Instruments, UK] mounted in a 1 cm heating block before and during mild thermal warming to 43 °C, in 8 heavy smokers [mean 50 y;19 cigarettes/day,30 pack years], 20 light smokers [23 y;11/day,4 pack years] and their age, sex and BMI matched non-smoking controls. Basal LDF analysed in the time domain was similar in all 4 groups[10–15 AU]. The increase in blood flux during the initial 10 min heating was attenuated in both light and heavy smokers vs controls [P<0.005]. Total hyperaemic response [AUC to 10 min] was also significantly attenuated in the heavy smokers [4 ± 2 vs 6 ± 2 x104 AU·sec] but not in the light smokers [8 ± 2 vs 10 ± 4]. The LDF trace was analysed in the frequency domain using a fast Fourier transform and total spectral power together with the contribution of the frequency intervals between 0.01 and 2 Hz, calculated. Attenuation of the hyperaemic response in the heavy smokers was associated with a reduction in total spectral power of >40%, attributable to a reduction in spectral power around 0.01 Hz and 0.1 Hz [P<0.05]. These data suggest that the attenuation of the sustained hyperaemic response to thermal warming in long-term smokers is associated with a reduction in vasomotion and that this is in part the result of a reduced endothelial and smooth muscle cell activity. These changes are also evident in younger smokers with a shorter smoking history, suggesting that the vasodilatory response is impaired even at this early stage.

Paget–Schroetter syndrome: a call for research and education

Primary upper limb deep vein thrombosis (DVT) or Paget –Schroetter Syndrome (PSS) was initially described separately by Sir James Paget (in 1875) and Von Schroetter (in 1884). It is an uncommon cause of DVT, but should be suspected in the setting of an acute onset of symptomatic upper limb swelling, often following repetitive or sustained abduction and external rotation of the arm, sometimes termed ‘effort thrombosis’. In PSS, the use of the terms ‘primary’ or ‘idiopathic’ no longer seem appropriate, as there is growing evidence that in most cases the aetiology is due to compression and chronic damage to the subclavian vein within a narrow thoracic outlet. Generally, patients are young and otherwise healthy, and thrombosis more frequently affects the dominant arm. The key point is that, if treated conservatively, a significant number of patients will be left with long-term disability (33–85% of cases), with arm swelling, pain and early exercise fatigue, resulting in reduced quality of life and reduced ability to carry out social and work-related activities. Because of this, there has been an increasing trend towards recommending interventional management – usually with a combination of acute thrombolysis and delayed thoracic outlet decompression. Conservative management with anticoagulation is less popular, with only 17% of members of the Vascular Society of Great Britain and Ireland electing for this method in a recent survey. Unfortunately, the treatment of PSS has never been subjected to randomized controlled trials. This causes difficulties when trying to produce evidence-based algorithms for care or in medicolegal situations. There is good (but not randomized) data that thrombolytic therapy is a safe and efficacious method of establishing immediate patency of the axillary/subclavian vein with low associated morbidity. However, without treatment of the point of compression at the thoracic outlet, recurrence is likely to occur. Balloon angioplasty or stenting alone has not been shown to be successful, although it may be useful in cases of residual stenosis following surgical thoracic outlet decompression. The majority of the literature recommends that surgical decompression should follow thrombolysis. With regard to surgical decompression, however, there is little consensus on the details of how this should be achieved and a number of issues remain controversial, including timing of surgery (immediate, early or late) and precise surgical approach (transaxillary first-rib resection, supraclavicular approaches, etc.). Venous thrombosis of the upper extremity is a different entity to lower-limb DVT, and clearly requires different active interventions. However, we suspect that currently many cases of PSS in the UK and elsewhere are treated inappropriately with oral anticoagulation alone. This may in part be due to a failure to educate those responsible for the routine management of patients with DVT to whom these patients initially present. It may also be due to the lack of randomized trial data showing that active treatment is superior. We strongly recommend that all PSS patients should be seen by a vascular specialist with access to thrombolysis and a surgeon able to decompress the thoracic outlet, usually by first-rib resection. To do this, we need to educate our colleagues about the condition and modern approaches to its management. We also desperately need more data from correctly carried out trials in this condition. Because of the relative rarity of PSS, such trials will probably have to be multicentre based.