Vascular diseases

To the Editor: Cullen and colleagues are to be congratulated on their most recent contribution to the assessment of emergency department patients presenting with possible acute coronary syndrome.1 The ability to safely reduce length of stay for a larger proportion of patients compared with the ADAPT study, pending external validation, is promising.1 The timing of the article also presents an invaluable opportunity to remind all clinicians that despite the progressive improvements in accelerated diagnostic pathways for chest pain, not all chest pain is cardiac. Accelerated diagnostic pathways, when used incorrectly, run the risk of introducing cognitive dispositions to respond such as availability bias (where a clinician may choose a diagnosis that is more familiar, such as acute coronary syndrome), omission bias (doing something easy and omitting something hard, such as ordering serial troponins instead of a computed tomography aortogram) and Sutton’s slip (settling on the most obvious interpretation of the problem).2 The potential for error is further compounded by error-producing conditions inherent in busy emergency departments, such as overcrowding, narrow time windows for assessment, surge phenomena and multiple transitions of care (eg, movement to short stay).3 It is pleasing to see that additional features were utilised in stratifying patients compared with previous accelerated diagnostic pathways.1 High-risk features such as prolonged duration and recurrence of chest pain as well as syncope may also be present in aortic dissection.4 It is possible that a patient presenting with an aortic dissection could be deemed low risk with criteria such as those in the ADAPT accelerated diagnostic pathway.5 Troponin levels do not provide a safeguard, as evidenced in a previous case where a 75-year-old woman was discharged home after two normal troponin test results only to die later the same day from progression of a type A aortic dissection.4 Aortic dissection is a lethal cardiovascular emergency that boasts significant morbidity and mortality.4 It has been astutely described as the “subarachnoid haemorrhage of chest pain”.4 Although it is rare and sometimes difficult to diagnose compared with acute coronary syndrome, clinicians are urged to include aortic dissection in their initial assessment of chest pain before implementing an accelerated diagnostic pathway.

Joe-Anthony Rotella

This is the first report of endovascular therapy for acute ischaemic stroke in a patient with atrial fibrillation who was taking the direct thrombin inhibitor dabigatran for stroke prevention. As more of these agents will ...

Andrew W Moey MB BS · Simon A Koblar MB BS, FRACP, PhD · Steve Chryssidis MB BS, RANZCR · Martin Robinson MB BS, FRACP · Jim Jannes MB BS, FRACP, PhD

A 58-year-old woman presented with multiple extensive, necrotic ulcers on the proximal lower limbs (Figure, A and B). A diagnosis of calciphylaxis in the absence of renal impairment was made. Although non-uraemic calciphylaxis has been described previously, the pathogenic mechanisms and significance of documented risk factors are poorly understood. Multiple risk factors were identified in this patient, of which the most prominent is likely to have been severe and longstanding hypoalbuminaemia of unexplained cause. In addition, obesity, European ancestry, female sex, hypovitaminosis D, an elevated alkaline phosphatase level, non-alcoholic steatohepatitis, weight loss and use of steroids were all features of this case that have documented associations with calciphylaxis.

Raffaela Armiento · Ilana Gory · Peter J Jenkins · Catriona A McLean

To the Editor: We read with interest the letter by Baschera et al1 regarding the retrieval of non-permanent inferior vena cava filters (IVCFs) in trauma patients. With the advent of retrievable devices, there has been a renewed interest in the use of prophylactic IVCFs after trauma. Retrievable IVCFs are a particularly attractive option for trauma patients, who are often young, with only a transient predisposition to develop venous thromboembolism (VTE). They theoretically provide prophylaxis against pulmonary embolism (PE) in high-risk patients for whom chemoprophylaxis is contraindicated, while avoiding long-term complications associated with permanent IVCFs. However, we share the authors’ concern about low retrieval rates of IVCFs due to loss of patients to follow-up.2,3 The decision to place an IVCF in a patient who has undergone trauma is based on a risk–benefit ratio. If such decisions are made on the presumption that IVCFs will be retrieved, while in practice many IVCFs are not retrieved, the increasing popularisation of retrievable filters may be under false pretences. At our institution, a level 1 trauma centre, all IVCFs are inserted by interventional radiologists under fluoroscopic guidance. At the time of insertion, patient and device details are entered into a purpose-built IVCF database that is run and maintained by the Department of Radiology. At this time, a follow-up appointment is also booked for the patient to attend the IVCF outpatient clinic run by the interventional radiologists. Here, ongoing VTE risk factors are evaluated and the timing of IVCF retrieval is determined. The timing of IVCF retrieval after trauma is controversial, and the occurrence of PE after retrieval is well documented. The risk period for PE after trauma is difficult to quantify, but likely to extend beyond the discharge date for many patients, especially if ongoing surgery is scheduled. For this reason, our practice is to retrieve IVCFs in the outpatient setting 3–4 months after injury. Prolonged IVCF dwell times must be balanced against the increasing difficulty of retrieval because of IVCF endothelialisation, but we feel that a timeframe of 3–4 months does not compromise retrieval rates. Successful retrieval of filters has been reported up to 317 days after insertion.4 As in the case described by Baschera et al,1 it is not uncommon to find a clot in the filter at the time of attempted retrieval, for which multiple causes have been proposed.5 In this situation, it is our practice to rebook patients for a repeat cavogram and second retrieval attempt after therapeutic anticoagulation for 1–2 months.

Lachlan M Batty · Jim Koukounaras · Stuart M Lyon

To the Editor: The article on home haemodialysis by Agar and colleagues describes a changing pattern of practice that has seen many patients enjoy the freedom of dialysing at night in their home environment.1 One consideration not mentioned is the need for appropriate vascular access. For a patient to engage in self-cannulation, a fistula needs to be created for ease of use. This requires a few imperatives in fistula design to be met. In my practice, an attempt is made to create an autogenous fistula for vascular access whenever possible. It is well documented that an autogenous arteriovenous fistula (AVF) is superior to prosthetic graft or catheter access in terms of access longevity and patient-related complications.2-4 In the past 11 years, I have found it necessary to create a new AVF with prosthetic material in no more than 1% of cases. For some patients, however, a fistula may be positioned where it is accessible to renal nursing staff but not for self-cannulation. This would make nocturnal home dialysis difficult and underpins the importance of surgical access design to facilitate it. For self-cannulating patients, great effort is made to create vascular access in the non-dominant arm, in the forearm rather than the upper arm, and with cephalic rather than basilic vein run-off. The cephalic vein lies on the upper outer aspect of the forearm with the limb in a neutral position, and a needle in it remains fairly secure when a patient is asleep. Guidelines on surgical placement of an AVF from the Society for Vascular Surgery, while not specifically prescriptive for patients wanting to self-cannulate, include the same recommendations.5 Use of a long saphenous vein loop fistula in the forearm, positioned appropriately, also provides ready access for a patient who may otherwise struggle with the dexterity required for venepuncture. A thigh loop is an alternative but less desirable option, as patients with chronic renal disease are likely to have lower-extremity occlusive disease, an increased incidence of groin infection, and a greater likelihood of vascular steal.5 I applaud efforts to facilitate nocturnal home dialysis, and enjoy the challenge of surgically creating vascular access to make this endeavour successful.

David N McClure

Carotid artery stenting has a place in managing symptomatic stenosis, but only sometimes Carotid stenosis remains one of the most readily treatable causes of ischaemic stroke. Its treatment has undergone many changes in recent years, with the advent of endovascular techniques seeming to offer great promise of a much less invasive procedure. In the late 1990s, the Australian Association of Neurologists published guidelines for the use of carotid balloon angioplasty alone (ie, without stenting) as a treatment for carotid stenosis, recommending cautious use in the absence of data from randomised controlled trials (RCTs).1 However, advances in vascular stent technology have resulted in a greatly increased use of carotid artery stenting (stenting), often with specialised filter devices deployed distal to the carotid stenosis to catch embolic debris that may arise from catheter or stent manipulation. Recent evidence from RCTs has cast doubt on the safety of widespread use of stenting for the treatment of patients with symptomatic or asymptomatic carotid stenosis. The overall results from these RCTs indicate that carotid endarterectomy (endarterectomy) is still the preferred treatment option for symptomatic carotid stenosis. The results of three major European studies into the treatment of symptomatic stenosis — Endarterectomy versus Angioplasty in Patients with Symptomatic Severe Carotid Stenosis (EVA-3S); Stent-Protected Angioplasty versus Carotid Endarterectomy (SPACE); International Carotid Stenting Study (ICSS) — showed that stenting was more hazardous than endarterectomy for the outcomes of stroke and death during the periprocedural period (30 days), and on longer-term follow-up.2-4 Perhaps in contrast, the recent North American Carotid Revascularization Endarterectomy vs Stenting Trial (CREST) demonstrated equivalent (non-significant) rates of stroke, myocardial infarction and death in its stenting and endarterectomy groups in the periprocedural period, and at 4 years.5 However, in CREST there was a significantly reduced rate of stroke and death in the endarterectomy group, but this was offset by an increased risk of myocardial infarction, in part due to the definition of myocardial infarction used, and a greater number of study patients with comorbid ischaemic heart disease.5 Use of cerebral protection devices during stenting was mandated in CREST but not in the European studies. The value of these devices is in question, with evidence indicating that they were no more effective in reducing the clinical risk of stroke than unprotected stenting.6,7 Moreover, data from a magnetic resonance imaging substudy undertaken as part of the ICSS indicated that, compared with endarterectomy, there was a threefold increase in silent brain infarctions in stenting with use of cerebral protection devices (adjusted odds ratio, 3.28 [95% CI, 1.5–7.2]).7 A meta-analysis of 11 RCTs (including EVA-3S, SPACE and ICSS, but not CREST) showed that endarterectomy was superior to stenting in short-term but possibly not longer-term outcomes, a difference largely driven by non-disabling stroke.8 The Australasian guidelines9,10 have now been upgraded following additional published data from CREST5 and a meta-analysis of the three large European trials (EVA-3S, SPACE, ICSS)11 indicating that stenting is at least as safe as endarterectomy in patients under 70 years of age, while it presents a greater risk of stroke for those older than 70 years (Box). The RCTs indicate that there is currently no clear evidence to support either endarterectomy or stenting as a treatment for asymptomatic carotid stenosis. Indeed, current medical therapies have reduced the risk of stroke in asymptomatic stenosis to as low as 0.5% per year.12 Ongoing RCTs continue to address this question (eg, the Asymptomatic Carotid Surgery Trial 2, comparing stenting and endarterectomy in the treatment of asymptomatic carotid stenosis).13 Until recently, in Australia and New Zealand, there were no specific published guidelines for carotid artery stenting. To redress this, an intercollegiate working group was formed — the Carotid Stenting Guidelines Committee — comprising expert representatives of the Royal Australasian College of Physicians, the Royal Australasian College of Surgeons, and the Royal Australian and New Zealand College of Radiologists. Consensus for guideline parameters was reached using the modified Delphi consensus method of iterative consultation. The committee’s guidelines recommend clinical selection criteria for carotid artery stenting, as well as cognitive and technical requirements that clinicians should meet before performing stenting.9,10 The guidelines do not deal with training criteria and procedural accreditation as these are determined by the Conjoint Committee for Recognition of Training in Peripheral Endovascular Therapy of the abovementioned colleges. On current evidence, the guidelines recommend that carotid artery stenting may be considered a treatment option in specific, high-risk patients with symptomatic severe stenosis who are considered unsuitable for endarterectomy (Box).10 It is important to note that these are relative contraindications to endarterectomy as there is no evidence to support stenting in these patients (indeed, they are often excluded from clinical trials). Finally, it is important that all patients being considered for a carotid intervention have preprocedural neuroimaging and independent neurological assessment before and after the procedure. This allows for an audit comparison with the results of RCTs where neurological evaluation of all patients is routine, and serves as a benchmark for best clinical practice. In summary, the evidence from RCTs indicates that, at present, a cautious approach should be taken to recommending carotid artery stenting — festina lente (hasten slowly). Stenting should not be performed in most patients with symptomatic severe carotid stenosis, and there is currently no evidence to support stenting as a treatment for asymptomatic carotid stenosis. Stenting warrants consideration in younger patients (< 70 years of age) and those with symptomatic severe carotid stenosis unsuitable for endarterectomy. These standards should apply in all health care settings, public and private. Advances in endovascular technologies, and evidence from future RCTs and meta-analyses, will guide revisions of the guidelines. Carotid Stenting Guidelines Committee: recommended indications and contraindications for carotid artery stenting (CAS)10 Indications Symptomatic carotid disease in the following conditions may be assessed at high surgical risk for carotid endarterectomy (CEA) by an appropriate clinician experienced in the management of carotid stenosis: post-radiation therapy block dissection of the neck in-situ tracheostomy recurrent stenosis following previous CEA severe cervical spine arthritis surgically inaccessible carotid stenosis (eg, obesity, high carotid bifurcation) contralateral recurrent laryngeal nerve injury contralateral internal carotid artery occlusion Symptomatic severe carotid stenosis* in patients under 70 years of age, where carotid revascularisation is considered appropriate Symptomatic or asymptomatic carotid stenosis where carotid revascularisation is considered appropriate, and the patient is randomised to CAS in a clinical trial Contraindications Absolute Carotid stenosis in a patient with significant contraindications to angiography Carotid stenosis with angiographically visible intraluminal thrombus Carotid occlusion Relative Carotid stenosis associated with an intracranial vascular malformation Contraindications related to vascular anatomy and atherosclerosis (eg, type 2–3 arch; bovine arch; severe aortic arch or ipsilateral common carotid atherosclerosis; severe proximal common carotid artery tortuosity; severe distal internal carotid artery tortuosity (possibly compromising embolic protection devices); sharply angulated internal carotid artery; carotid string sign; circumferential calcification of carotid plaque; loose thrombus associated with carotid plaque) * Severe carotoid stenosis is defined as ≥ 70% using North American Symptomatic Cartoid Endarterectomy Trial criteria.5

on behalf of the Carotid Stenting Guidelines Committee (Australia and New Zealand)

The take-home message is not only early intervention but education and teamwork I was due to fly out to the United States the next morning. I was bending down to clean the floor of my car when it happened. First my right hand wouldn’t respond and I fumbled picking up a spoon from the floor, then my right leg wouldn’t support my weight. I tried to call out to my wife but only grunts came out, except of course the f-word when I knew what had happened. I crawled to the front door of the house, my intensivist wife called 000 and the ambulance was there in 3 minutes! The paramedics ignored my pleas to go to the closer private hospital ... “no you’re off to the Stroke Unit at The Alfred” ... and wasted no time — scoop and run. I was in the resuscitation bay of the emergency department (ED) in 20 minutes and, despite it being late on a Friday night, I was assessed, I had my computed tomography (CT) scan to exclude an intracranial haemorrhage, and the intravenous thrombolytic therapy was running within 60 minutes. The next day a repeat CT scan and a magnetic resonance imaging scan confirmed multiple small infarcts in the insula consistent with an embolic stroke. A patent foramen ovale (PFO) showed up on the transoesophageal echocardiogram on Day 3 and the PFO was occluded, percutaneously, on Day 7. I was home the next day and back at work 3 weeks later, with no significant residual deficit. Bending over in the car may have been the trigger, with a Valsalva that opened up the PFO and caused the clot to flip up my left middle cerebral artery (MCA) into the insular cortex. It is pleasing when published data justifies one’s own teaching; it is even more encouraging when it justifies treatment that affects one’s own life and health. Every 10 minutes, up to 20 million neurones will die in a typical infarct in the MCA territory, if not recanalised.1 A recent updated pooled analysis of eight trials using multivariate logistic regression has been used to assess the relationship of onset-to-treatment time with 3-month morbidity, brain haemorrhage and mortality.2 When selected by symptoms and CT findings, the critical time from onset of symptoms to the intravenous infusion of recombinant tissue plasminogen activator (rt-PA) seems to be 3 hours, though that window of opportunity can be increased to 4.5 hours, after which risk may outweigh benefit. After 4.5 hours, the risk, particularly of reduced recovery of brain function, brain haemorrhage and death, increases. However, not all patients benefit. It was shown that about five patients need to be treated within 0–90 minutes of symptom onset, nine patients within 91–180 minutes or 15 patients within 181–270 minutes for one of them to have an excellent outcome attributed to treatment. Clearly rt-PA is not a panacea, and other interventions need to be analysed for the ultimate objective of reperfusion of 100% of patients rather than 40%. Other modalities need to be investigated, particularly the therapeutic combinations of thrombolytics, neuroprotectives and antithrombotics in addition to ultrasound and endovascular mechanical clot manipulation.1 My experience with swift prehospital assessment and efficient ED intervention with intravenous rt-PA, after sustaining an acute ischaemic stroke, with full recovery, emphasises that time is critical.1 However, the take-home message here is not only early intervention but education and teamwork, similar to the model in trauma care — the “golden hour” and a well trained trauma team.3 For stroke management, this means the development of stroke centres, training of prehospital and emergency staff, prioritisation of patients to achieve door-to-needle times of less than 60 minutes and public education programs on acting early with the onset of symptoms.1,4 For me, it may have been luck: stroking out at home and not in the air; having a medico wife who recognised the signs; a paramedic crew trained to scoop and run and to take me to an ED with a stroke unit, not just passing by the end of my street when they got the call; ED staff who wasted no time; a neurology registrar who started the rt-PA immediately, though pointing out to me and my wife the risks of intracranial haemorrhage; and having a well trained team of health professionals in the Stroke Unit. Some cynics might say I got red carpet treatment because I am a professor of surgery. I disagree. I believe it was not just a stroke of luck but that I benefited from the ideal model of care of stroke management that should be available to all Australians.

Bruce P Waxman FRACS, FACS, MRACMA

Objectives: To assess the prevalence of and risk factors for claudication and its association with subsequent cardiovascular events.Design, setting and participants: Observational cohort study of 12 203 Western Australian men aged 65 years and over, recruited from 1996 to 1999, and followed up from 2001 to 2004.Main outcome measures: Prevalence of claudication and incidence of peripheral arterial disease (PAD); risk factors for claudication and its association with subsequent cardiovascular events.Results: The prevalence of claudication was 5.3% (638 of 11 970 men). At follow-up, after exclusion of 148 men with claudication at baseline and 76 with missing data at follow-up, the crude average annual incidence of new PAD (claudication or procedure for PAD) was 0.85% (95% CI, 0.72%–0.96%). The risk factors for prevalent claudication and incident PAD were similar, with age, smoking, hypertension, diabetes and history of cardiovascular disease dominating. Of the men with claudication at baseline, nearly half (47.5%; 303 of 638) were not taking aspirin. At follow-up, 42.5% (82 of 193) of the men with incident PAD were not taking aspirin. Claudication at baseline was associated with twice the risk of cardiovascular death (hazard ratio, 2.00; 95% CI, 1.52–2.64). There was a J-shaped relationship between aortic diameter, and both prevalent claudication and subsequent cardiovascular events.Conclusions: Among older men, claudication is prevalent and is associated with factors that can still be modified in older age, including smoking, exercise and diet. Relatively few men with claudication or at risk of PAD use aspirin. Claudication is a significant predictor of cardiovascular outcome.

Rahul Lakshmanan MB BS · Zoë Hyde BSc, PGradDipHlthProm, MPH · Konrad Jamrozik MB BS, DPhil · Graeme J Hankey MD, FRACP, FRCP · Paul E Norman BSc(Hons), DS, FRACP

To the Editor: Pregnancy following aorto-iliac bypass or replacement grafting is uncommon, as most patients requiring this operation are beyond childbearing age. However, conditions may occur at earlier ages that necessitate such a procedure and, as the case described here illustrates, the surgery is no bar to pregnancy. In 1982, a 13-year-old girl presented to hospital after two episodes of abdominal pain. Ultrasound examination showed a large dumbbell-shaped retroperitoneal tumour widely separating the aorta and vena cava. Laparotomy revealed a large tumour firmly adherent to the inferior vena cava and completely surrounding the aorta. Biopsy showed it to be a ganglioneuroma. It was possible to separate the tumour from the vena cava but not the aorta, as no plane could be defined, and during the dissection a hole was made in the vessel. The involved aorta was resected and the tumour was able to be completely removed. The removed segment was replaced with a 10 mm woven dacron tube graft (compatible with the host aorta) from the infrarenal level to the aortic bifurcation. Five years later, the aortic graft thrombosed. Exploration showed no evidence of recurrence of the tumour, and the previous graft was replaced with a 14 × 7 mm gelatin-impregnated, knitted dacron bifurcated prosthesis from the infrarenal aorta to each common iliac artery. The patient had regular follow-up, including ultrasound and magnetic resonance imaging scans. In June 2007, after I had retired from vascular surgery, I was contacted by the patient (now aged 39 years), who was seeking information about her previous operations because she was 14 weeks pregnant and her obstetrician was concerned about the uterine blood supply. She had approached the hospital, but was told that her records had been destroyed. Fortunately, I still had my personal records of her previous surgery. The patient had required in-vitro fertilisation for conception because her uterine tubes were blocked. The pregnancy proceeded normally until the 36th week, when signs of eclampsia developed. Caesarian section was performed at 37 weeks and a healthy infant was delivered. A review of the literature revealed six other reported cases of pregnancy occurring in patients who had had previous aortic grafting for aneurysmal or atherosclerotic disease.1-6 Two patients had caesarean section and the others were delivered vaginally; all infants were viable. Possible concerns expressed by clinicians in cases such as this include compromise of the pelvic circulation, affecting foetal development; compression of the graft by the fetal head during delivery; uterine contractions contributing to graft occlusion; reduction of blood flow through the graft because of the patient’s position during labour; and false aneurysm formation at the anastomotic sites, with an increased risk of rupture. With adequate assessment and supervision by obstetric and vascular surgical teams, the outcome of pregnancy in women with a history of aortic grafting should be favourable.

H Reginald Magee

To the Editor: There is generally a high level of awareness about the burden of disease associated with diabetes and its complications in Indigenous Australians.1 While high rates of renal failure, retinopathy and cardiovascular disease in Indigenous people are frequently emphasised, diabetes-related foot complications receive relatively little attention. As part of the Western Australian Department of Health’s Cardiovascular Health Network initiative (http://www.healthnetworks.health.wa.gov.au/network/cardio.cfm), we reviewed the trends in amputations for arterial disease or diabetes-related complications in Western Australia for the period 2000–2008. Discharges from hospital for any lower-limb amputations were identified using the relevant International Classification of Diseases, 10th revision, Australian modification, codes.2 Each individual was included only once, regardless of whether they had a further amputation. Age-standardised rates were calculated for Indigenous and non-Indigenous people residing in Western Australia, with and without diabetes. Toe or foot amputations were defined as “minor”, and amputations below or above the knee as “major”. Among those aged 25–49 years with diabetes, minor amputations were 27 times more likely, and major amputations 38 times more likely, in Indigenous people (Box). These data have not been validated by chart review, but there is no reason to suspect systematic bias. Nearly all (98%) of the amputations in Indigenous people were associated with diabetes. Although it is difficult to estimate the role of macrovascular arterial disease using administrative data, the literature suggests that peripheral neuropathy, ulceration and sepsis are important causal factors in these amputations.3 There is ample evidence that simple interventions such as foot screening, education and appropriate footwear are cost-effective measures to reduce amputations in patients with diabetes.4 Although there are some excellent programs and services for Indigenous people with diabetic foot problems throughout Australia, they are few in number, often fragmented and generally poorly resourced. Multidisciplinary foot clinics — considered international best practice5 — typically remain centred in capital city tertiary hospitals, requiring Indigenous people from rural and remote areas to travel long distances onto someone else’s land, with unfamiliar surroundings and devoid of family support. Although further research is required to better understand the underlying reasons for this disparity in amputation rates, there is a more urgent need to implement culturally appropriate versions of simple interventions among Indigenous people and ensure foot care is a standard component of comprehensive, multidisciplinary diabetes management. Age-standardised amputation rate* (crude number) by age group, 2000–2008 Minor amputations† Major amputations‡ 25–49 years ≥ 50 years 25–49 years ≥ 50 years Indigenous with diabetes 46.4 (93) 185.0 (118) 15.0 (30) 76.8 (49) Non-Indigenous with diabetes 1.7 (108) 28.9 (1408) 0.4 (26) 13.1 (638) Indigenous without diabetes 0.0 (0) 4.7 (3) 1.0 (2) 3.1 (2) Non-Indigenous without diabetes 0.3 (21) 6.5 (317) 0.3 (17) 12.8 (628) * Per 100 000 Indigenous and non-Indigenous people (irrespective of diabetic status) using the 2001 Census as the standard population. † Toe or foot amputations. ‡ Amputations below or above the knee.

Paul E Norman · Deborah E Schoen · Joel M Gurr · Marlene L Kolybaba

Comment on Millar: The application of appropriate prophylaxis for venous thromboembolism (VTE) is recognised as an important patient safety measure. In a systematic review ranking 79 safety interventions, the Agency for Healthcare Research and Quality in the United States found that, based on the strength of overwhelming evidence that thromboprophylaxis reduces adverse patient outcomes and decreases overall costs, the highest-ranked safety practice was the appropriate use of prophylaxis to prevent VTE.1 However, it has been shown that, worldwide, the application of appropriate VTE prophylaxis is underutilised.2 The Australia and New Zealand Working Party on the Management and Prevention of Venous Thromboembolism first convened in 1997. It comprises a group of specialists from medical and surgical disciplines actively involved in VTE management and representing all Australian states and New Zealand. Its objective was to produce a practical, pocket-sized booklet summarising published evidence-based guidelines, drawing on those of the American College of Chest Physicians (ACCP)3 and the International Consensus Statement.4 The Working Party has never attempted to produce a new set of guidelines. The first edition of the Guidelines was published in 1998, with subsequent editions published in 2001, 2006 and 2008. Support from various companies in the medical industry was accepted to allay the cost of bringing Australian and New Zealand representatives to a meeting venue, usually an airport hotel meeting room on a Saturday. Members of the Working Party willingly gave of their time for these meetings, and none received payment. In return for their support and their assistance in distribution of the Guidelines, it was agreed that the companies could place their logo on the back cover of the booklets. It is erroneous to state that “the Guidelines are sponsored by a global pharmaceutical company and are professionally marketed”. The statement that “the current (fourth) edition of the Guidelines acknowledges commercial sponsorship by a ‘non directed’ grant from Sanofi-Aventis, the manufacturer of the LMWH enoxaparin” is incorrect. It is clearly stated in the Guidelines that “The Working Party members wish to acknowledge the support of the medical industry through their provision of non-directed educational grants. The opinions expressed in this booklet are entirely those of the expert clinicians on the Working Party”. The concern expressed in the article that “the Guidelines overstate the need for pharmacological prophylaxis in medical patients, and that patients at low risk of VTE will be exposed unnecessarily to the risk of bleeding complications” is at variance with the recommendation from the latest ACCP guidelines, which advocate low molecular weight heparin (Grade 1A recommendation), low-dose unfractionated heparin (Grade 1A), or fondaparinux (Grade 1A) for acutely ill medical patients admitted to hospital.5 The Working Party advocates that VTE risk assessment should become standard practice for all surgical and medical patients on admission to hospital. From experience since publication of the first edition of the Guidelines, it is anticipated that there will be an ongoing demand for a pocket-sized booklet that summarises current best practice in VTE prevention, and we will endeavour to continue to meet this need.

John P Fletcher

Clinical record A 68-year-old man presented to our general district hospital in December 2006 with the chief complaint of sore throat, which had started abruptly 2 hours earlier. The pain was described as intense with a stabbing character. He reported minimal improvement after being given 10 mg of morphine subcutaneously. The patient did not report experiencing any cardiac or pulmonary discomfort, and he had no pertinent past medical history. His family history included one sister who had died of a ruptured aortic aneurysm. The patient was a non-smoker and denied any recent medication use. Physical examination showed that the patient’s vital signs were stable, with a normal level of consciousness, a regular pulse of 61 beats/min, and a blood pressure equal at both arms of around 115/70 mmHg. He was slightly tachypnoeic and diaphoretic. An ear, nose and throat examination did not provide any diagnostic clues as to the cause of the pharyngeal pain. Findings of a cardiovascular examination were normal apart from an audible right carotid artery bruit. No other physical abnormalities were detected. Results of laboratory tests were unremarkable, except for a markedly elevated d-dimer level (8.41 mg/L; upper limit of normal, 0.50 mg/L). Routine chest radiography was suggestive of mediastinal widening (Figure A). On the basis of these findings, a thoracic computed tomography scan was performed, which showed a 5.4 cm dissecting ascending aortic aneurysm (Figure B). The dissection involved the aortic root, ascending part of the aorta and aortic arch, and propagated into the right brachiocephalic trunk and left common carotid artery (Figure C). Transthoracic echocardiography additionally showed the presence of a bicuspid aortic valve with moderate grade 2/4 aortic insufficiency. Thoracic aortic dissection was diagnosed, classified as a Stanford type A dissection, given the involvement of the ascending aorta. A congenital bicuspid aortic valve and an ascending aortic aneurysm were predisposing factors for aortic dissection. The patient successfully underwent emergency surgery with graft replacement of the aortic valve and the dissected aortic segment. A: Chest x-ray showing mediastinal widening. The upper normal mediastinal width is defined as a mediastinum to chest-width ratio of over 0.25, measured at the level of the aortic arch (illustrated by the length of the solid line); this is noticeably exceeded in our patient (dashed line). B: Computed tomography scan showing an aneurysmatic dilatation of the ascending aorta with a classical dissection flap (black arrowhead) separating a true and false lumen. C: Propagation of the dissection process into the supra-aortic vessels (white arrows). The clinical presentation in our case was rather trivial, but the combined results from two basic investigations — an elevated d-dimer level and an abnormal chest x-ray — heightened our clinical suspicion for aortic dissection and led us to perform aortic imaging. Thoracic aortic dissection generally results from a laceration of the intimal lining of the aorta. This allows blood leakage into the aortic wall resulting in a propagating separation of the aortic media, thereby creating a false blood-filled lumen.1 Hence, the major criterion for definitive diagnosis of aortic dissection includes visualisation of a so-called intimomedial flap that divides the aorta into a true and a false lumen. Several aortic imaging techniques can be used for this purpose, of which contrast-enhanced computed tomography (CT) and transoesophageal echocardiography (TOE) are the most feasible to perform in an emergency department setting.1,2 Moreover, these investigations help to localise the dissection, thereby allowing appropriate classification. Currently, the Stanford classification of aortic dissection is the most widely adopted system.1,2 This system has the virtue of merely dividing aortic dissection into two subtypes, depending on whether the ascending aorta is involved (type A) or not (type B).1,2 While the definitive diagnosis of aortic dissection is usually straightforward, making the initial clinical diagnosis can be extremely challenging. Aortic dissection is associated with a dramatic rate of misdiagnosis and delayed recognition.3 This is no doubt partially explained by the highly variable clinical presentation of the condition. Our case is a striking illustration of why acute aortic dissection is colourfully called a “clinical chameleon”.1 Although most patients with aortic dissection present with severe chest or back pain (Box 1), the pain can be variably localised to the neck, jaw or throat.4 Throat pain occurs most often in cases of a dissection of the aortic arch, particularly when the supra-aortic vessels are involved. Our patient complained only of a sore throat, and denied having thoracic pain. Only two similar cases have been previously reported.5,6 Moreover, findings on physical examination can be very subtle.1 Classical signs consistent with the diagnosis of thoracic aortic dissection, such as an aortic insufficiency murmur or decreased femoral arterial pulsation, were not present in our patient. According to the International Registry of Acute Aortic Dissection,7 these so-called typical findings are infrequently detected during physical examination (Box 1). In our case, the only notable features of the physical examination were diaphoresis and a right carotid artery murmur. The latter was presumably the result of propagation of the dissection into the right brachiocephalic trunk. Because symptoms and signs of aortic dissection can be diverse and sometimes treacherously trivial, the initial diagnostic suspicion might rely on abnormalities observed during the basal diagnostic work-up. This routinely consists of laboratory testing with d-dimer analysis and chest radiography. d-dimer analysis has only recently come to the fore, with several studies focusing on the stringent association between the d-dimer level and aortic dissection.3,8,9 The pathophysiological mechanism for this relationship is well explained by the release of tissue factor from the dissected aortic wall. This sets off a cascade of events — activation of the extrinsic coagulation system, generation of fibrin, and secondary fibrinolysis with d-dimer formation.8 The d-dimer assay is reported to have an excellent sensitivity and negative predictive value for aortic dissection (Box 1). The quoted sensitivity is equal for both types of dissection, although absolute d-dimer values tend to be higher in type A aortic dissections as they are usually more extended.10 Given its high sensitivity and negative predictive value, d-dimer testing is an attractive tool for the diagnostic work-up of aortic dissection, particularly in the setting of a low pretest probability for aortic dissection. In such cases, a normal d-dimer result can reliably exclude the presence of aortic dissection, hence obviating the need for further investigations.9,10 Besides elevation of the d-dimer level, the clinical suspicion for aortic dissection should also be heightened if the chest radiograph is abnormal (Box 1). Mediastinal widening (relative mediastinum to chest-width ratio > 0.25;11 Figure A) is the most common radiographic finding in aortic dissection.7 Of note, absolute estimations of the mediastinal width are practically inaccurate, as these measurements are influenced by the distance between the roentgenographic source and the thorax.12 It is worth mentioning that one in three patients with aortic dissection has a normal chest x-ray.11 Thus, relying on chest radiography alone as the initial diagnostic modality is inefficient as it clearly carries a high risk of misdiagnosis. When readily available, contrast-enhanced CT and TOE are the preferred imaging modalities in an acute care setting. Both investigations have a comparable diagnostic accuracy and allow a definitive diagnosis of aortic dissection to be established.1,2 However, the diagnosis must first be suspected before it can be confirmed — this case serves as a reminder of this life-threatening condition’s wide variability in clinical presentation, and the need to maintain continuing vigilance. 1 Clinical and basic diagnostic features of thoracic aortic dissection, and percentages of patients presenting with these features who are subsequently diagnosed with Stanford type A or B aortic dissection1,2 Stanford classification Features Type A* Type B† Clinical symptoms and signs7 Presence of any pain 94% > 95% Retrosternal pain 71% 44% Interscapular pain 33% 41% Back pain 47% 64% Abdominal pain 22% 43% Blood pressure Hypotension or shock/tamponade < 25% < 5% Hypertension 35% 70% Aortic insufficiency murmur < 45% < 15% Decreased or absent peripheral pulsations < 20% < 10% Laboratory analysis8,9 d-dimer sensitivity (cutoff, 0.50 mg/L) > 95% > 95% d-dimer negative predictive value (cutoff, 0.10 mg/L) 100% Not reported Chest radiography7 Mediastinal widening 63% 56% Abnormal or blurred aortic contour 47% 53% Other radiographic features‡ < 25% < 25% * Dissection with involvement of the ascending aorta. † Dissection of the descending aorta without involvement of the ascending aorta. ‡ Such as displaced aorta, aortic calcification, tracheal displacement, pleural effusion. Lessons from practice Thoracic aortic dissection is characterised by a highly variable clinical picture, which has led to the condition being called a “clinical chameleon”. d-dimer testing can be of value in excluding aortic dissection. A normal chest x-ray does not rule out the possibility of aortic dissection. Advanced aortic imaging should be performed early in patients who have symptoms suggestive of aortic dissection in order to prevent misdiagnosis.

Sébastien Anguille MD · Aurélie M Derweduwen MD · Jeroen Lenz MD · Luc Vanuytsel MD, PhD · Frank J Cools MD

To the Editor: In the 3 November 2008 issue of the Journal, Millar recommends against routine thromboprophylaxis in medical patients.1 The evidence base for clinical decision making regarding thromboprophylaxis in medical patients remains limited. Although its overall benefit may be low, the absolute benefit to the community is significant. As up to 40% of cases of venous thromboembolism (VTE) occur in patients recently hospitalised for medical illness,2-3 there is a significant burden of disease that justifies prophylaxis in patients at high risk of VTE. The challenge is to identify medical patients at greatest risk of VTE, and to provide appropriate pharmacological prophylaxis, but to avoid using prophylaxis in patients at lower risk of VTE. Millar states that aspirin is as effective as heparin, with reference to the Pulmonary Embolism Prevention (PEP) trial.4 However, the PEP trial compared aspirin with placebo, and many participants also received heparin — it did not compare aspirin with heparin. Participants were undergoing surgery for hip fracture, and none were medical patients. A reduction in the endpoint of fatal pulmonary embolus (PE) is difficult to demonstrate in trials where imaging is used to detect disease at an early stage. This prompts treatment of asymptomatic deep vein thrombosis and modifies the natural history, leading to low reported PE rates. Rather than recommend for or against routine thromboprophylaxis in medical patients, we advise that patients should have a VTE risk assessment and that appropriate prophylaxis should be given according to evidence-based guidelines such as those of the American College of Chest Physicians5 and the International Consensus Statement6 (which we have attempted to summarise and condense into a practical, pocket-sized booklet7).

John P Fletcher · Donald MacLellan · Harry Gibbs · Geoff Matthews

To the Editor: A 56-year-old woman was recently admitted with recurrent large-volume haemoptysis associated with left-sided tearing thoracic pain. Growing up on a sheep farm in rural New South Wales, she had been diagnosed at age 8 years with pulmonary hydatidosis, which remained dormant on periodic clinical assessments. However, 2 years before presentation she started to cough up gelatinous material containing scolices of Echinococcus granulosus. Surgery was declined at that time due to the anticipated complexity of the operation and associated high perioperative risk. Long-term anthelmintic therapy was commenced. On admission, a computed tomography (CT) scan showed a contained aortic pseudoaneurysm (Box), consistent with rupture of the aorta into the hydatid cyst. Other images showed the cyst containing gas, indicating communication with the airway. After stabilisation, the patient was transferred to a cardiothoracic centre. A left upper lobectomy with dissection and removal of the mediastinal cyst was undertaken through a median sternotomy, and the aortic fistula was successfully repaired using bovine pericardial strips. Intraoperatively, there was no evidence of pericardial involvement. Histopathological examination showed a disrupted and degenerate hydatid cyst without a germinal layer and no protoscolices. The patient received albendazole for 6 months after surgery and her recovery was uneventful. Hydatid disease is caused by the intestinal parasitic tapeworm E. granulosus which, in Australia, is most prevalent in the eastern half of NSW at higher altitudes.1 Symptomatic intramural aortic-wall hydatidosis causing aortic-wall rupture and pseudoaneurysm formation has been described in fewer than a dozen cases.2 Hypotheses for arterial-wall invasion include dissemination during cardiac surgery; entry through vasa vasorum or pre-existing small intimal tears or aneurysms; or partial incorporation of the aortic wall into the hydatid pericyst.2,3 We identified four case reports in adults describing fistula formation between a pulmonary hydatid cyst and the aorta, including three European cases3-5 and one South African case (published twice).6,7 All patients were middle-aged men: two presented with chest pain and large-volume haemoptysis, one with anaphylactic shock and bilateral ischaemic lower limbs from aortic-wall hydatid cyst emboli, and one with a cyst eroding the abdominal aorta (found incidentally during surgery for a coeliac trunk aneurysm). One patient died during removal and another patient after removal of the primary cyst. Haemoptysis in pulmonary hydatid disease is a common presenting symptom. Mechanisms include pressure erosion of a bronchus, obstructive infection, cyst rupture or — very rarely, and emphasised in our case — erosion of a major vascular structure. Aortobronchial fistula resulting from pulmonary hydatidosis A: Contrast-enhanced thoracic computed tomography scan showing consolidation and cavitation within the left upper lobe. A multiloculated 4 cm diameter peripherally calcified hydatid cyst was present in the medial aspect of the left upper lobe (white arrows), penetrating under the aortopulmonary window. Contrast medium extended posteriorly into the base of the lesion, suggestive of an aortic leak (black arrow). B: Coronal reconstruction of the aortic arch demonstrated a round collection of contrast medium with a 1.4 cm base (black arrow), consistent with a contained saccular aortic pseudoaneurysm.

Stefan Buchholz · David Sowden · Troy Stapleton · Peter Pohlner · Craig Wright