In this programme, module 1 has explained the mechanisms and functions of haemostasis, and of the importance of the balance between coagulation and the dual processes of inhibition and fibrinolysis. Module 2 has considered the pathology of arterial thrombosis, and the use of antiplatelet agents to treat or prevent this. Module 3 has looked at the therapeutic indications for anticoagulants in acute coronary syndromes and non-valvular atrial fibrillation (AF), as well as their use in cardioversion for AF. This module also considers the choice of anticoagulant for stroke prevention, as well as peripheral arterial disease, venous thromboembolism and the expanding role of direct oral anticoagulants (DOACs).
Peripheral arterial disease
Peripheral arterial disease (PAD) is a cardiovascular disease affecting arteries in the legs. It is most commonly due to atherosclerosis of an artery (the pathophysiology of which was discussed in module 1). The Edinburgh Artery Study (EAS) described the prevalence of asymptomatic and symptomatic PAD by performing the World Health Organisation questionnaire on intermittent claudication and ankle brachial systolic pressure on 1,592 participants aged between 55 to 74 years. This found the prevalence of:
- Intermittent claudication was 4.5% (95% CI: 3.5–5.5%)
- Major asymptomatic disease causing a significant impairment of blood flow was 8.0% (95% CI: 6.6–9.4%); this group also had more evidence of ischaemic heart disease than the normal population with a relative risk of 1.6 (95% CI 1.3–1.9%)
The study confirmed that intermittent claudication was equally common in men and woman, and that prevalence increases with age and a lower social class.1
Intermittent claudication is pain that occurs on walking and improves with rest. This can become a critical ischaemia if:2
- rest pain develops (this may be worse in bed when the leg is elevated)
- the leg is red/purple in colour when not elevated
- there is early pallor on elevation
- there are skin changes including impaired wound healing and absent foot pulses.
The site of where symptoms arises varies according to the artery involved (see figure 1).
The ankle brachial pressure index can be used in the assessment of PAD but needs to be used with caution in those with diabetes due to medial sclerosis. It compares the blood pressure in the ankle and arm. If the results are normal, it does not exclude a diagnosis of PAD (see figure 2).3
Management of PAD2
If available, all patients with intermittent claudication should receive a supervised exercise programme and risk factor modification. Secondary prevention of cardiovascular disease in people with PAD includes:
- smoking cessation
- diet, weight management and exercise
- lipid modification and statin therapy
- prevention, diagnosis and management of diabetes and hypertension
They should be referred for consideration of angioplasty or bypass surgery when a supervised exercise programme has failed, and risk factors have been modified. Naftidrofuryl oxalate can be used if there is no improvement with exercise and patients do not wish to be referred for angioplasty or bypass surgery. This is a vasodilator agent with an antagonistic effect on 5-HT2 receptors of smooth muscle cells. It also activates intracellular aerobic metabolism by reducing lactic acid and increasing adenosine triphosphate (ATP). This action protects against ischaemia. This action protects against ischaemia. Further information is available in reference 5.
The DVLA may need to be informed if peripheral vascular disease (PVD) occurs.
Current guidelines suggest the use of clopidogrel 75 mg once daily as the preferred antiplatelet agent with aspirin for use if clopidogrel is contraindicated or not tolerated.6 The Cardiovascular Outcomes for People Using Anticoagulation Strategies (COMPASS) trial,7 a multi-centre, double-blind, randomised, controlled trial, has compared:
- rivaroxaban 2.5 mg twice daily with aspirin 100 mg once daily
- rivaroxaban 5 mg twice daily (with aspirin placebo once daily)
- aspirin 100 mg once daily (with rivaroxaban placebo twice daily).
Eligible patients had a history of PAD of the lower extremities, of the carotid arteries or coronary artery disease with an ankle brachial pressure index <0.90. Primary outcome was cardiovascular death, myocardial infarction or stroke; the primary PAD outcome was major adverse limb events including major amputation. The study recruited 7,470 patients with PAD from 558 centres. It concluded that low-dose rivaroxaban taken twice daily with aspirin reduced major adverse limb events when compared with aspirin alone (1.2% vs. 2.2% respectively; HR, 0.54: 95% CI: 0.35–0.84), although there was an increase in major bleeding (not in fatal or critical bleeding). The most common site for bleeding was gastrointestinal. Rivaroxaban alone reduced major adverse limb events but increased major bleeding.
Venous thromboembolism (VTE) includes deep vein thrombosis (DVT) and pulmonary embolism (PE). The pathophysiology of VTE is discussed in module 1. Provoking factors must be considered when a VTE is diagnosed (see table 1).
If no risk factors are found, it must be remembered that the prevalence of undiagnosed cancer in patients who have an unprovoked VTE is 6.1% at presentation, increasing to 10% at 12 months.9 Extensive screening in this cohort for an undiagnosed malignancy is a contentious issue. Studies have shown that extensive screening can identify underlying malignancies at an earlier stage.10,11 The advantages of screening, however, are outweighed by the anxiety associated with this, the unknown long-term effects of radiation, and the degree of false positive results. The National Institute of Health and Care Excellence (NICE) have concluded that in those over the age of 40 with an unprovoked VTE, screening for cancer should be considered, but not routinely performed.12
Treatment options for VTE, since the advent of DOACs, have increased allowing for more patient choice. Table 213–26 shows the licenses of the DOACs. They have been viewed favourably due to the reduced frequency of blood tests required and the generally ‘one size fits all’ nature of the medications. There is ongoing research into the use of these medications at extremes of body weight27 and use outside of the prescribing parameters. Real world registries, such as the Follow-up in Rivaroxaban Patients in Setting of Thromboembolism (FIRST) registry, will be able to provide more information on this.28
The duration of anticoagulation following a VTE is dependent on provoking risk factors and location so should be considered on an individual basis. Einstein Choice is a clinical trial that looked at patients with VTE who had completed six to 12 months of anticoagulation and had clinical equipoise for continuation of anticoagulation. It compared the use of reduced dose rivaroxaban (10 mg once daily) with standard dose rivaroxaban (20 mg) with aspirin (100 mg/day). Rivaroxaban at either dose was found to be more effective than aspirin in preventing recurrent VTE events without a significant increase in major bleeding.29
Cancer-associated thrombosis (CAT)
Two studies have predominantly guided current management of VTE in cancer. These include the Comparison of LMWH versus Oral Anticoagulant Therapy for the Prevention of Recurrent VTE in Patients with Cancer (CLOT)30 and Comparison of Acute Treatments in Cancer Haemostasis (CATCH) study.31 As a result of these studies, low molecular weight heparin (LMWH) currently forms the cornerstone of treatment of VTE in cancer patients.
The evidence for the use of DOACs in the cancer cohort is gradually expanding. Recent evidence has demonstrated that edoxaban is non-inferior to subcutaneous dalteparin32 for the treatment of VTE. Select-D, which compares DOACS and LMWH for the treatment of VTE in patients with cancer, has recently reported that rivaroxaban has a very low VTE recurrence rate at six months.33 There are a number of other studies that are soon to report on this including the CANVAS study (NCT02744092) which is comparing DOACs and LMWH or warfarin.
Current guidelines suggest that treatment of cancer-associated thrombosis should be for at least six months, but prolonged treatment should be considered if the provoking risk factor is still present – for example, if the patient continues to have active cancer.34
DOAC use in catheter ablation in AF
If pharmacological measures have been unsuccessful in controlling symptoms of AF, then left atrial catheter ablation can be considered.35 Those anticoagulated with warfarin (INR 2–3) should continue this during ablation. There are multiple studies comparing the use of uninterrupted warfarin and uninterrupted DOACs in this setting and there appears to be similar safety and efficacy data.36 Anticoagulation should be continued for at least eight weeks post ablation.37
The use of DOACs in more specialised areas is expanding, such as in antiphospholipid syndrome, heparin-induced thrombocytopenia (HIT) and cancer.
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8. National Institute for Health and Care Excellence (NICE). Venous thromboembolism in over 16s: reducing the risk of hospital-acquired deep vein thrombosis or pulmonary embolism. Clinical guideline (NG89). London: NICE, March 2018 . https://www.nice.org.uk/guidance/ng89 (last accessed 23rd October 2018).
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