Stable Angina: How Does the SIGN Guideline Compare With NICE?

Dr Alan Begg Compares SIGN and NICE Recommendations on the Diagnosis, Assessment, and Treatment of Stable Angina

In April 2018, SIGN published Guideline 151 on the Management of stable angina¹ replacing Guideline 96, which was published in 2007.² The SIGN methodology has changed in the intervening years with the recommendation grading changed from A, B, C levels to two levels of ‘strong’ or ‘conditional’, with recommendations that ‘should’ or ‘should not’ (be implemented) or those that should be ‘considered’ for implementation, respectively.

In the 2018 guideline, there are 19 new sections and two new algorithms. A further 21 sections are completely revised, nine are updated, with six sections receiving minor updates. SIGN guidance is the national clinical guidance for use in Scotland but NICE guidance is often quoted, especially if there is an opportunity for cost-saving or reduction of an existing service.

The NICE guidance equivalent to SIGN 151 is the part of NICE Clinical Guideline (CG) 95 that relates to people presenting with stable chest pain and also NICE CG126, Stable angina: management.^3,4 The former was published in 2010 and the latter in 2011; both were updated in 2016.

Clinical Characteristics of Angina and Making a Diagnosis

Certain characteristics of angina pain will increase the likelihood of making a diagnosis. Those outlined in SIGN 151 are shown in Box 1.¹

NICE describes three features of angina pain that can help determine a diagnosis:³

• constricting discomfort in the front of the chest, or in the neck, shoulders, jaw, or arms
• pain precipitated by physical exertion
• pain relieved by rest or glyceryl trinitrate (GTN) within about 5 minutes.

The presence of all three features represents typical angina, two features signifies atypical angina, and if one or none of the three features are present, the pain is defined as non-anginal.^1,3

The likelihood of a diagnosis of angina increases with the number of cardiovascular risk factors in individual patients, such as:^1,3

• smoking
• hypertension
• diabetes
• previous history of coronary artery disease (CAD) or other vascular disease
• family history of CAD
• hyperlipidaemia
• chronic kidney disease.

SIGN defines a positive family history as a history of premature CAD in a male first-degree relative aged less than 55 years or female first-degree relative aged less than 65 years.¹ NICE CG95 gives a similar list of cardiovascular risk factors but also states that a diagnosis of stable angina is more likely in men; however, the defining typical and atypical features are the same in men and women and different ethnic groups.³ NICE CG95 states that a diagnosis of angina is less likely if the chest pain is continuous and/or very prolonged, unrelated to activity, brought on by breathing in, or associated with symptoms such as dizziness, palpitations, tingling, or difficulty swallowing.³ Both guidelines outline what they individually consider to be the important aspects of clinical examination, with SIGN outlining the necessary baseline laboratory investigations. Conditions that exacerbate angina, such as anaemia, should be identified by appropriate blood tests.

SIGN makes it clear that if the diagnosis is uncertain, the clinician should avoid giving the patient the impression that they have angina as it may lead the patient to have false beliefs, which may be difficult to change even after further investigations have ruled out angina as the diagnosis.¹ Both guidelines agree that diagnostic tests for myocardial ischaemia should not be offered to those with non-cardiac/non-angina chest pain unless there are resting electrocardiogram (ECG) ST-T changes or Q waves.^1,3

Assessment Approach

A 12-lead ECG is an essential part of the assessment and NICE gives guidance on changes that may indicate ischaemia or previous infarction:³

• pathological Q waves
• left bundle branch block
• ST-segment and T wave abnormalities (such as flattening or inversion).

Deciding on Diagnostic Investigations

SIGN indicates that in patients with suspected angina, if there is diagnostic uncertainty from the history, a CT-coronary angiogram should be carried out as an anatomical investigation to determine the presence of obstructive CAD (Figure 1). Those with non-obstructive CAD should receive medical therapy and only invasive coronary angiography if they have ongoing symptoms despite optimal medical therapy (Figure 2). Those with left main-stem or severe three-vessel disease should receive invasive coronary angiography.¹

NICE CG95 states that clinical judgment, ECG changes, as well as people’s preferences and co-morbidities should be taken into account when considering diagnostic testing using a 64-slice (or above) CT-coronary angiography.³

Both guidelines agree that in patients with previously diagnosed CAD, non-invasive functional testing should be considered.^1,3 SIGN includes exercise tolerance testing in the list of choices,¹ with the NICE options being:³

• myocardial perfusion scintigraphy with single photon emission computed tomography (MPS with SPECT)
• stress echocardiology
• first-pass contrast-enhanced magnetic resonance (MR) perfusion
• MR imaging for stress-induced wall motion abnormalities.

NICE is clear that exercise ECG or MR coronary angiography should not be used to diagnose stable angina. SIGN states that an exercise tolerance test (exercise ECG) should not be used as a first-line diagnostic test, and only discusses cardiac MR in the context of stratifying risk.

Exercise Tolerance Testing (ETT) versus Computed Tomography–Coronary Angiography (CT-CA)

Exercise tolerance testing (ETT) as an initial test for patients with angina symptoms and suspected to have CAD should be replaced by computed tomography-coronary angiography (CT-CA). The latter is noted to have an excellent diagnostic performance with a sensitivity of up to 99%, specificity of up to 92%, and a negative predictive value approaching 100%.¹ The diagnostic accuracy of ETT, by contrast, varies depending on many features such as age and gender and the cohort of patients studied. A major drawback to the implementation of this new approach, however, is the lack of CT-CA capacity to implement the guidance; however, cardiologists in the author’s area are hopeful that this will not be too slow to change.

Medical Therapy

General practice has an important role in the management of angina, which is predominately medical therapy especially if there is a clear history of stable angina (Figure 2). This consists of two separate approaches: relieving symptoms (Table 1) and using therapeutic preventative therapy (Table 2) to prevent secondary vascular events. SIGN and NICE recommendations vary slightly, especially in symptom relief, so practices should consider developing their own implementation approach based on local prescribing policies and cost-reduction initiatives. Both guidelines show less variation in the therapeutic approach to prevention of cardiovascular events.

Table 1: Symptomatic Management of Stable Angina^1,4

Table 2: Drugs to Prevent New Vascular Events^1,4

Revascularisation

The path to invasive coronary angiography for possible revascularisation is clear in SIGN 151 (Figures 1 and 2):

• obstructive left main-stem or severe three-vessel disease on CT-CA
• non-obstructive CAD on CT-CA but patient remains symptomatic on optimal medical therapy
• patient high risk on functional assessment.

In all other situations, optimal medical treatment is the ideal and if there are still symptoms and the patient is not suitable for revascularisation then treatments for refractory angina should be considered.¹

Choice of Revascularisation

Percutaneous coronary intervention (PCI) involves dilating the artery by inflating a fine balloon and inserting a fine lattice scaffold (stent) to prevent the artery from recoiling. Stents are coated with drugs to prevent or retard endothelialisation.¹

Coronary artery bypass grafting (CABG) involves bypassing a section of the coronary artery narrowed by atheroma by a section of healthy saphenous vein or internal mammary artery. SIGN does not come to a conclusion as to whether CABG is superior to PCI in terms of prognostic benefit.¹

NICE CG126 says that when either procedure is appropriate, take into account the potential survival advantage of CABG over PCI for people with multi-vessel disease and who:³

• have diabetes or
• are over 65 years or
• have anatomically complex three-vessel disease, with or without involvement of the left main stem.

NICE 126 also indicates that CABG should be offered if symptoms are not controlled medically, if the anatomy is suitable, and if PCI is felt not to be appropriate; conversely, offer PCI when CABG is not appropriate.

Ideally, revascularisation options should be agreed following review by a multidisciplinary ‘heart team’ including cardiac surgeons, cardiac anaesthetists, and interventional cardiologists, and discussion with the patient.

Advice Related to Surgery

The Society of Thoracic Surgeons recommends that aspirin should be stopped for 3–5 days before elective CABG and then restarted early after surgery.^1,8 The routine use of perioperative beta-blocker therapy to reduce perioperative myocardial infarction in patients undergoing non-cardiac surgery is now not recommended.¹ Similarly, the use of aspirin to reduce perioperative cardiac events in patients undergoing non-cardiac surgery, including those with known stable CAD, is also not recommended.¹ Patients undergoing non-cardiac surgery should have their statin therapy continued through the perioperative period.¹

Managing Refractory Angina

Refractory angina is defined in SIGN 151 as ‘persisting unsatisfactory control of angina symptoms despite maximal tolerated medical therapies and without further revascularisation options’. SIGN does not, however, make any recommendations for invasive interventions for refractory angina. Comprehensive rehabilitation is suggested, with patients following an ‘educational and rehabilitative approach, progressing to a cognitive behaviourally-informed approach where appropriate’.¹ The one recommendation made is that patients with angina should be assessed by appropriately trained staff for the impact of angina on mood, quality of life, and function.¹

NICE CG126 advises against the use of transcutaneous electrical nerve stimulation (TENS), enhanced external counterpulsation (EECP), or acupuncture to manage stable angina.⁴ SIGN states that transmyocardial laser revascularisation is not recommended for the treatment of stable angina.¹

For patients who have not responded to drug treatment and/or revascularisation, comprehensive re-evaluation and advice may include:⁴

• exploring the patient’s understanding of their condition
• exploring the impact of symptoms on the person’s quality of life
• reviewing the diagnosis and considering non-ischaemic causes of pain
• reviewing drug treatment and considering future drug treatments and revascularisation options
• acknowledging the limitations of future treatment
• explaining how the person can manage the pain themselves.

Psychological Health in Patients with Angina

Angina can have an adverse effect on the patient’s wellbeing and quality of life. It is important that patients are assessed for this effect and managed appropriately. Interventions such as the Angina plan can help.⁹ This is a patient-held workbook and relaxation programme delivered in primary care, which has been shown to significantly reduce the mean number of self-reported angina attacks and physical limitation, with a reduction in anxiety and depression.¹

Implementation

With the publication of the SIGN 151 angina guideline,¹ practitioners now have access to professionally produced guidance that gives an up-to-date overview of the evidence, especially in relation to assessment, medical management, and revascularisation. Primary care has an important role in the first two of these aspects even though there has been an increase in revascularisation in recent years, with more insertion of drug-eluting stents in particular. The use of CT-CA as the main investigation to determine the presence and extent of obstructive CAD does, however, stand out as requiring significant investment before this guideline can be successfully implemented.

Dr Alan Begg

GP, Montrose; GPwSI in cardiovascular disease; trustee of Chest, Heart, and Stroke Scotland (CHSS); and trustee of Scottish Heart and Arterial Risk Prevention Group (SHARP); specialist reviewer of SIGN 151