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The grading A–C for each of the clinical recommendations has been applied according to the definitions used by the Scottish Intercollegiate Guidelines Network1 (see appendix I).
Good practice and audit points
- ✔ Recommended best practice based on the clinical experience of the guideline development group, and appropriate for audit.
Presentation and initial management
- Patients presenting with symptoms consistent with an acute coronary syndrome should be referred urgently for further assessment:
- those with prolonged (> 15 minutes) cardiac pain at rest should be taken to an acute hospital by emergency ambulance;
- those with worsening angina should be referred to and assessed by a specialist on the day of presentation.
- All patients should have a 12 lead ECG performed. Patients with persistent ST segment elevation or acute Q wave myocardial infarction, and those with alternative diagnoses, exit from this guideline and should be managed appropriately.
- Patients with a suspected acute coronary syndrome should be observed, with repeat 12 lead ECG recording, during symptoms if the opportunity arises. Blood samples for cardiac troponin (troponin T or I) should be taken a minimum of 12 hours after the onset of symptoms. New ischaemic changes on the ECG or elevation of troponin confirm the diagnosis (see table 1 and recommendation 5).
- If at least 12 hours after the onset of symptoms of a suspected acute coronary syndrome:
- the symptoms have not recurred;
- the cardiac troponin is normal;
- the ECG remains normal (or unchanged compared with a recording from before the current presentation);
- and the cardiac enzymes are not raised;
- the patient can be mobilised and discharged. Risk assessment with stress testing should be performed unless contraindicated, preferably before discharge from hospital.
- ✔ A
- Patients with a confirmed acute coronary syndrome should be admitted to a cardiac care unit or high dependency unit with continuous ECG rhythm monitoring. If symptoms recur the 12 lead ECG should be repeated.
- ✔ C
- Confirmed acute coronary syndrome. Patients who have had ischaemic ECG changes, or cardiac troponin release or raised CK-MB enzyme demonstrated at any time during admission, have a confirmed acute coronary syndrome. When free from symptoms and ischaemic ECG changes for > 48 hours, and any intravenous treatments and heparin have been stopped for > 24 hours, risk assessment with stress testing should be performed, unless contraindicated; stress testing for risk assessment is unnecessary if the patient is already in a high risk category for which coronary angiography is indicated.
Risk assessment and referral for coronary angiography
- Patients with unstable angina or non-Q wave myocardial infarction should have their cardiac prognosis assessed by estimation of their risk of death or further cardiac events. In patients whose symptoms and condition have become stable after initial treatment, this assessment should include stress testing. Treatment should be directed at reducing their risk.
- ✔ A
- Referral for coronary angiography. Patients with recurrent or refractory angina should be referred for coronary angiography with a view to myocardial revascularisation for relief of symptoms; these patients are also in a category at high risk of further cardiac events.
- ✔ A
- Those patients with unstable angina or non-Q wave myocardial infarction whose condition has stabilised, but who are at high risk of death or further cardiac events, should be referred for coronary angiography.
- Referral for coronary angiography in medically stabilised patients: risk stratification using the results of troponin and stress tests (see table 2):
- Low risk: If the cardiac troponin result is negative or low (troponin T < 0.01 μg/l or troponin I equivalent), and the stress test result indicates a low risk category, the patient can be discharged; if free from cardiac symptoms, no further cardiac interventions are necessary. Subsequent outpatient review is appropriate for further investigations to confirm or exclude a coronary diagnosis, and adjustment or cessation of drug treatment.
- Intermediate risk: Patients without high risk features, such as evidence of impaired left ventricular function, or haemodynamic abnormalities or arrhythmia during the acute phase, and who have either: • a normal cardiac troponin result (troponin T < 0.01 μg/l, or troponin I equivalent) and with a stress test indicating intermediate risk; or • moderately elevated cardiac troponin (troponin T 0.01 μg/l to 0.1 μg/l, or troponin I equivalent) and with a stress test result indicating a low risk category; are at an intermediate level of risk. Many cardiologists perform coronary angiography on patients in these categories of intermediate risk, and this practice has been recommended; but coronary angiography cannot be considered mandatory in the current absence of clear evidence that routine investigation of such patients results in an improved outcome.
- High risk: If the maximal cardiac troponin result is high (troponin T > 0.1 μg/l, or troponin I equivalent), or the stress test result indicates a high risk category, coronary angiography should be arranged, unless contraindicated, and performed urgently, before discharge from hospital. Those with acute ischaemia associated with hypotension, arrhythmia, or heart failure, are also in a high risk category and should be referred for coronary angiography.
- Patients unable to exercise: If the patient is unable to perform an exercise ECG, an alternative non-exercise (pharmacological) stress test, such as a stress echocardiograph or isotope myocardial stress perfusion study, should be arranged unless contraindicated; coronary angiography should be undertaken according to the risk category determined, if indicated as described above. If no stress test can be performed, and the maximal cardiac troponin result is intermediate or high, coronary angiography should be arranged, unless contraindicated. If no stress test can be performed, and if the troponin result is low and there are no further symptoms or ECG changes, the patient may be able to be discharged and reviewed in the outpatient clinic.
- All patients with a confirmed acute coronary syndrome should be given aspirin, unless contraindicated, as soon as the diagnosis is made; low dose aspirin once daily should be continued subsequently, unless contraindicated.
- ✔ A
- Low molecular weight heparin should be given for at least two days, and for up to eight days or longer in cases of recurrent ischaemia or where myocardial revascularisation is delayed or contraindicated.
- ✔ A
Medical anti-ischaemic treatment
- To reduce their risk of infarction, all patients with a confirmed acute coronary syndrome should be treated with a β blocker without intrinsic sympathomimetic activity, and where there is no contraindication. Where there is a contraindication to the use of β blockers, a heart rate slowing calcium channel antagonist should be given to all patients with a confirmed acute coronary syndrome with no evidence of heart failure or left ventricular dysfunction to reduce their risk. Nitrates should be given to relieve pain or ischaemia in patients with an acute coronary syndrome; if further symptoms or ischaemia occurs, a calcium channel antagonist can be added to the β blocker. A potassium channel opener should be given in addition to nitrates and β blockers (or calcium channel antagonists) if there are recurrent symptoms or ischaemia.
- ✔ A
Management of cases at high risk …
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