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CDHB

Acute Coronary Syndromes

Definition

The pain experienced with unstable angina is similar to stable angina, though often more intense and of longer duration. It may also be associated with other signs such as sweating and nausea. Very often it is difficult to distinguish between unstable angina and acute myocardial infarction during the initial assessment of the patient. Thus, management in the first few hours will often be similar to that for myocardial infarction.

The following may be defined as acute coronary syndromes (ACS):

• Angina of recent origin (<1 month) which is severe and/or frequent.
• Severe prolonged or more frequent angina superimposed on previous stable angina.
• Angina developing at rest or with minimal exertion.
• Non-ST elevation myocardial infarction.

Causes

• Coronary artery disease, often with intracoronary thrombus at the site of a ruptured plaque.

Investigation and Management

This is similar to the treatment of acute myocardial infarction except that thrombolysis is not indicated. Angioplasty may be indicated for persistent or recurrent rest pain with ECG changes (discuss with Cardiologist).

• Daily ECG and cardiac injury markers on at least two occasions are mandatory, as is assessment of cardiac risk factors including lipids.
• Elevation of troponins indicates non-ST elevation MI and a higher risk of subsequent complications.
• ECG changes such as ST depression or T wave inversion or any serial change over the first 24 hours suggest a poorer prognosis.
• Enoxaparin at 1 mg/kg subcut q12h should be started in patients with ECG changes suggesting ischaemia, a positive troponin, or a high index of suspicion of ACS. The usual duration of enoxaparin treatment is 48 hours. The dosage of LMWH will need to be reduced if there is significant renal impairment (CrCl <60 mL/min) or for extremes of weight. See the VTE section.
• Anti-Xa monitoring is recommended if the duration of LMWH therapy is >48 hours. Treatment for longer than 48 hours is associated with an increased risk of haemorrhagic complications and would normally only be considered in patients with ongoing unstable ischaemic symptoms, following discussion with the Consultant, and with intensified monitoring for haemorrhagic complications.
• Start aspirin. Consider adding clopidogrel if ticagrelor is not to be given. Ticagrelor should be started if the patient is being scheduled for angiography/angioplasty. Seek Cardiologist advice. See Management of ST Elevation Myocardial Infarction for dosage recommendations.
• Start nitrate and a beta-blocker (or calcium antagonist if beta-blocker is contraindicated). If patient has presented with unstable angina on anti-anginal therapy, plan to discharge on increased doses or add another anti-anginal. Remember to investigate for anaemia, hyperthyroidism, heart failure and arrhythmias as precipitants for angina. Plasma lipids and body weight should be assessed and treated as appropriate. Statins should be considered in all patients unless contraindicated.
• Oxygen should be considered only if sat.O₂ <92%.
• Telemetry monitoring if troponins are raised or the patient's condition is unstable; monitor for 48 hours.
• Coronary angiography ± intervention should be considered prior to discharge.
• Tirofiban, a IIb/IIIa inhibitor should be considered if pain or ST changes recur despite above therapy in patients who are troponin positive or with dynamic ST changes. Consult Cardiologist.
• Review and treat risk factors as for myocardial infarction.

References:

Non-ST-elevation acute coronary syndromes: New Zealand management guidelines. Cardiac Society of Australia and New Zealand. NZMJ. 2012 Jun 29;125(1357):122-47.

Topic Code: 1325