What medical treatments of unstable angina are of proven benefit?

The treatment of unstable angina is dictated by the underlying pathophysiology, namely, rupturing of an atheromatous plaque and secondary platelet aggregation, vasoconstriction and thrombus formation.

Anti-ischaemic therapy

• Nitrates relieve ischaemic pain but there is no evidence of prognostic benefit from their use.
• Calcium antagonists are effective anti-ischaemic and vasodilator drugs. However, in the absence of beta blockade, nifedipine should be avoided due to reflex tachycardia. Verapamil and diltiazem have useful rate-lowering properties, but should be used cautiously in patients with ventricular dysfunction and patients already taking beta blockers.
• Beta-adrenoceptor blockers are an important treatment in unstable angina, not only relieving symptoms but also reducing the likelihood of progression to infarction and cardiac death. There is no evidence to favour one class of beta blocker over another.

Antithrombotic therapy

• Aspirin has an important and undisputed role in the treatment of unstable angina, reducing the risk of fatal/non-fatal MI by 70% acutely, by 60% at 3 months and by 52% at 2 years.1 A first dose of 160-325mg should be followed by a maintenance dose of 75mg daily.
• Ticlopidine and clopidogrel, antagonists of ADP-mediated platelet aggregation, are possible alternatives in patients unable to take aspirin, although ticlopidine has important side effects and trials using clopidogrel have yet to be completed (e.g. CURE study).
• Glycoprotein IIb/IIIa inhibitors (e.g. abciximab, tirofiban and eptifibatide) are potent anti-platelet agents and are effective, but costly, in patients with unstable angina undergoing PTCA. More recent data support a wider role for their use in the medical management of high-risk patients with unstable angina i.e. recurrent ischaemia, raised troponia levels, haemodynamic instability, major arrhythmia and early post-infarction unstable angina.
• Unfractionated heparin reduces ischaemic episodes but most trials have not shown greater benefit from heparin and aspirin compared with aspirin alone. However, a meta-analysis gave a 7.9% incidence of death/MI with the combination compared with 10.4% with aspirin alone.
• Low molecular weight heparins (e.g. dalteparin, enoxaparin) are at least as effective as heparin and are tending to replace heparin as standard therapy.