A 49-year-old male presented to the Accident and Emergency Department with a one-hour history of severe central chest pain. He smoked 30 cigarettes per day. Physical examination was normal. The 12-lead ECG revealed ST segment elevation in leads V1–V4. There were no contraindications to thrombolysis.
What is the best treatment to improve coronary perfusion?
a. IV Streptokinase.
b. IV Tenectoplase.
c. IV Alteplase.
d. Half-dose tenectoplase and half-dose abciximab.
e. Primary coronary angioplasty.
e. Primary coronary angioplasty
Coronary reperfusion may be achieved with thrombolytic agents (which promote fibrinolysis) or by coronary angioplasty. In the UK patients with ST elevation myocardial infarction are conventionally treated with thrombolytic agents. Early treatment is crucial to salvage myocardium and reduce the risk of sudden death and severe left ventricular dysfunction. Current goals for the speed of treating with a thrombolytic agent include a door-to-needle time of 20 minutes or a call-to-needle time of 60 minutes. Thrombolytic agents used commonly include streptokinase, alteplase, tenectoplase and reteplase. Streptokinase is less favoured compared with the other thrombolytic agents because it is less effective at restoring coronary perfusion and is associated with slightly worse outcomes. The GUSTO I study compared front-loaded alteplase therapy with streptokinase in patients with ST EMI. Alteplase was superior to streptokinase in reducing mortality (1% absolute reduction in mortality at 30 days with alteplase) and was associated with greater coronary patency rates. In the GUSTO trial the benefit was greatest in patients aged under 75 years and those with anterior myocardial infarction. However, streptokinase is still used extensively in developing countries and in many hospitals in the UK. Alteplase, tenectoplase and reteplase appear to be equally effective. Tenectoplase and reteplase are easier to administer (as a single bolus).
There have been trials evaluating the role of combined half-dose thrombolytic therapy and half-dose platelet glycoprotein IIb/IIIa receptor blockers, e.g. tenectoplase plus abciximab (ASSENT 3) and reteplase plus abciximab (GUSTO IV). These trials suggest that the combination may be associated with slightly higher coronary patency rates and fewer ischaemic events but they have not demonstrated a mortality benefit. These trials have also demonstrated higher rates of intracranial bleeding in the elderly, hence combination therapy is not recommended at present. Although thrombolytic treatment is associated with a significant reduction in mortality from myocardial infarction, it does have important limitations. Firstly, greatest benefit from thrombolysis is achieved in patients treated within 4 hours of the onset of symptoms. Even with thrombolysis normalization of blood flow is seen in only 50–60% of cases. Recurrent ischaemia occurs in 30% of cases and frank thrombotic coronary occlusion in 5–15%. Re-infarction occurs in up to 5% of cases while in hospital. Also major bleeding is recognized in 2–3% of cases. For these reasons several trials were set up comparing primary angioplasty with thrombolysis in STEMI. Primary angioplasty is superior to thrombolysis. It is associated with lower mortality and lower re-infarction rates. The likelihood of a pre-discharge positive exercise test is also reduced by primary angioplasty. In hospitals where facilities for primary angioplasty are available, primary angioplasty should be considered over thrombolysis. Best results occur when the door-toballoon time is less than 2 hours.