STEMI Reperfusion Therapy
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Direct answer
Primary percutaneous coronary intervention is the preferred reperfusion strategy for ST-elevation myocardial infarction, with fibrinolysis reserved for patients in whom angioplasty cannot be delivered promptly. The benchmark is a first-medical-contact-to-device time within 120 minutes for PCI and a fibrinolytic bolus within 30 minutes of arrival at a hospital without catheterisation facilities, because every delay in restoring flow costs myocardium.
What you must remember
- Time targets: door-to-needle within 30 minutes for fibrinolysis; door-to-balloon within 90 minutes for PCI in a catheterisation centre, with the 120-minute first-contact-to-device window used in European practice.
- Choosing PCI: preferred whenever a skilled team can open the artery within the window, and superior to lysis in cardiogenic shock and in patients with contraindications to fibrinolysis.
- Fibrinolytic agents: streptokinase is cheap and widely used in Indian public hospitals, but it causes hypotension and allergy and cannot be repeated; fibrin-specific agents such as alteplase, reteplase and tenecteplase are preferred where affordable, tenecteplase being a single weight-adjusted bolus.
- Adjuncts: aspirin 150 to 300 mg chewed, a clopidogrel loading dose (the P2Y12 inhibitor used with lysis) and parenteral anticoagulation with enoxaparin or unfractionated heparin accompany the lytic.
- Absolute contraindications: prior intracranial haemorrhage, intracranial neoplasm or vascular malformation, recent ischaemic stroke (textbooks differ on the interval), active bleeding, suspected aortic dissection and significant recent head or facial trauma.
- Relative contraindications: uncontrolled hypertension above 180 over 110 mmHg, therapeutic anticoagulation, traumatic or prolonged resuscitation, pregnancy and active peptic ulcer.
- Successful lysis: at least 50 per cent ST-segment resolution at 60 to 90 minutes, with pain relief and no reperfusion arrhythmia; failure triggers immediate rescue PCI.
A worked choice at a district hospital
A 52-year-old man arrives two hours after the onset of central pain, with inferior ST elevation in leads II, III and aVF and suspected right ventricular involvement. His ECG is recorded within ten minutes of arrival, which meets the first benchmark.
- Choose fibrinolysis: The nearest catheter laboratory is ninety minutes away by road, so a first-contact-to-device time inside 120 minutes is unlikely. Fibrinolysis is therefore appropriate, but only after a rapid check for contraindications.
- Screen for contraindications: A past stroke, a blood pressure of 190 over 100, or recent surgery or trauma would change the plan.
- Give the lytic: If none applies, the lytic is given within 30 minutes of arrival, with aspirin, a P2Y12 inhibitor and anticoagulation.
- Assess the response: The response is assessed at 60 to 90 minutes, looking at ST resolution, pain and rhythm. Successful lysis allows a pharmacoinvasive strategy, with transfer to a catheter centre for angiography in the window of two to 24 hours, as current European guidance recommends.
- Rescue if lysis fails: Had the ECG shown less than half the ST elevation resolved with ongoing pain, the plan would switch to rescue PCI as soon as possible, not a second dose of the same agent.
- Protect the right ventricle: The V4R lead screens for right ventricular involvement. Nitrates and diuretics are avoided because the right ventricle depends on preload, so fluid is given carefully.
Where the exam tries to catch you
Three traps recur in reperfusion questions.
- Trap: mixing up the clocks Correct: the 30-minute door-to-needle target belongs to fibrinolysis, while the 90-minute door-to-balloon target and the 120-minute first-contact-to-device window belong to primary PCI, and examiners ask which applies to a patient transferred from a primary centre.
- Trap: believing streptokinase can be repeated Correct: antibodies formed after the first course neutralise a second dose, and it also causes hypotension and allergy.
- Trap: answering "no contraindications" without taking a history Correct: the scenario tests whether you ask about prior stroke, recent surgery and bleeding, and in an Indian public hospital the viva answer names the contraindications, the transfer decision and the window, not the drug alone.
Frequently asked questions
What is the door-to-needle target for fibrinolysis in STEMI?
Thirty minutes is the widely used target, measured from arrival at hospital to administration of the fibrinolytic bolus. Primary PCI uses a door-to-balloon target of 90 minutes in centres with catheterisation facilities.
Why is streptokinase not repeated in the same patient?
Streptokinase is derived from streptococci, so antibodies formed after the first exposure neutralise a second dose and can cause allergic reactions. It also causes hypotension, which is why fibrin-specific agents are preferred where cost allows.
Which findings define successful fibrinolysis?
Successful reperfusion is defined by at least 50 per cent resolution of ST elevation at 60 to 90 minutes, together with relief of chest pain and absence of reperfusion arrhythmia. Failure requires immediate rescue PCI rather than a repeat lytic.
When is rescue PCI indicated after failed fibrinolysis?
Rescue PCI is indicated when less than half the ST elevation resolves at 60 to 90 minutes, when chest pain persists, or when haemodynamic or electrical instability develops after lysis. It should be performed as soon as possible in a catheter centre.