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Reperfusion therapy

Reperfusion therapy is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Reperfusion therapy rather than just read about it. In short: Reperfusion therapy is a medical treatment to restore blood flow, either through or around, blocked arteries, typically after a heart attack (myocardial infarction (MI)). Reperfusion therapy includes drugs and surgery.

Reperfusion therapy — main illustration
Reperfusion therapy — illustration

Key takeaways

  • Reperfusion therapy belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Reperfusion therapy to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Reperfusion therapy from memory before moving on to harder problems.

Reference excerpt

Reperfusion therapy is a medical treatment to restore blood flow, either through or around, blocked arteries, typically after a heart attack (myocardial infarction (MI)). Reperfusion therapy includes drugs and surgery. The drugs are thrombolytics and fibrinolytics used in a process called thrombolysis. Surgeries performed may be minimally-invasive endovascular procedures such as a percutaneous coronary intervention (PCI), which involves coronary angioplasty. The angioplasty uses the insertion of a balloon and/or stents to open up the artery. Other surgeries performed are the more invasive bypass surgeries that graft arteries around blockages. If an MI is presented with ECG evidence of an ST elevation known as STEMI, or if a bundle branch block is similarly presented, then reperfusion therapy is necessary. In the absence of an ST elevation, a non-ST elevation MI, known as an NSTEMI, or an unstable angina may be presumed (both of these are indistinguishable on initial evaluation of symptoms). ST elevations indicate a completely blocked artery needing immediate reperfusion. In NSTEMI the blood flow is present but limited by stenosis. In NSTEMI, thrombolytics must be avoided as there is no clear benefit of their use. If the condition stays stable a cardiac stress test may be offered, and if needed subsequent revascularization will be carried out to restore a normal blood flow. If the blood flow becomes unstable an urgent angioplasty may be required. In these unstable cases the use of thrombolytics is contraindicated. At least 10% of treated cases of STEMI do not develop necrosis of the heart muscle. A successful restoration of blood flow is known as aborting the heart attack. About 25% of STEMIs can be aborted if treated within the hour of symptoms onset.

Thrombolytic therapy

Myocardial infarction Thrombolytic therapy is indicated for the treatment of STEMI – if it can begin within 12 hours of the onset of symptoms, and the person is eligible based on exclusion criteria, and a coronary angioplasty is not immediately available. Thrombolysis is most effective in the first 2 hours. After 12 hours, the risk of intracranial bleeding associated with thrombolytic therapy outweighs any benefit. Because irreversible injury occurs within 2–4 hours of the infarction, there is a limited window of time available for reperfusion to work. Thrombolytic drugs are contraindicated for the treatment of unstable angina and NSTEMI and for the treatment of individuals with evidence of cardiogenic shock. Although no perfect thrombolytic agent exists, ideally it would lead to rapid reperfusion, have a high sustained patency rate, be specific for recent thrombi, be easily and rapidly administered, create a low risk for intracerebral bleeding and systemic bleeding, have no antigenicity, adverse hemodynamic effects, or clinically significant drug interactions, and be cost effective. Currently available thrombolytic agents include streptokinase, urokinase, and alteplase (recombinant tissue plasminogen activator, rtPA). More recently, thrombolytic agents similar in structure to rtPA such as reteplase and tenecteplase have been used. These newer agents boast efficacy at least as well as rtPA with significantly easier administration. The thrombolytic agent used in a particular individual is based on institution preference and the age of the patient. Depending on the thrombolytic agent being used, additional anticoagulation with heparin or low molecular weight heparin may be of benefit. With tPa and related agents (reteplase and tenecteplase), heparin is needed to keep the coronary artery open. Because of the anticoagulant effect of fibrinogen depletion with streptokinase and urokinase treatment, it is less necessary there.

Failure Thrombolytic therapy to abort a myocardial infarction is not always effective. The degree of effectiveness of a thrombolytic agent is dependent on the time since the myocardial infarction began, with the best results occurring if the thrombolytic is used within two hours of the onset of symptoms. Failure rates of thrombolytics can be as high as 50%. In cases of failure of the thrombolytic agent to open the infarct-related coronary artery, the person is then either treated conservatively with anticoagulants and allowed to "complete the infarction" or percutaneous coronary intervention (and coronary angioplasty) is then performed. Percutaneous coronary intervention in this setting is known as "rescue PCI" or "salvage PCI". Complications, particularly bleeding, are significantly higher with rescue PCI than with primary PCI due to the action of the thrombolytic.

Side effects Intracranial bleeding (ICB) and subsequent stroke is a serious side effect of thrombolytic use. The risk factors for developing intracranial bleeding include a previous episode of intracranial bleed, advanced age of the individual, and the thrombolytic regimen that is being used. In general, the risk of ICB due to thrombolytics is between 0.5 and 1 percent.

Coronary angioplasty

… excerpt ends here. Continue reading the full article.

Illustrations

Reperfusion therapy illustration
Reperfusion therapy: Coronary artery bypass surgery during mobilization (freeing) of the right coronary artery from its surrounding tissue, adipose tissue (yellow). The tube visible at the bottom is the aortic cannula (returns blood from the HLM). The tube above it (obscured by the surgeon on the right) is the venous cannula (receives blood from the body). The patient's heart is stopped and the aorta is cross-clamped. The patient's head (not seen) is at the bottom.
Coronary artery bypass surgery during mobilization (freeing) of the right coronary artery from its surrounding tissue, adipose tissue (yellow). The tube visible at the bottom is the aortic cannula (returns blood from the HLM). The tube above it (obscured by the surgeon on the right) is the venous cannula (receives blood from the body). The patient's heart is stopped and the aorta is cross-clamped. The patient's head (not seen) is at the bottom.

Worked examples

Example 1 — a first encounter with Reperfusion therapy

Start with the simplest possible case. Write down what Reperfusion therapy claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Reperfusion therapy before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Reperfusion therapy ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Reperfusion therapy

In research
Reperfusion therapy appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Reperfusion therapy in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Reperfusion therapy is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cardiac procedures, so understanding it makes those chapters shorter.
In everyday life
Look for Reperfusion therapy outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Reperfusion therapy in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Reperfusion therapy means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Reperfusion therapy out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Reperfusion therapy in simple terms?

Reperfusion therapy is a medical treatment to restore blood flow, either through or around, blocked arteries, typically after a heart attack (myocardial infarction (MI)). Reperfusion therapy includes drugs and surgery.

Why does Reperfusion therapy matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Reperfusion therapy?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Reperfusion therapy.

Tags

  • Cardiac procedures

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