Reperfusion therapy

Reperfusion therapy
Thrombus material (in a cup, upper left corner) removed from a coronary artery during an angioplasty to abort a myocardial infarction. Five pieces of thrombus are shown (arrow heads).
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Reperfusion therapy is a medical treatment to restore blood flow, either through or around, blocked arteries, typically after a heart attack (

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.^[2] 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.^[3]

At least 10% of treated cases of STEMI do not develop

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.^[5] Thrombolysis is most effective in the first 2 hours. After 12 hours, the risk of intracranial bleeding associated with thrombolytic therapy outweighs any benefit.^[3][6][7] Because irreversible injury occurs within 2–4 hours of the infarction, there is a limited window of time available for reperfusion to work.^{[citation needed]}

Thrombolytic drugs are contraindicated for the treatment of unstable angina and NSTEMI^[3][8] and for the treatment of individuals with evidence of cardiogenic shock.^[9]

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

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.[17]^[18] Failure rates of thrombolytics can be as high as 50%.^[19] 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.^[20] 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.^{[citation needed]}

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.^[11]

Coronary angioplasty

The benefit of prompt, primary angioplasty over thrombolytic therapy for acute STEMI is now well established.^[21][22][23] When performed rapidly, an angioplasty restores flow in the blocked artery in more than 95% of patients compared with the reperfusion rate of about 65% achieved by thrombolysis.^[21] Logistic and economic obstacles seem to hinder a more widespread application of angioplasty,^[24] although the feasibility of providing regionalized angioplasty for STEMI is currently being explored in the United States.^[25] The use of a coronary angioplasty to abort a myocardial infarction is preceded by a primary percutaneous coronary intervention. The goal of a prompt angioplasty is to open the artery as soon as possible, and preferably within 90 minutes of the patient presenting to the emergency room. This time is referred to as the door-to-balloon time. Few hospitals can provide an angioplasty within the 90 minute interval,^[26] which prompted the American College of Cardiology (ACC) to launch a national Door to Balloon (D2B) Initiative in November 2006. Over 800 hospitals have joined the D2B Alliance as of March 16, 2007.^[27]

One particularly successful implementation of a primary PCI protocol is in the

The current guidelines in the United States restrict angioplasties to hospitals with available emergency bypass surgery as a backup,[5] but this is not the case in other parts of the world.^[29]

A PCI involves performing a coronary

Accelerated idioventricular rhythm which looks like slow ventricular tachycardia is a sign of a successful reperfusion.^[44] No treatment of this rhythm is needed as it rarely changes into a more serious rhythm.^[45]

See also

• Perfusion scanning
• Reperfusion injury
• Revascularization
• TIMI
• Ischemia-reperfusion injury of the appendicular musculoskeletal system

References