Reperfusion therapy is a medical treatment to restore blood flow, either through or around, blocked arteries, usually after a heart attack (myocardial infarction (MI)). Reperfusion therapy includes medications and surgery. They are thrombolytic and fibrinolytic used in a process called thrombolysis. Surgery may be a minimally invasive endovascular procedure such as percutaneous coronary intervention (PCI), followed by coronary angioplasty. Angioplasty uses balloon insertion to open the arteries, with the possibility of using one or more additional stents. Another operation performed was a more invasive bypass surgery that grafted the artery around the blockage.
If MI is presented with ECG proof from ST elevation known as STEMI, or if bundle branch blocks are presented in the same way, reperfusion therapy is required. In the absence of ST elevation, an increase in non-ST MI, known as NSTEMI, or unstable angina may be considered (both indistinguishable from baseline evaluation of symptoms). Improved ST shows a fully blocked artery that requires immediate reperfusion. In NSTEMI blood flow is present but is limited by stenosis. In NSTEMI, the same thrombolytics are used for STEMI, but they are also often stabilized with antiplatelets and anticoagulants. If the condition remains stable a heart stress test can be offered, and if necessary subsequent revascularization will be performed to restore normal blood flow. If the blood flow becomes unstable, urgent angioplasty is necessary. In this unstable case, the use of thrombolytics is contraindicated.
At least 10% of treated STEMI cases do not develop cardiac muscle necrosis. Successful blood flow recovery is known as heart attack abortion. About 25% STEMI can be undone if treated within one hour of symptom onset.
Video Reperfusion therapy
Terapi trombolitik
Infark miokard
Thrombolytic therapy is indicated for the treatment of STEMI - if it can be started within 12 hours of onset of symptoms, and the person is eligible based on exclusion criteria, and coronary angioplasty is not readily available. Thrombolysis is most effective in the first 2 hours. After 12 hours, the risk of intracranial hemorrhage associated with thrombolytic therapy outweighs any benefit. Because irreversible injuries occur within 2-4 hours of infarction, there is a limited time window 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 there is no perfect thrombolytic agent, ideally this would lead to rapid reperfusion, high levels of patency, specific to new thrombi, given easily and quickly, creating a low risk for intracerebral hemorrhage and systemic bleeding, lacking antigenicity, adversely affecting hemodynamic effects , or drug interactions that are clinically significant, and cost-effective. Thrombolytic agents currently available include streptokinase, urokinase, and alteplase (recombinant tissue plasminogen activator, rtPA). Recently, similar thrombolytic agents in structures for rtPA such as reteplase and tenecteplase have been used. This new agent has the efficacy of at least the same as rtPA with much easier administration. Thrombolytic agents used in certain individuals are based on institutional preferences and patient age.
Depending on the thrombolytic agent used, additional anticoagulants with low molecular weight heparin or heparin may be beneficial. With tPa and related agents (reteplase and tenecteplase), heparin is required to keep the coronary artery open. Because of the anticoagulant effects of fibrinogen depletion with the treatment of streptokinase and urokinase, it is less necessary there.
Failure
Thrombolytic therapy to abort myocardial infarction is not always effective. The degree of effectiveness of thrombolytic agents depends on the time since myocardial infarction begins, with best results occurring if thrombolytics are used within two hours of the onset of symptoms. The thrombolytic failure rate can be as high as 50%. In the case of failure of thrombolytic agents to open coronary artery infarction, the person is then treated conservatively with anticoagulants and allowed to "complete infarction" or percutaneous coronary intervention (and coronary angioplasty) is then performed. The percutaneous coronary intervention in this setting is known as "PCI rescue" or "PCI salvage". Complications, particularly bleeding, were significantly higher with PCI rescue than with primary PCI due to thrombolytic action.
Side effects
Intracranial hemorrhage (ICB) and subsequent stroke are serious side effects of thrombolytic use. Risk factors for developing intracranial hemorrhage include previous episodes of intracranial hemorrhage, advanced age of the individual, and the thrombolytic regimen being used. In general, the risk of ICB due to thrombolytics is between 0.5 and 1 percent. Coronary angioplasty
The benefits of primary and rapid angioplasty for thrombolytic therapy for acute STEMI have now been demonstrated. When performed rapidly, angioplasty restores flow in the clogged arteries in more than 95% of patients compared to the 65% reperfusion rate achieved by thrombolysis. The logistical and economic barriers seem to hinder the wider application of angioplasty, although the feasibility of providing regionalized angioplasty for STEMI is currently being explored in the United States. The use of coronary angioplasty to abort myocardial infarction is preceded by primary percutaneous coronary intervention. The purpose of angioplasty immediately is to open the arteries as soon as possible, and preferably within 90 minutes of patients coming to the emergency room. This time is called door-to-balloon time. Some hospitals may provide angioplasty within the 90-minute intervals, prompting the American College of Cardiology (ACC) to launch a national Door to Balloon (D2B) Initiative in November 2006. More than 800 hospitals have joined the D2B Alliance on March 16, 2007.
One of the most successful implementations of primary PCI protocols is in the Calgary Health Area under the Libin Cardiovascular Institute of Alberta. Under this model, an EMS team responding to emergencies can send ECG directly to a digital filing system that enables emergency room staff to immediately confirm the diagnosis. This in turn allows for the transfer of an EMS team to a facility that is ready to perform a critical angioplasty of time. This protocol has resulted in an average time of treatment for 62 minutes.
Current guidelines in the United States restrict angioplasty to hospitals with emergency bypass operations available as reserves, but this does not occur in other parts of the world.
PCI involves performing a coronary angiogram to determine the location of the infarcting vessels, followed by balloon angioplasty (and often intracoronary stent spread) from the stenosed arterial segment. In some settings, extraction catheters can be used to try aspiration (throw) thrombus before balloon angioplasty. While the use of intracoronary stents did not improve short-term outcomes in primary PCI, the use of stents was widespread due to decreased levels of procedure for treating restenosis compared with balloon angioplasty.
Adjuvant therapy during angioplasty includes intravenous heparin, aspirin, and clopidogrel. Glycoprotein IIb/IIIa inhibitors are often used in the setting of primary angioplasty to reduce the risk of ischemic complications during the procedure. Because of the number of antiplatelet agents and anticoagulants used during primary angioplasty, the risk of bleeding associated with the procedure is higher than during elective procedures.
Maps Reperfusion therapy
Coronary artery bypass operation
Emergency bypass surgery for the treatment of acute myocardial infarction (MI) is less common than PCI or thrombolysis. From 1995 to 2004, the percentage of people with cardiogenic shock treated with primary PCI increased from 27.4% to 54.4%, while surgical increment of coronary artery bypass surgery (CABG) only from 2.1% to 3.2 %. Emergency CABG is usually performed to simultaneously treat mechanical complications, such as a ruptured papillary muscle, or ventricular septal defect, with cardiogenic shock. In uncomplicated MI, mortality rates can be high when surgery is done immediately after the infarction. If this option is consoled, the patient should be stabilized before surgery, with supportive interventions such as the use of intra-aortic balloon pumps. In patients with cardiogenic shock after myocardial infarction, PCI and CABG are satisfactory treatment options, with similar survival rates.
Coronary artery bypass surgery involves the artery or vein of the patient being implanted to bypass the constriction or occlusion in the coronary artery. Some arteries and veins may be used, but internal mammary arterial grafts have demonstrated a much greater long-term severity than large saphenous vein grafts. In patients with two or more coronary arteries affected, bypass surgery is associated with higher long-term survival rates compared with percutaneous interventions. In patients with single vessel disease, surgery is considered safe and effective, and may be a treatment option in a particular case. Bypass operations have a higher cost at first, but become cost effective in the long run. The surgical bypass graft is more invasive initially but bears less risk than repeated procedures (but this may be minimally invasive anymore).
Reperfusion arrhythmias
The accelerated idioventricular rhythm that looks like slow ventricular tachycardia is a sign of reperfusion success. There is no need for this rhythm treatment because it rarely changes to a more serious rhythm.
See also
- Perfusion scan
- Reperfusion injury
- Revascularization
- TIMI
- Ischemia-reperfusion injury to the appendicular musculoskeletal system
References
Source of the article : Wikipedia
0 Comments