Overview of the acute management of acute ST elevation ...

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Overview of the acute management of ...

Official reprint from UpToDate? upt odat e.c om ?2011 UpToDate?

Overview of the acute management of acute ST elevation myocardial infarction

Authors Guy S Reeder, MD Harold L Kennedy, MD, MPH Robert S Rosenson, MD

Section Editors Christopher P Cannon, MD James Hoekstra, MD

Deputy Editor Gordon M Saperia, MD, FACC

Last literature review version 19.1: Janeiro 2011 | This topic last updated: Outubro 4, 2010

INTRODUCTION -- The first step in the management of the patient with an acute ST elevation myocardial infarction (STEMI) is prompt recognition, since the beneficial effects of therapy with reperfusion are greatest when performed soon after presentation. For patients presenting to the emergenc y department with chest pain suspicious for an acute coronary syndrome (ACS), the diagnosis of STEMI can be confirmed by the ECG. Biomarkers may be normal early. (See "Criteria for the diagnosis of ac ute myocardial infarction" and "Management of suspected acute c oronary syndrome in the emergency department".)

Once the diagnosis of an ac ute STEMI is made, the early management of the patient involves the simultaneous achievement of several goals, as outlined by an ACC/AHA task force [1,2]:

Relief of isc hemic pain

Assessment of the hemodynamic state and correction of abnormalities that are present

Initiation of reperfusion therapy with primary percutaneous coronary intervention (PCI) or fibrinolysis

Antithrombotic therapy to prevent rethrombosis or ac ute stent thrombosis

Beta blocker therapy to prevent recurrent ischemia and life-threatening ventric ular arrhyt hmias

This is then followed by the in-hospital initiation of different drugs that may improve the longterm prognosis [1]:

Antiplatelet therapy to reduce the risk of recurrent coronary artery thrombosis or, with PCI, c oronary artery stent thrombosis

Angiotensin converting enzyme (ACE) inhibitor therapy to prevent remodeling of the left ventric le

Statin therapy

Anticoagulation in the presence of left ventricular thrombus or chronic atrial fibrillation to prevent embolization

This topic will summarize emergent/early management issues for patients with acute STEMI and then direc t the reader to a more detailed discussion in other topic s. The management of the patient after a reperfusion strategy has been c hosen and carried out is discussed separately. (See "Overview of the non-acute management of acute ST elevation myocardial infarc tion".)

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The management of the patient with a non-ST elevation MI (NSTEMI) or with a c omplication of

an ac ute MI (eg, c ardiogenic shock, mitral regurgitation, ventricular septal defect) is discussed

separately. (See "Overview of the ac ute management of unstable angina and acute non-ST

elevation myocardial infarc tion" and "Prognosis and treatment of c ardiogenic shoc k complic ating

ac ute myocardial infarction" and "Mechanic al complications of ac ute myocardial infarction".)

GENERAL PRINCIPLES -- The 2004 American College of Cardiology/Americ an Heart Association (ACC/AHA) guidelines on STEMI rec ommended that all hospitals establish multidisc iplinary teams to develop guideline-based, institution-specific written protoc ols for triaging and managing patients who present with symptoms suggestive of myocardial ischemia [1,2]. In addition the 2009 foc used update recommended that each community develop a STEMI system of care that encourages [3]:

Ongoing multidisciplinary team (including emergency medic al servic es, non-PCI c apable hospitals/STEMI referral c enters, and PCI capable hospitals/STEMI receiving c enters) meetings to evaluate outcomes and measures of performanc e.

A proc ess for prehospital identific ation and ac tivation

Transfer protoc ols for patients who arrive at STEMI referral c enters who are c andidates for primary PCI.

An increasing number of centers use struc tured algorithms, chec klists, or critic al pathways to sc reen patients with a suspected ACS [4-9]. These strategies combine diagnostic evaluation such as elec troc ardiography and serum biomarkers with therapeutic interventions such as aspirin, beta blockers, antithrombotic therapy, and primary PCI or fibrinolytic therapy (table 1). (See "Management of suspected acute coronary syndrome in the emergency department".)

Elderly patients -- Although the majority of myoc ardial infarc tions (MI) in the elderly population present with ECGs that are nondiagnostic or have ST segment depression, STEMI is not uncommon [10]. It is estimated that 60 to 65 percent of STEMIs occ ur in patients 65 years of age and 28 to 33 percent occur in patients 75 years of age [10-12]. In addition, as many as 80 percent of all deaths related to MI oc cur in persons 65 years of age. (See "Overview of the ac ute management of unstable angina and acute non-ST elevation myoc ardial infarction", section on 'Elderly patients'.)

Although patients age 75 and older have been underrepresented in c linic al trials of ACS, the following observations c onc erning ac ute MI in elderly compared to younger patients are generally ac cepted [10]:

Elderly patients more frequently have an atypical presentation, including silent or unrec ognized MI [10,13]. As an example, chest pain is present in 57 perc ent of patients 85 years of age compared to 90 perc ent for those under age 65. Left bundle-branc h bloc k and Killip c lass 2 ac ute heart failure are much more common in patients 85 years of age (34 and 45 percent, respectively). Delays in diagnosis have been well documented and often lead to delays in therapy.

Patients 75 years of age have a higher in-hospital mortality, whic h often occ urs in those with electric al and mechanic al c omplications [10].

Outcomes in elderly patients, as in younger patients, appear to be better with primary PCI than fibrinolysis [10]. (See 'Percutaneous coronary intervention' below.)

Elderly patients are more likely to have frequent and severe bleeding as a c onsequence of antithrombotic therapy [10]. As an example, the risk of stroke as a consequenc e of fibrinolysis is approximately 2.9 percent in patients 85 years of age [10]. Nevertheless, patients 85 years of age who have no contraindications to fibrinolysis, including a high

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risk for intrac ranial hemorrhage, can be treated with fibrinolysis. (See 'Fibrinolysis' below

and "Fibrinolytic (thrombolytic ) agents in acute ST elevation myoc ardial infarc tion:

Therapeutic use", section on 'Stroke'.)

Women -- The approach to women and men should be the same, despite the fac t that women have more atypical symptoms, are older, have greater delays to presentation, and have higher prevalenc e of hypertension. In addition they are at higher risk of bleeding.

Cocaine associated MI -- MI is a well-described complic ation among patients presenting with cocaine-induced ischemic symptoms. (See "Cardiovascular complic ations of cocaine abuse", section on 'Myocardial infarc tion'.)

We agree with the 2008 American Heart Association sc ientific statement on the management of cocaine-associated chest pain and myocardial infarction, whic h states that these patients should be managed in a manner similar to other ACS patients [14]. The following two points were also made:

Benzodiazepines should be administered early

Beta blockers should not be used in the setting of ac ute cocaine intoxication with chest pain due to the possibility of exac erbation of c oronary artery vasoconstriction

Possible stent thrombosis -- The in-hospital mortality of STEMI is higher in patients with coronary artery stent thrombosis (ST) as the c ause, as opposed to a ruptured plaque. Immediate PCI is the treatment of choice, similar to spontaneous MI. Fibrinolysis has also been used for patients with STEMI due to coronary artery stent thrombosis. (See "Coronary artery stent thrombosis: General issues" and "Coronary artery stent thrombosis: Prevention and management".)

INITIAL ASSESSMENT -- Clinical assessment of the patient with a possible acute c oronary syndrome (ACS) begins as soon as the patient arrives in the emergency department and continues in the coronary c are unit. Initial assessment c onsists of ac ute triage and early risk stratification. An ECG should be obtained within 10 minutes of arrival, if it has not been obtained already by EMS providers in the prehospital arena. A detailed approac h to the evaluation and management of patients with an ACS in the emergency department is found separately. (See "Management of suspected ac ute coronary syndrome in the emergenc y department".)

Acute triage -- A focused evaluation on presentation should address, in order of importance, those findings that permit rapid triage and initial diagnosis and management [1]:

Responsiveness, airway, breathing and circ ulation -- In patients who present with respiratory or cardiorespiratory arrest, the appropriate resuscitation algorithms should be followed. (See "Advanced c ardiac life support (ACLS) in adults" and "Supportive data for advanced cardiac life support in adults with sudden cardiac arrest" and "Basic life support (BLS) in adults".)

Evidence of systemic hypoperfusion (hypotension; tachycardia; impaired cognition; c ool, clammy, pale, ashen skin) -- Cardiogenic shock c omplicating acute MI requires aggressive evaluation and management. This issue is disc ussed in detail separately. (See "Clinical manifestations and diagnosis of cardiogenic shock" and "Prognosis and treatment of cardiogenic shock c omplicating acute myocardial infarc tion".)

Left heart failure with hypoxia -- Patients who present with dyspnea, hypoxia, pulmonary edema, and/or impending respiratory compromise require aggressive oxygenation, airway stabilization, diuretic therapy, and afterload reduction in addition to the standard treatments. (See "Treatment of acute dec ompensated heart failure: General c onsiderat ions".)

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Ventricular arrhythmias -- Sustained ventric ular tachyarrhythmias in the periinfarc tion period must be treated immediately because of their deleterious effec t on cardiac output, possible exac erbation of myocardial ischemia, and the risk of deterioration into VF. (See "Clinic al features and treatment of ventricular arrhythmias during ac ute myocardial infarc tion" and 'Arrhythmia management' below.)

Early risk stratification -- Analyses from several large c linical trials and registries have established a number of c linical predictors of adverse outcomes among patients with STEMI. There are many clinical prognostic fac tors that are immediately available to the physician based upon the initial history, physical examination, electrocardiogram (ECG), and c hest X-ray. Given the speed with whic h reperfusion therapy is administered in patients with STEMI, their clinic al utility in early medical decision making in the ED is often limited. They do provide good prognostic information that has utility in the post-reperfusion period, however, and may provide guidance regarding the optimum method of reperfusion.

High-risk features include advanced age, low blood pressure, tachycardia, heart failure (HF), and an anterior MI. Specific scoring systems, suc h as the TIMI risk sc ore, permit a fairly precise determination of the risk of in-hospital mortality (calculator 1) [15,16].

Patients at high risk require an aggressive management strategy in addition to standard medical management. Direct prehospital transport or, less optimally, prompt interhospital transfer to a facility with revascularization capabilities is recommended for suc h patients [1].

INITIAL THERAPY -- The patient with STEMI should have continuous c ardiac monitoring, oxygen, and intravenous acc ess. Therapy should be started to relieve ischemic pain, stabilize hemodynamic status, and reduce ischemia while the patient is being assessed as a c andidate for fibrinolysis or primary PCI. Other routine hospital measures inc lude anxiolytics, serial ECGs, and blood pressure monitoring. The 2004 ACC/AHA guidelines recommended that all initial therapy be carried out in the emergency department based upon a predetermined, institution-specific, written protoc ol [1,2].

The following sections summarize ac ute therapy. A detailed description of the initial therapy in STEMI is found separately. (See "Management of suspected ac ute coronary syndrome in the emergenc y department", section on 'Immediate ED interventions'.)

Oxygen -- We recommend supplemental oxygen to patients with an arterial saturation less than 90 percent, patients in respiratory distress, or those with other high-risk features for hypoxia [17].

The role of supplemental oxygen in patients without hypoxia has not been well studied. A 2010 Coc hrane review evaluated three trials of 387 patients with presumed myocardial infarction (MI) who were randomly assigned to supplemental oxygen or room air. Enrolled patients were either hypoxic and normoxic. The study found no signific ant differenc e in mortality (pooled relative risk 2.88, [95% CI 0.88-9.39] in an intention-to-treat analysis and 3.03, [95% CI 0.93-9.83] among those with c onfirmed MI). No subgroup analysis was performed on those with normoxia [18].

The suggestion of harm with supplemental oxygen found in this Cochrane review is of concern, particularly in patients with normoxia, as a pathophysiologic basis for such harm has been articulated [19]. Hyperoxia, which might occ ur with the administration of oxygen to normoxic individuals, has been shown to have a direc t vasoconstrictor effect on the coronary arteries [19].

Until better evidenc e to support the use of supplemental oxygen in normoxic patients with ac ute MI is available, we suggest (a weak recommendation) its use.

Reperfusion -- Prompt restoration of myoc ardial blood flow is essential to optimize myocardial salvage and to reduc e mortality (figure 1) [20]. A dec ision must be made as soon as possible as to whether reperfusion will be achieved with fibrinolytic agents or primary (direct) percutaneous

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coronary intervention (PCI). (See "Selec ting a reperfusion strategy for acute ST elevation myocardial infarction".)

Percutaneous coronary intervention -- If high-quality PCI is available, multiple randomized trials have shown enhanced survival c ompared to fibrinolysis with a lower rate of intracranial hemorrhage and recurrent MI [21]. As a result, 2007 foc used update of the ACC/AHA 2004 Guidelines for the Management of Patients With STEMI recommended the use of primary PCI for any patient with an acute STEMI who c an undergo the procedure within 90 minutes of first medical contact by persons skilled in the procedure (table 2) [2]. This was not changed in the 2009 update [3].

Patients with typic al and persistent symptoms in the presence of a new or presumably new left bundle branc h bloc k are also considered eligible. (See "Primary percutaneous c oronary intervention in ac ute ST elevation myocardial infarction: Determinants of outcome".)

For patients presenting 12 to 24 hours after symptom onset, the performance of primary PCI is reasonable if the patient has severe HF, hemodynamic or elec tric al instability, or persistent isc hemic symptoms [1]. Randomized trials of routine late PCI have shown an improvement in left ventric ular func tion but not in hard clinic al end points. This approac h is not rec ommended (table 2). (See "Coronary artery patency and outc ome after myoc ardial infarction", sec tion on 'Late PCI to open an occ luded artery'.)

If primary PCI is not available on site, rapid transfer to a PCI c enter c an produce better outcomes than fibrinolysis, as long as the door-to-balloon time, including interhospital transport time, is less than 90 minutes. This door-to-balloon time is diffic ult to obtain unless rapid transport protocols and relatively short transport distances are in place. (See "Primary percutaneous coronary intervention in ac ute ST elevation myoc ardial infarction: Determinants of out c ome".)

We suggest the following approach for patients with STEMI at hospitals without on-site PCI c apabilit y:

For patients who present within two hours of the onset of symptoms we suggest full dose lytic therapy and transfer to a PCI center. This assumes that primary PCI cannot be performed in less than 90 minutes at a loc al PCI center.

For patients who present with symptoms greater than two to three hours we suggest transfer for primary PCI (and give a glycoprotein IIb/IIIa inhibitor before transfer). However, there are times when the patient presents after two hours, PCI c annot be acc omplished in less than 120 minutes. In this setting clinical judgement needs to be exerc ised; fibrinolytic therapy may be appropriate in patients with up to 12 hours of sympt oms.

As noted above, all patients who undergo primary PCI should be pretreated at diagnosis with anticoagulant and antiplatelet therapy. (See 'Antiplatelet therapy' below and 'Anticoagulant therapy' below.)

Fibrinolysis -- The 2007 ACC/AHA focused update (not changed in the 2009 foc used update) recommended the use of fibrinolytic therapy in the following patients [2,3,22]:

Any patient with STEMI who presents within 12 hours of symptom onset has no contraindic ations for fibrinolysis (table 3A-B), and presents to a fac ility without the capability for expert, prompt intervention with primary PCI within 90 minutes of first medical contac t (table 4A-B) [1].

Patients who present to a facility in which the relative delay necessary to perform primary

PCI (the expected door-to-balloon time minus the expec ted door-to-needle time) is

greater than one hour.

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