There are infarctions that do not cause ECG changes typically smaller infarctions and there are cases in which the thrombus is dynamic in size. The thrombus may become larger or smaller, with minute-to-minute variation, and thus cause varying ECG changes. Most patients undergo coronary angiography with the purpose of performing PCI. Angiography is performed within 24 hours but sooner if the patient is a high risk patient. ECG changes, troponin levels, clinical status and comorbidities will dictate if angiography must be performed promptly.
Collateral circulation, which is common among patients with coronary artery disease, implies that the ischemic area obtains blood flow from two coronary arteries or branches of arteries.
This type of circulation arise when ischemic myocardium stimulates surrounding arteries to sprout out vessels to the ischemic area VEGF [Vascular Endothelial Growth Factor] plays a critical role in the development of collateral circulation. Figure 6 below summarizes classification of acute myocardial infarction and coronary syndromes. ST-T changes are normalized within days or weeks. The duration is longer if ischemia results in infarction.
QRS changes are mostly permanent, particularly Q-waves. Note that treatment and reperfusion therapy may modify the speed by which the ECG normalizes. Early risk assessment can improve outcomes in patients with acute coronary syndromes.
Such risk assessment should address the probability that the syndrome is in fact an acute coronary syndrome and, secondly, the probability of adverse outcomes myocardial infarction and death. These models typically include information regarding medical history, ECG findings, presenting features notably hemodynamic status and cardiac troponins. These vary with respect to the type of risk estimated short-term, long-term, myocardial infarction, death. Clinical application of the ECG in chest pain and myocardial infarction.
Introduction to Coronary Artery Disease. Myocardial infarction: diagnostic criteria, definitions and use of ECG. Myocardial Reaction in Ischemia and Infarction. View all chapters in Myocardial Ischemia and Infarction.
No products in the cart. Sign in Sign up. Search for:. Introduction to ECG Interpretation. Clinical electrocardiography and ECG interpretation. Arrhythmias and arrhythmology. Mechanisms of cardiac arrhythmias: from automaticity to re-entry reentry. Conduction Defects. Overview of atrioventricular AV blocks. Atrial and ventricular enlargement: hypertrophy and dilatation on ECG.
Exercise stress test treadmill test, exercise ECG : Introduction. Diagnosis is more challenging when test results are discordant with pre-test probability, in which case serial cTn levels often help. A patient with low pre-test probability and an initially slightly elevated cTn that remains stable on repeat testing probably has non-ACS cardiac disease eg, heart failure, stable coronary artery disease.
Angiography provides detailed images of blood vessels When possible, emergency coronary angiography and PCI are done as soon as possible after the onset of acute myocardial infarction primary PCI. In many tertiary centers, this approach has significantly lowered morbidity and mortality and improved long-term outcomes. Frequently, the infarction is actually aborted when the time from pain to PCI is short Angiography is obtained urgently for patients with STEMI, patients with persistent chest pain despite maximal medical therapy, and patients with complications eg, markedly elevated cardiac markers, presence of cardiogenic shock, acute mitral regurgitation, ventricular septal defect, unstable arrhythmias.
Patients with uncomplicated NSTEMI whose symptoms have resolved typically undergo angiography within the first 24 to 48 hours of hospitalization to detect lesions that may require treatment.
This cardiac MRI shows the right ventricle red arrow and left ventricle green arrow separated by the septal myocardium blue arrow.
There is late gadolinium subendocardial enhancement characteristic of a small myocardial infarct in the lateral wall of the left ventricle white arrow. After initial evaluation and therapy, coronary angiography may be used in patients with evidence of ongoing ischemia ECG findings or symptoms , hemodynamic instability, recurrent ventricular tachyarrhythmias, and other abnormalities that suggest recurrence of ischemic events. Global risk should be estimated via formal clinical risk scores Thrombosis in Myocardial Infarction [TIMI] or a combination of the following high-risk features:.
It causes immediate syncope and death within minutes. Treatment is with cardiopulmonary Most fatalities occur in the first 3 to 4 months.
Persistent ventricular arrhythmia, heart failure, poor ventricular function, and recurrent ischemia indicate high risk. Many authorities recommend stress ECG before hospital discharge or within 6 weeks.
Good exercise performance without ECG abnormalities is associated with a favorable prognosis; further evaluation is usually not required. Poor exercise performance is associated with a poor prognosis. Cardiac performance after recovery depends largely on how much functioning myocardium survives the acute attack.
Acute damage adds to scars from previous infarcts. Prehospital care: oxygen, aspirin , nitrates, and triage to an appropriate medical center. Drug treatment: Antiplatelet drugs, antianginal drugs, anticoagulants, and in some cases other drugs.
Reperfusion therapy: Fibrinolytics or angiography with percutaneous coronary intervention or coronary artery bypass surgery. Choice of drug therapy Drugs for Acute Coronary Syndromes Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications A reliable IV route must be established, oxygen given typically 2 L by nasal cannula , and continuous single-lead ECG monitoring started.
Prehospital interventions by emergency medical personnel including ECG, chewed aspirin [ mg], and pain management with nitrates can reduce risk of mortality and complications. Early diagnostic data and response to treatment can help determine the need for and timing of revascularization Revascularization for Acute Coronary Syndromes Revascularization is the restoration of blood supply to ischemic myocardium in an effort to limit ongoing damage, reduce ventricular irritability, and improve short-term and long-term outcomes Drug therapy with antiplatelet drugs, anticoagulants and other drugs based on reperfusion strategy.
On arrival to the emergency room, the patient's diagnosis is confirmed. Drug therapy and timing of revascularization depend on the clinical picture and diagnosis. For patients with NSTEMI, angiography may be done within 24 to 48 hours of admission if the patient is clinically stable.
If the patient is unstable eg, ongoing symptoms, hypotension or sustained arrhythmias , then angiography must be done immediately see figure Approach to myocardial infarction Approach to myocardial infarction Acute myocardial infarction is myocardial necrosis resulting from acute obstruction of a coronary artery.
New data suggest that morphine attenuates activity of some P2Y12 receptor inhibitors and may contribute to worse patient outcomes. Absence of any of these events is termed uncomplicated.
All patients should be given antiplatelet drugs Antiplatelet Drugs Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications The specific drugs used depend on the reperfusion strategy and other factors; their selection and use is discussed in Drugs for Acute Coronary Syndrome Drugs for Acute Coronary Syndromes Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications Patients with acute myocardial infarction should be given the following unless contraindicated :.
Antiplatelet drugs Antiplatelet Drugs Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications Anticoagulants Anticoagulant Drugs Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications All patients are given aspirin to mg not enteric-coated , if not contraindicated, at presentation and 81 mg once a day indefinitely thereafter.
Chewing the first dose before swallowing quickens absorption. Aspirin reduces short-term and long-term mortality risk. In patients undergoing PCI, a loading dose of clopidogrel to mg orally once , prasugrel 60 mg orally once , or ticagrelor mg orally once improves outcomes, particularly when administered 24 hours in advance.
For urgent PCI, prasugrel and ticagrelor are more rapid in onset and may be preferred. Either a low molecular weight heparin LMWH , unfractionated heparin , or bivalirudin is given routinely to patients unless contraindicated eg, by active bleeding. Unfractionated heparin is more complicated to use because it requires frequent every 6 hours dosing adjustments to achieve target activated partial thromboplastin time aPTT.
The LMWHs have better bioavailability, are given by simple weight-based dose without monitoring aPTT and dose titration, and have lower risk of heparin -induced thrombocytopenia Heparin-induced thrombocytopenia Platelet destruction can develop because of immunologic causes viral infection, drugs, connective tissue or lymphoproliferative disorders, blood transfusions or nonimmunologic causes sepsis Bivalirudin is recommended for patients with a known or suspected history of heparin -induced thrombocytopenia.
Anticoagulants are continued for:. Duration of hospital stay in patients on LMWH or 48 hours in patients on unfractionated heparin in all other cases. Abciximab , tirofiban , and eptifibatide appear to have equivalent efficacy, and the choice of drug should depend on other factors eg, cost, availability, familiarity.
This agent is continued for 6 to 24 hours. Chest pain can be treated with nitroglycerin or sometimes morphine. Nitroglycerin is preferable to morphine , which should be used judiciously eg, if a patient has a contraindication to nitroglycerin or is in pain despite nitroglycerin therapy. Nitroglycerin Nitrates Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications Morphine 2 to 4 mg IV, repeated every 15 minutes as needed, is highly effective but can depress respiration, can reduce myocardial contractility, and is a potent venous vasodilator.
Evidence also suggests that morphine use interferes with some P2Y12 receptor inhibitors. A large retrospective trial showed that morphine may increase mortality in patients with acute myocardial infarction 1, 2 Treatment references Acute myocardial infarction is myocardial necrosis resulting from acute obstruction of a coronary artery. Hypotension and bradycardia secondary to morphine can usually be overcome by prompt elevation of the lower extremities. Standard therapy for all patients with unstable angina includes beta-blockers, ACE inhibitors, and statins.
Beta-blockers Beta-Blockers Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications Beta-blockers reduce heart rate, arterial pressure, and contractility, thereby reducing cardiac workload and oxygen demand.
ACE inhibitors Other Drugs Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications If an ACE inhibitor is not tolerated because of cough or rash but not angioedema or renal dysfunction , an angiotensin II receptor blocker Other Drugs Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications Statins Other Drugs Treatment of acute coronary syndromes ACS is designed to relieve distress, interrupt thrombosis, reverse ischemia, limit infarct size, reduce cardiac workload, and prevent and treat complications For patients with NSTEMI: Immediate percutaneous coronary intervention for unstable patients or within 24 to 48 hours for stable patients.
For STEMI patients, emergency PCI is the preferred treatment of ST-segment elevation myocardial infarction when available in a timely fashion door to balloon-inflation time 90 minutes by an experienced operator.
If there is likely to be a significant delay in availability of PCI, thrombolysis should be done for STEMI patients meeting criteria see Infarct extent Infarct extent Acute myocardial infarction is myocardial necrosis resulting from acute obstruction of a coronary artery. Reperfusion using fibrinolytics is most effective if given in the first few minutes to hours after onset of myocardial infarction. The earlier a fibrinolytic is begun, the better.
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Recognizing the symptoms can help you quickly receive the correct treatment. Health Conditions Discover Plan Connect. Acute Myocardial Infarction heart attack. Symptoms Causes Risk factors Diagnosis Treatments Outlook Prevention Acute myocardial infarction, also known as a heart attack, is a life-threatening condition that occurs when blood flow to the heart muscle is abruptly cut off, causing tissue damage.
What are the symptoms of acute myocardial infarction? What causes acute myocardial infarction? Who is at risk for acute myocardial infarction? How is acute myocardial infarction diagnosed?
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