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ACUTE MYOCARDIAL INFARCTION

ACUTE MYOCARDIAL INFARCTION. AMI. Myocardial Infarction. Occurs when there is a sudden and total occlusion or near-occlusion of blood flowing through an affected coronary artery to an area of heart muscle

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ACUTE MYOCARDIAL INFARCTION

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  1. ACUTE MYOCARDIAL INFARCTION AMI Acute Myocardial Infarction

  2. Myocardial Infarction • Occurs when there is a sudden and total occlusion or near-occlusion of blood flowing through an affected coronary artery to an area of heart muscle • Results in ischemia, injury, and necrosis of the area of myocardium distal to the occlusion • Most often associated with atherosclerotic heart disease (ASHD) Acute Myocardial Infarction

  3. Myocardial Infarction • More than 1,000,000 people suffer from an MI each year and 500,00 die each year from CAD. • Mortality usually occurs within the first several hours of onset and at home. • Factors that have been implicated in the pathogenesis of MI include atherosclerotic rupture and spasm: • Acute intracoronary thrombosis • Arterial spasm Acute Myocardial Infarction

  4. Myocardial Infarction • Both are potentially reversible. • Intervention should be early and aggressive. • The time period from the onset of symptoms to initiation of therapy is the key determinant of success. Acute Myocardial Infarction

  5. Myocardial InfarctionPathophysiology • Infarction produces major changes in myocardial cell function: • Electrical depolarization • Contractility • Complications of AMI are caused by one or both of these events. • The amount of infarcted tissue is a critical factor in determining prognosis, morbidity and mortality. Acute Myocardial Infarction

  6. Myocardial InfarctionPathophysiology • Arrhythmias in AMI are another concern, the most frequent arrhythmias are: • Tachyarrhythmias and ventricular ectopy, caused by the electrical differences between adjacent areas of normal and ischemic myocardium. • Bradyarrhythmias and atrioventricular blocks are due to either increased vagal tone or infarction directly affecting the conduction system. Acute Myocardial Infarction

  7. Myocardial InfarctionPathophysiology • Impaired contractility results in: • Left Ventricular Pump Failure • 25% impaired, results in heart failure • 40% impaired, results in cardiogenic shock • Papillary Muscles (mitral valve) impaired will result in: • Acute mitral regurgitation which may cause acute pulmonary edema and hypotension. Acute Myocardial Infarction

  8. Myocardial InfarctionPrimary Cause • Coronary Artery Disease (CAD) • Common cause of CAD is arteriosclerosis. • Definition: a degenerative disease of the arteries that causes thickening, loss of elasticity and hardening of the walls from calcium. • Most common type of arteriosclerosis is atherosclerosis. Acute Myocardial Infarction

  9. Atherosclerosis • A disease process characterized by progressive narrowing of the lumen of medium and large arteries (e.g., the aorta and its branches, cerebral arteries, coronary arteries). • Results in the development of thick, hard atherosclerotic plaque called atheromas or atheromatous lesions which are most commonly found in areas of turbulent blood flow. Acute Myocardial Infarction

  10. Atherosclerosis • Usually occurs with aging. • It is often linked to overweight, hypertension, and diabetes. Acute Myocardial Infarction

  11. Hypertension Cigarette smoking Diabetes Elevated cholesterol Lifestyle Diet Obesity Sex  male being at higher risk Family history Type A personality AtherosclerosisRisk Factors Acute Myocardial Infarction

  12. Atherosclerosis • Gradual process that continues to obstruct the coronary arteries. • As obstruction continues other vascular pathways enlarge  collateral coronary circulation. • These arteries serve as an alternate route for blood flow around the obstructed artery to the myocardium. Acute Myocardial Infarction

  13. Atherosclerosis — Effects • Two major effects on blood vessels: • The disease disrupts the intimal surface, causing a loss of vessel elasticity and an increase in thrombogenesis • The atheroma reduces the diameter of the vessel lumen and thus decreases the blood supply to tissues Acute Myocardial Infarction

  14. Myocardial InfarctionSigns & Symptoms • The classic symptom is severe anginal pain, lasting longer than 15 to 30 minutes. • The pain often radiates to the jaw, neck, shoulders and arms. • The pain is described as crushing, pressing, constricting, oppressive, or heavy. Acute Myocardial Infarction

  15. Myocardial InfarctionSigns & Symptoms • Less common presentation is high epigastric discomfort, which may be a manifestation of myocardial ischemia and may be dismisses as indigestion. • Any prolonged or unusual indigestion should raise suspicion, particularly in a high-risk individual. Acute Myocardial Infarction

  16. Myocardial InfarctionSigns and Symptoms • Pain is similar to anginal pain and may radiate to the arms, neck, jaw, or back • Dyspnea • Anxiety/Agitation • Syncope • Sense of impending doom • Nausea and vomiting • Diaphoresis • Cyanosis • Palpitations Acute Myocardial Infarction

  17. Myocardial InfarctionSigns & Symptoms • Less common symptoms include: • CVA • Pulmonary edema • Shock • Ventricular tachycardia • The out-of-hospital morality in AMI is almost entirely due to arrhythmias: primarily ventricular fibrillation. Acute Myocardial Infarction

  18. Myocardial InfarctionManagement • Treatment is based on patient history and presenting symptoms. • A normal ECG cannot be relied on to exclude the diagnosis of AMI. Acute Myocardial Infarction

  19. Myocardial InfarctionGeneralized Management • Oxygen: preferably with a NRM; if not tolerated a nasal cannula (4-6 lpm) is acceptable. • ECG Monitoring • Bradycardias occur in up to one third of patients (inferior wall MI). • Atrial dysrhythmias occur in 10-15% (atrial fibrillation), and are usually due to significant left ventricular dysfunction. • Ventricular dysrhythmias of some type occur in almost 100% of patients with MI. Acute Myocardial Infarction

  20. Myocardial InfarctionGeneralized Management • IV access should be established as soon as possible: • 18 gauge catheter with crystalloid solution or saline lock • May need a route for medication administration Acute Myocardial Infarction

  21. Myocardial InfarctionGeneralized Management • Relief of Pain • When a patient presents with chest pain, sublingual nitroglycerinis tried first unless the patient is hypotensive. If the chest pain and ECG changes resolve promptly, infarction is less likely. • Morphine Sulfate – Only to be used if SL NTG is not successful in relieving pain. • Relief of pain alleviates anxiety and, thus, excretion of catecholamines. Acute Myocardial Infarction

  22. Types and Locations of Infarcts • Infarction develops distally to the occluded artery • Size of the infarct determined by: • Metabolic needs of the tissue supplied solely or predominantly by the occluded vessel • Presence of collateral circulation • Duration of time until flow is reestablished Acute Myocardial Infarction

  23. Types and Locations of Infarcts • Emergency care is directed at: • Increasing oxygen supply by administering supplemental oxygen • Decreasing the metabolic needs and in providing collateral circulation • Reestablishing perfusion to the ischemic myocardium as quickly as possible after the onset of symptoms Acute Myocardial Infarction

  24. Types and Locations of Infarcts • Most AMIs involve the left ventricle or interventricular septum, which is supplied by either of the two major coronary arteries • Some patients sustain damage to the right ventricle Acute Myocardial Infarction

  25. Types and Locations of Infarcts • Anterior, lateral, or septal wall infarction is usually the result of left coronary artery occlusion • Inferior wall infarction (of the inferior-posterior wall of the left ventricle) is usually the result of right coronary artery occlusion Acute Myocardial Infarction

  26. Myocardial Infarction • Infarction can be classified into one of three ischemic syndromes based on the rupture of an unstable plaque in an epicardial artery: • Unstable angina • Non-ST-elevation myocardial infarction • ST-elevation myocardial infarction Acute Myocardial Infarction

  27. Infarction • Unstable Angina • The early thrombus has not completely obstructed coronary flow • Causes an intermittent ischemic episode that may eventually result in complete occlusion and AMI • Non-ST-elevation MI • Evident only with ST-segment depression or T-wave abnormalities Acute Myocardial Infarction

  28. Infarction • ST-elevation MI • Q-wave MI • Diagnosed by development of abnormal Q waves • Pathologic Q waves; sign of old infarct • Greater than 5 mm in depth or greater than .04 sec in duration in two or more contiguous leads Acute Myocardial Infarction

  29. Death of Myocardium • When blood flow to the myocardium ceases, cells switch from aerobic to anaerobic metabolism • This contributes to produce ischemic pain (angina) • As cells lose their ability to maintain their electrochemical gradients, they begin to swell and depolarize • If collateral flow and reperfusion are inadequate, much of the muscle distal to the occlusion dies Acute Myocardial Infarction

  30. Heart Attack Videos • YouTube - What causes a heart attack? • YouTube - how heart attack happens?. Acute Myocardial Infarction

  31. Myocardial InfarctionOther Therapies - Fibrinolytics • Rationale: • Evidence that AMI is most often caused by the formation of a thrombus superimposed on a chronic atherosclerotic lesion in a major coronary artery. • Reperfusion therapy with a fibrinolytic agent can successfully reopen the occluded artery and restore blood flow to the distal myocardium, thereby salvaging myocardium that is not yet irreversibly damaged. Acute Myocardial Infarction

  32. Myocardial InfarctionOther Therapies - Fibrinolytics • Myocardial cell death is not an instantaneous process but actually takes place over a period of hours. Because of this fibrinolytic therapy initiated within this time interval can accomplish reperfusion. Acute Myocardial Infarction

  33. Myocardial InfarctionOther Therapies - Fibrinolytics • Major benefits and Risks • Reduction in Infarct-Related Mortality • Bleeding complications: • Primary concern is the possibility of intracranial bleeding and stroke • Careful screening of patients for contraindications and precautions can minimize this complication. Acute Myocardial Infarction

  34. Myocardial InfarctionOther Therapies - Fibrinolytics • Indications for Fibrinolytic Therapy • Recent onset of chest pain (less than 6 hours), that is not relieved by nitroglycerin. • ST-segment elevation (greater than or equal to 1 mm) in two or more associated lead. Only true absolute indicator. • Tall or peaked T waves in two or more associated leads • New onset Bundle Branch Block Acute Myocardial Infarction

  35. Absolute Contraindications to Fibrinolytic Therapy • History of CVA, aneurysm • Intracranial or spinal surgery or trauma within 2 months • Severe uncontrolled hypertension • Known bleeding diathesis • Current treatment with an anticoagulant • Active internal bleed within 10 days • Significant surgical or biopsy procedure within the last 8 weeks • Suspected pregnancy Acute Myocardial Infarction

  36. Relative Contraindications to Fibrinolytic Therapy • Dependent on the fibrinolytic agent selected. Acute Myocardial Infarction

  37. Fibrinolytic TherapyReperfusion • May be indicated by resolution of chest pain and/or degree of resolution of acute ECG changes. • Patient may develop perfusion arrhythmias, (ventricular tachycardia, accelerated idioventricular rhythm bradycardia), which suggest improved coronary blood flow. Acute Myocardial Infarction

  38. Fibrinolytic TherapyReperfusion • Lidocaine and atropine should be readily available. • It may be advisable to initiate prophylactic lidocaine with the initiation of thrombolytic Acute Myocardial Infarction

  39. Myocardial InfarctionOther Therapies - Angioplasty • Definition: Surgical procedure performed to open coronary vessels in hopes of reperfusing myocardial tissue. • Potentially advantageous because it is effective in reducing the degree of residual stenosis in the infarct related artery and because it may open stenotic vessels when other therapies have failed. Acute Myocardial Infarction

  40. Coronary Angioplasty • Intervention may not be suitable for all patients. There may be a significant risk of dissection of the artery. • There has been a high incidence of restenosis or reocclusion after angioplasty • This intervention is limited and should be performed only at centers that have cardiac surgical backup. Acute Myocardial Infarction

  41. Coronary Angioplasty • Fibrinolytic therapy should be the first line of intervention with angioplasty as the backup. • AHA recommends that all patients receive fibrinolytic therapy followed by angioplasty, (combined has longer duration of effect). Acute Myocardial Infarction

  42. Coronary Angioplasty Video • YouTube - ANGIOPLASTY STENT Acute Myocardial Infarction

  43. Myocardial InfarctionOther Therapies • Coronary Artery Bypass Grafting (CABG) • Definition: An open heart surgery to relieve a blocked heart artery. An artificial tube or part of a blood vessel is attached to the diseased coronary artery. It is then connected to the aorta, bypassing the damaged artery. Surgery will improve the blood supply to the heart muscle, ease the work of the heart and help anginal pain. Acute Myocardial Infarction

  44. Coronary Artery Bypass Grafting • Significant improvement, has been demonstrated, in left ventricular function after CABG in AMI. • Because there are no clear indications as to which patients would benefit compared to those that would be harmed by this surgery. It is not practical for widespread use in AMI. Acute Myocardial Infarction

  45. Myocardial InfarctionOther Therapies - AICD • AICD = Automatic Internal Cardioverter Defibrillator • Developed for ambulatory patients at risk of sudden death from ventricular fibrillation. • The defibrillators monitor the ECG continuously, recognize ventricular fibrillation and ventricular tachycardia, and defibrillate or cardiovert with 10-20 joules. • The charge is delivered by two cup electrodes surgically applied over the apex and base of the heart. Acute Myocardial Infarction

  46. Myocardial InfarctionComplications • Congestive Heart Failure • Left Ventricular Pump Failure • Cardiogenic Shock • Acute Mitral Regurgitation • Ventricular Septal Rupture Acute Myocardial Infarction

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