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Chapter 53

Chapter 53. Management of ST-Elevation Myocardial Infarction. ST-Elevation Myocardial Infarction (STEMI). Myocardial infarction (MI): necrosis of the myocardium resulting from ischemia STEMI: acute MI caused by complete interruption of regional myocardial blood flow

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Chapter 53

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  1. Chapter 53 Management of ST-Elevation Myocardial Infarction

  2. ST-Elevation Myocardial Infarction (STEMI) • Myocardial infarction (MI): necrosis of the myocardium resulting from ischemia • STEMI: acute MI caused by complete interruption of regional myocardial blood flow • Causes elevation of the ST segment on the electrocardiogram (ECG) • Managed differently than non–ST-elevation MI (partial blood flow blockage)

  3. Pathophysiology of STEMI • Blood flow to a region of myocardium is stopped (platelet plugging and thrombus formation) • Hydrogen ions accumulate • Local metabolic changes occur • Myocardial injury triggers ventricular remodeling • Degree of residual cardiac impairment depends on amount/location of damage

  4. Diagnosis of STEMI • Chest pain • Severe substernal, crushing/constricting, down arm and jaw • Characteristic ECG changes • Sweating, weakness, sense of impending doom • 20% of patients with STEMI experience no symptoms • Biochemical markers for MI

  5. Management of STEMI • Routine drug therapy • Oxygen • Aspirin (not NSAIDs) • Morphine • Beta blockers • Nitroglycerin

  6. Management of STEMI • Reperfusion therapy • Primary percutaneous coronary intervention • Fibrinolytic (thrombolytic) therapy • Action:to dissolve clots; converts plasminogen to plasmin

  7. Management of STEMI • Adjuncts to reperfusion therapy • Heparin • Antiplatelet drugs

  8. Management of STEMI • Thrombolytic drugs • Alteplase, a tissue plasminogen activator • Reteplase • Streptokinase • Tenecteplase • Urokinase • Percutaneous coronary intervention (PCI)

  9. Primary Percutaneous Coronary Intervention • Primary refers to the use of angioplasty rather than fibrinolytic therapy • Stents may be placed • Goal: primary PCI within 90 minutes of patient contact • Success rate with PCI somewhat higher than with thrombolytics

  10. Fibrinolytic (Thrombolytic) Therapy • Dissolves clots • Converts plasminogen to plasmin (proteolytic enzyme) • Alteplase, a tissue plasminogen activator • Reteplase • Streptokinase • Tenecteplase • Urokinase

  11. Fibrinolytic (Thrombolytic) Therapy Most effective when patient presents early; not given if pain has been present longer than 12 hours (best if given during first 4–6 hours) Goal: to improve ventricular function, limit size of infarct, and reduce mortality Timely administration = Opening of occluded artery in 80% of patients Guidelines suggest 30-minute target time Best for patients younger than 75 years

  12. Adjuncts to Reperfusion Therapy:Management of STEMI • Unfractionated heparin used for treatment lasting less than 48 hours • Low-molecular-weight (LMW) heparin used for treatment lasting longer than 48 hours • Antiplatelet drugs • Clopidogrel (Plavix) • Glycoprotein (GP) IIb/IIIa inhibitors • Low-dose aspirin • May use concurrently with clopidogrel • Should take indefinitely • Higher dose for PCI patients

  13. Adjuncts to Reperfusion Therapy:Management of STEMI • Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) • Decrease short-term mortality in all patients • Start treatment within 24 hours • ACE inhibitors studied more extensively than ARBs • Calcium channel blockers • Antianginal, vasodilation, and antihypertensive actions

  14. Complications of STEMI • Ventricular dysrhythmias • Develop frequently and are major cause of death after MI • Prophylactic antidysrhythmics not successful • Cardiogenic shock • Results from tissue perfusion reduction • 7%–15% of post-MI patients develop shock in first few days

  15. Complications of STEMI • Ventricular dysrhythmias • Cardiogenic shock • Heart failure • Cardiac rupture

  16. Secondary Prevention of STEMI • Discharge 6–10 days after event • 5%–5% of patients have another infarct in first year • Outcome improved with risk factor reduction • Cholesterol control, smoking cessation, exercise, blood pressure (BP) control, diabetes control • All post-MI patients should take: • Beta blocker • ACE inhibitor • Antiplatelet drug or anticoagulant

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