Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Chapter 53 Management of ST-Elevation Myocardial Infarction

2Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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)

3Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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

4Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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

5Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Management of STEMI  Routine drug therapy  Oxygen  Aspirin (not NSAIDs)  Morphine  Beta blockers  Nitroglycerin

6Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Management of STEMI  Reperfusion therapy  Primary percutaneous coronary intervention  Fibrinolytic (thrombolytic) therapy  Action: to dissolve clots; converts plasminogen to plasmin

7Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Management of STEMI  Adjuncts to reperfusion therapy  Heparin  Antiplatelet drugs

8Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Management of STEMI  Thrombolytic drugs  Alteplase, a tissue plasminogen activator  Reteplase  Streptokinase  Tenecteplase  Urokinase  Percutaneous coronary intervention (PCI)

9Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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

10Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Fibrinolytic (Thrombolytic) Therapy  Dissolves clots  Converts plasminogen to plasmin (proteolytic enzyme) 1.Alteplase, a tissue plasminogen activator 2.Reteplase 3.Streptokinase 4.Tenecteplase 5.Urokinase

11Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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

12Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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

13Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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

14Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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

15Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Complications of STEMI  Ventricular dysrhythmias  Cardiogenic shock  Heart failure  Cardiac rupture

16Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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