Snapshot A 55-year-old man presents to the emergency department due to substernal chest pain. His symptoms began a few hours ago. He describes the pain as "crushing" and it radiates down the left arm. Medical history is significant for type 2 diabetes and hypertension. On physical exam the patient is diaphoretic. An electrocardiogram demonstrates ST-segment elevations and cardiac troponins are significantly elevated. Introduction Clinical definition death of myocardial tissue secondary to prolonged and severe ischemia also known as a "heart attack" Types ST-segment elevation myocardial infarction (STEMI) an acute coronary syndrome (ACS) with ST-segment elevations found on electrocardiogram (ECG) biomarkers of myocardial necrosis are present Non-STEMI (NSTEMI) an ACS without ST-segment elevations found on ECG biomarkers of myocardial necrosis are present unstable angina an ACS login to view 2 more bullets Epidemiology incidence increases with age risk factors hypertension cigarette smoking hyperlipidemia hypercholesterolemia male postmenopause genetic and behavioral predispositions to arteriosclerosis login to view 1 more bullet Etiology occlusion of a coronary artery can be caused by atheromatous plaque rupture with subsequent thrombi expansion vasospasm emboli, which can be secondary to login to view 4 more bullets Pathophysiology occlusion of a coronary artery disrupts the blood supply to a region in the myocardium ischemia ensues, the myocytes become rapidly dysfunctional login to view 2 more bullets infarction patterns subendocardial login to view 3 more bullets transmural login to view 2 more bullets ECG Changes and STEMI ECG Changes and STEMI Infarction Location Involved ECG Leads Involved Coronary Artery Inferior wall II, III, and aVF RCA Antero-apical V3 and V4 LAD (distal) Antero-septal V1 and V2 LAD Antero-lateral V5 and V6 LAD or LCX Lateral I and aVL LCX Posterior ST depression and tall R waves in V1-3 V7-V9 Posterior descending artery Evolution of MI Morphological Myocardial Changes in an MI Time Gross Features Light Microscopy Complications 0-24 hours Initially no gross findings; however, over the course of the first 24 hours, dark mottling ensues Early coagulation necrosis Wavy fibers Elongated myocytes Neutrophil infiltration Arrhythmia Heart failure 1-3 days Mottling with a yellowish infarct center Extensive coagulation necrosis Brisk neutrophil infiltration Fibrinous pericarditis 3-14 days 3-7 days hyperemic with central yellowing 7-10 days yellow-tan with reddish tan margins 10-14 days reddish gray infarct borders Macrophage infiltration and tissue granulation Myocardial wall rupture may lead to cardiac tamponade Papillary muscle rupture mitral regurgitation posterolateral muscle rupture is more likely than anteromedial muscle rupture Pseudoaneurysm of a ventricular wall may rupture 2 weeks - several months 2-8 weeks gray-white scar > 2 months complete scar Collagenous scar Dressler syndrome Heart failure True ventricular aneurysm a thrombus may form Presentation Symptoms chest pain features login to view 3 more bullets radiation login to view 3 more bullets nausea and vomiting dyspnea asymptomatic typically seen in patients with diabetic neuropathy login to view 1 more bullet Physical exam diaphoresis variable findings e.g., S3 or S4, signs of heart failure, bradycardia (in cases of an inferior wall MI) Imaging Coronary angiography indication diagnostic study to assess coronary anatomy and to determine where the occlusion is Studies 12-lead ECG perform as soon as possible findings STEMI login to view 7 more bullets NSTEMI login to view 2 more bullets Late login to view 3 more bullets Biomarkers Troponin preferred marker as it has a high sensitivity and specificity for myocardial necrosis troponin I increases after 4 hours and peaks around 24 hours login to view 1 more bullet CK-MB a sensitive but not specific biomarker since skeletal muscle can also release it useful for assessing reinfarction Differential Unstable angina differentiating factor no elevation in cardiac biomarkers Costochondritis differentiating factor chest pain that is reproducible with palpation Treatment Conservative lifestyle modification e.g., smoking cessation Medical initial medical treatments include aspirin oxygen nitroglycerin login to view 1 more bullet morphine login to view 2 more bullets P2Y12 (ADP) receptors blockers indication login to view 1 more bullet heparin indication login to view 1 more bullet β-blockers indication login to view 1 more bullet statin indication login to view 1 more bullet angiotensin-converting enzyme (ACE) inhibitor indication login to view 6 more bullets contraindication login to view 3 more bullets Reperfusion therapy percutaneous coronary intervention (PCI) indications login to view 2 more bullets coronary artery bypass graft (CABG) indication login to view 3 more bullets fibrinolytic therapy indication login to view 1 more bullet Complications Heart failure Sudden cardiac death Arrhythmia Myocardial stunning