Snapshot A 60-year-old man presents to the emergency department due to substernal chest pain. He describes the pain as "crushing" and it radiates down the left arm. Medical history is significant for hypertension and hypercholesterolemia. On physical exam the patient is diaphoretic. An electrocardiogram demonstrates ST-segment elevations and cardiac troponins are significantly elevated. After appropriate acute therapy, the coronary catheterization lab is activated and cardiology is consulted. 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 cocaine use male postmenopause genetic and behavioral predispositions to arteriosclerosis e.g., high-fat diet coronary heart disease risk equivalents diabetes mellitus chronic kidney disease noncoronary atherosclerotic disease login to view 3 more bullets Etiology Occlusion of a coronary artery can be caused by atheromatous plaque rupture with subsequent thrombi expansion vasospasm emboli, which can be secondary to atrial fibrillation, sending an embolus from the left atrium to the coronary arteries vegetations from infective endocarditis material from an intracardiac prosthetic paradoxical emboli 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 STEMIInfarction LocationInvolved ECG LeadsInvolved Coronary ArteryInferior wallII, III, and aVFRCAAntero-apicalV3 and V4LAD (distal)Antero-septalV1 and V2LADAntero-lateralV5 and V6LAD or LCXLateralI and aVLLCXPosteriorST depression and tall R waves that can be seen anywhere in V2-5 (not all leads mandatory)ST elevations in V7-V9Posterior descending artery Evolution of MI Morphological Myocardial Changes in an MI Time Gross Feature 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 Neutrophil infiltration Arrhythmia Heart failure 1-3 days Mottling with a yellowish infarct center Extensive coagulation necrosisBrisk neutrophil infiltration Fibrinous pericarditis 3-14 days 3-7 dayshyperemic with central yellowing7-10 daysyellow-tan with reddish tan margins10-14 daysreddish gray infarct borders Macrophage infiltration and tissue granulation Myocardial wall rupture - sudden hypotension, tachycardia, and pulseless electrical activity - may lead to cardiac tamponade Papillary muscle rupture -mitral regurgitation Pseudoaneurysm of a ventricular wall - may rupture 2 weeks - several months 2-8 weeksgray-white scar> 2 monthscomplete scar Collagenous scar Dressler syndrome Heart failure True ventricular - aneurysma thrombus may form - evaluate with echocardiograph - ECG with persistent ST elevation in original MI leads with a deep QS wave 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, and 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 26 more bullets NSTEMI login to view 2 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 can be elevated in other conditions including states of physiologic stress such as hypotension or sepsis 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 Hibernating myocardium decreased contractility of the myocardium secondary to ischemia without necrosis reversible when stenting restores bloodflow Brugada syndrome sodium channelopathy coved ST elevation risk for sudden cardiac death Wellens syndrome deeply inverted or biphasic T waves indicative of critical left anterior descending artery stenosis De Winter T waves ST depression and peaked T waves in precordial leads anterior STEMI equivalent requires cardiac catheterization Cerebral T waves inverted and wide T waves prolonged QT associated with head trauma and intracranial pathology (such as a subarachnoid hemorrhage) Arrhythmogenic right ventricular dysplasia common cause of syncope and sudden death epsilon wave on ECG Precordial catch syndrome sudden, sharp, and severe paroxsyms of chest pain no ECG or troponin abnormalities Spontaneous coronary artery dissection (SCAD) more common in women, postpartum period, and connective tissue disorders may cause unstable angina, NSTEMI, or STEMI Treatment Conservative lifestyle modification e.g., smoking cessation Medical initial medical treatments include aspirin login to view 2 more bullets oxygen nitroglycerin login to view 3 more bullets morphine login to view 2 more bullets benzodiazepines in cocaine-induced myocardial ischemia login to view 1 more bullet 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 contraindication login to view 2 more bullets 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 cardiac catheterization and percutaneous coronary intervention (PCI) indications login to view 2 more bullets complications 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 Erectile dysfunction (commonly caused by anxiety)