Diagnosis: Acute Anterior STEMI

The patient's ECG revealed grossly elevated ST segments in anterior leads including "tombstone T-waves" consistent with diagnosis of acute anterior ST-segment elevation myocardial infarction. The Cath Lab was immediately activated by the ED and the patient started on a heparin drip after negative FOBT. 

In the Cath Lab the patient was found to have 100% stenosis of the proximal left anterior descending (LAD) artery, 80% stenosis of the mid LAD artery, and 70% stenosis of the proximal right coronary artery (RCA). A stent was placed in the LAD reducing the occlusion to 0% stenosis. The patent's left ventricular ejection fracture post-procedure was 35-40%. 

The patient expired 2 days later in the Cardiac Intensive Care Unit secondary to respiratory complications.

In the ECG below, note that there are ST-segment elevations in leads V1 through V6 and slight elevation in lead I suggesting septal (V1-V2), anterior (V3-V4) and lateral (V5-V6, I) wall involvement, as well as reciprocal changes in the inferior wall leads (II, III, aVF) 

ED Management of Acute STEMI

Why we care? 

• Acute coronary syndromes are a leading cause of death in adults in many developed countries 

Quick Pathophys Review

• Coronary blood flow fails to meet myocardial O2 demand --> ischemia/infarction

• Most coronary stenosis preceding an acute MI is <50% - the problem is acute plaque rupture

• Acute plaque rupture --> platelet activation --> thrombus formation --> acute total occlusion --> exacerbated by subsequent vasospasm

• Further damage due to reperfusion injury secondary to oxygen free radicals, calcium, and neutrophils

ED Management

• Primary goal = early coronary patency and revascularization 
• primary angioplasty vs fibrinolysis 
• treatment within first 1-2 hours of event confers substantial benefit 

• Management goals for ED provider: IV, O2, Monitor
• early recognition (history, physical, ECG) 
• early activation of hospital "STEMI system" and cardiology consult
• early pharmacological therapy

• Nitroglycerin (0.4 mg or 400 ug sublingual) 
• reduce preload --> reduce myocardial O2 demand --> pain relief 
• reduces afterload to lesser extent
• thought to increase myocardial perfusion by increasing collateral coronary flow
• mostly provides pain relief, no significant mortality benefit identified
• CAUTION in preload-dependent states:
• inferior wall MI
• right ventricular infarction
• sudden drop in preload may cause profound hypotension

• Morphine (2-5 mg IV q5-30 min)
• additional pain relief agent when symptoms refractory to nitroglycerin 
• pain relief and anxiolysis reduce O2 consumption and myocardial work
• some preload reduction as well
• CAUTION in hypotensive patients as can further reduce BP

• Aspirin (160-325 mg po)
• large RCTs have demonstrated as much as a 25-50% reduction in mortality
• irreversibly inhibits platelet cyclooxygenase --> block thromboxane A2 enzyme production (platelet aggregator) --> reduced thrombus formation

• Heparin (80 units/kg bolus, 18 units/kg drip)
• strong synergistic effect with aspirin in preventing death from acute MI 
• activates antithrombin III --> inactivates Factors II and X --> prevent conversion of fibrinogen to fibrin --> inhibits clot propagation (no clot lysis) 
• CAUTION in patients with any signs, symptoms or history of bleeding
• always perform FOBT before administering 

• Fibrinolytic therapy - tPA, Streptokinase 
• activates intrinsic tissue plasminogen enzyme --> dissolves thrombus
• ACC/AHA Level I Recommendation in acute MI
• The Good
• well-studied
• improves coronary flow
• limits infarct size
• improves survival in acute MI
• The Bad
• numerous relative and absolute contraindications limit its use
• high risk for bleeding complications including intracranial hemorrhage

• Percutaneous coronary intervention (PCI)
• mechanical clot disruption by endovascular instrumentation under fluoroscopy
• increased number of eligible patients
• lower risk for intracranial bleeding
• significantly higher reperfusion rate 
• earlier characterization of coronary anatomy to guide surgical intervention
• risk stratification allowing early and safe hospital discharge 

Disposition = Cath Lab

• studies suggest <90 minute door-to-ballon time necessary for optimal myocardial salvage
• Time = Myocardium!

References: 

Kurz MC, Mattu A, Brady WJ, Rosen's Emergency Medicine Concepts and Clinical Practice, 8th Ed, 2014, Chapter 78: Acute Coronary Syndrome

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