In Part 2 of this Episode on Acute Coronary Syndromes Management, the evidence for various medications for ACS, from supplemental oxygen to thrombolytics are debated, and decision making around reperfusion therapy for STEMI as well as NSTEMI are discussed. Finally, there is a discussion on risk stratification of low risk chest pain patients and all it’s attendant challenges as well as disposition and follow-up decisions.

Dr. Eric Letovsky, the Head of the CCFP(EM) Program at the University of Toronto, Dr. Mark Mensour & Dr. Neil Fam, an interventional cardiologist answer questions like: What is the danger of high flow oxygen in the setting of ACS? When, if ever, should we be using IV B-blockers in AMI patients? How can you predict, in the ED, who might go on to have an urgent CABG, in which case Clopidogrel is contra-indicated? Which anticoagulant is best for unstable angina, NSTEMI and STEMI – unfractionated heparin (UFH), low molecular weight heparin (LMWH), or fonduparinux? Is there currenly any role for Glycoprotein 2b3a Inhibitors in ACS in the ED? When is thrombolysis better than PCI for STEMI? When should we consider facilitated angioplasty and rescue angioplasty? Which low risk chest pain patients require an early stress test? CT coronary angiography? Stress Echo? Admission to a Coronary Decision Unit (CDU)? and many more…….

Written Summary and blog post by Lucas Chartier, edited by Anton Helman June 2011

Cite this podcast as: Letovsky, E, Mensour, M, Fam, N, Helman, A. Part 2: Acute Coronary Syndromes Management. Emergency Medicine Cases. June, 2011. Accessed [date].

Medications in Acute Corononary Syndromes

  • Oxygen indicated only if pt 1. SOB 2. signs of AHF 3. Shock 4. O2sat<94% (AHA guidelines)
    • hyperoxia causes decreased coronary blood flow, so high flow O2 is not indicated if O2sat>94%
  • ASA 160-320mg chewed: NNT=19 saves one life at 30 days
  • Nitroglycerin: never shown to decrease mortality
    • indicated in pts with CHF with high BP, cocaine associated ischemia, failure to reperfuse after lytics
  • Morphine: helps to dampen pt’s sympathetic response and decrease preload but may increase mortality in NSTEMI pts (CRUSADE study – number needed to harm = 125 when given in high doses)
  • IV B-blockers: AHA guidelines advises against routine use in MI because increases incidence of cardiogenic shock in pts with 1. AHF 2. age >70 3. SPB110 or
  • older studies show NNT=31 to save one life at 90 days
  • Clopidogrel:
    • in STEMI with Fibrinolysis, NNT = 15 for recurrent MI or death (CLARITY), dose: <75y/o 300mg,
    • >75y/o 75mg
    • in STEMI with PCI, dose: <75y/o 600mg (OASIS-7), >75y/o consider 300mg
    • in NSTEMI or UA with ischemic ECG changes NNT 47 for CV death, nonfatal MI, stroke (CURE) dose:
    • <75y/o 300mg, >75y/o consider 75mg
    • Prasugrel & Ticagrelor- newer faster acting platelet inhibitor; compared to Clopidogrel may reduce ischemic events but have higher risk of bleeding complications
  • Anticoagulants: Unfractionated Heparin (UFH), Low Molecular Weight Heaprin (LMWH eg. Enoxaparin), & Fondaparinux prevent infarct related re-thrombosis, indicated in MI and UA with any ischemic ECG changes or positive biomarkers
    • STEMI pts going for PCI: IV UFH 60IU/kg preferred by interventional cardiologists
    • STEMI with lytics: LMWH and Fondaprinux preferred over UFH
    • NSTEMI & UA: LMWH or Fondaprinux preferred over UFH
    • Fondaprinux may have lower risk of major and minor bleeding complications compared to LMWH

Management of Cocaine-induced Ischemia

  • patients who are chronic cocaine users are more likely to have atherosclerotic dz and acute cocaine use causes coronary vasospasm
  • mainstays of medical therapy are benzodiapines and nitrates
  • PCI is the re-perfusion treatment of choice in cocaine-related ischemia

Fibrinolysis vs PCI for STEMI

  • Fibrinolysis is generally preferred if: early presentation (90mins OR door-to-balloon time minus door-to-needle time >1hr, AND no C/I to fibrinolysis
  • PCI is generally preferred if: late presentation (>3hrs from symptom onset), door-to-balloon time
  • additionally, PCI is generally preferred for cocaine-induced STEMI and pts with LBBB who do not fulfill Sgarbosa’s criteria, as there is uncertainty of the diagnosis of MI
  • risk of IC bleed with fibrinolysis ranges from 0.25% to 2.5% depending on: age >65, weight <70kg, HTN in ED >180/110
  • Absolute C/Is to fibrinolysis in STEMI: prior ICH, known structural cerebral vascular lesion, known malignant intracranial neoplasm, ischemic stroke within 3 months, suspected aortic dissction, active bleeding or bleeding diathesis (excluding menses), significant closed-head trauma or facial trauma within 3 months
  • for Emergency Departments located a few hours from a PCI centre, a ‘pharmaco-invasive strategy’ (facilitated PCI) can be considered according to the TRANSFER-AMI study in which high risk STEMI pts received standard-dose tenecteplase, ASA and either UFH or Enoxaparin and Clopidogrel. Pts were randomized to either standard treatment (including rescue PCI, if required, or delayed angiography) or a strategy of immediate transfer to a PCI centre within 6 hours after fibrinolysis. Pts in the ‘pharmaco-invasive strategy’ group had fewer ischemic complications, but there was no mortality benefit.

Disposition Decisions in Low Risk Chest Pain Patients

  • while the risk of a cardiac event or death in 30 days is <1-2% after a a negative ED cardiac work-up (normal serial ECGs and 2 sets of normal cardiac biomarkers), it is not zero
  • the decision to admit a pt who is at low risk for ACS after a negative ED cardiac work-up for invasive testing must be weighed against the potential complications of invasive cardiac testing (radiation exposure, bleeding etc)
  • Jeffery Kline (of PERC rule fame) determined with computer modelling that with a pretest probability of ACS less than or equal to 2%, the risk of testing will exceed its benefits; this has yet to be validated
  • there are no chest pain decision rules that have a low enough acceptable miss rate to be used clinically in the ED as the sole means for making disposition decisions
  • TIMI score: 7 point score based on age>65, 3+ CVS Risk Factors, prior coronary stenosis >50%, ST deviation on ECG >0.5mm, 2+ anginal equivalents in 24hr, ASA use in the last 7 days, elevated cardiac biomarkers
    • originally developed for use in pts with UA or NSTEMI as apposed to the undifferentiated ED CP pt
    • CMAJ, 2010. Diagnostic accuracy of the TIMI risk score in patients with chest pain in the emergency department: a meta-analysis. Conclusion: “Although the TIMI risk score is an effective risk stratification tool for pts in the ED with potential ACS, it should not be used as the sole means of determining patient disposition”
  • pts who are discharged from the ED who are considered to be low risk for ACS and require further cardiac testing, should have that test performed and interpreted within 48-72hrs
  • ideally low risk CP pts should have a stress test before discharge
  • treadmill stress test, while having poor sensitivity and specificity is inexpensive and easily accessible compared to nuclear testing, stress Echo and CT coronary angiography
  • CT coronary angiography positives: excellent negative predictive value, identifies other diseases, shows vessel wall abnormalities (not just stenosis) which can lead to unstable plaques, ideal for moderate risk pts (>10% ACS risk)
  • CT coronary angiography negatives: poor specificity with many false positives in low risk patients, radiation exposure
  • Clinical Decision Units or Chest Pain Observation Units have been shown to reduce length of stay, hospital admissions, diagnostic accuracy and healthcare costs but have never been shown to reduce adverse cardiovascular outcomes, particularly mortality

For more on acute coronary syndromes on EM Cases:
Episode 15 Part 1: Acute Coronary Syndromes Risk Stratification
Best Case Ever 1 Is Thrombolysis Better Than PCI for STEMI?
Best Case Ever 4 Acute Coronary Syndrome From Venous Source
Journal Jam 5 One Hour Troponin to Rule Out and In MI

Key References

Tintinalli J, Stapczynski J, Ma OJ et al. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, Seventh Edition (Book and DVD). Mcgraw-hill; 2010.

Hockberger RS, Walls RM. Rosen’s Emergency Medicine – Concepts and Clinical Practice, 2-Volume Set,Expert Consult Premium Edition – Enhanced Online Features and Print,7, Rosen’s Emergency Medicine – Concepts and Clinical Practice, 2-Volume Set. Elsevier Health Sciences; 2009.