Acute coronary syndrome – 11/20/17

Unstable angina = symptoms with negative biomarkers and EKG
NSTEMI or STEMI = symptoms with positive biomarkers and EKG

Types of stress

  • Exercise
  • Dobutamine (works by increasing contractility)
  • Vasodilators – lexiscan or adenosine (not a true “stress” but causes vasodilation of the vessels and if there is an occlusion in one, then more blood will be shunted to the other ones leading to the “steal” phenomenon)

Types of imaging

  • EKG
  • Echo
  • Nuclear medicine study

When deciding what kind of stress and what kind of imaging to use you must take a few things into consideration:

  • If possible, always try to stress a patient with exercise as that gives you information about their exercise tolerance and functional capacity
    • Exercise can be paired with an EKG, echo, or nuclear medicine study
  • If a patient cannot exercise, consider dobutamine or a vasodilator
  • Dobutamine is best to use when a patient has a contraindication to a vasodilator e.g. a patient cannot use adenosine because they have bronchospastic airway disease (COPD or asthma)
    • Dobutamine can be paired with an echo or a nuclear medicine study
  • Vasodilators are ideal if a patient has a LBBB because it is not affected by the fact that in a LBBB you have a delayed contraction of the septum which can cause a false positive for obstruction if done with exercise or dobutamine
    • Vasodilators can only be paired with a nuclear study

Contraindications to using an EKG as your form of imaging are:

  • LBBB
  • Ventricular paced rhythm
  • ST changes > 1 mm

Anti-anginal medications:

  • BB
  • Nitrate (give a medication free period at night to avoid tachyphylaxis)
  • CCB
  • Ranolazine (4th line medication if the others have failed)

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