Case of the Month: March 2013, Page 4

Answer: B. Send the patient urgently back to the ER and call the ER attending informing him of the findings.

Discussion:

  • This patient demonstrated a large, severe resting defect. There is no need to proceed with the stress portion of the study, which could exacerbate the patient's clinical and hemodynamic status.
  • These findings, while nonspecific from an imaging standpoint, are compatible with an acute coronary syndrome in the appropriate clinical setting.
  • The fact that there is no perfusion to the RCA and LAD coronary distributions suggests at least a very large fixed perfusion defect.
  • While a fixed perfusion defect most commonly suggests infarcted myocardium, no assessment of the myocardial viability can be made with in this instance without viability testing using FDG-PET to evaluate for glucose metabolism.

Coronary Artery Disease General Features

  • Genetics: Family history: Significant if first cardiac event occurs < age 55 in close male relative or < age 65 in close female relative
  • Etiology: 

Gross Pathologic and Surgical Features

  • Fatty streaks → fibrous cap → plaque rupture → thrombus formation
  • Calcified plaques: More stable, less likely to rupture

Microscopic Features

  • Acute obstruction (platelet aggregation); vasospasm; inflammation

Presentation

  • Most common signs/symptoms
    • Typical angina: Substernal chest pain, exacerbated by stress, relieved by rest or nitroglycerin
    • Often vague symptoms or asymptomatic: Women, diabetes mellitus
    • No prior symptoms: 50% of men and 64% of women with sudden CAD death
  • Other signs/symptoms: Dyspnea: Common presenting symptom of myocardial ischemia

Demographics

  • Age: 1:2 men, 1:3 women > age 40 have CAD
  • Gender: Average age of first heart attack: 65.8 y in men and 70.4 y in women

Natural History & Prognosis
 

  • Annual mortality: 2-3% in patients with recent onset exertional angina
  • Untreated unstable angina: 30% risk of hard cardiac event ≤ 3 months

Treatment

  • Medical: Lifestyle modification; antiplatelet, lipid-lowering, antihypertensive drugs
  • Interventional: Revascularization most effective when myocardial ischemia affects > 10% of myocardium

Imaging Findings

  • Reversible perfusion defect, worse on stress: Ischemia
  • Fixed perfusion defect with associated wall motion abnormalities: Infarction
  • TID: Multivessel or left main disease, subendocardial ischemia: Decreased subendocardial perfusion and apparent dilation
  • Decreased ventricular function post-stress compared to rest: Ventricular stunning due to extensive ischemia; more commonly when imaged at time of stress, e.g., Tl-201, Rb-82
  • Tc-99m agents (tetrofosmin, sestamibi): No redistribution for several hours
  • Tl-201: Rapid redistribution (minutes); lung-heart ratio of > 0.5 is poor prognostic sign (stress-induced ventricular dysfunction)
  • PET perfusion imaging: Quantification of absolute myocardial blood flow
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