Acute Coronary Syndromes

First Things First (assess for & treat the following)

• Is patient hemodynamically stable?
• Is patient continuing to have ischemia symptoms?
• Are high-risk features present (see below under specific treatment)?
  • Start anticoagulation and antiplatelet therapy.
• Does ECG show ST-segment elevation or new LBBB?
  • Consider angioplasty vs. thrombolytic therapy.
  • Are there contraindications to thrombolytic therapy (if indicated)?

Clinical syndromes

Chronic stable angina

• Fixed & stable coronary stenosis with absence of ischemia at rest
• Ischemia provoked by increases in myocardial metabolic demand (e.g., physical exertion, emotional stress, postprandial)

Acute coronary syndrome: defined as spectrum of clinical syndromes that arise from coronary plaque rupture & intracoronary thrombus formation (unstable angina, NSTEMI, STEMI)

• Unstable angina:
  • Self-limited ischemia in the absence of myocardial damage
  • Absence of serum cardiac enzyme elevation
  • Coronary plaque rupture with accumulation of intracoronary platelets & formation of transiently obstructing thrombus
    • Angina at rest, may be nocturnal
    • May follow recent history of MI
    • Represents the highest-risk group of patients with unstable angina
  • Progressive narrowing coronary stenosis
    
    • Restenosis in the months following angioplasty
    • Gradually worsening exertional angina
  • Ischemia provoked by abnormal physical states (despite fixed coronary arteries)
    • Increased myocardial metabolic demand: anemia, fever, tachyarrhythmia, hypotension, hyperthyroidism, cocaine
    • Symptoms abate as underlying disease process is corrected.
  • Coronary vasospasm
• Myocardial infarction:
  • Death of myocardium & abnormal elevation of serum cardiac enzymes
  • Non-ST-segment-elevation MI (NSTEMI)
    • Infarction without elevation of ST segment
    • Occlusive thrombus, coronary vasospasm or fixed stenosis
    • Supply-demand mismatch: myocardial oxygen demand exceeds oxygen delivery
  • ST-segment-elevation MI (STEMI)
    • Infarction with elevation of ST segment
    • ST elevation localized to the region of infarcting myocardium
    • Persistent coronary occlusion results in significant myocardial necrosis.