UA is part of the continuum of ACS and overlaps with NSTEMI. A patient
experiencing severe UA has a prognosis and risk profile similar to that of a patient
with a mild NSTEMI.
Short-term, high-risk factors for death or nonfatal MI in patients with unstable
angina include:
■ Rest pain >20 minutes
■ CHF or pulmonary edema
■ Rest pain with dynamic ECG changes
■ Chest pain with new or worsening mitral regurgitation (MR) murmur
■ Chest pain with hypotension
Myocardial Infarction (MI)
MI encompasses both NSTEMI and STEMI. It is defined as myocardial cell
death and necrosis as diagnosed by a rise and fall of cardiac enzymes (in asso-
ciation with appropriate clinical presentation) or by pathologic findings of
prior MI (eg, new Q waves on ECG).
PATHOPHYSIOLOGY
ACS results from insufficient O 2 supply to meet cardiac muscle demands:
■ Progressive fixed atherosclerotic lesions within the coronary arteries →
↓luminal diameter and ↓coronary blood flow
■ Acute coronary artery plaque disruption →exposed thrombogenic endo-
thelium→platelet aggregation and thrombus formation
■ Coronary artery vasospasm
■ Less common: dissection of the coronary arteries, microemboli, excess
demand states, vasculitis, vasospasm
Risk factors:
■ Smoking
■ HTN
■ Diabetes
■ Dyslipidemia
■ Family history
■ Advanced age
■ Male gender
■ Cocaine use
■ SLE
■ Obesity
■ Postmenopausal state
SYMPTOMS
■ Classic symptoms include chest pain or pressure (may radiate to the arm,
back, chest, or jaw), shortness of breath, sweating, nausea, and impending
sense of doom.
■ Beware of atypical presentations (more common in diabetics, the elderly,
and women).
■ Fatigue or generalized weakness
■ Shortness of breath without chest pain
■ Epigastric abdominal pain or “indigestion”
■ Consider a cardiac etiology in any patient with GERD-type symp-
toms on the boards even if symptoms abate with antacids.
■ Mental status change
CARDIOVASCULAR EMERGENCIESPatients with severe UA have
a prognosis similar to patients
with mild NSTEMI.Maintaining a high index of
suspicion for MI is essential as
the initial ECG is diagnostic for
MI <50% of the time and
may be normal in up to 5% of
cases.