Acute coronary syndrome

Acute coronary syndrome (ACS) is a group of cardiac diagnoses along a spectrum of severity due to the interruption of coronary blood flow to the myocardium, which in decreasing severity are:

• ST elevation myocardial infarction (STEMI)
• non-ST elevation myocardial infarction (NSTEMI)
• unstable angina

Stable angina is not considered an ACS.

Epidemiology

Of all patients who present to emergency departments with symptoms of ACS, only 20-25% will have ACS confirmed as their discharge diagnosis .

Pathology

Etiology

The most common cause by far is atherosclerotic plaque rupture in coronary artery disease. Other less common causes include:

• aortic or coronary artery dissection
• vasculitis
• connective tissue diseases
• drugs: cocaine
• coronary artery spasm

Unusual variants:

• Kounis syndrome: allergic / hypersensitivity precipitant

Differential diagnosis

Several other pathological entities may mimic an acute coronary syndrome in both electrocardiographic appearance and clinical presentation;

• the differential diagnosis for ST segment elevation on the ECG includes :
  • myocarditis and/or pericarditis
  • left ventricular hypertrophy
  • left ventricular aneurysm
  • Tako-tsubo cardiomyopathy
  • electrolyte abnormalities
    • including hyperkalemia and hypercalcemia
  • acute pulmonary embolism
  • coronary artery vasospasm
  • acute CNS pathology
    • including subarachnoid hemorrhage and intracranial hemorrhage
  • benign early repolarization
  • elevated intraabdominal/intrathoracic pressure
    • critically ill patients with free fluid and/or air in their thorax/abdominal cavity may, rarely, present with bizarre ECG patterns, including ST segment elevations
      • the "spiked helmet sign" refers to the characteristic appearance of the sharp upstroke of the baseline leading into ST elevation
      • most commonly noted to occur in massive gastric dilatation, small bowel obstruction, and pneumothorax 

Other serious causes of acute chest pain which may mimic the presentation of ACS include;

• thoracic aortic dissection
• esophageal rupture
• pulmonary embolism
• pneumothorax
• cardiac tamponade