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 ^1,2.

Pathology

Aetiology

The most common cause by far is atherosclerotic plaque rupture in coronary artery disease. Other 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 ⁵:

  • myocarditis and/or pericarditis

  • left ventricular hypertrophy

  • left ventricular aneurysm

  • Tako-tsuboTakotsubo cardiomyopathy

  • electrolyte abnormalities

    • including hyperkalemiahyperkalaemia and hypercalcemiahypercalcaemia

  • acute pulmonary embolism

  • coronary artery vasospasm

  • acute CNS pathology

    • including subarachnoid hemorrhagehaemorrhage and intracranial hemorrhagehaemorrhage

  • benign early repolarizationrepolarisation

  • 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 ³

      • most commonly noted to occur in massive gastric dilatation, small bowel obstruction, and pneumothorax⁴

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

• thoracic aortic dissection

• esophagealoesophageal rupture

• pulmonary embolism

• pneumothorax

• cardiac tamponade