Non-ST Elevation Acute Coronary Syndrome (NSTE-ACS)

Myocardial Infarction:

Classified into 5 types based on etiology and circumstances:

• Type 1: Spontaneous MI caused by ischemia due to a primary coronary event (eg, plaque rupture, erosion, or fissuring; coronary dissection).
• Type 2: Ischemia due to increased oxygen demand (eg, hypertension), or decreased supply (eg, coronary artery spasm or embolism, arrhythmia, hypotension).
• Type 3: Related to sudden unexpected cardiac death. 
• Type 4a: Associated with percutaneous coronary intervention (signs and symptoms of myocardial infarction with cTn values > 5 × 99th percentile URL). 
• Type 4b: Associated with documented stent thrombosis. 
• Type 5: Associated with coronary artery bypass grafting (signs and symptoms of myocardial infarction with cTn values > 10 × 99th percentile URL).

Infarct location

• Right ventricular infarction usually results from obstruction of the right coronary or a dominant left circumflex artery; it is characterized by high RV filling pressure, often with severe tricuspid regurgitation and reduced cardiac output.
• An inferoposterior infarction causes some degree of RV dysfunction in about half of patients and causes hemodynamic abnormality in 10 to 15%. RV dysfunction should be considered in any patient who has inferoposterior infarction and elevated jugular venous pressure with hypotension or shock. RV infarction complicating LV infarction significantly increases mortality risk.
• Anterior infarcts tend to be larger and result in a worse prognosis than inferoposterior infarcts. They are usually due to left coronary artery obstruction, especially in the anterior descending artery; inferoposterior infarcts reflect right coronary or dominant left circumflex artery obstruction.