Angina

Snapshot

A 52-year-old man presents to the emergency department due to chest pain. He describes the pain as pressure-like that initially worsened with activity and improved with rest. However, he noticed that the pain was still present with decreasing physical activity to the point that it persists with rest. On physical exam, the patient appears uncomfortable and anxious. An electrocardiogram demonstrates mild ST-segment depressions in V1-V2. Cardiac troponins are not elevated. (Unstable angina)

Introduction

Clinical definition
- substernal chest discomfort secondary to myocardial ischemia; however, myocyte necrosis is not present
  - note that patient will likely report discomfort rather than pain
Epidemiology
- risk factors
  - smoking
  - atherosclerosis
  - poor dietary habits
  - high altitude
Pathogenesis
- background
  - myocardial ischemia occurs when the heart’s demand for oxygen exceeds oxygen supply
    - factors that increase the heart’s demand for oxygen includes
      - heart rate
      - contractility
      - systolic blood pressure
      - myocardial wall tension/stress
    - determinants of oxygen supply include
      - oxygen carrying capacity
      - unloading of oxygen from hemoglobin
      - coronary artery blood flow
- pathology
  - myocardial ischemia leads to acidosis, a ↓ ATP supply, and the release of chemical substances (e.g., adenosine)
    - sympathetic sensory neurons become activated and result in the perception of pain in a dermatomal distribution
      - e.g., chest, neck, jaw, and down the left (most commonly) arm
      - geriatric or diabetic patients may not experience chest discomfort or pain due to impaired sensory nerve conduction (e.g., diabetic neuropathy)

Types of Angina
Types	Pathology	Clinical Presentation	Comments
Stable angina	Typically secondary to atherosclerosisthis impairs coronary perfusion in the setting of increased cardiac demand (e.g., exertion)	Chest pain that develops with exertion but relieves with rest or nitroglycerin	Electrocardiogramusually completely normal though case reports have described rare ST segment depressions
Unstable angina	Incomplete coronary artery occlusion by a thrombus indicative of a ruptured plaque with subsequent clot formation	Chest pain that persists whether with decreasing physical activity or rest	Electrocardiogrammay demonstrate ST segment depressions or T wave inversions
Prinzmetal angina	Coronary artery spasms	Chest discomfort unrelated to physical activity and is episodic	TriggerscocainealcoholtriptansElectrocardiogramappears similar to a STEMImay demonstrate ST segment elevations with reciprocal ST depressionsTreatmentcalcium channel blockerssmoking cessationnitrates