Atherosclerosis and Angina
Histopathology of Atherosclerosis
Tetiana Povshedna
Learning Objectives
By the end of this chapter, you will be able to:
- Relate key pathophysiological changes in the progression of atherosclerosis to the cell/tissue changes visible on the histological slide.
- Interpret lipid and elastin histological stains.
Histopathology of Atherosclerosis
We will examine the histopathology of atherosclerosis using two slides of atheroma of the aorta coming from the same patient – a 65 y.o. man with a history of hypertension – one of the main risk factors of atherosclerosis.
Both slides are stained with special stains (fat stain and elastic tissue stain) that allow for visualization of specific tissue components that would not be clearly identifiable by the classic H&E stain.
While examining tissue slides, please note epithelial damage – an initial step of atherosclerosis progression that triggers subsequent inflammation and atherosclerotic plaque formation.
Histopathology of atherosclerosis (aorta) by Tetiana Povshedna licensed under CC BY 4.0 created with BioRender.com. Histology slides are DHPLC specimens PATH 425-032 (fat stain) and PATH 425-033 (elastin stain)
Fat Tissue Stain: Key Takeawats
- Irregularly thickened tunica intima as a result of lipid accumulation
- Numerous lipid deposits in both tunica intima and tunica media
On a cellular level, this stage of atherosclerosis development is associated with the pro-inflammatory state, macrophage recruitment, and foam cell formation with subsequent necrotic core development.
Elastin Stain: Key Takeaways .
- Irregularly thickened tunica intima; loss of elastic fibers in tunica intima (compare this elastic stain to an example of the normal human aorta in Gross anatomy and histology of normal aorta and note the amount of elastic fibers in tunica intima)
- Elastic tissue appears compressed and fragmented in the superficial layers of tunica media. This fragmentation and weakening of the aorta wall might facilitate the formation of aneurysm
- On higher magnification, cholesterol crystals appear as stellate empty spaces in tunica intima
- Areas of calcification appear as dark dense spots within tunica intima
While all the histological slides and gross anatomy specimens above focused on various regions of aorta as a site of atherosclerotic plaque formation, coronary arteries are also one of the common and clinically relevant sites of atherosclerosis. Plaque formation within these arteries can cause hypoxia of the heart muscle which, if left untreated, can lead to a heart attack.
The video below examines the key features of atherosclerosis in coronary arteries. Clinically, these changes would reflect the pathophysiology of ischemic heart disease.
Histopathology of atherosclerosis (coronary artery). Created and presented by Jonathan Bush. Histology slide is from private collection.
Key Takeaways
- Numerous immune cells in tunica externa reflect inflammatory process triggered by atherosclerosis.
- A blood clot is obstructing the lumen, making tunica intima hard to identify.
- Fibrotic areas (appear pale pink and do not contain a lot of cell nuclei) reflect lipid accumulation.
- Foam cells that engulfed oxidized LDL in tunica media .
Section Review
On gross anatomy specimens, early atherosclerotic lesions appear as yellow streaks/patches on the luminal side of the vessel. As the severity of atherosclerosis increases, atherosclerotic plaques grow in size and number and can cause ulceration. Advanced atherosclerotic vessels have an irregular luminal surface, numerous plaques, areas of calcification, ulceration, and clot formation. One of the most common clinical outcomes of advanced atherosclerosis is an aneurysm or clot formation.
Histologically, lipid deposits are visible within the tunica intima and tunica media of atherosclerotic vessels. Endothelial damage, which is necessary for lesion initiation, is often present. During the advanced stages, cholesterol crystals and calcium deposits can be visualized in tunica intima, while tunica media can appear fragmented.
Review Questions
1. Fill in the blanks.On gross anatomy specimens, atherosclerotic plaques appear as _____ lesions. (indicate colour)
2. Finish the following sentence. Common clinical outcomes of advanced atherosclerosis include:
Select all that apply.
- Aneurysm formation
- Clot formation
- Decreased blood pressure
- Arythmias
3. Fill in the blank.
As atherosclerosis progresses, _____ can form on the luminal surface of the vessel, exposing underlying layers of the vessel wall.
4. Finish the following sentence. Aneurysm is usually a consequences of a weakened:
- Tunica intima
- Tunica media
- Tunica externa
5. Fill in the blank.
_____ damage is necessary for atherosclerotic lesion initiation.
6. In atherosclerosis, lipid deposits can accumulate in both tunica intima and tunica media.
- True
- False
7. Fill in the blank.
_____ deposits in advanced atherosclerosis harden the vessel wall and make it brittle.
Answer Key
- Yellow
- Aneurysm formation, clot formation
- Ulcers
- Tunica media
- Endothelial
- True
- Calcium
same as atherosclerotic plaque
elevated blood pressure
(also, tunica interna) innermost lining or tunic of a vessel
middle layer or tunic of a vessel (except capillaries)
abnormal ballooning/ widening of the blood vessel wall cause by it's weakness. Aneurysm rupture is very dangerous and often fatal
lack of oxygen supply to the tissues
branches of the ascending aorta that supply blood to the heart; the left coronary artery feeds the left side of the heart, the left atrium and ventricle, and the interventricular septum; the right coronary artery feeds the right atrium, portions of both ventricles, and the heart conduction system
(also, tunica adventitia) outermost layer or tunic of a vessel (except capillaries)
