Pathology of CV Disease Flashcards
Causes of CV disease
Atherosclerosis
Atherosclerosis (AS) is the major predisposing factor for cerebrovascular disease. Severity of AS involvement may differ between intracranial and extracranial vessels. It is important to note that intracranial damage can result from disease in the extracranial (neck) vessels (ICA, vertebral artery) in the absence of disease in intracranial vessels.
Causes of CV disease
Important vascular diseases
- arteriosclerosis and arteriolosclerosis due to chronic hypertension and diabetes mellitus
- aneurysms (saccular, atherosclerotic, mycotic, etc.) * cerebral amyloid angiopathy
- others (e.g., vasculitis, vascular malformations, CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarctions and leukoencephalopathy) * clotting disorders (coagulopathies, RBC diseases, etc.)
Brain is supplied by which vessels internal carotid arteries (anterior circulation) give rise to: vertebral arteries (posterior circulation) give rise to:
internal carotid arteries (anterior circulation) give rise to
- middle cerebral arteries (MCA),
- anterior cerebral arteries (ACA)
vertebral arteries (posterior circulation) give rise to
- basilar artery and branches
- posterior cerebral arteries (PCA) are terminal branches of basilar artery
Major cerebral arteries
path
Most major cerebral arteries ramify in the leptomeninges over the brain surface and then penetrate the brain as superficial or deep perforators. Important perforators include the lenticulostriate arteries arising from MCA, supplying the basal ganglia, and thalamic perforators arising from the PCA, supplying the thalamus.
General considerations of CNS vasculature
- collateral circulation is poorly developed:
- perforating arteries are end arteries: collaterals exist only at capillary level and are usually inadequate.
- border zones (“watershed zones”) between arterial
territories are susceptible to decreased blood flow or
oxygen delivery. - occlusion of vessel can lead to a well defined infarction limited to that vessel’s territory.
- because of limited collateralization of major intracranial vessels, occlusion of proximal portions of these vessels in the neck may cause major intracranial damage.
Stroke
def
Many cerebrovascular diseases present as stroke, defined as: “an acute neurologic dysfunction, global or focal, usually developing over minutes or hours and continuing for more than 24 h, occurring as a result of parenchymal damage due to a vascular process.”
NOTE: a vascular process whose symptoms resolve in less than 24 h is called transient ischemic attack (TIA)
Strokes are caused by…
- cerebral infarctions (“ischemic stroke”)
2. non-traumatic intracranial hemorrhages (“hemorrhagic stroke”)
Other forms of vascular disease in stroke
- diffuse hypoxic-ischemic injury, usually reflecting a global brain insult such as systemic hypotension or hypoxia
- acute or chronic hypertensive encephalopathy
Trauma can mimic or result in some forms of CV disease
- traumatic hemorrhages
- diffuse brain damage
- cerebrovascular consequences of trauma
Cerebral infarctions
Def/arise from…
focal ischemic necrosis of brain tissue due to occlusive vascular disease or other forms of vascular insufficiency
Most cerebral infarctions arise from occlusion of an artery due to atherosclerosis and/or thromboembolus.
Ischemic stroke
Clinical presentation
rapid onset of neurologic deficit
maximal deficit develops rapidly
secondary effects may occur
recovery is variable
Lacunes
def
lacunes are small infarcts (<1 cm) arising from occlusion of small vessels, generally in the setting of chronic hypertension.
Physiology of brain vascular damage
Injury may result from…
a. ischemia (reduced blood flow)
* focal cerebral ischemia: reduced flow in one vessel
* global cerebral ischemia: failure of systemic circulation
b. hypoxia (usually systemic)
c. hypoglycemia (usually systemic)
Physiology of brain vascular damage
mechanism
a. O2 deprivation: functional hypoxia
b. metabolic disruption: Ca++, lactate, free radicals
c. injury by released excitotoxins: glutamate, aspartate
Physiology of brain vascular damage
Factors affecting patterns and extent of injury
Selective vulnerability
cell type: neurons > oligodendrocytes > astrocytes
sensitive populations of neurons
Physiology of brain vascular damage
Factors affecting patterns and extent of injury
Duration of ischemic injury
~ 8-10 seconds: cessation of function
~ 4-8 minutes: irreversible damage begins
Physiology of brain vascular damage
Factors affecting patterns and extent of injury
BP/temp
maintenance of blood flow (blood pressure) can reduce injury, possibly by removing toxic metabolites
temperature: hypothermia (under 30°C) permits longer period of ischemic cell survival
Physiology of brain vascular damage
Factors affecting patterns and extent of injury
Glucose stores
hyperglycemia: may promote damage
hypoglycemia: when mild, may prevent damage
Physiology of brain vascular damage
penumbra
following an injury, tissue at the transition between already necrotic and viable tissue (the “penumbra” of the infarct) may be at risk for damage by apoptosis but still salvageable by appropriate timely intervention
Physiology of brain vascular damage
reperfusion
reperfusion of a previously ischemic area may save marginally injured cells but may promote free radical production with further injury or even conversion to hemorrhagic infarct