Page 8 - Carotid and peripheral vascular interventions textbook

CAROTID AND PERIPHERAL VASCULAR INTERVENTIONS: STEP-BY-STEP

PATHOPHYSIOLOGY plaque buildup and greater carotid intima-media
thickness. The global prevalence of carotid disease,
The most common pathophysiology of carotid artery def ned as greater carotid intima-media thickness by
stenosis is the progressive narrowing of the carotid artery 1.0 mm or greater in people ages 30-79 years, was estimated
caused by development of atherosclerosis plaque, which to be 27.6%. However, the prevalence of carotid stenosis,
is composed of lipid substances, calcium, and thrombus. def ned as 50% or greater stenosis, was only 1.5%. These
These plaques have a tendency to develop at the points of numbers are consistent with another study that revealed
carotid bifurcation and along vessel areas of curvature (10). the incidence of carotid stenosis in the general population
Hemodynamic forces acting at carotid bifurcation to be about 3% (18). This f nding suggested that routine
locations have a function in restricting intimal thickening screening to detect carotid stenosis should not be
in these areas. Both in vitro and in vivo studies have recommended for general adults.
reported that disrupted f ow and low-shear conditions
cause endothelial dysfunction and cause stenosis (11,12). ETIOLOGY

The two primary mechanisms of stroke in
extracranial ICA disease are distal embolization The most common etiology of carotid artery
and low-f ow phenomenon due to insuff cient stenosis is atherosclerosis. The other causes are
collateral circulation distant from a hemodynamically f bromuscular dysplasia (FMD), vascular injury, and
signif cant occlusion or stenosis (13). A diffuse-weight carotid dissection or radiation therapy. Patients that have
imaging MRI study showed that an acute ischemic vascular disease at other territories as well as risk factors
injury in ICA occlusive disease is mostly multiple (14). such as hypertension, diabetes mellitus, hyperlipidemia
These results reinforce the fact that embolism from and smoking have greater risk for developing carotid
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an atherosclerotic plaque rupture is the principal artery atherosclerosis. The lesion is normally unifocal
mechanism of ischemic stroke. In addition, thrombosis and 90% are identif ed within 2 cm from the ICA origin.
and low cerebral blood f ow are other possible mechanisms FMD is a rare disease that mainly involves
which are caused by gradual plaque growth and luminal medium-sized arteries. The vessels involved are usually
narrowing. Hemodynamic insuff ciency can occur when at the mid and distal ICA and renal arteries (19). This
any conditions that interfere with cerebral perfusions disease most commonly affects middle-aged females.
such as orthostatic, hypotension or volume depletion The clinical manifestation varies from asymptomatic
are added on to the carotid occlusion, particularly if to TIAs or cerebral infarction, associated with stenosis,
the contralateral carotid disease has severe stenosis. dissections, aneurysms, or complete occlusion.
This low f ow mechanism can explain the infarction in Vascular injury can cause subsequent carotid stenosis.
the border zone areas or so called ‘watershed infarction’. Torsion and transient occlusion have the effect of creating
a temporary functional arterial stenosis. Sometimes this
EPIDEMIOLOGY vascular injury results in an intimal tear and thrombus

formation.
The prevalence of atherosclerotic carotid disease Dissection of the extracranial ICA can happen
differs between studies, depending on the def nition spontaneously or linked with trauma, such as penetrating
used, race, population risk factors, and investigative neck injuries, intraoperative lacerations and percutaneous
tool used for diagnosis (15,16). From a recent study carotid angiography. The etiology of carotid artery
using ultrasonography on people aged 30-79 years dissection results from an intimal tear. That tear may cause
(17), there were substantial variations in prevalence complete or partial occlusion, traumatic pseudoaneurysm,
between each region worldwide. The Western Pacif c cerebral emboli, or dissection. Cystic medial necrosis
region experienced the biggest share of global cases, with deterioration of muscle f bers together with internal
followed by the regions of South-East Asia, Europe, elastic laminae have also been identif ed.
the Americas, the Eastern Mediterranean, and Africa. Radiation therapy is normally used to treat malignant
Current smoking habits, hypertension and diabetes neck tumors and can affect extracranial carotid vessels.
were conf rmed as general risk factors for both carotid Such radiation-induced carotid stenosis has been linked