Arterial Disease: Risk Factors

Arterial Disease Risk Factors - Controllable

• Diabetes is a controllable arterial disease risk factor.
• Medial Calcinosis is the hardening of arterial walls with loss of elasticity, but is unrelated to stenosis.
• Incompressible walls result in inaccurate pressure measurements.
• Diabetics have a low rate of aortoilliac occlusive disease but a higher rate of distal popliteal and tibial occlusive disease.
• Neuropathy caused by diabetes increases the risk of trauma, gangrene, and amputations.
• Hyperlipidemia, another controllable risk factor, involves too many lipid fats in the blood.
• Hyperlipidemia is associated with atheromatous plaque development, hypertension, and is exasperated by smoking.

Arterial Disease Risk Factors - Uncontrollable

• Aging is an uncontrollable risk factor, with older age increasing disease risk.
• Family History is an uncontrollable risk factor.
• Gender is an uncontrollable risk factor, with males at higher risk for disease.
• Thrombophilia, a hereditary predisposition for blood clots, is an uncontrollable risk factor.

Cerebrovascular Disease Mechanisms

• Atherosclerosis or atherosclerosis obliterans commonly occurs at branches, bifurcations, and vessel origins.
• Atherosclerosis causes stenosis or narrowing of the vessel lumen.
• Significant stenosis can cause detectable hemodynamic changes
• Atherosclerosis can cause hypoperfusion and embolization, leading to cerebral ischemia.
• Thromboembolism is when a blood clot or foreign substance travels in an artery and lodges in a distal smaller vessel, causing stenosis or complete occlusion.
• Thromboembolism is a common cause of cerebral ischemia from hypoperfusion and embolization of atherosclerotic plaque..
• A carotid body tumor is a highly vascular paraganglioma/chemodectoma within the adventitia layer of the carotid bifurcation between the ICA and ECA.
• Carotid body tumors can compress the external ICA and may exist bilaterally.
• Symptoms of a carotid body tumor include neck pain, dizziness, palpable neck mass, hoarseness, dysphasia, and syncope.

Atherosclerosis

• Atherosclerosis obliterans involves thickened, hardened vessel walls with loss of elasticity
• Plaque is composed of lipids, complex carbohydrates, blood and blood byproducts, fibrous tissues, calcium deposits, smooth muscle cells, collagen, fibrin, and platelets.
• Fatty Streak is a type of plaque that is homogeneous and a thin layer on the intima.
• Fibrous Plaque is homogeneous accumulations.
• Complex Lesion plaque is heterogeneous, with bright echoes and shadowing due to collagen and calcium deposits.
• Ulcerative Lesion is a deteriorated smooth fibrous plaque that may cause emboli and intraplaque hemorrhage.
• Thromboembolism involves obstruction of a blood vessel by a foreign substance or blood clot.
• Emboli may be solid, liquid, or gas.
• Plaque breaking free and traveling distally is the most frequent cause of a thromboembolism, until it gets caught in a small vessel.
• Thromboembolisms may cause occlusion or stenosis where the embolus lodges.
• Paraganglioma/chemodectoma is a highly vascular tumor.
• The tumor is located in the adventitia of the carotid bifurcation, between the ECA and ICA, and may be bilateral.
• External compression of the ICA causes neck pain, dizziness, palpable neck mass, hoarseness, dysphasia, and syncope.

Aneurysm

• The occurance of an aneurysm is rare in the cervical CCA
• Berry aneurysm is a type of small saccular out-pouching on one side of an artery that affects intracranial vessels.
• Ruptured aneurysms cause extensive subarachnoid hemorrhage
• Dissection involves blood tearing through the intimal layer, splitting the arterial wall and is common in the aorta, CCA, and proximal ICA.
• Dissection may cause a mobile or fixed echogenic flap, caused by trauma or spontaneously with symptoms of acute, severe, localized headache and neck pain.
• Pseudoaneurysm is due to trauma or graft blow-out.
• Neointimal Hyperplasia is hyperplasia of the intimal wall layer from overgrowth of cells post-endarterectomy.
• Neointimal Hyperplasia is common at surgical sites for carotid endarterectomy, and will show the same signs and symptoms as significant stenosis if extensive enough.

True Aneurysm

• True aneurysm involves bulging of all three layers of the arterial wall.
• Patients with one aneurysm are more likely to develop another one..
• Unknown causes, poor arterial nutrition, congenital defects, infection, atherosclerosis, trauma, and iatrogenic treatments can cause a true aneurysm.
• True aneurysms can be focal, fusiform (diffuse circumferential dilatation), saccular (localized out-pouching of weakened arterial wall), and concentric. True aneurysms may be found in the distal aorta, thoracic aorta, femoral, popliteal (usually bilateral), carotid, renal, and splenic arteries.
• Complications of a true aneurysm include rupture, distal embolization, and thrombus formation.
• Dissecting Aneurysm has a small tear in intima wall layer that allow blood to form cavity between the intima and media layers, and appears as a second false lumen with possible blood flow to distal branches.
• A dissecting aneurym occurs due to weakened media with intimal tearing and is usually seen in the thoracic aorta.
• Pseudoaneurysm is a pulsating hematoma, where a hole in arterial wall allows blood to escape under pressue.
• This leads to a hematoma forming in a contained tissue area with blood flowing into it through a communication channel from the vessel.
• Pseudoaneurysm is due to a wall defect after catheter insertion for angiography, an endovascular procedure, or after dialysis.

Neointimal Hyperplasia

• Neointimal Hyperplasia is the overgrowth of intimal cells.
• It can occur after surgical plaque removal via endarterectomy.
• This can also occur in venous anastomosis and the outflow vein of hemodialysis access grafts, as well as in venous bypass grafts.
• Fibromuscular Dysplasia is a nonatherosclerotic disease, that is the Dysplasia of medial wall layer from overgrowth of collagen leading to multiple stenoses.
• Fibromuscular Dysplasia can be found in carotid and renal arteries.
• Fibromuscular Dysplasia mostly occurs in young females, but is rare in males.
• Fibromuscular Dysplasia has nonspecific findings, showing a bead like appearence on an angiography.

Stroke Basics

• Hemorrhagic Stroke involves bleeding within the brain when a blood vessel bursts.
• Common causes of a hemorrhagic stroke include hypertension and aneurysm
• An Ischemic Stroke is when there is interrupted blood supply causing decrease in oxygen to the brain.
• The most common cause is a blood clot or emboli from atherosclerosis.
• A Lacunar stroke is a nonatherothrombotic obstruction of small perforating arteries supplying deep cortical brain structures and i most common in elderly diabetes or poorly controlled hypertension patient.
• Stroke symptoms are usually asymptotic, but can include Subclavian steal syndrome with significant ICA disease and posterior hemisphere neurological symptoms.
• Transient Ischemic Attack (TIA) symptoms appear suddenly and resolve within 24 hours: example Amaurosis Fugax (monocular blindness).
• TIA symptoms causes higher risk of TIA and CVA.
• Dysphasia or Aphasia can be a symptom (partial ability or inability to speak).
• Stroke symptoms can also include Hemiparesis (contralateral paralysis) and Behavioral Disturbances.
• Reversible/Resolving Ischemic Neurological Deficit (RIND) symptoms appear suddenly and last longer than 24 hourse than revert to normal.
• Symptoms are the same as with a TIA only differ in duration.
• Vertebrobasilar Insufficiency (VBI) occurs causes of flow disturbances within vertebrobasilar arteries or posterior circulation resulting in Ataxia (inability to coordinate muscle activity), Drop Attacks or Limb Weakness (falling without loss of consciousness), and Paresthesia (numbness and tingling).
• VBI can also cause Vertigo (spinning), Bilateral visual disturbances, and Diplopia (double vision).
• Non-Focal Non-Localizing Stroke symptoms include Dizziness, Syncope, Headache, Confusion, and Dysarthria (difficulty with muscle impairment).
• Cerebrovascular Accident (CVA) is a complete stroke with permanent neurological deficiits like Dysphasia or aphasia, Hemiparesis, Misc neurological deficits, and Death.
• CVA Classification can come in Acute (sudden unstable), Stroke in Evolution (come and go unstable), and Complete (permanent stable).