Disorders of Cardiovascular System - Aneurysms PDF

Disorders of arterial circulation Aneurysms  Aneurysms: Objectives 8.1.3. Differentiate between true and false aneurysm 8.1.4. Differentiate between berry and saccular aneurysms 8.1.5. Describe the etiology and pathogenesis of the following aneurysms:...

Disorders of arterial circulation Aneurysms  Aneurysms: Objectives 8.1.3. Differentiate between true and false aneurysm 8.1.4. Differentiate between berry and saccular aneurysms 8.1.5. Describe the etiology and pathogenesis of the following aneurysms: Abdominal Aortic Dissecting  ANEURYSM An aneurysm is an abnormal localized dilation of a blood vessel. Aneurysms can occur in arteries and veins, but they are most common in the aorta.  Aneurysm True Aneurysm False or Pseudo aneurysm Bounded by a complete vessel wall. Bounded only by the outer layers of the vessel wall or supporting tissues. Remains within the vascular compartment. A localized dissection or tear in the inner wall of the artery with formation of an extravascular hematoma that causes vessel enlargement.  Aneurysm True and False  Aneurysm Aneurysms can assume several forms and may be classified according to (1) their cause, (2) location, and (3) anatomic features: 1. Berry Aneurysm 2. Saccular Aneurysm 3. Fusiform Aneurysm 4. Dissecting Aneurysm  Aneurysm 1. Berry Aneurysm Is a true aneurysm that consists of a small, spherical dilation of the vessel at a bifurcation. Usually found in the circle of Willis in the cerebral circulation.  Aneurysm 2. Saccular Aneurysm Is a true aneurysm that extends over part of the circumference of the vessel and appears saclike.  Aneurysm 3. Fusiform Aneurysm Is a true aneurysm that involves the entire circumference of the vessel. Characterized by a gradual and progressive dilation of the vessel. They vary in diameter (up to 20 cm) and length, may involve (1) the entire ascending and transverse portions of the thoracic aorta or may extend over (2) large segments of the abdominal aorta.  Aneurysm 4. Dissecting Aneurysm Is a false aneurysm resulting from a tear in the intimal layer of the vessel that allows blood to enter the vessel wall, dissecting its layers to create a blood-filled cavity. If dissection occurs in the aorta, it is a life-threatening condition. Aneurysm  Aneurysm Aortic aneurysms Aortic aneurysms may involve any part of the aorta: 1. the ascending aorta 2. aortic arch 3. descending aorta 4. thoracoabdominal aorta 5. abdominal aorta.  Aneurysm Aortic aneurysms Etiology: 2 most common causes of aortic aneurysms are: ✔ Atherosclerosis ✔ Degeneration of the vessel media. Half of the people with aortic aneurysms have hypertension. More frequent in men after the age of 50 years who smoke cigarettes.  Aneurysm Abdominal aortic aneurysms Are located most commonly below the level of the renal artery (>90%) and involve the bifurcation of the aorta and proximal end of the common iliac arteries. Most abdominal aneurysms are asymptomatic. Because an aneurysm is of arterial origin, a pulsating mass may provide the first evidence of the disorder. Aneurysms larger than 4 cm are palpable. Calcification, which frequently exists on the wall of the aneurysm, may be detected during abdominal radiologic examination.  Aneurysm Abdominal aortic aneurysms: Pathogenesis Abdominal aortic aneurysm Expansion of aneurysm (1) Compress lumbar (3) Stasis of blood (2) Extend to & impinge on the nerve roots renal, iliac or mesenteric arteries or to the vertebral arteries Thrombus formation Lower back pain that radiates to the posterior aspects of the legs May develop peripheral emboli Disrupt the blood supply to the spinal cord Symptomatic arterial insufficiency Erosion of vertebra  Aortic Dissection Aortic dissection (dissecting aneurysm) is an acute, life-threatening condition. It involves haemorrhage into the vessel wall with longitudinal tearing of the vessel wall to form a blood-filled channel. More than 95% of the cases of dissecting aneurysm show transverse tear in the intima and internal media. The dissection can originate anywhere along the length of the aorta.  Aortic Dissection ✔ The majority of the dissections involve the ascending aorta. ✔ The second most common site is the thoracic aorta just distal to the origin of the subclavian artery.  Aortic Dissection ❖ Etiology: Aortic dissection is caused by conditions that weaken or cause degenerative changes in the elastic and smooth muscle of the layers of the aorta. It is most common in the 40- to 60-year-old age group and more prevalent in men than in women. 2 risk factors predispose to aortic dissection: ✔ Hypertension and ✔ Degeneration of the medial layer of the vessel wall.  Aortic Dissection ❖ Etiology: Other predisposing factors are: ✔ Associated with Marfan syndrome ✔ During pregnancy ✔ Congenital defects of aortic valve ✔ Aortic Coarctation ✔ Potential complication of cardiac surgery or catheterization.  Aortic Dissection: Types Types A Type B The more common proximal lesions, Those not involving the ascending aorta involving the ascending aorta only or both and usually beginning distal to the the ascending and the descending aorta. subclavian artery. More serious in terms of complications.  Aortic Dissection: Types Aortic dissections are also classified according to time of onset as acute or chronic. Chronic dissections are defined as the persistence of the dissection flap or channel for greater than 2 weeks after initial event. Dissections usually extend distally from the intimal tear.  Aortic Dissection:Pathogenesis Aortic dissections In ascending aorta Expansion of the wall of the aorta may Expansion of the wall of the aorta impair closure of the aortic valve. Risk of rupture Blood moving into the pericardium Compresses the heart  Aortic Dissection:Pathogenesis It is possible for the abdominal aorta to be involved with progression into the renal, iliac, or femoral arteries. Partial or complete occlusion of the arteries that arise from the aortic arch or the intercostal or lumbar arteries may lead to: ✔ Stroke ✔ Ischemic peripheral neuropathy or ✔ Impaired blood flow to the spinal cord.  Aortic Dissection:Pathogenesis Two important factors that participate in propagating the dissection are: 1. High blood pressure and 2. The steepness of the pulse wave. Without intervention, these forces continue to cause extension of the dissection.