THE LATEST CONCEPT OF AORTIC ANEURYSM
INTRODUCTION • Prevalence: – 3/4 confined to the abdominal aorta – 1/4 involve the thoracic aorta • Risk factors: – Decreased type III collagen to type I collagen ratio – Hypertension – Atherosclerosis
PATHOGENESIS Mechanisms: – Atherosclerosis erodes the aortic wall, destroying the medial elastic elements – This weaken the aortic wall and leads to fusiform or saccular dilation – Laplace’s law: tension is proportional to the product of pressure & radius – Vicious circle: Dilatation results in greater tension, which in turn leads to acceleration in the rate of enlargement of the aneurysm
ABDOMINAL ANEURYSM • Most arise just below the renal arteries and extend to the aortic bifurcation • Only 2 ~ 5% are suprarenal (these usually result from the distal extension of a thoracic aneurysm into the abdomen) • Majority are asymptomatic & are discovered on routine PE or X-ray • In contrast to musculoskeletal back pain, it is not affected by movement • A palpable, pulsatile abdominal mass
AAA RUPTURE • 80% rupture retroperitoneally, 20% rupture into the periotoneal cavity • > 6 cm in diameter: 50% rupture 6 cm in diameter • Expanding or ruptured AAA are true surgical emergencies: sudden onset of severe low back or abdominal pain, may radiate to the groin, buttocks, or legs • Rupture, stabilized by using a compression G-suit
THORACIC ANEURYSM • Spontaneous rupture without warning is less common • Saccular are more common than fusiform • Symptoms: tracheal deviation, wheezing cough, dyspnea, stridor, hemoptysis, recurrent pneumonitis, hoarseness, dysphagia, superior vena caval syndrome • Steady & boring, sometimes pulsating, pain due to compression & erosion of adjacent musculoskeletal structures • Rupture is heralded by the dramatic onset of excruciating pain • Surgical excision is the procedure of choice for = or > 7 cm in diameter in the ascending or the descending aorta
THE LATEST CONCEPT OF AORTIC DISSECTION
INTRODUCTION • Prevalence: – Male to female = 2:1 • Peak incidence: – 6th & 7th decades • Mortality rate: (Untreated) – >25% within the first 24 h – >50% within the first week – >75% within one month – >90% within one year
PATHOGENESIS Two possible mechanisms: – Rupture of the intima with secondary dissection into the media – Hemorrhage within a diseased media followed by disruption of the subjacent intima & subsequent propagation of the dissection through the intimal tear
CLINICAL PICTURE • The most common symptom is pain (>90%) – Contrast to AMI, most painful at onset, not crescendo – “Tearing” – Migrating – Proximal dissection: anterior chest – Distal dissection: back • Pulse deficits, “pseudohypotension” • Syncope, CVA • Cardiac tamponade • Aortic regurgitation • AMI (1 - 2%), Mesenteric infarction, Renal infarction