Abdominal aortic aneurysm (AAA) occurs when atherosclerosis or plaque buildup causes the walls of the abdominal aorta to become weak and bulge outward like a balloon. An AAA develops slowly over time and has few noticeable symptoms. The larger an aneurysm grows, the more likely it will burst or rupture, causing intense abdominal or back pain, dizziness, nausea or shortness of breath. Most people with an abdominal aortic aneurysm do not have any symptoms. Often, the aneurysm grow slowly and go unnoticed. Many never reach the point of bursting; others enlarge quickly. When an abdominal aneurysm expands, the patient may notice a throbbing in the middle or lower part of the stomach, lower back pain, or tenderness in the chest. Most abdominal aneurysms are identified during routine medical exams.
The aorta, the largest artery in the body, is a blood vessel
that carries oxygenated blood away from the heart. It originates just after the
aortic valve connected to the left side of the heart and extends through the
entire chest and abdomen. The portion of the aorta that lies deep inside the
abdomen, right in front of the spine, is called the abdominal aorta.
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Over time, artery walls may become weak and widen. An
analogy would be what can happen to an aging garden hose. The pressure of blood
pumping through the aorta may then cause this weak area to bulge outward, like
a balloon (called an aneurysm). An abdominal aortic aneurysm (AAA, or
"triple A") occurs when this type of vessel weakening happens in the
portion of the aorta that runs through the abdomen.
The majority of AAAs are the result of atherosclerosis, a
chronic degenerative disease of the artery wall, in which fat, cholesterol, and
other substances build up in the walls of arteries and form soft or hard
deposits called plaques. Large aneurysms are rare, but can be very serious. If
a large aneurysm bursts, it causes huge internal bleeding and is usually fatal.
Abdominal aortic aneurysms typically develop slowly over a
period of many years and hardly ever cause any noticeable symptoms.
Occasionally, especially in thin patients, a pulsating sensation in the abdomen
may be felt. The larger an aneurysm grows, the greater the chance it will
burst, or rupture.
Major risk factors for an AAA include family history,
smoking and longstanding high blood pressure. According to the Centers for
Disease Control and Prevention (CDC), men who have a history of smoking should
receive a one-time screening for triple A between the ages of 65 and 75. Men
with a family history of AAA should be screened at age 60.
Abdominal aortic aneurysm (AAA) is a life-threatening
condition which requires monitoring or treatment depending upon the size of the
aneurysm and/or symptomatology. AAA may be detected prevalently or at the time
of rupture. An arterial aneurysm is defined as a permanent localized dilatation
of the vessel at least 150% compared to a relative standard adjacent diameter
of that artery.
Treatment depends on a variety of factors, including size
and location of the aneurysm within the abdominal aorta and the patient's age,
kidney function and other conditions. Patients with aneurysms that are smaller
than five centimeters in diameter are typically monitored with ultrasound or CT
scans every six to 12 months and may be advised to:
·
quit smoking
·
control high blood pressure
·
lower cholesterol
There are two
treatment options:
Traditional (open) surgical repair: In this type of surgery,
an incision is made in the abdomen and the damaged part of the aorta is removed
and replaced with a synthetic tube called a stent graft, which is sewn into
place.
Endovascular surgery: In this procedure, which is less
invasive than an open repair, the stent graft is attached to the end of a thin
plastic tube called a catheter, inserted through an artery in the leg and
maneuvered up into the abdomen, where it is positioned inside the aneurysm and
fastened in place with small hooks.
Medical Management:
The medical therapies available to slow the growth of
thoracic aortic aneurysms and reduce their risk of dissection or rupture are
quite limited. Once β-blocker therapy is maximized (or in the event that
β-blockers are contraindicated or not tolerated), any persistent hypertension should
be treated with other antihypertensive agents to bring the blood pressure down
to a low-normal range, e.g., a systolic pressure of 105 to 120 mm Hg. The 2005
ACC/AHA guidelines (1) recommended beta-blocker therapy in patients with an AAA
who do not undergo surgery. Because of the possible attenuation of aneurysm
expansion, beta-blockers are also a preferred drug for patients with
hypertension or angina with care taken in patients with atrioventricular
blocks, bradycardia, chronic obstructive pulmonary disease and peripheral
vascular disease.
Antibiotic therapy: Interest in antibiotic therapy in the
management of AAA is based on evidence of chronic inflammation in AAA,
inhibition of proteases and inflammation by antibiotics, and possible
involvement of Chlamydia pneumoniae in the pathogenesis of AAA.
Although cardiovascular disease is widely recognized as the
leading cause of death, a lesser-known fact is that aortic aneurysm (AA) is the
15th leading cause of death over the age of 65 years in the US. The golden
standard of the treatments in Abdominal Aortic Aneurysm are invasive
interventions either with open surgical repair (OS) or endovascular aneurysm
repair (EVAR). The concept of medical treatment is to prevent abdominal aortic
aneurysm (AAA) from rupture and avoid surgical treatment by preventing aneurysm
enlargement or even reducing aneurysm size. Matrix metalloproteinases (MMP) are
structurally related metalloendopeptidases that can degrade the extracellular matrix,
and is thought to play important roles in AAA. There are many proposed
pharmacological treatments, including β-blockers, angiotensin-converting enzyme
inhibitor (ACE inhibitors), angiotensin-receptor blocker (ARB), statins, macrolides
and, doxycycline, an inhibitor of the MMP. Specific treatment is based on the
age, overall health, medical history, extent of the disease, signs and
symptoms, tolerance of specific medications, procedures, or therapies.
Unfortunately, no pharmacotherapy for AAA has been realized
despite considerable effort, and there are several challenges that need to be
addressed. First, it is possible that appropriate drug targets in human AAA
have not been identified. Indeed, many animal studies have assessed the effects
of interventions in limiting AAA development rather than the effects on
pre-established AAA. Also, the experimental opportunities for analyzing human
AAA specimens have decreased in recent years. Continued efforts, including the
appropriate use and interpretation of animal models, and full utilization of
human samples are essential to gain a better understanding of human AAA
pathophysiology and pathogenesis. Second, it is important for pharmacotherapy
to be sufficiently concentrated at the AAA site. Third, there is a possibility
that the heterogeneity of human AAA might not be fully appreciated or taken
into account when testing therapeutic agents since patients with AAA are
heterogeneous in terms of their characteristics, clinical history, and genetic background.
The other factors that shall further expedite the growth of
Abdominal Aortic Aneurysm market include increasing awareness about available
treatments during the forecast period (2019–2030). Overall, the increasing
prevalence, disease awareness, and promising emerging pipeline therapies will
propel the market size forward during the forecast period. A better
understanding of disease pathogenesis will also contribute to the development
of novel therapeutics for Abdominal Aortic Aneurysm.
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