Abdominal Aortic Aneurysm

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Introduction   

An aneurysm is an abnormal dilatation of an artery with a change in diameter of at least 150% compared to a healthy artery nearby (1). Triple-A is a severe medical condition that can lead to death if undetected or untreated. It is usually asymptomatic and often detected incidentally while looking for another medical issue. At times, if it is undetected, it will rupture and become an emergency (1).   

The U.S., U.K., and other countries have developed programs where male clients may have a free screening for early detection of Triple-A at age 65 or over. Clients with co-morbidities such as family history, cardiovascular artery disease, hypertension, COPD, peripheral artery disease, and a past or current smoker are at greater risk. These clients should take part in these screenings if available (2). 

Epidemiology 

In a 2019 report, 19 countries were studied, revealing a prevalence of 35.12 million cases of Triple-A worldwide for clients between the ages of 30 and 79 being (5). The number of clients with a Triple-A increases after age 60, and that number peaks each following decade (1).   

Another article reported that Triple-A numbers have decreased to 2% from 4%-8% in the past (4). The reduced rate is estimated to be due to people no longer smoking and practicing healthier lifestyles (4). Mortality occurs when a Triple-A ruptures and the client cannot reach the hospital in time, and when this occurs, the client has a mortality rate of 50% either during or post-surgery (4).   

A clinical research study by the Veterans Administration demonstrated that a screening program lowered the mortality and morbidity rates of clients with a Triple-A (6). This study included all those who had screenings and those who did not. Screenings cost $143.00 per client. The cost of repairing a Triple-A for 1183 clients out of 19,649 screened was $2,809.807 over 11 years (6). Most clients have several scans and CT scans to follow up, which are included in this number.  These costs increased with the size of the aneurysm and emergency repair (6). In this study cohort, the average life years after the repair is 5.8 + 3.5, and the “mean cost per life-year lived was $ 10,686 or $ 490.00 per life year lived after screening” (6). 

Etiology 

Triple-A is categorized as an asymptomatic progressive enlargement of the diameter of the aorta. It is caused by many factors that will be discussed in this course (7).  The aorta is subdivided into the thoracic and abdominal areas. The abdominal aorta extends from the diaphragm to the bifurcation of the aorta, perfusing the lower extremities (8). 

Most Triple-As are small but must be monitored for enlargement to predict the probability and prevention of rupture. Once found, they are watched closely for an increase in diameter (1). Each 0.5 centimeter (cm) of growth of the Triple-A doubles the likelihood of rupture and increases the enlargement rate per year to 0.5 cm (3). 

The aorta has different segments depending on how the client’s embryo was formed and developed (embryogenesis) (7). Because each of these segments is dependent on embryogenesis, the tissues of the aorta carry different “extracellular matrix, microfibril density, and vascular smooth muscle cell reactivity” in different segments (7).  

A Triple-A can occur in these differing segments of the vessel. Infrarenal is below the renal artery, para-renal is classified as involvement with the renal arteries, supra-renal is above the renal arteries, and para-visceral is if they involve the visceral arteries (8).  

The most common Triple-A is infra-renal because the pressure needed to reach the iliac bifurcation of the aorta and wall stress increases the chance of dilatation of the aorta. This pressure is associated with the aneurysm’s size and the vessel’s weakness. An abdominal aorta is considered a problem when it is greater than 3 cm in diameter (1, 4). Researchers have also identified a chronic inflammation in the aorta’s wall but are unsure of the cause (1).   

The rupture rate is almost four times higher in women than men, although the higher prevalence of Triple-A is in males. Other influences in rupture have been found on microscopic examination of the walls of the aorta (4). These include “fragmentation of the internal elastic membrane, with decreased elastin and increased collagen” (4). Also, researchers found that muscle cells in the medial layer of the aortic wall were lost (4).  The mortality rate for rupture is 50%-80% (8). 

History, Physical, and Risk Factors 

Any risk that affects the cardiovascular system will also affect the occurrence of Triple-A and increase the risk of needing repair. Significant risks associated with the development of a Triple-A are advanced age (over 65), family history, male gender, smoking, and atherosclerosis (1).  Smoking and family history are the highest risk factors (3). Diagnosis is most often made with an abdominal ultrasound followed by a CT scan to locate the exact placement of the Triple-A (1).  The findings of these tests often show intense inflammation, thickened walls of the vessel from plaque buildup, and adhesions to structures near the dilated aorta (1). These findings may be the most common cause of an aneurysm (2). 

Women who smoke have a higher risk of developing a Triple-A, and as stated earlier, they are at the highest risk of rupture as well (3). If clients have ceased smoking for 25 years or longer, they will have the same risk as non-smokers. Interestingly, diabetes and peripheral vascular disease do not affect the enlargement of the aneurysm (10). 

Risk factors that a client can change include smoking, hypertension, high BMI, triglycerides and high LDL, and atherosclerotic cardiovascular disease (3). Of these, smokers are at the most significant risk since their lungs may be affected during surgery. It is recommended that smokers cease smoking for at least 8 or more weeks before surgery (3). These at-risk clients may also have underlying cardiac or respiratory disease (3). 

Providers should palpate and auscultate the abdomen for a pulsatile mass when history and physical are performed. Of note, obesity may decrease the ability of the provider to determine the presence of an aneurysm (4). Medications the client is on should be looked at and optimized before surgery (30). 

Some telltale signs of rupture are hypotension, back or flank pain, and pulsatile mass in the abdomen. There can also be groin and lower extremity pain (4).  If the rupture occurs in the posterolateral wall of the aorta, there is less blood, and the client will usually survive in an emergency. The majority of clients with anterolateral rupture (most common) usually do not live before they get to the hospital. 

Case Study 

This case occurs in an urgent care facility. Clients can call the nurse telephone line, and the nurses triage the clients telephonically and either give advice or schedule same-day appointments. A nurse assigned to telephone triage receives a call from an older client reporting abdominal pain for the last 2 hours.  

The triage nurse assesses the client appropriately, asking about any other signs or symptoms, gastric issues, referral of pain, and if there is any medical history that the staff and providers should be aware of. The client replies that they have a hernia and wears an abdominal binder to hold it in, but that is all the information the client gives to the nurse.  

The triage nurse attempts several times to get more history and information but the client responds no to all questions. The nurse advises the client to come to Urgent Care immediately. When they arrive, the triage nurse meets the client in their room to greet them and give the primary nurse a report. The triage nurse says to the primary nurse, “Maybe we should not take the binder off,” while the primary nurse is removing it.   

Within seconds, the client drops back on the stretcher and codes. The provider quickly enters the room, stabilizing the client while the administrative staff calls EMS and the staff calls the emergency department. EMS arrives within minutes and the client is taken to surgery.  

As the client was transported to surgery, their spouse spoke to the nurse. The spouse said they wanted to call an ambulance to their home, but the client adamantly refused. The client also refused to allow the spouse to talk to the triage nurse as they would have given all of the client’s medical history. The spouse stated the client had cardiac issues and open-heart surgery in the past. The spouse also said that after that surgery, part of the sternum had to be removed from the client due to post-operative infections and complications.  

The surgery went well and the ruptured Triple-A was repaired. Unfortunately, the client passes away during recovery from ventricular tachycardia. The triage nurse questioned themself over this for a few days, wondering if they had made the wrong decision to bring the client in. When the nurse spoke later that week to the doctor who was attending to the client, they reassured the staff that they were correct in having the client come in and that they probably would have died sooner had they not called and presented.  

Treatment 

As stated earlier, once a Triple-A is diagnosed, depending on size and the client’s medical history, lifestyle, age, and comorbidities, there will be an observation period for Triple-As less than 5.5 cm for males and up to 5.4 cm for women (3). It is also essential to know that some aneurysms may grow larger slowly, while others may increase rapidly (1).  

If surgery is not needed or the client is at greater risk because of lifestyle, age, and history, then prevention is the option. This includes smoking or tobacco cessation, blood pressure management with beta-blockers or other anti-hypertensives if needed, medications for high cholesterol (statins), a healthy diet low in saturated fats, and mild exercise. The aneurysm will be monitored and other diagnostic tests will be done once a year until it grows larger than 5cm or the client has symptoms.   

If the aneurysm is small but grows 0.5cm in 6 months, it is considered a high risk for rupture.  Otherwise, if the aneurysm is small, yearly checkups are recommended (10). 

Two surgeries can be utilized to repair Triple-As: endovascular aortic repair (EVAR) and open surgical repair (9). The option for one surgery over the other should include a frank discussion and education to the client regarding risk factors and “anatomic stability” (9). 

If EVAR is selected, there will be percutaneous puncture wounds and ultrasound so the surgeon can view the procedure without significant surgery. The aneurysm is left alone while the surgeon reroutes blood flow through stents placed in the aorta with ultrasound assistance that bypasses the aneurysm. This endoscopic procedure is less expensive and has fewer post-operative complications. It also prevents the aneurysm from rupturing (10). Anatomy must be intact, and the vascular surgeon must ensure no blood leaks in the area to prevent re-intervention or rupture.  Studies show a 1.2% mortality rate for clients who have this procedure (9). EVAR is performed more often than open abdominal surgery in institutions with well-trained vascular surgeons and a vascular center (9). The only requirements after this procedure are lifelong imaging and blood work follow-up (9). 

If open triple-A repair is opted for, there are more extensive exposures to the site because the surgeon is surgically opening the abdomen (9). There is a longer time for “end-organ ischemia” (9). There is also a higher incidence of mortality and morbidity with the open procedure.   

To visualize the aneurysm, the vascular or thoracic surgeon will make an abdominal incision, possibly including a part of the chest or lateral side of the chest if the aneurysm is thoracic (11). The aorta will be clamped above and below the aneurysm, and the client will be on heart-lung bypass to keep the rest of the body perfused. A graft or stent will be placed at the site of the aneurysm to act as a vessel bypassing the aneurysm and be sewn to stay in place. This procedure takes 3-4 hours.  

The client will have a urinary catheter and nasogastric tube in place. They will be intubated and on a ventilator as the procedure is done under general anesthesia. They will receive anticoagulants and wear compression socks or boots to prevent blood clots. As with any major surgery, nursing will be very involved in the client’s recovery and advancement. 

This surgery is most often done when a rupture occurs or when a client is at great risk of rupture.  There is less possibility of rupture after an open repair versus an EVAR, and the surgeon will follow up with the client only if a problem arises or if the age and anatomy of the client pose a particular problem (9). 

As with any major surgery, nursing will be very involved in the recovery and advancement of the client. 

Research 

At present, researchers are focusing on genomics and “rapid molecular testing” to identify early pathology processes that underline the development of this disease (7). The challenge for researchers now and in the future is to use bioinformatic information along with genetic modeling to identify clients at higher risk of the disease and be able to predict the disease early.   
They also examine machine learning (artificial intelligence) and better screening tools to predict those at higher risk of developing an aortic aneurysm (7). 

Conclusion

We know that Triple-As have one of the highest rates of mortality around the world. Open surgery was the standard operation for this disease in the past; however, there have been many advances in prevention, such as screening for family and lifestyle history. Endovascular repair is the intervention used most often, resulting in fewer surgical complications than the open option; however, surgeons with client input must use discretion when deciding which approach to use.   

We have discussed the sizes of aneurysms in terms of rupture risk in men and women and the latest screening processes to detect an aneurysm early for monitoring and, if necessary, eventual repair. The case presented in this course was a learning curve about how quickly a client may die from a rupture if not treated.  

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