AAA
Written by: John Paul Kwak, MD
Edited by: Joann Hsu, MD
The case:
88 year old male with hx of HTN HLD DM, COPD, CKDs4, CHF, CAD, AAA, Prostate Ca, presenting with Chest pain and SOB that began this morning. He woke up with shortness of breath. Chest pain is like an ache in left lower chest wall.
Physical exam significant for an abdominal pulsatile mass, and colostomy and urostomy pouches in the lower quadrants of the abdomen
In the setting of a known AAA and chest pain, you decide to evaluate Aorta with US, obtaining the proximal, and middle aorta views seen below, but unable to obtain bifurcation view as the colostomy and urostomy bags overly the skin of the umbilicus.
Abdominal US for AAA has a sensitivity 95-100%, specificity 98%-100%, 93-100% PPV, 100% NPV when performed by ED providers.
AAAs are mostly fusiform in morphology, and specific recommendations on surveillance as well as management based on size and rates of growth have been established in the 2017 Society for Vascular Surgery Guidelines, the 2019 European Society for Vascular Surgery Guidelines, and most recently slightly modified in the 2022 AHA/ACC Guidelines.
However, no clear cut evidence based thresholds for how to manage saccular aneurysms exist to help guide/inform our shared decision making, patient education, or how/when to advocate for surgical intervention.
One study done in the Netherlands in 2019, showed that of the patients with acute (symptomatic/ruptured) saccular aneurysms, 25.2% of patients had diameters <5.5cm, and 8.4% had diameters <4.5cm, compared to patients with fusiform aneurysms 8.1% had diameters <5.5cm and 0.6% had diameters <4.5cm.
While this study has its own limitations, it does show that saccular aneurysms have a higher risk of rupture.
The etiology of saccular aneurysms includes a broad differential, including:
Autoimmune conditions (RA, SLE, ankylosing spondylysis, Behet’s, Cogan’s syndrome)
Vasculitis (takeyasu, giant cell arterities)
Sex chromosomal disorders (Turners, Kleinfelter’s syndromes)
Genetic connective tissue disorders (Ehlers danlos, Marfan’s, Noonan’s, Loey-Deitz’s syndromes)
Infectious “mycotic aneurysms” (syphilis, endocarditis, RMSF, aspergillosis)
Previous aortic instrumentation
Trauma
Mortality of AAA with rupture is 85-90%, with estimated 50% that don’t make it to hospital.
Even if patients do, operative mortality (with rupture) is ~50%. The 2022 AHA/ACC guidelines paper lists risk factors for rupture including rapid aortic growth, symptomatic aneurysms, underlying connective tissue disorders, heritable tissue disease, saccular aneurysm morphology, female sex, and infected aneurysm as criteria for repair at lower diameter thresholds.
Ultrasound is a good screening tool to find, characterize, and surveil known aneurysms. Knowledge of the rare saccular morphology and its high risk features as well as broad etiology is helpful to advocate for the best long term outcomes and appropriate followup for these patients.
Resources:
https://www.ncbi.nlm.nih.gov/books/NBK557867/
https://pubmed.ncbi.nlm.nih.gov/10541605/
https://pubmed.ncbi.nlm.nih.gov/30073493/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4379792/
https://pubmed.ncbi.nlm.nih.gov/31498185/
https://www.ahajournals.org/doi/10.1161/CIR.0000000000001106
https://www.jvascsurg.org/article/S0741-5214(17)32369-8/fulltext
Egorova N, Giacovelli J, Greco G, et al. National outcomes for the treatment of ruptured abdominal aortic aneurysm: comparison of open versus endovascular repairs. J Vasc Surg 2008; 48:1092.
IMPROVE Trial Investigators, Powell JT, Sweeting MJ, et al. Endovascular or open repair strategy for ruptured abdominal aortic aneurysm: 30 day outcomes from IMPROVE randomised trial. BMJ 2014; 348:f7661.
Lindholt JS, Vammen S, Juul S, et al. The validity of ultrasonographic scanning as screening method for abdominal aortic aneurysm. Eur J Vasc Endovasc Surg 1999; 17:472.