Patients with large AAAs see higher five-year mortality with EVAR compared to open repair

Large abdominal aortic aneurysm (AAA) repair is associated with higher adjusted five-year mortality, reintervention and rupture rates after endovascular aneurysm repair (EVAR)—but not after open repair, a prize-winning paper at the recently concluded SVS ONLINE digital conference concluded.

Nevertheless, an increasing majority of patients with a large AAA undergo EVAR, the researchers behind the findings revealed during the late-breaking Scientific Session 9 on July 2.

The study, presented by Livia de Guerre, MD, a research fellow at the department of vascular and endovascular surgery at Beth Israel Deaconess Medical Center, Harvard Medical School, in Boston, was the winning entry in the SVS ONLINE e-Poster Competition: “EVAR for large abdominal aortic aneurysms is associated with higher late reinterventions, ruptures and mortality.”

In introducing the subject matter, de Guerre drew attention to previous research that shows a large variation in repair diameter. And a large proportion of patients who undergo surgery are above the Society for Vascular Surgery (SVS) thresholds of 5.5cm in men and 5cm in women, according to de Guerre et al.

“However the risk of AAA rupture strongly increases with increasing aneurysm diameter,” she told attendees. “Also, comparison of predictive preoperative risk of operative mortality stratified by AAA diameter category shows increasing mortality risk in larger aneurysms: 20.8% of the large AAAs are of medium mortality risk compared to 3.5% in the medium-sized AAAs, and 1.3% in small AAAs. However, the effect of the large preoperative aneurysm diameter on long-term outcomes is unknown.”

So de Guerre et al set out to investigate the association of large AAA diameter with late outcomes, and compare EVAR and open repair in patients with large AAAs. They deployed the Vascular Quality Initiative (VQI) registry linked with Medicare claims for long-term outcomes.

The investigators included all patients who underwent elective open or endovascular infrarenal aneurysm repair between 2003 and 2016, with a large AAA diameter defined as above 65mm. Primary outcomes were five-year reintervention, rupture and mortality rates.

The study population consisted of 21,749, of which 19,527 underwent EVAR while 2,222 received open repair. Of the EVAR patients, 14.6% had a large AAA; meanwhile, 24.4% of the latter contingent bore a AAA classified as large.

“Concerning baseline characteristics, the large AAA cohort was older, more commonly male, more likely to have renal disease and congestive heart failure compared with patients with smaller aneurysms,” de Guerre said. “Also, preoperative medication use was lower in patients with large AAAs. Patients with large AAAs were less likely to use statins, aspirin and P2Y12s.”

With EVAR’s usage for large AAAs increasing over time, she pointed to a statistic for endovascular repair of these aneurysms from 2016: Some 88% were carried out by way of the minimally invasive method. That compares to 36% in 2003, de Guerre added.

“Five-year freedom from reintervention after EVAR was lower for large AAAs with 75%, compared to 84% for smaller AAAs” she explained. “However, after open repair, reintervention rates were similar between larger and smaller aneurysms.

“Adjusted five-year freedom from late rupture after EVAR was also lower for large AAA repairs, with 91% vs. 95% for smaller AAA repairs. However after open repair these rates were smaller and similar between aneurysm sizes. Also, adjusted five-year survival after EVAR was lower in large AAA compared to smaller AAA EVAR, with 58% vs. 66%. And after open repair, there was no significant difference in survival with large and smaller AAA repair.”

Looking only at patients with large AAAs, and comparing EVAR and open repair, de Guerre continued, adjusted survival at five years was lower after EVAR: 55% vs. 63%. Yet, when comparing EVAR and open repair survival after smaller aneurysm repair, “the survival benefit lasted longer and five-year was similar.”

In short, she said, patients with large AAA diameter compared to smaller AAA repair undergoing EVAR had higher mortality, reinterventions and rupture rates, “while after open repair these outcomes were similar.”

Furthermore, de Guerre went on, “EVAR for large AAA is associated with worse adjusted five-year survival compared to open repair, which is not seen in patients with smaller aneurysms.”

The researchers used the VQI risk score to calculate predicted open repair mortality for large AAA patients who are currently selected for EVAR. Some 73% had a predicted open repair mortality below 5%. “As the SVS suggested elective open repair for AAA be performed at centers with a documented perioperative mortality of 5% or less, our application of this predictive model shows that the majority of patients currently undergoing large AAA EVAR have an acceptable open repair operative risk,” de Guerre added.

Concluding, the research team elaborated: “Large AAA diameter was associated with higher five-year mortality after AAA repair, regardless of repair type. After EVAR for large AAA, there was a higher likelihood of five-year mortality, reinterventions, and ruptures compared to open repair for large AAAs and compared to EVAR for smaller aneurysms. Therefore, in patients with large AAAs who are medically fit, open repair should be strongly considered. Furthermore, these findings highlight the necessity for rigorous long-term follow-up after EVAR.”