Abdominal aortic aneurysm : uncharted aspects of rupture

Abstract

Unlike intact abdominal aortic aneurysm (iAAA), ruptured abdominal aortic aneurysm (rAAA) is a lethal condition demanding immediate resuscitation and surgical intervention. Where the former is a silent disease with slow expansion of the infrarenal aorta, rAAA is symptomatic with abdominal/back pain and possibly even hemorrhagic shock. Repair of an iAAA has low mortality rates while repair of rAAA is associated with much higher complication rates and postoperative mortality. In Sweden, the prevalence of iAAA amongst 65-year-old men is 1.2–1.5 %. Every year 175–200 patients with rAAA are treated at hospitals across the country. With decreasing autopsy rates, the overall number of ruptures remains unknown and many studies lack the reporting of untreated patients. The overall aim of this thesis was to investigate less commonly studied aspects of AAA epidemiology, with particular emphasis on rAAA; from broad epidemiology with time trends in incidences and repair modality, to population-based investigations of the prevalence of previously known AAA in patients with rupture. Furthermore, the effect of sex and socioeconomic position (SEP) on the severity of disease and outcome of repair was studied.

Studies I and II are retrospective population-based studies of all individuals with a rAAA admitted to a hospital in the Stockholm county region and Gotland county, 2009–2013. The aim of these studies, based on a study cohort of all admitted rAAA patients, was to explore the proportion of untreated rAAA patients, and of previously diagnosed AAA patients that are found in a cohort of ruptured patients. Study I demonstrated that the majority (75 %) of patients with rAAA who reach an emergency department will undergo corrective repair. Repair rates, modality of repair and outcome were similar between the sexes. Study II showed that one third of patients with rAAA had a previously known aneurysm and the most common reasons for not having undergone repair included denied elective surgery (36 %), missed surveillance (31 %) and patient choice (18 %). Study III is a population-based study of 41,222 patients nationwide that aimed to investigate if low SEP was associated with presenting with a rAAA rather than iAAA and with poorer repair outcome. Also, the study describes time-trends in AAA incidence and rAAA mortality for 2001– 2015. After adjustment for age, sex and comorbidity a continued strong association between low SEP and the risk of presenting with a rAAA and dying within 90 days of repair persisted. Study IV, also a nationwide study, included 10,724 patients with rupture. Using a propensityscore-matched analysis, women were matched with men and an analysis was performed to determine whether: women are less often treated for their rAAA; women are less often treated with EVAR; outcome after repair is worse for women compared to men. The average treatment effect for women was -0.08, p<.001 for receiving repair and 0.086, p<.001 for 90-day mortality. However, when adjusting for postoperative complications, only short-term mortality was higher in women. No difference in repair modality was seen between the sexes. Complication rates were similar between the sexes. Time trends indicate a decrease in the number of rAAA among men, especially aged 65–84, in contrast to the unchanged rates in women.

The incidence of AAA overall and rAAA specifically is declining while the use of EVAR in ruptures is increasing. On a regional level, sex differences in rAAA were not evident but nationwide sex differences were prominent and alarming. Apparent positive trends in the care of men with rAAA can be found that are partly associated with the implementation of screening and with improved cardiovascular prevention in the population. However, the results unfortunately do not reflect equally in the female population. Alarmingly, our results emphasize the presence of inequality in the health care system for women and those with low income and a low level of education.