Discussion
This report presents the mid-term outcome (median follow-up of 20
months) and predictors of survival after endovascular procedures with
the use of all type of available endografts for the treatment of AAA by
our single endovascular team. Freedom from all-cause mortality was 93%
at 1 year, 81% at 3 years and 62% at 5 years. Main predictors of lower
survival rates after EVAR were poor ventricular function, aneurysms
above 6 cm and various comorbidities that are decreased renal function
and anemia.
In recent two decades, EVAR is increasingly becoming the standard
treatment modality for un-complex infrarenal AAA.2EVAR has numerous advantages especially early survival benefit compared
to open surgery, including the fact that the procedure has a minimally
invasive nature and has a shorter recovery period.
During a median follow-up of 20 months 36 deaths (16.5%) had occurred
in our study population. 5-year overall mortality was documented as
73.6% at meta-analysis of four randomized trials 3.
The main controversy of this reported value is the selection criteria of
the patients in the randomized trials and all the patients in the trial
were within limits of IFU. The numbers at the real world are slightly
different from the randomized trials. ENGAGE registry which documented
the outcomes of a single endograft (Medtronic Endurant™) reported that
17.8% of 1263 patients were out of IFU limits and above 10% with
hostile necks. The 5-year overall survival rate was reported as 67% at
ENGAGE registry 11. Other earlier real-world reports
have reported similar survival rates between 63% and 72% as well.10,12 The survival rates of the current study occurred
as 93% at one-year, 81% at 3-years and 62% at 5-years which is very
comparable with the real-world data. On the other hand, Jeon-Slaughter
et al demonstrated that inferior mid-term survival after EVAR is
independently associated with larger AAA diameters, especially above 6.0
cm. 10. Five-year survival rates of < 6.0 cm
and ≥ 6.1 cm were 73% and 52% respectively in the current study which
is comparable with the above-mentioned report.
Anatomical factors predicting survival after EVAR stay as the main topic
of several studies in the literature. 7,8,10,13,14Aneurysm diameter, the anatomical properties of aneurysm and neck angle
was determined to be associated with midterm survival.15 The initial aneurysm diameter independently
predicted mortality at long-term. There was an almost three-fold
increase of mortality risk at patients with initial aneurysm diameter ≥
6.0 cm in this study. Similarly, a recent study investigating the
database of Vascular Quality Initiative has demonstrated a one and a
half fold increase of 5-year mortality at patients with large aneurysms
(≥ 6.5 cm). 16 Jeon-Slaughter et al have reported
increased mid-term mortality risk with aneurysm above 6.0 cm.10 Furthermore, shorter life expectancy and higher
rupture risk at endovascularly treated large aneurysms were documented
by Zarins et al. 17 Median diameter of AAA in our
series was 60 mm with 58% of which was equal or above to 60 mm.
Majority of reports and registries assessing predictors for mortality
have mean diameter of aneurysms between 5.5 and 6.0 cm.7,8,14,17 Registry of Vascular Quality Initiative
which composed of over 18000 EVAR patients have reported to have
aneurysms above 6.0 cm at only 24% of the registry.7Moreover, the mean diameter of aneurysm has been reported as 58 mm at
Vascular Study Group of New England risk prediction
model.8 Three-fold increase of mortality risk in our
series which is more than other series may be clarified with the
relative increased diameter of our patient population.
In addition to aneurysm diameter, some demographic features and
comorbidities have been found to decrease survival for EVAR
patients.7,9,14 Simplified risk score model that has
been mentioned at the report of Neal et al, recognized that low ejection
fraction has a very high score (+5 score) for risk
prediction.9 Similarly, preoperative ejection fraction
below 30 was predictive of mortality with five-fold increase at risk in
our study. Piffaretti et al, reported an almost similar predictive value
of heart failure on late all-cause mortality.18 In
addition, several other studies also have documented heart failure as a
risk factor for long-term mortality.19,20
On the other hand, age, gender and some comorbidities such as diabetes
and chronic obstructive pulmonary disease were not associated with
survival. The association between survival and age along with gender has
been previously reported by numerous studies.7,8,14Majority of the studies reporting predictors of survival has a mean age
of over 70’s.13,18,20 Limited number of studies could
not associate age with survival.21 The relatively
younger population and small number of the study may be the reason for
no relationship of age and survival.
Gender is generally reported as a covariate for survival20,22-24, although there are some controversies about
its predictive value at other
studies.12,20,25-27Women who undergo endovascular repair tend to be older than men in most
of the studies and the older age may contribute to its predictive
effect. However, the median age of women in our study was not
significantly different from men’s age. The results of our study are
nevertheless reliable in high-volume
reports.12,20,25-27 The other confounding issue was
the male predominance of our study (91%) which may impede the
clarification of results regarding gender.
Alternatively, overall all-cause mortality at midterm was significantly
three times lower for the patients without renal disease or anemia.
Saratzis et al concluded that impaired renal function was independently
associated with an increase mortality following
EVAR.21 Similarly, Khashram et al identified baseline
renal impairment (creatinine > 1.7 mg/dl) as an important
predictor of survival.20 Additionally, there are
several other studies reporting hazard ratios between 1.6 and 2.1 and
confirming the results of our study.24,28 On the other
hand, concerning anemia, a few single center observational studies have
reported an association with reduced mid- and long-term
survival.28 Another observational study regarding
severe anemia (< 10 gr/dl) which is similar to our definition,
reported 2.6 fold increased risk of in-hospital mortality after
EVAR.29 Furthermore, our study is unique given that
poor mid-term survival is associated preoperative severe anemia (HR
3.4). This relationship is very reasonable that anemia may present
itself with a diminished cardiac reserve and associated comorbid
conditions. The underlying condition may be addressed to overcome this
condition.