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.