Risk Factors and Clinical Insights: Aneurysm Management in Native Arteriovenous Fistulas Before Chronic Hemodialysis

According to the American Society of Vascular Surgery, a pseudoaneurysm is a focal dilatation of the vascular wall caused by neointimal and fibrous tissue that can affect both an artery and a vein, but a real aneurysm is a confined dilation of all three vascular layers [1]. True Arteriovenous Aneurysms (AVA) or pseudoaneurysm-like formations can complicate Autologous or Native Arteriovenous Fistulas (NAVF) [1,2]. According to the current K/DOQI guidelines, a pseudoaneurysm is a vascular anomaly that resembles an aneurysm but is not bounded by a true vessel wall, but rather by external fibrous tissue. An aneurysm is defined as an abnormal blood-filled dilatation of the blood vessel wall resulting from vessel wall disease [3].

Arteriovenous aneurysms can therefore be real or fake [2, 3]. Most frequently, they are either acquired or congenital. Vascular trauma is the primary cause of these acquired AVAs [4]. 4% to 12% of AVAs occur in the West as a result of arteriovenous surgery, primarily the formation of native arteriovenous fistulas [5]. In Côte d’Ivoire, where end-stage renal disease cases have led to a resurgence of interest in NAVF during the 2000s, there is a lack of epidemiological and surgical information regarding AVA after NAVF.

Therefore, we undertake this study to specify epidemiological and clinical profile and the surgical risk factors in order to improve the surgical management of AVA following NAVF while waiting for hemodialysis through identification of renal insufficiency patients likely to develop this post-NAVF AVA.

Material and Methods

We conducted a cross-sectional study of patients received in the main Emergency Medical Care and Assistance Services (SAMU) of Abidjan (University Hospital of Cocody, Yopougon, and Treichville) and of Bouaké between March 2014 and February 2018 in Abidjan and from March 2018 to September 2023 in Bouaké. All of the NAVF were prepared using Brescia Cimino’s surgical method [6] (Figure 1).

In case of occurrence of post-NAVF AVA whose clinical size was greater than 20 mm, the criteria for the operability of these AVA were: Pain, ultrasound external diameter > 35 mm, and AVA rupture. Beyond these criteria, we studied HIV seroprevalence, epidemiological, clinical, biological, Doppler ultrasound characteristics, surgical indications, postoperative results, follow-up, and risk factors of AVA reinterventions. Arteriovenous Doppler echocardiography was used when there was evidence of clinical deterioration caused in the endstage renal disease patient by injury to the native arteriovenous fistula (stenosis, thrombosis, deterioration, or insufficiency) or its pathway. Follow-up data and information were complete in 96.5% of patients. Clinical assessments were obtained during inpatient visits, telephone interviews, or letters addressed directly to the attending nephrologist or to the emergency physicians of the SAMU (Emergency Medical Care and Assistance Services). In case of a lack of reply, the contact of other resource persons (parents, municipal authorities) was necessary to complete our cross-sectional study at the peak date. The terms morbidity, mortality, 30-day mortality, and in-hospital mortality were used according to the definitions of the “Guidelines” after vascular surgery procedures [7].

The prevalence of arteriovenous aneurysms on native arteriovenous fistulas being of the order of 4% in the literature, the expected sample by applying the statistical formula is equal to (1.962x (0.04) (1–0.04)/0.052), i.e., 59 patients with a precision of 0.05%. Given the existence of two cardiovascular surgery centers in the Ivory Coast, and the underestimation of the parent population of insufficient renal patients who receive regular hemodialysis, the inclusion rate was doubled. Thus, for a representative sample, we successively included all patients with arteriovenous aneurysms consecutive to a native arteriovenous fistula that met the research protocol, i.e. (59 x 2-1). All patients with a Native Arteriovenous Fistula (NAVF) usually followed in nephrology, and Emergency Medical Care and Assistance services and who present a deformation or alteration of the fistula site or path, thrombosis pre-rupture syndrome or rupture of the NAVF are referred to a cardiovascular surgery service.

Clinical, biological, ultrasonographic, diagnostic, operative data, and follow-up medical record is written and kept. A protocol reading sheet that focuses on the variables in our study summarizes the entirety of the medical record. Postoperative adverse events (complications, fatalities, causes, and dates of occurrence) were documented by the medical visit to the bed, telephone, or postal survey, both within and outside the hospital, with consideration given to the dates on which they transpired. After NAVF, missing data on arteriovenous aneurysms was found in the research protocol reading sheets. The standard deviation (SD) of the mean was used to express quantitative variables. For qualitative variables, comparisons were conducted using the Mantel Haenszel, Fisher, and Chisquare tests. The significance threshold for each of these tests was set at p < 0.05.

Exclusion criteria:

All patients carrying NAVF who developed AVA outside the upper extremity venous network used for puncture for chronic hemodialysis were excluded from the study. Patients who did not respond to the follow-up protocol or telephone/mail surveys and had missing data greater than 10% of the protocol items were excluded after one month of attempts to harmonize the database by the cardiovascular surgery resident.

Definitions:

✓ The pre-hospital renal clearance is calculated during the preoperative check-up of the native arteriovenous fistula.

✓ The terms morbidity, mortality, 30-day mortality, and inhospital mortality were used according to the definitions

Results: 

All patients carrying NAVF who developed AVA outside the upper The prevalence of AVA remote from all patients carrying NAVF who developed AVA outside the upper extremity venous network used for puncture for chronic hemodialysis was 5.9% (117/2013 cases collected). The mean age was 42.30 years ± 13.31 years [extremes: 11 years and 75 years] with a sex ratio (M/F) of 2.37. The age range of 10 years to 50 years represented 68.38% (Figure 2). 

The patients’ clinical and Ultrasound Doppler characteristics were summarized in (Table 2A, 2B, and 2C). The mean prehospital renal clearance was 39.7 ml/min ± 1.2 ml/min [Extremes: 17 ml/ min–91 ml/min]. All patients carrying NAVF who developed AVA outside the upper extremity venous network used for puncture for chronic hemodialysis were predominantly located in the left forearm (86.09%). The epidemiological aspects of our patients are summarized in (Table 1). HIV seroprevalence was 11.97%. The frequently observed cardiovascular risk factors were hypertension alone (n = 90; 84.11%) or associated with diabetes (n = 8; 7.47%). Of these, 11.7% performed cardiac ultrasound coupled with Doppler, which revealed a cardiac intracavity thrombus in 6 cases. The AVAs were located at the site of the primary NAVF (n = 81; 69.23%) (Figure 3) and at the site of arterialized vein puncture (n = 36; 30.77%) as illustrated by the Valenti D classification [8] in (Table 2B). The overall mean time to AVA occurrence after NAVF was 18.14 months ± 12 months [extremes: 26 Days and 84 months].

HIV- positive patients (35.71%) developed more false AVAs than HIV-negative patients (14.56%) [HR = 1.3290; CI95 (0.8922– 1.9747); p = 0,049]. On native veins, false AVAs appeared early at 8.72 months ± 7.75 months [Extremes: 1 month–36 months] versus 20.08 months ± 16.8 months [Extremes: 0 month–88 months] with true AVAs (p = 0.038). The mean NAVF flow at the time of AVA occurrence was 367.87 ml/min ± 27 ml/min [0 ml and 502 ml]. False aneurysms (n = 20) and true AAV (n = 97) accounted for 17.09% and 82.91%, respectively. There was ultrasoundDoppler of the aneurysm (Figure 4), 44.44% stenosis regardless of their site, and 18.80% thrombosis of the arteriovenous aneurysm summarized in (Table 2C). The frequency of AVA thrombosis in HIV-positive patients was 27, 26% (n = 6) versus 15.53% (n = 16) of HIV-immunocompetent patients [HR = 1.4782; CI95 [0.9321–2.3442]; p = 0.014]. Fifty patients (42.74%) underwent re- operation for AVA. Clinical criteria for AVA operability were pain (100%), ultrasound External Diameter of AVA > 35 mm (n = 31; 62%), and AVA rupture (n = 19; 38%). The surgical procedures consisted of a total arteriovenous aneurysmectomy (n = 41) after mobilizing AVA (Figure 5), a first removal of the NAVF by a double proximal and distal ligation of the radial artery, and then of the arterialized vein. Then, the NAVF was immediately recontoured at a distance from the first (n = 10) (Figure 6) or secondarily (n = 31) by a cephalo-radial arterial anastomosis, termino-lateral (n = 26) and termino-terminal (n = 5). We also performed a partial aneurysmectomy with immediate reconfection of the NAVF in 9 cases. In the case of AVA surgery, the rate of NAVF conservation was 18% (n = 9), with a rate of NAVF delocalization that was 28% (n = 14). Remotely, NAVF consisted of anastomosing a reverse saphenous vein graft between the arterial ends first and then secondarily anastomosing it to the cephalic vein (n = 26). False AVAs underwent more interventions (80.61%) than 67.35% true AVAs (HR = 3.299; CI95 [1.3573–8.0183]; p = 0.00015). The mean length of hospital stay was 6.128 ± 4.4917 Hours [Extremes:0 Hour and 48 Hours]. The mean follow-up was 4.74 patients per year [extremes: 0 year–12 years]. The loss of sight rate was 4.5%. Immediate postoperative mortality was 18% versus 10.30% for surgical abstention (HR = 1.188; CI95 [0.709–1.999]; p = 0.48). Postoperative mortality at 1 year and 5 years was 2.7% and 17.1%, respectively. We noted 17 immediate postoperative complications (34%) due to fistula hyper flow syndrome (n = 7) illustrated on fistula echo doppler, surgical wound suppuration (n = 4), AVA recurrence (n = 1), severe anemia (n = 1), and hemorrhage (n = 4).