Preoperative arterial microcalcification and clinical outcomes of arteriovenous fistulas for hemodialysis

Abstract

Background: Arteriovenous fistulas (AVFs) often fail to mature, but the mechanism of AVF nonmaturation is poorly understood. Arterial microcalcification is common in patients with chronic kidney disease (CKD) and may limit vascular dilatation, thereby contributing to early postoperative juxta-anastomotic AVF stenosis and impaired AVF maturation. This study evaluated whether preexisting arterial microcalcification adversely affects AVF outcomes.

Study design: Prospective study.

Setting & participants: 127 patients with CKD undergoing AVF surgery at a large academic medical center.

Predictors: Preexisting arterial microcalcification (≥1% of media area) assessed independently by von Kossa stains of arterial specimens obtained during AVF surgery and by preoperative ultrasound.

Outcomes: Juxta-anastomotic AVF stenosis (ascertained by ultrasound obtained 4-6 weeks postoperatively), AVF nonmaturation (inability to cannulate with 2 needles with dialysis blood flow ≥ 300mL/min for ≥6 sessions in 1 month within 6 months of AVF creation), and duration of primary unassisted AVF survival after successful use (time to first intervention).

Results: Arterial microcalcification was present by histologic evaluation in 40% of patients undergoing AVF surgery. The frequency of a postoperative juxta-anastomotic AVF stenosis was similar in patients with or without preexisting arterial microcalcification (32% vs 42%; OR, 0.65; 95% CI, 0.28-1.52; P=0.3). AVF nonmaturation was observed in 29%, 33%, 33%, and 33% of patients with <1%, 1% to 4.9%, 5% to 9.9%, and ≥10% arterial microcalcification, respectively (P=0.9). Sonographic arterial microcalcification was found in 39% of patients and was associated with histologic calcification (P=0.001), but did not predict AVF nonmaturation. Finally, among AVFs that matured, unassisted AVF maturation (time to first intervention) was similar for patients with and without preexisting arterial microcalcification (HR, 0.64; 95% CI, 0.35-1.21; P=0.2).

Limitations: Single-center study.

Conclusions: Arterial microcalcification is common in patients with advanced CKD, but does not explain postoperative AVF stenosis, AVF nonmaturation, or AVF failure after successful cannulation.

Keywords: AVF non-maturation; AVF survival; Arteriovenous fistula (AVF); arterial micro-calcification; arteriovenous access; cannulation; chronic kidney disease (CKD); hemodialysis; juxta-anastomotic AVF stenosis; vascular access; vascular calcification; vascular ultrasound; von Kossa staining.

Fig. 1

Representative von Kossa stains of arterial specimens obtained during AVF creation. Calcium stains black, and calcification was quantified as the percent of the total tissue specimen staining black. A, an artery with 0.25% calcification. B, an artery with 20.7% calcification. I, intima; M, media; A, adventitia.

Fig. 2

Representative vascular ultrasound images. A. Longitudinal high-resolution image of left brachial artery showing good depiction of intimal-medial arterial layers (cursors), without arterial micro-calcification. B. Longitudinal high resolution image of left brachial artery in a different subject showing heavy calcifications (small white dots) in the anterior arterial wall which are confluent (arrowheads), limiting visualization of the far wall (cursors).

Fig. 3

Flow chart illustrating how the patients were selected for the final study sample.

Fig. 4

Distribution of histologic arterial micro-calcification in patients with or without arterial micro-calcification by preoperative ultrasound (p=0.001). The solid black lines represent the means.

Fig. 5

Unassisted primary survival after successful cannulation of AVF that achieved maturation for dialysis. The endpoint was the first AVF intervention after maturation (angioplasty, thrombectomy or surgical revision). P=0.2 by the log rank test.