Murine Model of Central Venous Stenosis using Aortocaval Fistula with an Outflow Stenosis

Summary

An aortocaval fistula was created by puncturing the murine infra-renal aorta through both walls into the inferior vena cava and was followed by creation of a stenosis in its outflow via partial ligation of the inferior vena cava. This reproducible model can be used to study central venous stenosis.

Abstract

Central venous stenosis is an important entity contributing to arteriovenous fistula (AVF) failure. A murine AVF model was modified to create a partial ligation of the inferior vena cava (IVC) in the outflow of the fistula, mimicking central venous stenosis. Technical aspects of this model are introduced. The aorta and IVC are exposed, following an abdominal incision. The infra-renal aorta and IVC are dissected for proximal clamping, and the distal aorta is exposed for puncture. The IVC at the midpoint between the left renal vein and the aortic bifurcation is carefully dissected to place an 8-0 suture beneath the IVC. After clamping the aorta and IVC, an AVF is created by puncturing the infra-renal aorta through both walls into the IVC with a 25 G needle, followed by ligating a 22 G intra-venous (IV) catheter and IVC together. The catheter is then removed, creating a reproducible venous stenosis without occlusion. The aorta and IVC are unclamped after confirming primary hemostasis. This novel model of central vein stenosis is easy to perform, reproducible, and will facilitate studies on AVF failure.

Introduction

Arteriovenous fistulae (AVF) are the most common accesses for hemodialysis, with superior patency and reduced infection compared to other accesses such as grafts or central venous catheters. However, up to 60% of AVF fail to mature^1,2,3; a recent systematic review reported that primary patency rates at 1 year were only 60%⁴. Stenosis along the venous outflow predominantly causes failure of AVF maturation^5,6. There are certain characteristic locations prone to stenosis proximal to the fistula: t....

Protocol

All experiments were performed with approval from the Yale University Institutional Animal Care and Use Committee (IACUC).

1. Anesthesia and pre-operative procedures

1. Sterilize all surgical instruments and materials by autoclaving. Turn on the thermal support device to be certain it is warm (40–42 °C).
2. Place a 9–11-week old C57BL/6 mouse into an acrylic induction chamber and anesthetize it with vaporized 2.5% isoflurane and 0.8 L/min oxygen. Anesthesia induction takes about 3 min.
3. Remove the mouse from the chamber. Confirm a deep plane of anesthesia by a toe pinch, an ear pinch and a tail pinc....

Results

Male mice underwent the operation mentioned above to create both an AVF and an IVC stenosis. Control mice underwent only laparotomy and dissection of the tissues surrounding the IVC, e.g., a sham procedure, or only creation of an IVC stenosis without simultaneous creation of an AVF.

The IVC was observed with Doppler ultrasound on day 7 after the surgical procedure (Figure 2). The fistula and stenosi.......

Discussion

The murine AVF model has been used to study the basic mechanisms and molecular events leading to AVF maturation^13,14. In this study, we modified an established murine AVF model to create a novel murine aortocaval fistula model with an IVC stenosis in the outflow tract of the fistula. Our ligation model is similar to several previously described murine models that use vascular ligation. A murine model of deep vein thrombosis was created using partial IVC ligation .......

Materials

Name	Company	Catalog Number	Comments
20-60 Mhz scan head	VisualSonics Inc.	RMV-704
8-0 Sterile Micro Suture, 6mm (140 µ), 3/8 Circle, TAP Point Needle	AROSuture	T06A08N14-13	polyamide monofilament sutures
Induction Chamber, 2 Liter 3.75"W x 9.00"D x 3.75"H	VetEquip	941444
Isoflo, Isoflurane liquid	Zoetis	26675-46-7
Mice, C57BL/6J	The Jackson Laboratory	664
Pet Bed Microwave Heating Pad	Snuggle Safe	6250
PrecisionGlide Needle 25G	BD	305122
Surflo I.V. Catheter 22G	Terumo	SR-OX2225CA	0.85mm outer diameter
Vascular clamp	Roboz Surgical Instrument	RS-5424
Vevo770 High Resolution Imaging System	VisualSonics Inc.	770