Arteriotomy

Arteriotomy Basics

Bypass construction begins by creating the largest possible inlets and outlets in arteries to minimize anastomotic resistance and maximize flow. Arteriotomies initiate new connections between disparate walls that will rejoin in suture lines in the anastomosis. Arteriotomies establish the location, size, and shape of the anastomosis and become its foundation. Arteriotomies refashion closed, cylindrical tubes that usually differ in caliber and shape into new geometries with open lines and curves.

Arteriotomies are made with three basic cuts: incision, excision, and transection (Table 8.1). Arteriotomies generate openings in basic shapes: lines, circles, ovals, quadrilaterals, and crescents. Seven basic arteriotomies are used in bypass surgery (Fig. 8.1): a longitudinal incision in a sidewall (linear incision arteriotomy), an oblique section across the entire artery (oblique transection arteriotomy), a combination of the two (fish-mouth arteriotomy), a transverse section (perpendicular transection arteriotomy), excision of a piece of wall (excision arteriotomy), and transections and incisions in bifurcations (transection and incision bifurcotomies).

Linear Incision Arteriotomy

A longitudinal incision in the sidewall that parallels the axis of the artery is the simplest and most common arteriotomy, used on intracranial recipients in end-to-side and side-to-side anastomoses, as well as on intracranial donors in side-to-side anastomoses. Its length should be three times the artery’s diameter to widen communication between the donor and the recipient. After marking the line with blue ink, the artery is pierced with a beveled 27-gauge needle whose shaft is angled 45 degrees off axis for tangential puncture. The needle shaft can be angled up to 90 degrees in long surgical corridors. Disposable needles are fresh and sharp every time, and are mounted on a tuberculin syringe as a thin handle. The puncture hole is entered with one blade of a microscissors and extended with straight cuts along the marked line. The microscissors is held flat in shallow fields to parallel the artery’s axis, but may lie perpendicular to the artery in deep fields. An angled microscissors, such as a miniaturized Potts scissors (Lawton micro-arteriotomy scissors, Mizuho America, Inc., Union City, CA), facilitates this arteriotomy with deep bypasses (Fig. 8.2). The initial puncture is situated at the midpoint of the arteriotomy, and the arteriotomy is then extended in the opposite direction by reversing the orientation of the micro-arteriotomy scissors. Smooth cuts in a straight line avoid a jagged, saw-toothed arteriotomy. The needle creates small transverse cuts in the arterial wall at the puncture site, which have the least impact in the middle of the suture line where the anastomosis is widest.

Fig. 8.1 (opposite) The three basic cuts used to make an arteriotomy are incision, excision, and transection, and they generate arterial openings in five shapes: lines, circles, ovals, quadrilaterals, and crescents. Seven basic arteriotomies are used in bypass surgery: (A) linear incision arteriotomy; (B) perpendicular transection arteriotomy; (C) oblique transection arteriotomy; (D) fish-mouth arteriotomy; (E) excision arteriotomy; (F) transection bifurcotomy; and (G) incision bifurcotomy.

Fig. 8.2 Linear incision arteriotomy is the simplest and most common arteriotomy, used in end-to-side and side-to-side anastomoses. (A) The artery is trapped with temporary clips and a line three times as long as the artery’s width is marked with blue ink. (B) The artery is pierced with a beveled 27-gauge needle whose shaft is angled 45 degrees off the axis for tangential puncture. (C) The puncture hole is created and (D) entered with one blade of a microscissors. (E) The arteriotomy is extended with smooth, straight cuts along the marked line in both directions.

Linear incision arteriotomies can be made alternatively with a pointed scalpel blade, such as a No. 11 blade, or with curved microscissors. A small snip in the artery with microscissors can initiate the arteriotomy instead of a needle puncture. The linear arteriotomy fashions straight suture lines that are the easiest to suture because relationships between the hands, instruments, needles, and tissues are constant along the entire line. This arteriotomy conserves the arterial wall to maintain luminal size, unlike excision arteriotomies that resect a piece of wall and can cause stenosis at the anastomosis. Linear arteriotomies are ideal with cerebral arteries whose thins walls are easily splayed by flow or the paired artery in the anastomosis, but may not open widely in thick, rigid arteries such as the ECA or CCA.

Fish-Mouth Arteriotomy

The “fish-mouth” arteriotomy creates a quadrilateral-shaped opening that optimizes the area of the anastomotic lumen, getting the most bang for the buck, or most flow for the cuts. Classically, this arteriotomy combines a perpendicular transection and a longitudinal linear incision in the sidewall, with its length equal to the artery’s diameter (Fig. 8.3). These cuts transform a small circular transection into a flared, quadrangular orifice described as a cobra head or spatula. Mathematically, an artery with diameter d that is transected perpendicularly has an anastomotic circumference of πd and an anastomotic area of πd²/4. In contrast, the same artery with a fish-mouth arteriotomy (perpendicular transection and longitudinal incision) has an anastomotic circumference of 2πd and an anastomotic area of πd². Therefore, fish-mouthing the artery doubles the anastomotic circumference and quadruples the anastomotic area, relative to perpendicular transection. For comparison, the same artery transected obliquely at a 45-degree angle without fish-mouthing has an anastomotic circumference of πd√2 and an anastomotic area of πd²/2 (double that of perpendicular transection).

Fig. 8.3 The fish-mouth arteriotomy creates a quadrilateral-shaped opening that optimizes the area of the anastomotic lumen, combining a 60-degree oblique transection and a longitudinal linear incision in the sidewall equal to the length of the oblique transection. (A) Mathematically, an artery with a diameter d that is transected perpendicularly has an anastomotic circumference of πd and an anastomotic area of πd²/4. (B) The same artery transected obliquely at a 45-degree angle without fish-mouthing has an anastomotic circumference of πd√2 and an anastomotic area of πd²/2 (double that of perpendicular transection). (C) The same artery with a fish-mouth arteriotomy (perpendicular transection and longitudinal incision) has an anastomotic circumference of 2πd and an anastomotic area of πd². Therefore, fish-mouthing the artery doubles the anastomotic circumference and quadruples the anastomotic area, relative to perpendicular transection.

These calculations are simplest with 45- and 90-degree angled cuts, but, in practice, the ideal fish-mouth arteriotomy combines a 60-degree angled arterial transection (60 degrees from the long axis of the artery) and a longitudinal linear incision in the sidewall equal to the length of that cut, or the hypotenuse of the 60-degree right-angled triangle (2d/√3, or 1.2d) rather than the artery’s diameter (Fig. 8.4). This geometry reduces slightly the anastomotic area but relaxes the angles of this quadrilateral, changing its shape from a square to a kite shape with obtuse angles (120 degrees) in the middle of the suture lines and acute angles (60 degrees) at the ends of the arteriotomy. The fish-mouth arteriotomy is widely used in EC-IC end-to-side anastomoses such as the STA-MCA bypass to prepare and enlarge scalp arteries as donors. It is also used in IC-IC end-to-side reimplantations and in reanastomoses when the two ends can be aligned in alternating fashion, heel to toe and toe to heel (double fish mouth anastomosis). The increased anastomotic area in fish-mouthed donors augments bypass flow and prevents stenosis. The matching arteriotomy in the recipient artery must be lengthened to accommodate this more capacious anastomosis, increasing from 1.5d (or πd/2) with the perpendicular transection arteriotomy, to 2.2d (or πd/√2) with the oblique transection arteriotomy, and to 3.1d (or πd) with the fish-mouth arteriotomy.