BTT Shunt Anastomosis — Surgical Techniques

Date
September 22, 2025
URL
https://x.com/WithAScalpel/status/1970095238351065513
Categories
Cardiac SurgeryTOFSingle VentricleSurgical Training

BTT Shunt Anastomosis — Surgical Techniques

image

Overview and Goals

The modified Blalock–Taussig shunt (mBTS) uses an interposed PTFE conduit from the subclavian or innominate artery to a branch pulmonary artery to provide controlled systemic-to-pulmonary flow. Contemporary practice evolved from de Leval’s flow-regulated concept, which favored PTFE over earlier woven Dacron, helping standardize hemodynamics and durability [1, 2]. The arterial anastomosis must be hemostatic, circular, and non-stenotic, resist respiratory/neck movement, and preserve ipsilateral arm perfusion.

Surgical Approach

Exposure route may be lateral thoracotomy or median sternotomy. Contemporary single-center and institutional series demonstrate comparable outcomes between approaches; choice should be individualized to anatomy, need for concomitant procedures, and re-entry considerations [3, 4, 5].

Preparation and Sizing

  • Anticoagulation. Heparinization to an ACT consistent with local policy (commonly ≥300 s) is standard; many neonatal series pair this with meticulous hemostasis and gentle inotropy to reduce early shunt complications [6]. (See Postoperative Antithrombotic Strategy for nuances.) PubMed
  • Graft selection. Typical infant conduits are 3.0–4.0 mm, with 3.5 mm a common default. Observational data support using a shunt size/weight ratio around 1.1–1.2 mm/kg as an initial target; ratios substantially above this are associated with overshunting or late hazard in some cohorts [7, 8, 9]. Weight-based rules of thumb (e.g., 3.0 mm for ≤3 kg; 3.5 mm for ~3.5 kg; 4.0 mm for >4 kg) remain reasonable when integrated with pulmonary artery size and overall physiology [10].
  • Field optimization. Warm, wet field; fine suction; loupe or microscope magnification per surgeon preference.

Arterial Exposure and Control

  • Mobilize the RSCA or innominate artery with minimal adventitial stripping to preserve vasa vasorum; control proximally/distally with loops or micro-bulldogs.
  • Avoid direct wall grasping; use adventitia, pledgeted picks, or traction stitches.

Arteriotomy and Exposure

  • Create a small longitudinal arteriotomy proportional to the graft bevel; extend with Potts scissors as needed.
  • Place a traction stitch on the distal lip to rotate the lumen into view without traumatic grasping.

Suture Material and Strategy

  • Continuous 7-0/8-0 polypropylene on double-armed needles is standard; many neonatal series specifically report 8-0 polypropylene for fine control and reduced needle-hole bleeding [6].
  • Use a posterior-wall-first, far-to-near sequence to maintain intraluminal visualization.
  • Keep short, equidistant bites; a slightly larger graft bite than arterial bite helps avoid purse-stringing and maintains a round stoma.

Step-by-Step Anastomosis (Arterial Side)

  1. Anchor at the far (posterior) corner. First bites: graft inside-out, artery outside-in for intima-to-intima apposition and to prevent edge inversion.
  2. Run the posterior wall with gentle, even tension; shallow trajectories prevent excessive arterial capture. Re-establish the intraluminal view every few bites.
  3. Turn the heel. Maintain a vector of traction through the graft (heel toward you) to keep the orifice circular and prevent dog-ears.
  4. Rotate exposure with the traction stitch, not with forceps.
  5. Switch needles for symmetry (or reverse direction) to minimize torque and step-offs.
  6. Anterior wall orientation: commonly graft outside-in / artery inside-out so the line lies flat without gapping.
  7. Set loops intraluminally. Slide/seat the running suture within the lumen rather than pulling the wall outward—protects geometry and avoids cheese-wiring.
  8. Space-making maneuver. Before the last bites, draw the graft caudally to confirm no posterior wall capture.
  9. Complete the toe and tie with firm—not strangulating—tension; check for step-offs/fish-mouth.

Intraoperative Assessment and Touch-Ups

  • De-air and flush both sides before release.
  • Hemostasis. Address corner ooze with fine interrupted polypropylene corner stitches rather than over-tightening the continuous line.
  • Confirm a smooth, non-kinked graft lie to the PA with the neck in neutral/flex/extend; avoid torsion/tension.
  • Ensure distal arm perfusion (palpation ± Doppler).

Pearls and Pitfalls

  • Handle with traction, not grasping. Traction stitches and graft vectoring preserve delicate arterial wall.
  • Bite geometry is destiny. Short, consistent bites with a slightly larger graft bite maintain circularity.
  • Corners decide hemostasis. “Pre-plan” heel/toe; add a protective interrupted stitch if unsure.
  • See the lumen—often. Frequent intraluminal checks are the best safeguard against posterior-wall capture.
  • Tension is a dial, not a switch. Set loops by sliding rather than pulling.

Finishing and Early Management

  • After both anastomoses are complete and clamps are released, assess run-in flow, exclude kinks, and verify hemostasis at physiologic pressure.
  • Antithrombotic strategy. Many centers administer early postoperative heparin followed by antiplatelet therapy; however, some series report acceptable outcomes without routine heparinization, emphasizing that technical factors and small PA caliber most strongly relate to thrombosis [6, 11]. Tailor anticoagulation to bleeding risk, anatomy, and institutional protocols.
  • Complications and surveillance. Contemporary series report hospital mortality ranging ~3–15% with higher risk in lower-weight neonates and single-ventricle physiology; thrombosis/stenosis ~20–25% and over-circulation ~30% are recurrent issues [7, 8, 12, 13, 14]. Early surveillance focuses on balancing systemic oxygen delivery vs Qp, ensuring arm perfusion, and monitoring for signs of shunt restriction or overshunting.

References

[1] de Leval MR, McKay R, Jones M, Stark J, Macartney FJ. Modified Blalock-Taussig shunt. Use of subclavian artery orifice as flow regulator in prosthetic systemic-pulmonary artery shunts. J Thorac Cardiovasc Surg. 1981;81(1):112-119.

[2] Yuan SM, Shinfeld A, Raanani E. The Blalock–Taussig shunt. J Card Surg. 2009;24(2):101-108.

[3] McKenzie ED, Khan MS, Samayoa AX, et al. The Blalock-Taussig shunt revisited: a contemporary experience. Ann Thorac Surg. 2013;95(6):2072-2079.

[4] Tarca A, Starling A, Hayward CS, et al. A single-centre retrospective review of modified Blalock-Taussig shunts: lateral thoracotomy outcomes across 22 years. Heart Lung Circ. 2023;32(2):251-260.

[5] Shauq A, Ayub M, Jacobs S. Surgical approaches to the Blalock shunt: sternotomy versus thoracotomy. Interact Cardiovasc Thorac Surg. 2010;11(4):431-434.

[6] Swain SK, Dhawan A, Sharma A, Chauhan S, Kiran U, Bisoi AK. Neonatal Blalock-Taussig shunt: technical aspects and postoperative management. Ann Card Anaesth. 2008;11(1):28-34.

[7] Dirks V, Prêtre R, Knirsch W, Valsangiacomo Buechel ER, Seifert B, Bauer U. Modified Blalock-Taussig shunt: a not-so-simple palliative procedure. Eur J Cardiothorac Surg. 2013;44(6):1096-1102. (Median shunt size/weight ≈ 1.2 mm/kg.)

[8] Sasikumar N, Corno AF, Al-Halees Z, et al. Outcomes of Blalock-Taussig shunts in the current era: a single-centre experience. Congenit Heart Dis. 2017;12(5):633-641. (Shunt thrombosis/stenosis ~23%; over-circulation ~30%.)

[9] Alahmadi MH, Bishop MA. Modified Blalock-Taussig-Thomas Shunt. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024–. (Practical size guidance by weight bands.)

[10] Myers JW, Ghanayem NS, Cao Y, et al. Outcomes of systemic-to-pulmonary artery shunts in neonates weighing less than 3 kg. J Thorac Cardiovasc Surg. 2014;147(2):672-677. (3.5–4.0 mm favored over 3.0 mm regarding re-intervention.)

[11] Mullen JC, Spence MS, Paredes M, et al. Modified Blalock-Taussig shunts: to heparinize or not? Ann Thorac Surg. 1996;62(3):580-586.

[12] Petrucci O, O’Brien SM, Jacobs ML, et al. Risk factors for mortality and morbidity after the neonatal Blalock-Taussig shunt procedure. Ann Thorac Surg. 2011;92(2):642-651. (Higher risk in very low weight and PA/IVS.)

[13] Ilbawi MN, Idriss FS, DeLeon SY, et al. Modified Blalock-Taussig shunt in newborn infants. Ann Thorac Surg. 1984;38(3):218-225. (Early occlusion ~3.3%; hospital mortality ~3.3%.)

[14] Oofuvong M, Hotha S, Punjasawadwong Y, et al. Predictors of death after receiving a modified Blalock-Taussig shunt in cyanotic heart disease: a retrospective cohort analysis. PLoS One. 2021;16(2):e0246531. (Hazard signal when shunt size/weight > 1.1 in some analyses.)