Blalock-Taussing-Thomas (BTT) Shunt Radiology | GetWellGo

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Blalock-Taussing-Thomas (BTT) Shunt Radiology | GetWellGo

  • Category

    General

  • Published By

    GetWellGo Team

  • Updated on

    19-May-2025

Blalock-Taussig shunt

A BT shunt is a form of heart surgery that increases blood flow to the lungs in infants or children with Tetralogy of Fallot or pulmonary atresia, among other cyanotic congenital heart defects. It is mainly used as a measure for relief, since the main surgery happens later.

BT shunt radiology

Blalock-Taussig shunt radiographic findings:

Chest X-ray (CXR)

  • Indications: Early post-operative imaging is needed to check the shunt’s condition and how well the lungs are being perfused.

Findings:

  • The vessels carrying blood to the lungs become larger (may be just to one or both lungs depending on the location of non-oxygenated blood).
  • Usually, one will notice surgical clips or coils next to the shunt site during an x-ray, especially with a modified BT shunt.
  • Possible asymmetry of lung vascularity.
  • There may be a shift or a change in the shape of the mediastinum if chest surgery was done before.
  • A shunt that is too large might cause the signs of pulmonary overcirculation or heart failure.

Echocardiography

  • Doctors typically use non-invasive methods, such as this one, for children.

Color Doppler shows:

  • A perpetual flow from the subclavian artery to the pulmonary artery takes place.
  • Serves for measuring the condition of shunts and seeing flow direction and velocity.
  • There are sometimes situations in post-op care where acoustic windows restrict language learning.

CT Angiography (CTA)

  • Used when echocardiography is inconclusive.

High-resolution images show:

  • It is common to connect the artery using a Gore-Tex graft or a part of the patient’s own artery.
  • Shunt course, patency, and size.
  • Things that might accompany it, such as narrowing of the blood vessel, blood clots within the blood vessel, or a pocket of blood that develops outside the artery.

MR Angiography (MRA)

  • Offers detailed imaging without radiation.
  • Useful in long-term follow-up.

Evaluates:

  • Shunt function
  • Pulmonary artery growth
  • Collateral circulation
  • Checking the amounts of blood in the ventricles and how effectively they pump

Cardiac Catheterization

  • Results of a cardiac catheterization provide the best assessment of a shunt’s openness, pressures in different areas, and pulmonary vascular resistance.
  • It is possible to insert a balloon angioplasty or a stent if the shunt narrows.

Blalock-Taussig Shunt Procedure

Anaesthesia and Preparation

  • Patient under general anaesthesia
  • Median sternotomy or thoracotomy approach
  • Systemic heparinization (to prevent clotting)

Exposure of Vessels

  • Cut open and separate out the subclavian artery (or innominate artery) on the chosen side.
  • Choose and get ready the branch of the pulmonary artery, which is usually the right or left twin.

Shunt Creation

  • About 3–4 millimeters of Gore-Tex tube is attached using surgical suturing.
  • Proximally to the subclavian/innominate artery
  • After the branch of the pulmonary artery
  • The anastomoses are typically end-to-side.

Establishing Flow

  • The clamps are taken away in a slow and steady way to let blood go through the shunt.

Flow is confirmed using:

  • Visual assessment (shunt pinking up)
  • Working professionals may use Doppler ultrasound or flow probes during surgery.

Hemostasis and Closure

  • Ensure no bleeding from anastomoses
  • Reverse heparin if needed
  • Place a drain and then close the patient’s chest.

Postoperative Care

  • Make sure the oxygen saturation improves.
  • Echocardiography for shunt patency
  • Prescribing antiplatelet drugs (e.g., aspirin) to stop blood clots
  • Pay attention to symptoms that may signal a shunt is either clogged up or working too much.

Blalock-Taussig Shunt Complications

While the BT shunt can save someone’s life, it often results in many short- and long-term problems. You can also see changes in the shunt, the lungs, or in general blood flow.

  • Shunt Thrombosis (Occlusion)
  • Shunt Stenosis (Narrowing)
  • Overcirculation to the Lungs
  • Unequal Pulmonary Artery Growth
  • Shunt Infection
  • Aneurysm or Pseudoaneurysm Formation
  • Hemorrhage or Bleeding
  • Neurologic Events
  • Subclavian Steal Syndrome
  • Mortality

Blalock-Taussig Shunt Indications

The BT shunt is most often done to increase blood reaching the lungs in heart diseases where pulmonary circulation is not enough. It is done until the child is ready for safe, permanent correction.

Primary Indications

  • Tetralogy of Fallot (TOF)
  • Pulmonary Atresia
  • Tricuspid Atresia    
  • Single Ventricle Physiology
  • Hypoplastic Left Heart Syndrome (HLHS)

Blalock-Taussig Shunt CT scan

Using CT angiography (CTA) can help check the results of the Blalock-Taussig shunt, most especially the modified shunt with a Gore-Tex (PTFE) graft. With this technique, you can see a high-quality 3D display of the shunt, the pulmonary arteries, and the structures close by.

The Important Aspects to Check on a CT Scan

Normal Findings

Tubular structure connecting:

  • Subclavian or innominate artery going to the pulmonary artery.
  • It shows up in the shape of a spotless, contrasted tube.
  • No parts where the bowel is squeezed or bent in an unusual way.
  • Even and better supply of blood to the lungs.

Blalock-Taussig Shunt Surgery

The Blalock-Taussig shunt is a surgery done on children to help increase blood reaching their lungs when they have congenital heart defects reducing the amount of blood getting to the lungs.

Purpose of the Surgery

To make a connection between the systemic and pulmonary arteries, so that blood with low oxygen enters the lungs when the native pulmonary outflow is blocked or fails to develop properly.

Types of BT Shunt Surgery

Classic BT Shunt (Historical)

  • Direct connection of the subclavian artery to the other artery going to the pulmonary artery.
  • Due to arm ischemia and narrow control over the vessel, it is now uncommon.

Modified BT (mBT) Shunt (The usual standard these days)

  • The synthetic PTFE graft joins the subclavian or innominate artery to the pulmonary artery.
  • Makes it possible to choose the size and the amount of flow in the shunt.
  • Ensures that the arm still receives blood from the innermost part of the arch.

Blalock-Taussig Shunt Technique

Preoperative Preparation

  • General anaesthesia with endotracheal intubation.
  • Systemic anticoagulation (usually heparin) administered.
  • Depending on how the operation will be done, the patient is placed either in the supine or the lateral decubitus position.

Surgical Approach

  • Operation can be done through the right thoracotomy, left thoracotomy, or median sternotomy, according to preference and the patient’s and anatomy’s needs.

Expose:

  • The subclavian artery goes by the other name innominate artery.
  • The branch called pulmonary artery, whether it is the right or left.

Vessel Preparation

  • The use of vessel loops or vascular clamps to control the arteries.
  • Administer heparin before clamping.
  • Try to keep dissection minimal so that the arteries are not cut off.

Shunt Graft Selection

  • Picking the right Gore-Tex (PTFE) graft (adjusted to the patient’s body size between 3.0 to 4.0 mm).
  • Cut the wires short enough so that the hose can move freely without getting stuck or kinked.

Anastomosis: Proximal End

  • Use 6-0 or 7-0 polypropylene sutures to attach the upper end of the graft directly to either the subclavian or innominate artery.
  • Check that there is no water leak or bubbling, and the valve is closed, before you start.

Anastomosis: Distal End

  • After dividing, open the proximal end of the graft and connect its distal end with the branch pulmonary artery by sewing them together.
  • If allowed, put a partial occlusion clamp on the PA to help maintain some blood flow through the lungs.
  • Make sure there is good flow again after putting in the final sutures.

Initiate Flow

  • Carefully remove vascular clamps.
  • Listen to the shunt for any pulsating flowabouts.
  • Color Doppler or watching the flow of blood can prove if the pathway is still working.

Hemostasis and Closure

  • Check for any bleeding at the points where the two blood vessels were joined.
  • If necessary, use protamine to overturn the effects of heparin.
  • Assemble the sternotomy or thoracotomy in a stepwise fashion after placing a chest drain.
     

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