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The Blalock–Taussig shunt is a palliative surgical procedure that creates a connection between the subclavian artery (or innominate artery) and the pulmonary artery, thereby increasing pulmonary blood flow.

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It is classically used in Cyanotic heart disease with decreased pulmonary flow, such as Tetralogy of Fallot (ToF).

Historical Context

First performed in 1944 by Alfred Blalock and Helen Taussig, with Vivien Thomas as surgical assistant.
Revolutionized the management of cyanotic congenital heart disease before definitive corrective surgery became widely available.

Etiopathology

Used in cyanotic congenital heart disease with right ventricular outflow tract obstruction (RVOTO) where pulmonary blood flow is reduced:

Tetralogy of Fallot (most common).
Pulmonary atresia with intact ventricular septum.
Tricuspid atresia with pulmonary stenosis.
Other complex congenital heart diseases with diminished pulmonary flow.

Types of Shunt

	Classical BT Shunt	Modified BT Shunt (preferred today)
Features	Direct end-to-side anastomosis between the subclavian artery and ipsilateral pulmonary artery.	Uses a synthetic Gore-Tex (PTFE) tube graft to connect the subclavian/innominate artery to the pulmonary artery.
Utility	Drawbacks: Subclavian artery sacrifice, limb ischemia, and distortion of pulmonary artery.	Advantages: Preserves subclavian artery, adjustable graft size, less risk of vascular steal.

Hemodynamic Effects

Increases pulmonary blood flow → improves oxygenation and relieves cyanosis.
Provides a temporary palliation until definitive corrective surgery can be performed (usually complete repair of TOF).