The classic or original BT shunt procedure was named after a surgeon in Baltimore, Alfred Blalock (1899–1964), and a cardiologist in Baltimore/Boston, Helen B. Taussig (1898–1986), who along with Blalock's African American laboratory technician Vivien Thomas (1910–1985), developed and described the procedure.
In 1943, Dr. Taussig approached Blalock and Thomas in their Hopkins laboratory to work on this shunt as it was hypothesized that a shunt mimicking PDA can relieve the cyanosis and improve oxygenation in congential cyanotic diseases.[1]
Unilateral pulmonary edema, Blalock-Taussig shunt in pulmonary atresia with a ventricular septal defect. Source: Dr. Charlie Chia-Tsong.
Management of Complications
Shunt failure
Failure of the shunt is the most immediate risk during the post-operative period which can lead to a drop in oxygen saturation secondary due to shunt thrombosis or kinking.
Shunt failure is a surgical emergency and should be managed as follows:
Anticoagulation should be started promptly with heparin. It should be administered again if there is less risk of bleeding usually 4 hours post-op (when the drainage of the chest shows <3ml/kg/h and aPTT is <60s). Heparin induced thrombocytopenia can occur and should be managed accordingly.
Patient is put on aspirin which is usually started at 3-5 mg/kg (max. dose 75mg) OD.
Heparin should be continued until there is a second dose of aspirin.
Blockage of BT shunt
Blockage or shunt thrombosis is another surgical emergency with a reported incidence of 12%.
If there's any recent onset murmur or a significant drop in oxygen saturation, it must be investigated.
Operative management is usually required and the shunt is usually repaired or replaced if necessary.
High pulmonary blood flow
The appropriate size of BT shunt is very important to prevent the long term complications regarding high pulmonary blood flow or high oxygen saturation.
Cases refractory to medical management are usually treated with a surgical approach that involves pulmonary artery banding or clamping.
Prognosis
Modified Blalock-Taussig Shunt has a superior prognostic value over classic Blalock-Taussig Shunts. Following prognostic factors are compared between the two procedures in multiple studies:[7][8][9][10][11][12]
The increase in saturation of oxygen is greater in the modified shunt as compared to the classic shunt.
Modified shunt has an 88.8% patency rate in 3-5 years. Whereas for the classic shunt, the patency rate is 90% in the first year, 62% in two years, and 78.0% in 3 years.
The risk of early shunt failure is 20.8% in modified and 51.7% in the classic shunt.
Post-shunt increase in pulmonary arterial index (mm2/m2) is 158 +/- 21 versus 117 +/- 52 in classic Blalock-Taussig shunt.
Internal mammary artery is used for this purpose and to create a systemic to pulmonary conduit after there has been a failure of previously used BT shunt.
It leads to adaptation of growth, and flow, and it also reduces the risk for graft infection.
↑Eghtesady, Pirooz (2015). "Potts Shunt for Children With Severe Pulmonary Hypertension". Operative Techniques in Thoracic and Cardiovascular Surgery. Elsevier BV. 20 (3): 293–305. doi:10.1053/j.optechstcvs.2016.02.003. ISSN1522-2942.
↑TRUCCONE, NESTOR J.; BOWMAN, FREDERICK O.; MALM, JAMES R.; GERSONY, WELTON M. (1974). "Systemic-Pulmonary Arterial Shunts in the First Year of Life". Circulation. Ovid Technologies (Wolters Kluwer Health). 49 (3): 508–511. doi:10.1161/01.cir.49.3.508. ISSN0009-7322.
