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Modified Blalock Taussig (B.T.) shunt with the use of Goretex graft.
Recent advances in the field of cardiac surgery have considerably changed the outlook of the sick cyanotic babies with Fallot's tetralogy and other cyanotic heart diseases associated with diminished pulmonary blood flow. Today, total correction for Fallot's tetralogy is being carried out in very small children and even in infancy with considerable success.[8] However, only a few centres in the world can claim such expertise and facilities for after-care. Hence palliative shunt procedures are being widely advocated to tide these very sick cyanotic babies to an age where they can undergo corrective surgery with ease and safety. The Blalock-Taussig (B.T.) shunt has for long been the mainstay in the management of cyanotic children. In fact, it is still one of the most widely practised systemic pulmonary shunts.[7] The Waterston shunt has been found useful in small babies where a standard B.T. shunt was considered not feasible.[13] This shunt, however, possesses the problem of kinking the right pulmonary artery. More recently there has been a growing interest in aorto-pulmonary shunt with the use of poly tetra fluoroethylene (PTFE) grafts.[5], [9] We have however used Goretex grafts to perform a modified B.T. shunt and are presenting our early experience and results of this procedure.
In this series, 8 children with severe central cyanosis were studied. Their ages ranged between 1½ and 3 years. Their haemoglobin ranged from 17 to 21 gm% with an average packed cell volume of 60%. These children weighed between 5 and 8 kg. In general, all these children were sick and intensely cyanosed and we felt that shunt procedure would be better than to offer total correction. All these children were operated as an emergency because of repeated hypoxic spells. Technique Under general anaesthesia with the patient placed in a lateral position, the chest is opened through the left fourth intercostal space. The apex of the lung is retracted down and the mediastinal pleura over the subclavian artery is cut. The subclavian artery is mobilised and tapes are passed around it. The pulmonary artery is mobilised close to the hilum to a length of about 1.5 cm. A PTFE (Goretex) graft, 5-6 mm in diameter, is kept ready for anastomosis. The proximal anastomosis of the graft is placed on the subclavian artery just distal to its origin [Fig. 1]. Subclavian artery is kept occluded with a vascular Cooley's clamp till both the proximal and distal anastomoses are completed. An end-to-side anastomosis is then made with the pulmonary artery proximal to the lobar branches. Use of a Cooley's clamp over the pulmonary artery is found useful during the distal anastomosis. Fine monofilament polypropylene sutures (six-`O' Prolene) were used for the anastomosis. Following completion of the distal anastomosis, the clamps over subclavian and pulmonary artery are released simultaneously. A continuous thrill is invariably felt as a confirmatory sign of a functioning shunt.
The new technique was used in 8 cases with no mortality. All patients were below the age of three years with PCV above 60%. All of them underwent emergency surgery because of hypoxic spells. In all cases functioning of the shunt was confirmed by a continuous murmur which could be heard in the left infrascapular region. The hypoxic spells disappeared after surgery in all cases. None of the patients went in congestive cardiac failure following surgery suggesting that the shunt was not excessive. One patient underwent aortogram one month after surgery which demonstrated functioning shunt [Fig. 2] .In all eight patients the left radial artery was well palpable as pulsatile flow to the left arm was maintained. [TAG:2}DISCUSSION[/TAG:2} The first palliative operation for cyanotic congenital heart disease was carried out by Blalock-Taussigl where a subclavian to pulmonary artery shunt was created. The major advantage of the Blalock-Taussig anastomosis is that the shunt is seldom excessive. The size of the anastomosis is limited by the cross sectional diameter of the subclavian artery and the flow is further limited by the resistance along the subclavian artery. However, this shunt is not without disadvantages. In infants where the size of the subclavian artery is small this shunt is not dependable. In the series published by Great Ormond Street the mortality after B.T. shunt under age of six months was 63%.[10] This shunt is an end-to-side anastomosis and results in disappearance of the radial pulse on the side of the shunt. Anastomosis is ideally performed on the side opposite the aortic arch. The subclavian artery tends to kink over the aortic arch if the anastomosis is performed on the side of the aortic arch.[12] Lateral shunts in the form of Pott's shunt or Waterston anastomosis are customarily preferred to within first six months of life. It has been recognised that Pott's anastomosis is frequently complicated by pulmonary over-circulation, left ventricular failure and pulmonary microvascular hypertension.[6] It is technically difficult to properly close these shunts at the time of total correction.[2] Most of the surgeons have abandoned Pott's shunt in favour of Waterston's shunt. Experience with Waterston shunt suggests that it also was frequently complicated by excessive shunting and left ventricular failure.[3] Furthermore with the growth of the child, the pulmonary artery always becomes scarred and non-compliant at the site of the shunt and small pulmonary artery frequently becomes kinked up to the aorta.[4] The use of Goretex graft in the present modification of Blalock-Taussig shunt takes care of the above disadvantages. In cases where the subclavian artery is small, Goretex graft can be easily interposed between the subclavian and pulmonary arteries. It still maintains the major advantage of Blalock operation that the shunt is rarely excessive being limited by the diameter of the subclavian artery at its origin. The lie is always good without kink at the subclavian or pulmonary artery. There is no chance of ischaemia as the subclavian artery is not ligated. It is expected that ligation of the shunt at the time of total correction will be easier because there will be minimum adhesion with less dissection in this area. A similar type of shunt has been performed by Szarnicki and De Leval[11] in case of pulmonary atresia with nonconfluent pulmonary arteries with good result.
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