Indications for Surgery
The diagnosis of tetralogy is considered as an indication for surgery. If the child is very symptomatic and anatomy for repair is suitable, one stage repair is advised at three months or above that age. In a baby of one or two months who is severely symptomatic and in whom pre-operative studies show the necessity of a trans annular patch, many surgeons will do a shunt. However there are some centers where intracardiac repair is done irsespective of the age of the baby. A shunt is followed by intra cardiac repais within twelve months. When the child is asymptomatic or only mildly symptomatic,intracasdiac repair can be postponed safely until the child is one or two y e a s old. There is no advantage in waiting any further.
Palliative Operations
Shunt Operations
Classic Blalock-l'aussig (BT) Shunt
Subclavian artery, which arises from innominate artery, is anastomosed to pulmonary artery. In a patient with left aortic arch, the operation is done on the right side. Child is placed in left lateral position and a right lateral thoracotomy through third inter costal space is done. Right lung is retracted downwards and posteriorly and right pulmonary artery is dissected and looped. The anastomosis should be done on the right pulmonary artery as medially as possible. (Posterior to superior vena cava). Then dissection is
carried superior to azygos vein to expose right subclavian artery. Vagus and recurrent laryngeal nerves ate identified. Dissection of the subclavian artery is carried out superiorly by ligating and dividing internal mammary and vertebral aterial branches. Subclavian artery is ligated at the point of exit from chest and divided after applying a vasculas clamp proximally. It is then taken medial to the vagus nerve and turned down to the right pulmonasy artery. Clamp is applied on proximal right puhonary artery. The distal bianches of pulmonary artery are looped and weighted down for haemostasis.
The diagnosis of tetralogy is considered as an indication for surgery. If the child is very symptomatic and anatomy for repair is suitable, one stage repair is advised at three months or above that age. In a baby of one or two months who is severely symptomatic and in whom pre-operative studies show the necessity of a trans annular patch, many surgeons will do a shunt. However there are some centers where intracardiac repair is done irsespective of the age of the baby. A shunt is followed by intra cardiac repais within twelve months. When the child is asymptomatic or only mildly symptomatic,intracasdiac repair can be postponed safely until the child is one or two y e a s old. There is no advantage in waiting any further.
Palliative Operations
Shunt Operations
Classic Blalock-l'aussig (BT) Shunt
Subclavian artery, which arises from innominate artery, is anastomosed to pulmonary artery. In a patient with left aortic arch, the operation is done on the right side. Child is placed in left lateral position and a right lateral thoracotomy through third inter costal space is done. Right lung is retracted downwards and posteriorly and right pulmonary artery is dissected and looped. The anastomosis should be done on the right pulmonary artery as medially as possible. (Posterior to superior vena cava). Then dissection is
carried superior to azygos vein to expose right subclavian artery. Vagus and recurrent laryngeal nerves ate identified. Dissection of the subclavian artery is carried out superiorly by ligating and dividing internal mammary and vertebral aterial branches. Subclavian artery is ligated at the point of exit from chest and divided after applying a vasculas clamp proximally. It is then taken medial to the vagus nerve and turned down to the right pulmonasy artery. Clamp is applied on proximal right puhonary artery. The distal bianches of pulmonary artery are looped and weighted down for haemostasis.
Modified Blalock-Taussig Shunt
This is usually done by iilterpositioning a PTFE (Goretex) graft of 3.5 or 4mm in a neonate. It is better done by a left lateral thoracotoiny. Left pulmonay artery is dissected and looped proximal to the origin of its branches. Left subclavian artery is also dissected and looped. After clamping and opening the subclavian arteiy, end to side anastomosis of the Goretex graft is done using 7-0 or 6-0 prolene. Then pulmonary artery is clamped and opened superiorly. Anastomosis between graft and pulmona~y artery is done with
7-0 prolene. On removing the clamp there should be continuous a thrill on the pulmonay artery.
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| Classic Ulalock-Tanssig (BT) Shunt |
Other Types of Systemic Pulnzonary Artery Shunts
Waterston Shunt
In this, direct anastomosis between the posterior aspect of ascending aoi-ta and anterior aspect right pulmonary artery is done directly. Care should be taken not to make too large an anastomosis. It is very easy to overdo this shunt. This will cause excessive flow and n~ay lead to pulmonary hypertension and pulmonary vascular disease later on.
Pott's Shunt
This is a similar shunt done through a left thoracotonly. Anastoinosis is done between left pulmonary artery aid descending thoracic sol-la. The disadvantage of this shunt is also the likelihood of excessive flow. To take down this shunt at the time of intra cardiac repair is a cardiac surgeon's nightmare. These two types of shunts are now almost given up.
Palliative Outflow Patch
Brock described closed pulmonslly valvotorny and infundibular resection using a punch on a beating heart. When both pulnlonary arteries are not suitable for shunt (less than 2.5 or 3 mm) systemic pulmonary shunts will no1 succeed. In these babies a palliative outtlow patch repair could be done on cardio puln~onary bypass. Ventricular septa1 defecl is left open. At a later stage when the pulmonary arteries are sufiiciently large, ventricular septal defect is closed with a patch.
Results
In excellent centers, the mortality is reported one per cent or less. In infants and babies with low weight, higher mortality is expected (2 to 3 per cent) and even up to 12 per cent from some centers. Time related survival in a hetcrogenous group at one month, lyear, Syears, 10 years and 20 years is reported to be 94 per cent, 92 per cent, 91 per cent, 90 per cent and 87 per cent.
Re- pera at ions and Other Interventions
These are required for residual VSD with significant shunt, residual RV obstruction and pulmonary valve regurgitation in a few cases.
Waterston Shunt
In this, direct anastomosis between the posterior aspect of ascending aoi-ta and anterior aspect right pulmonary artery is done directly. Care should be taken not to make too large an anastomosis. It is very easy to overdo this shunt. This will cause excessive flow and n~ay lead to pulmonary hypertension and pulmonary vascular disease later on.
Pott's Shunt
This is a similar shunt done through a left thoracotonly. Anastoinosis is done between left pulmonary artery aid descending thoracic sol-la. The disadvantage of this shunt is also the likelihood of excessive flow. To take down this shunt at the time of intra cardiac repair is a cardiac surgeon's nightmare. These two types of shunts are now almost given up.
Palliative Outflow Patch
Brock described closed pulmonslly valvotorny and infundibular resection using a punch on a beating heart. When both pulnlonary arteries are not suitable for shunt (less than 2.5 or 3 mm) systemic pulmonary shunts will no1 succeed. In these babies a palliative outtlow patch repair could be done on cardio puln~onary bypass. Ventricular septa1 defecl is left open. At a later stage when the pulmonary arteries are sufiiciently large, ventricular septal defect is closed with a patch.
Results
In excellent centers, the mortality is reported one per cent or less. In infants and babies with low weight, higher mortality is expected (2 to 3 per cent) and even up to 12 per cent from some centers. Time related survival in a hetcrogenous group at one month, lyear, Syears, 10 years and 20 years is reported to be 94 per cent, 92 per cent, 91 per cent, 90 per cent and 87 per cent.
Re- pera at ions and Other Interventions
These are required for residual VSD with significant shunt, residual RV obstruction and pulmonary valve regurgitation in a few cases.
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