**3. Procedure**

The procedure as described by Quandt and Stumper et al. [13] include detailed pre-procedure work up and is usually performed under general anaesthesia and mechanical ventilation, since the children are usually hypoxic and sick and can deteriorate fast during the procedure.

Ambient temperature should be maintained by using Bair Hugger to prevent hypothermia.

Prostaglandin infusions are usually continued and all the emergency drugs should be available.

The child is to be positioned on the table with the arms elevated and the area to be painted and draped.

Access is usually via the right femoral vein in a majority of cases but sometimes an internal jugular venous approach is preferred if crossing of RVOT is difficult, especially in smaller children. A right femoral artery cannula is inserted for continuous blood pressure monitoring and for blood gas analysis. Once the right femoral venous sheath (usually 5F) is inserted, 50–100 IU/Kg of Heparin is given. The child also receives a prophylactic antibiotic (Cefazolin) dose.

A right ventricular cineangiogram is performed through an NIH or any other diagnostic catheter placed within the apex of the right ventricle; 30° RAO with 20° cranial tilt and a straight lateral projection are used. Some centres prefer to do angiograms in LAO view instead of lateral view. The intent is to delineate the RVOT, its length and diameter, the diameter of pulmonary valve annulus and the size of branch pulmonary arteries.

Selection of the size and the type of stent to be implanted is guided by the size of the patient, the dimensions of the outflow tract and the anticipated length of palliation.

For smaller children and neonates with short term palliation- coronary stent is preferred.

For older children or those who required medium to longer-term palliation- a bare metal peripheral vascular stent, preferably Cook Formula pre-mounted 414 or 418 stent, may be used.

The advantage of Cooks Formula stent is that it can be re-dilated if required and provided long term palliation. Sometimes, the availability of the specific stent is an issue; in such situations, any peripheral stent may be used. Balloon mounted stents are preferred. However, these stents may require thicker wire (0.035) either Amplatz superstiff or even Teflon wire for the stent delivery. Another disadvantage is that the stiffer wire may precipitate RVOT spasm and the child may have significant desaturation during the procedure.

After the selection of the stent, the appropriate delivery sheath or guide catheter is used. For coronary stents, a 4 French (F) Flexor sheath (Cook Europe, Bjaeverskov, Denmark) or a 60 cm 6 F right Judkins guide catheter (Cordis Corp, Miami Lakes FL) may be used.

A 0.014″ coronary wire is advanced across the RVOT via an end-hole catheter and a stable position is achieved by placing the wire in distal branch pulmonary arteries (PAs). Once the coronary wire is stable in the distal branch pulmonary artery, the selected delivery sheath or guide catheter replaces the diagnostic catheter. In older children where a stiff wire is required, firstly, a softer catheter such as a Glide catheter is passed into the distal branch PAs and then advance a 0.032 Terumo wire and final diagnostic catheter like (Judkins

Right) JR or Multipurpose catheter may be used for replacing the Terumo wire with the stiff wires like Amplatz superstiff. The whole exercise is done due to hypertrophied infundibular area which may not allow the diagnostic catheter to pass over the coronary wire.

Cook Formula stents are implanted through either 5 or 6 F Flexor sheaths or sometimes Mullins sheath may be needed. The disadvantage of using a stiffer sheath is that it normally does not easily crosses the infundibular area, especially in older children who present late and have very hypertrophied RVOT. In these cases, the sheath is placed just below the infundibular area with multiple side arm injections; the stent is negotiated across the RVOT avoiding the annulus. However, if the annulus is small or if there is supravalvular PA narrowing, the stent may be placed across the pulmonary valve achieving a two-point fixation, one at infundibular and another at valve annulus level.

In infants and young children, the pre-mounted stent is placed over the wire but within the delivery sheath and advanced to the intended position within the RVOT and the stent is fully uncovered after checking with test angiograms. When the position of the stent appears satisfactory, (confirming it on echocardiography when necessary), the balloon is inflated. Following placement of the stent, the balloon is slowly deflated whilst the delivery sheath was advanced over the balloon, so as to re-sheath it. The position of the stent is confirmed on the check angiogram (**Figures 1** and **2**) via the side arm of the sheath. The position of the stent, opacification of the branch PAs and pulmonary valve movements are recorded on the final angiogram.

Echocardiography is performed for confirmation of the position of the stent, ventricular function, any interference with tricuspid valve function and evidence for effusion. A repeat blood gas analysis is obtained and improvement in PO2 is recorded. When we are confident of the implanted stent, the coronary wire along with the delivery sheath is removed under fluoroscopic monitoring and manual haemostasis is achieved.

The infant/child is transferred to the Neonatal/Paediatric ICU, as appropriate and vital signs are monitored. Patients who experienced an increase of oxygen saturation in excess of 20% are commenced on twice-daily diuretics. Chest X-ray is performed for any evidence of flooding of the lungs. In our experience, a peak gradient in excess of 40 mm Hg across RVOT on Doppler echocardiography post stenting usually does

#### **Figure 1.**

*RVOT stenting: (a) shows RV angiogram (LAO30/cranial30 view) in a 5 month old patient of tetralogy of Fallot. There was severe infundibular and valvular stenosis with diffusely narrow LPA and RPA. RVOT stenting was done using 4 mm × 19 mm bare stent (Evermine) and a RV angiogram was done in a/P view which showed RVOT stent in situ with relief of infundibular stenosis as shown in figure (b).*

#### **Figure 2.**

*Successful RVOT stenting: (a) shows RV angiogram done in LAO 30/cranial 30 view in a one year old TOF patient which showed severe infundibular stenosis. RVOT stenting was done in this patient using 8 mm x 37 mm bare stent. (b) shows RV angiogram in the same patient done one year after the RVOT stenting procedure which showed RVOT stent in situ and adequately sized branch PA's.*

not have over circulation. Heparin infusion is continued and replaced with Aspirin (3–5 mg/kg) once the child starts to take it orally and the aspirin is continued till the child undergoes complete repair. RVOT stenting usually leads to a uniform growth of branch pulmonary arteries as shown in **Figure 2** where a repeat angiogram one year post procedure showed adequate sized pulmonary arteries amiable for complete repair.
