Percutaneous implantation of a pulmonary valve: an illustrative case

Abstract

Surgical reconstruction of the right ventricular outflow tract (RVOT) with valved conduits in infants and children with congenital heart disease leads to re-intervention in later life as the ensuing pulmonary regurgitation and stenosis of the degenerating conduit impacts negatively on right ventricular function. Percutaneous pulmonary valve implantation (PPVI) provides a safe alternative to early surgical re-intervention in these patients. We describe this procedure as performed on an 11- year-old boy. Difficulty may be experienced crossing the RVOT prior to PPVI. We describe several techniques that may be used to encourage the distal movement of the delivery system through the RVOT. (Neth Heart J 2007;15:27-30.)

Right ventricular outflow tract (RVOT) reconstruction with valved conduits in infancy and childhood leads to re-intervention for pulmonary regurgitation and stenosis in later life as pulmonary valve dysfunction impacts negatively on right ventricular function. Preliminary data suggest that percutaneous pulmonary valve implantation (PPVI) provides a promising and safe alternative to early surgical reintervention in these patients.^1-3 This technique uses a valved stent assembly implanted by means of a double balloon catheter delivery system. The device is a bovine jugular venous valve sutured inside a 34 mm platinumiridium stent.¹

We report on an 11-year-old Dutch boy who recently underwent this procedure. Due to a severe pulmonary homograft stenosis with calcification, difficulty was experienced in crossing the homograft prior to valve implantation. The distal movement of the delivery system through the RVOT can be encouraged in several ways. These techniques are described as they were performed in this patient.

Case report

The diagnosis of a double outlet right ventricle of the Tetralogy of Fallot type was made in this patient soon after his birth. A right Blalock-Taussig shunt was performed at the age of 4 months followed by a total correction at the age of 11 months. A re-operation was performed a month later due to intractable right ventricular failure and a 20 mm pulmonary homograft was surgically implanted in the RVOT. Severe stenosis and calcification of this homograft with regurgitation developed. Prior to the percutaneous implantation of the pulmonary valved stent, the patient was mildly symptomatic with complaints of light-headedness and palpitations during exercise. This patient is also a known case of Asperger’s syndrome.

Our patient was a healthy looking young boy with a height of 141 cm and a weight of 40 kg. His pulse rate was 70 beats/min and his blood pressure 106/51 mmHg. He had lateral thoracotomy and median sternotomy scars. His apex beat was not displaced but he had a precordial impulse due to right ventricular hypertrophy. His first heart sound was normal and the second widely split. A 3/6 pulmonary ejection systolic murmur of pulmonary stenosis and a 2/4 early diastolic murmur of pulmonary regurgitation were audible. He had normal breath sounds and there was no hepatosplenomegaly. All his pulses were present and equal.

His ECG showed a sinus rhythm with a complete right bundle branch block. He was able to perform reasonably well during an exercise test with an adequate heart rate and blood pressure response. His VO₂ max was 34 ml/kg/min (77% of predicted). An MRI showed a mildly dilated and hypertrophied right ventricle. There was mild aneurysmal dilatation of the RVOT with a stenotic homograft, (12 x 16 mm at its narrowest point). A mild kinking of the RVOT was seen. The pulmonary artery branches were well developed without any narrowing. The right ventricular volume at the end of diastole was 142 ml with a corresponding left ventricular volume of 90 ml. The pulmonary regurgitation fraction was 20% and a flow velocity of 5.5 m/s was measured over the stenotic homograft.

The patient underwent a cardiac catheterisation with the intention to perform a percutaneous implantation of a pulmonary valve. The systolic pressure in the right ventricle was 74 mmHg and 90 mmHg in the left ventricle. A gradient of 48 mmHg was measured over the stenotic homograft. The pulmonary angiogram (figure 1) showed a localised stenosis at the level of the homograft with mild homograft calcification. On the lateral view the stenosis looked less impressive. The aortagram showed that the coronary arteries were located far enough from the homograft so as not to be compromised during valved-stent deployment (figure 2).

Figure 1.

Pulmonary angiograms in anteroposterior and lateral views using a Multitrack catheter positioned in the homograft over a guide wire. Note the stenosis at the level of the homograft. This narrowing appears less impressive on the lateral view. Moderate pulmonary regurgitation is also seen with opacification of the right ventricle.

Figure 2.

Aortic angiogram in anteroposterior and lateral views performed at the time of predilation of the homograft. Note that the coronary arteries are not compromised by the balloon.

The stented valve was loaded on an 18 Fr delivery system and sheath. Special care was taken to ensure that the valve was correctly mounted on the delivery system, thus not upside down. An ultrastiff Cook wire (0.035 inch) was positioned in the right pulmonary artery, and after predilation of the femoral vein with a 22 Fr dilator, the delivery sheath was passed over the wire. It proved difficult to pass the delivery sheath through the RVOT. In order to facilitate a better angle of the delivery system in the RVOT, a loop was made in the right atrium and an attempt was made to milk the delivery system through the RVOT. When this failed the sheath was withdrawn slightly so that more of the proximal somewhat more flexible part of the delivery system was available to encourage a better angle of the delivery sheath in the RVOT. This did not have the required effect and so the guide wire was repositioned in the left pulmonary artery, with the hope that the new alignment of the wire in the RVOT would facilitate the passage of the delivery system. Unfortunately an attempt to pass the delivery system over the RVOT with the wire in the left pulmonary artery was also unsuccessful.

Next, predilatation of the homograft using an 18 mm ultrahigh pressure Mullins balloon was performed. With reduction of the stenosis it was hoped that the delivery system would pass through the RVOT. However, this again proved to be unsuccessful. At this point it became apparent that access via the femoral vein would not result in a successful crossing of the RVOT. A jugular approach was then tried. The delivery system was introduced via the internal jugular vein with the guide wire in the right pulmonary artery. This time, with a more favourable angle of the delivery system in the RVOT, it was possible to pass the delivery sheath through it. The final position of the valved stent in the homograft was slightly distal to the point of stenosis, but this position was accepted for fear that attempts to withdraw the delivery system would cause it to fall back into the right ventricle. The valve was successfully deployed and then dilated with a 20 mm ultrahigh pressure Mullins balloon.

The post deployment angiograms showed a very mild pulmonary regurgitation (figure 3). The gradient over the RVOT was reduced to 12 mmHg and the right ventricular pressure was now less that half the systemic pressure.

Figure 3.

Pulmonary artery angiogram in anteroposterior and lateral views performed after deployment of the valved stent and dilatation to 20 mm. Note that there is only an extremely mild residual pulmonary regurgitation visible on the lateral view. Compare these images with figure 1.

Discussion

Although surgical pulmonary valve replacement can be performed at low risk, it still involves morbidity and mortality and sets up a substrate for future operations. Risks include those of cardiopulmonary bypass, infection, bleeding, and ventricular dysfunction.⁴ PPVI seems to offer a safe alternative to early re-operation.

We considered this young boy a good candidate for PPVI for the following reasons. In view of his age and the anticipated degeneration of implanted homografts, re-operation may be required in the future. He had already undergone three operations including a resternotomy. He was mildly symptomatic but had significant pulmonary valve dysfunction with stenosis as the major lesion. His right ventricle was dilated with preservation of function and PPVI at this stage would prevent loss of right ventricular function.

Congenital heart disease patients with predominant postoperative stenosis of the pulmonary valve can present the interventionalist with problems crossing the RVOT. In the presence of calcification the homograft may be less amenable to dilatation and there is a risk of homograft rupture. Possible coronary artery compression by the valved stent after deployment can be avoided by doing an aortogram prior to PPVI. The relationship of the coronary arteries to the RVOT conduit can then be evaluated and if necessary a decision can be made to abort the procedure.

In our patient, the difficulty experienced in negotiating the RVOT with the delivery sheath can be explained by the tight stenosis and also the kink in the RVOT seen on the MRI. This kinking of the RVOT led to the underestimation of the homograft stenosis on the lateral pulmonary angiogram (figure 1). Several techniques may be employed to assist passage through the RVOT as described. These include making a loop in the right atrium with the delivery system, withdrawing the delivery sheath a little without exposing the valved stent, so that the delivery system is more flexible, changing the guide wire position and predilation of the homograft. Should predilation be necessary, care should be taken to dilate the valve to a diameter less than the intended final diameter of the valved stent. Excessive predilation will lead to an unstable position of the valve. Finally, if all of these techniques fail, a jugular approach should be considered as was required in this patient.

Conclusion

We have reported a successful PPVI in an 11-year-old Dutch boy with a stenotic and incompetent homograft after surgical correction of a double outlet right ventricle of the Fallot type. PPVI provides a promising and safe alternative to early surgical re-intervention in patients with operated congenital heart disease with pulmonary valve dysfunction.² During this procedure problems may be encountered in passing the delivery system through the RVOT especially when stenosis is the major lesion. We have described the various techniques that can be used in order to facilitate the passage of the delivery system through the RVOT.