atresia, and pulmonary atresia with intact septum

Progress PedLic

Cardiology Progress in Pediatric Cardiology 6 (1996) 105-116

New pediatric applications and techniques for balloon valvuloplasty: Tetralogy of Fallot, complex pulmonary stenosis/atresia, and pulmonary atresia with intact septum Wolfgang A.K. Radtke* South Carolina

Children’s

Heart Center,

Medical University of South Carolina, South Carolina 294250680, USA

171 Ashley Avenue,

Charleston,

Abstract

Palliative pulmonary balloon valvuloplasty in Tetralogy of Fallot hasbeen proposedto promote growth of the pulmonary valve so that it can be incorporated in a later repair without transannularpatch to avoid the late complicationsfrom free pulmonary regurgitation. We have usedthe procedurein patients with severehypoxemialessthan 3 monthsold. Synopsisof 141publishedcasesand our own experiencein 15 patientsshowstechnicalsuccessin 93%, a complicationrate of 5%, cyanotic spellsin 9%, and a mortality of 0.6%. Arterial oxygensaturation instantly increasedfrom 78 to 91%. Basedon the intention to treat, emergent surgery was avoided in 65%. Despite a significant increasein pulmonary valve diameter, the incidence of transannularpatch was reduced in only one study, partly reflecting the surgeon’spreference. Palliative pulmonary balloon valvuloplasty can also promote pulmonary artery growth in other complexcyanotic lesions.In pulmonary valve atresiawith intact ventricular septum without right ventricular dependent coronary circulation, catheter valvotomy and subsequent pulmonary balloon valvuloplasty can establishright ventricle to pulmonary artery continuity. Perforation of the atretic valve can be accomplishedwith a bare wire (rarely>, with a hot tip laserwire or with a radiofrequencywire if available.We usea standardsteerable5 French electrodecatheter to deliver radiofrequencypulsesat 8-26 watt with subsequentdilatation using a 7-8 mm low profile balloon. If tricuspidvalve diameteror right ventricular sizeare below normal, additional stentingof the ductus with a flexible stent expandedto 4-5 mm diameter should be performed. In patients with severehypoplasia,stent placementacrossthe outflow tract is necessary.With this strategy, overall outcome shouldbe superiorto the publisheddata on 68 attempted catheter perforations: Out of the 74% technically successfulprocedures,only 47% remainedwithout surgical intervention during early follow-up. Copyright 0 1996Elsevier ScienceIreland Ltd. Tetralogy of Fallot; Pulmonaryatresia;Pulmonary balloonvalvuloplasty; Radiofrequencyvalvotomy; Interventional catheterization Keywords:

1. Introduction

The success of balloon valvuloplasty in isolated pulmonary stenosis has established the pulmonary valve as an excellent target for catheter intervention.

* Tel.: + 1 803 7928900, fax: + 1 803 7923284.

Its anatomical location and the hemodynamic and clinical resilience towards induced pulmonary insufficiency permits the use of oversized balloons [l] resulting in virtual elimination of stenosis. Excellent results in critical pulmonary stenosis have demonstrated that balloon valvuloplasty is equally effective in newborns with small or compromised ventricles and minimal valve opening [2]. This experience and the concept of combining surgery and catheter intervention to optimize the repair of congenital heart

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disease led to the application of pulmonary balloon valvuloplasty to avoid palliative surgery and promote growth of pulmonary valve and pulmonary arteries in Tetralogy of Fallot or complex pulmonary stenosis. This concept is carried further in complex lesions with pulmonary atresia when continuity between right ventricle and pulmonary arteries is established by catheter intervention. In pulmonary atresia with intact ventricular septum, catheter perforation of the atretic segment and subsequent balloon dilatation can create a functional communication between right ventricle and pulmonary arteries and may, in fact, be a curative approach to complex congenital heart disease previously the domain of surgical therapy. Indications, techniques and results of these new applications of balloon valvuloplasty are presented based on our own experience and review of the current literature. 2. Palliative pulmonary Tetralogy of Fallot

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Patients with Tetralogy of Fallot generally undergo surgical correction during infancy. Several surgical centers advocate repair during the first 6 months of life or even during the neonatal period for symptomatic patients. However, young age at repair remains a risk factor for early post-operative death [3,4] and early repair more frequently requires a transannular patch [3,5] with possible late complications from free pulmonary regurgitation. Palliative pulmonary balloon valvuloplasty has been proposed to allow elective repair, e.g. at 6-12 months of age to promote growth of pulmonary arteries and pulmonary valve annulus in the interim with the goal to avoid transannular patch and thereby, preserve pulmonary valve competence. Following this approach, several centers have elected to perform palliative balloon valvuloplasty on all patients with Tetralogy of Fallot irrespective of symptoms, degree of cyanosis or cyanotic spells [6-81. We, and other authors have used the procedure only in patients with severe hypoxemia or spells less than 3 months of age who would otherwise require urgent surgery. Of course, balloon valvuloplasty is only indicated, if echo- or angio-cardiography demonstrate significant valvar stenosis. 2.1. Technique

The technique of palliative pulmonary balloon valvuloplasty in Tetralogy of Fallot is similar to standard pulmonary balloon valvuloplasty except for the precautions to prevent hypoxemic spells and the modified technique to negotiate the sometimes tight, angled and elongated infundibulum and the hypoplastic

valve without excessive mechanical irritation. Prior to the procedure, the patient is well hydrated and IV fluids are continued in the cardiac catheterization laboratory. Deep sedation is used preferably with Ketamine utilizing its beneficial effect of systemic vasoconstriction to improve pulmonary blood flow. Patients with marginal oxygen saturations or a high propensity for hypoxemic spells are electively intubated and catheterized under mechanical ventilation. Precautions are in place to treat hypoxemic spells including preparation of a neo-synephrine drip. Standard cardiac catheterization and angiocardiography precedes valvuloplasty to provide all necessary information for surgical correction. The right ventricular angiogram performed in lateral and posterior-anterior projection with 30-40” cranial angulation is used to measure pulmonary valve annulus, main pulmonary artery size and assess possible branch pulmonary artery stenosis. If tolerated, the pulmonary valve is then crossed with a balloon tip end hole catheter to place a guide wire in the distal left or right pulmonary artery. In unstable patients and severe hypoxemia, infundibulum and pulmonary valve are crossed only with a soft steerable guide wire directed through a 4 or 5 French balloon tip end hole or right coronary catheter. Mechanical irritation of the infundibulum is kept at a’ minimum. After proper placement of the guidewire, a low profile 1.5- or 2-cm long dilatation balloon with a diameter 50% larger than the valve annulus is used for valvuloplasty. A second balloon inflation confirms disappearance of the stenotic waist. Typically, arterial oxygen saturation increases instantly with successful valvuloplasty. A persistent waist on the balloon at 3 atm inffation pressure usually indicates significant supravalvar stenosis at the sinotubular junction. The balloon is withdrawn and right ventricular angiography is repeated to document increase in pulmonary valve mobility and decrease in right to left shunt across the ventricular septal defect. In patients with additional proximal right or left pulmonary artery stenosis, we have attempted to achieve a balloon position straddling both pulmonary valve and proximal pulmonary artery stenosis or have performed additional pulmonary artery balloon angioplasty during the same procedure (three of 15 patients). 2.2. Results

Our own experience includes 15 patients with a median age of 41 days (2 days to 9 months) and a median weight of 3.9 kg (2.8-8.0 kg>. Indication was severe cyanosis in ten and cyanotic spells in five patients. Five patients had previously required intubation. Six patients had diminutive pulmonary arteries, one patient had additional complete atrioventricular

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canal, one had meconium aspiration and one had concurrent respiratory syncytial virus infection. Pulmonary valve annulus ranged between 3.6 and 10 mm (mean 6.0 f 1.6 mm). Pulmonary valvuloplasty was accomplished in 14 of 15 patients (93%) with an increase in mean systemic oxygen saturation from 80 f 8% to 93 f 5%. Cyanotic spells occurred in three patients (21%) and were successfully treated medically or by the balloon valvuloplasty. On angiography, right to left shunt was significantly reduced in ten of 14 (Fig. 1). In four patients, palliation was inadequate and surgery was performed within the next 2 days. Ten patients were adequately palliated and underwent elective repair after a median interval of 9 months. The one patient in whom valvuloplasty could not be accomplished expired during surgery. The use of transannular patch placement during surgical repair was not significantly reduced. However, a prospective study [6] including 19 consecutive unselected infants (age l-20 weeks, median 9 weeks; body weight 2.3-7 kg, median 4.2 kg) demonstrated a significant decrease in the incidence of transannular patch placement at subsequent elective surgical correction: only five of 16 patient (31%), 30-40% less than predicted required a transannular patch. A similar immediate increase in arterial oxygen saturation from 79 +_8% to 90 + 5% was found eliminating the need for early surgery in 79% of the patients (15 of 19). Cyanotic spells occurred in four of 19 patients (21%) without sequelae. Pulmonary valve annulus 2 score increased from - 4.8 &- 1.2 before dilatation to - 2.7 f 1.4 at pre-operative catheterization. Right pulmonary artery diameter increased from a Z score of -2.5 + 1.7 to - 0.06 f 1.16 and left pulmonary artery Z score increased from -2.2 + 1.9 to 0.04 k 1.52 at pre-operative catheterization. Increase in pulmonary artery size was greatest in patients with marked pulmonary artery hypoplasia initially. Kreutzer et al. [9] reported a study of ten patients aged 17 days to 12 years in whom palliative balloon valvuloplasty was performed to promote growth of diminutive pulmonary arteries. In their study, the Nakata index increased from 67 k 28 mm*/m* to 143 &- 84 mm*/m*. Subsequently, nine of the ten patients could undergo one stage repair with closure of the ventricular septal defect and acceptable right ventricular pressures. The synopsis of 141 published patients [6-101 and 15 patients from our own experience with Tetralogy of Fallot, mostly aged between 1 day and 5 months who underwent palliative pulmonary balloon valvuloplasty reveals a technical success rate of 93% with a complication rate of 5%. Cyanotic spells occurred in 9% and mortality was 0.6% for this collective experience. Arterial oxygen saturation increased from 78% to 91% on average. Overall, based on the intention to treat, early surgery was avoided in

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65% (102 of 156 patients). Although several studies showed a significant increase in pulmonary valve and pulmonary artery diameter, a reduced incidence of transannular patch placement was not consistently demonstrated. This may in part be due to the surgeons’ preference and willingness to accept a still somewhat hypoplastic pulmonary valve annulus with a mean Z score of -2.7 as demonstrated by Sluysman et al. [6]. No predictors of successful palliation other than significant increase in oxygen saturation immediately after balloon valvuloplasty could be identified. In our experience supravalvar stenosis at the sino-tubular junction limited the success of balloon valvuloplasty in three of 14 patients. The contribution of supravalvar stenosis was not always appreciated on angiography prior to balloon dilatation, but became apparent by the persistent waist on the balloon at 3 atm inflation pressure. The treatment strategies for Tetralogy of Fallot patients appear to be early primary surgical correction or palliative pulmonary balloon valvuloplasty with delayed surgical repair to preserve pulmonary valve function. Using the latter concept, palliative balloon valvuloplasty would ideally be performed during the newborn period when ductus patency can be maintained with prostaglandin infusion and when the growth potential of pulmonary arteries and pulmonary valve annulus is greatest. Only a prospective study would validate this hypothesis supported by Sluysmans et al. [6]. The incentive for this prospective study would depend on further evidence of the late detrimental consequences of free pulmonary insufficiency associated with transannular patch placement. Currently, correlations between pulmonary insufficiency and decreased exercise performance [ll], increased incidence of late sudden death 1121, significant ventricular arrhythmias [131, and the need for re-operation [3] have been established. 3. Palliative pulmonary balloon valvuloplasty complex lesions with pulmonary stenosis

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In complex cyanotic heart disease, primary repair is often not feasible within the first months of life at the time when obstruction to pulmonary flow becomes clinically significant and requires intervention. Palliative shunt surgery still is typically used to secure adequate pulmonary blood flow. There is, however, a sub-population of patients in whom palliative pulmonary balloon valvuloplasty can provide adequate pulmonary blood flow and promote growth of the pulmonary arteries [10,14]. Its application in Tetralogy of Fallot has demonstrated that significant improvement in pulmonary blood flow can be accomplished despite additional levels of stenosis. Whenever the pulmonary obstruction has a significant valvar component along

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Fig;. 1. Lateral and posterior-anterior angiogram with 30” cranial angulatic In in a 3.4-kg infant with TetraIogy of Fallot before (top) and after pal ‘liative pulmonary balloon valvuloplasty (bottom). Improved filling of tht: pulmonary arteries and marked reduction of right to left shunt on ;ight ventricular injection is demonstrated.

with additional sub-valvar stenosis or a small enough valve annulus to prevent pulmonary over-circulation and pulmonary hypertension, palliative balloon valvuloplasty is a viable treatment option eliminating the risk of pulmonary artery distortion often induced by shunt placement. However, limited control over the increase in pulmonary blood flow and the degree of pressure restriction may be a concern in patients heading for modified Fontan operation. Therefore, careful case by case patient selection is important. 3.I. Technique

The technique is similar to palliative pulmonary balloon valvuloplasty in Tetralogy of Fallot although the approach to enter the pulmonary artery has to be

modified according to each patient’s individual anatomy. The risk of hypoxemic spells is usually low, but adequate hydration remains important in significantly cyanotic patients. Unstable patients benefit from elective intubation and pharmacological increase in systemic vascular resistance to direct more blood flow to the lungs during the procedure. Standard hemodynamic catheterization and angiocardiography is performed. Pulmonary artery anatomy and the levels of obstruction to pulmonary flow are determined and the pulmonary valve annulus diameter is measured. Typically, a balloon l-l.3 times the pulmonary valve annulus diameter is chosen. The preferred approach to cross the pulmonary valve is antegrade using a balloon tip end hole catheter or right coronary catheter to either directly cannulate the pulmonary

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Fig. 2. Lateral and posterior-anterior aortogram (top) in a 6-day-old newborn (3.8 kg) with D-transposition of the great arteries, posterior malalignment ventricular septal defect, subvalvar and valvar pulmonary stenosis with retrograde opacification of the pulmonary arteries through the tortuous ductus. The bottom panel shows the inflated 7-mm balloon positioned across the pulmonary valve over a steerable guide wire advanced retrograde through the ductus into the left ventricle and snared with a 4 French Gooseneck snare introduced from the femoral vein into the left ventricle.

artery or manipulate a steerable guidewire into distal pulmonary artery branches. With the guidewire positioned in a distal pulmonary artery, a 1.5-2 cm long low profile balloon dilatation catheter is positioned across the valve and inflated to 2-3 atm of pressure with elimination of a waist. Absence of the waist is documented with a second inflation. Arterial oxygen saturation increases instantly with successful valvuloplasty. In newborns with complex cyanotic heart dis-

ease, it may occasionally be difficult to enter the pulmonary artery antegrade. In such cases, pulmonary balloon valvuloplasty can be performed retrograde through the ductus arteriosus as illustrated in Fig. 2. In this case, only a soft tip steerable guidewire could be manipulated retrograde across the stenotic valve. This wire did not provide enough stability to advance the balloon dilatation catheter across the stenosis. Therefore, a Gooseneck snare was advanced ante-

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grade through right and left atrium into the left ventricle where the tip of the steerable guidewire was snared. Over this guidewire rail, the balloon could be advanced across the stenosis and valvuloplasty was successfully performed. 3.2. Results Published reports [10,14] are anecdotal and parallel our own experience in a diverse group of sporadic patients. The procedure can be accomplished in about 80% of attempts and, if the valvular component of stenosis is significant, a significant increase in arterial oxygen saturation is achieved. No complications were reported and no complications occurred in our experience. Adequate palliation can be accomplished in approximately 65% of the patients with excellent growth of the pulmonary arteries as illustrated in Fig. 3. This was a 5-week-old patient with {S,L,D) transposition of the great arteries, multiple ventricular septal defects, rudimentary right ventricle with severe Ebstein’s malformation of the tricuspid valve and severe subvalvar and valvar pulmonary stenosis with increasingly severe cyanosis. Pulmonary valve annulus diameter was 7 mm. Palliative pulmonary balloon valvuloplasty was performed using a lo-mm balloon with an increase in oxygen saturation to 81% and excellent palliation until hemi-Fontan operation was performed 7 months later. A significant increase in pulmonary artery size from a Nakata Index of 61 mm2/m2 to 289 mm2/m2 was documented by pre-op-

erative angiography. Pulmonary artery pressure and pulmonary vascular resistance remained low. Certain patients after repair of cyanotic heart disease can also benefit from palliative pulmonary balloon valvuloplasty, e.g. patients in whom a homograft or valved conduit was placed bridging a stenotic, but patent native right ventricular outflow tract. Palliative balloon valvuloplasty of the native pulmonary valve (or even transvalvar stent placement) can be a viable option to delay replacement of a stenotic conduit. Figure 4 illustrates this approach in one of our patients. This g-year-old boy had undergone repair of Tetralogy of Fallot with homograft placement for anomalous origin of the left anterior descending coronary artery from the right coronary artery almost 7 years prior to catheterization. Severe homograft stenosis was documented with a right ventricular pressure at 115% of systemic and marginal right ventricular function. Right to left shunt across a patent foramen ovale resulted in an arterial oxygen saturation of 92%. With the native right ventricular outflow tract probe patent (annulus diameter of the severely stenotic pulmonary valve 10.5 mm>, pulmonary balloon valvuloplasty was performed with a balloon diameter of 15 mm resulting in a gradient reduction from 77 to 36 mmHg, reduction in right ventricular pressure to 57% systemic and elimination of the right to left shunt across the patent foramen ovale with an arterial oxygen saturation of 97%. Now, 1 year after the procedure the patient remained asymptomatic with unchanged right ventricular pressure.

Fig. 3. Left ventriculogram in posterior-anterior projection in a S-week-old severely cyanotic infant with {S,L,D} transposition of the great arteries, multiple ventricular septal defects, rudimentary right ventricle with severe Ebstein’s malformation of the tricuspid valve and severe subvalvar and valvar pulmonary stenosis before (left) and 6 months after palliative pulmonary balloon valvuloplasty. A significant increase in pulmonary artery size from a Nakata Index of 61 mm2/m2 to 289 mm2/m2 was documented.

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Fig. 4. Right ventriculogram in 35” right anterior oblique and lateral projection in an S-year-old boy with severe homograft stenosis 7 years after repair of Tetralogy of Fallot before (top) and after (bottom) balloon valvuloplasty of the native pulmonary valve. After valvuloplasty, right ventricular output is mostly directed through the native outflow tract bypassing the markedly stenotic and calcified homograft.

4. Catheter valvotomy in pulmonary ventricular septum

atresia with intact

Pulmonary valve atresia with well developed infundibulum and main pulmonary artery separated only by an imperforate valve plate does not appear substantially different from critical pulmonary valve stenosis with a smaller than pin hole opening. These lesions constitute the mid points of a continuum spanning from mild pulmonary stenosis to long segment fibro-muscular atresia of right ventricular outflow tract and main pulmonary artery. Based on the excellent success of pulmonary balloon valvuloplasty in critical pulmonary stenosis even in cases with ‘sub-atresia’ of

the valve [21, the concept was extended to membranous pulmonary valve atresia using catheter perforaBy now, tion and subsequent balloon valvuloplasty. the procedure has also been successfully -applied to long segment fibro-muscular atresia [El. Although over 100 procedures have been performed worldwide at this time, controversy still exists over its merit with respect to outcome, over proper patient selection and the need for additional supportive catheter interventions, e.g. stenting of the ductus arteriosus to bridge the time of hemodynamic transition. Right ventricle dependent coronary circulation manifest by extensive coronary fistnlas and significant stenosis of one or both proximal coronary arteries has

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been established as a contraindication for right ventricular decompression [ 16,171. These patients should receive a palliative shunt only. Right ventricle dependent coronary circulation is associated with extremely small right ventricles and, hence, plays a role in the previously suggested correlation of outcome and right ventricular size [16]. Coronary fist&s without right ventricular dependence of coronary perfusion, however, are no contraindication to right ventricular decompression and do not influence outcome [16-B]. Such fistulas can also be present in critical pulmonary stenosis. Figure 5 illustrates a case from our own experience in whom coronary fistulas disappeared immediately after successful pulmonary balloon valvuloplasty without compromise to left ventricular function or evidence of myocardial ischemia on EKG. Right

ventricular size and tricuspid valve diameter are the most controversial factors with possible iniluence on outcome. A multi-institutional study mostly based on report review [19] suggested small tricuspid valve diameter and small right ventricular size as important determinants of outcome concluding that neither valvotomy nor right ventricular outlknv tract patch should be performed if the tricuspid valve 2 value is less than -4. A right ventricular outflow tract patch with shunt implantation was recommended for tricuspid valve 2 values of - 1.5 to - 4, valvotomy with shunt implantation for tricuspid valve 2 values between - 1.5 and - 0.15 and valvotomy without shunt implantation was suggested for tricuspid valve 2 values of -0.15 or larger. Other authors [16,17,20] have found that right ventricular size and tricuspid valve

Fig. 5. Right ventriculogram in posterior-anterior 20” cranial angulation and lateral projection in a 5-day-old newborn with critical pulmonary stenosis before (top) and after balloon valvuloplasty (bottom). The fistulas to right coronary and left anterior descending artery disappeared after balloon valvuloplasty which reduced the right ventricular pressure from 200% to 80% of systemic.

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diameter do not influence outcome, if patients with right ventricle dependent coronary circulation are excluded. Adequate growth of right ventricle and tricuspid valve to support biventricular repair was documented irrespective of the initial degree of hypoplasia. Even very small ventricles demonstrated adequate growth [16-l&20,21]. Necessary prerequisite for adequate growth of the right ventricle was creation of functional right ventricle to pulmonary artery continuity [18,20,21]. Consequently, small right ventricular size or small tricuspid valve diameter are not contraindications to catheter valvotomy and balloon dilatation in pulmonary atresia as long as a widely patent communication to the pulmonary artery can be established. Therefore, a relatively well developed right ventricular outflow tract and adequate ‘virtual pulmonary valve annulus’ are necessary prerequisites. If, however, stent implantation across the right ventricular outflow tract [15] is used to complement the procedure, this limitation may become less relevant. The surgical experience with valvotomy alone or transannular outflow tract patch alone in patients with pulmonary atresia and intact ventricular septum has shown that a large proportion subsequently requires shunt implantation to augment pulmonary blood flow even if the right ventricle was well developed [16,18,19,21] to bridge the time until resolution of marked right ventricular hypertrophy with poor diastolic function. Hanley et al. [19] concluded that valvotomy alone without shunt implantation would only be successful if the tricuspid valve 2 value was approximately 0.0. Based on this surgical experience, we conclude that if the tricuspid valve 2 value is less than 0.0, catheter valvotomy of pulmonary atresia with intact ventricular septum should be complemented by stenting of the ductus arteriosus. If right ventricle and/or right ventricular infundibulum are significantly hypoplastic a stent should be implanted in the right ventricular outflow tract across the ‘virtual pulmonary valve annulus’. With this strategy, right ventricular size and tricuspid valve annulus diameter should not be a contraindication to catheter repair of pulmonary atresia with intact ventricular septum. 4.1. Technique Standard hemodynamic catheterization and angiocardiography is performed to rule out right ventricle dependent coronary circulation by determining absence or presence of significant proximal coronary artery stenosis. Right ventricular size, tricuspid valve diameter, and infundibular dimensions are determined from right ventricular angiography. Retrograde aortic or, after passage of the ductus arteriosus,

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main pulmonary artery angiography is used to assess the spatial relationship of infundibulum and main pulmonary artery, length of the atretic segment and the diameter of the ‘virtual pulmonary valve ammlus’. After the target is established and the road map obtained, wire perforation of the pulmonary valve is attempted using standard guidewires of different size directed to the atretic valve with a 4 or 5 French right coronary catheter. Some authors have sharpened the guidewire by exposing the stiff core [22]. The stiffness of the wire tends to dislodge the guiding catheter with possible malperforation. If brief attempts at wire perforation are unsuccessful, a 0.018-inch ‘hot tip’ laser wire (l-3 exposures at 3-5 W for 3-5 s> or a radiofrequency wire (multpile exposures at 5-20 W for 3-6 s) can be used to penetrate the atretic valve by thermal ablation. These ‘active’ wires are also aimed at the atretic valve through a right coronary catheter positioned in the infundibulum. The ‘hot tip’ laser wire typically is not available in pediatric cardiac catheterization laboratories. Fiber-optic ‘wires’ emitting laser energy coaxially with defined depth of penetration would be ideal [231, but are usually unavailable in pediatric cardiac catheterization laboratories. The radiofrequency wire is currently not available in the Unites States. We are, therefore, using a standard steerable 5 French electrode catheter to deliver radiofrequency energy to open the atretic valve [24]. This catheter can easily be positioned against the atretic valve aiming at the main pulmonary artery. Proper position is repeatedly confirmed by aortic or pulmonary artery contrast injection (Fig. 6) or echocardiography. Seven to 13 pulses (6-40 s) of radiofrequency energy at 8-26 W are delivered after administration of 100 IV/kg of heparin. After seven pulses, wire perforation using a standard guidewire is attempted. If successful, the wire is advanced across the patent ductus arteriosus into the descending aorta where it is snared with a 4 French Gooseneck snare to establish an arterio-venous guidewire rail. Over this guidewire rail, dilatation of the atretic pulmonary valve first with a 3.5-mm coronary angioplasty balloon and then with a low profile 7 or 8 mm angioplasty balloon is performed. If indicated, a long sheath is subsequently advanced over the guidewire rail across the ductus, a 1.5-cm long coronary stent is placed in the ductus arteriosus and expanded to 4-5 mm diameter dependent on angiographic ductus diameter. The stent should be flexible and needs to cover the entire length of the ductus [25]. Prostaglandin infusion is discontinued, stent position and patency of the ductus is assessed by aortography. The communication created between right ventricle and main puhnonary artery is evaluated by right ventricular angiography (Fig. 7). If infundibular hypoplasia causes significant obstruction, stent placement across the right

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Fig, 6. The 5 French electrode catheter positioned against the atretic pulmonary valve in posterior-anterior projection with 20” cranial angulation and lateral projection. Contrast hand iniection is performed in the main pulmonary artery (reproduced with permission from Am J Cardiol 1996;77:1370-137%.

ventricular outflow tract may be considered. The stem would be expanded dependent on right ventricular size, but preferably to 5 or 6 mm diameter. After the procedure, anticoagulation is continued with heparin for 24 h overlapping with aspirin. If the ductus arteriosus has not been stented, prostaglandin infusion is continued for up to 3 weeks with intermittent attempts to wean. 4.2. Results We have used a standard steerable 5 French electrode catheter in two newborns aged 4 days (4.2 kg and 2.7 kg; tricuspid valve 2 scores - 1.5 and 0) and successfully established a functional communication between right ventricle and main pulmonary artery with good antegrade flow [24] as illustrated in Fig. 7. In the patient with a tricuspid valve 2 score of 0 prostaglandin could be weaned successfully. The synopsis of eight reports published between 1991 and 1996 [22,24-30) includes 68 attempted catheter perforations using guidewires, hot tip laser wires, radiofrequency wires and our results with 5 French electrode catheters. The procedures could be accomplished in 74% of attempts. Mortality was 12% (8 of 68) including two late deaths. Non-fatal complications occurred in 12%. After a technically successful procedure, 46% (23 of 50) of the patients remained without surgical intervention during follow-up. Based on attempted

procedures, only 34% of the patients (23 of 68) remained event free. An ongoing population based study in the United Kingdom [26] showed an event free survival at 6 weeks of 39% for the group undergoing catheter perforation and 68% for the group undergoing surgical palliation (P < 0.05). These numbers reflect and confirm the previous experience with surgical valvotomy: most patients who initially underwent valvotomy or right ventricular outflow tract patch placement required subsequent shunt placement to overcome small right ventricular size and/or poor right ventricular compliance. In accordance with the previous surgical experience it is clear that patient selection is crucial if valvotomy alone is attempted and that stenting of the ductus arteriosus should routinely be performed at the time of catheter valvotomy in patients with less than normal sized right ventricle or tricuspid valve. 5. Palliative catheter valvotomy in pulmonary with ventricular septal defect

atresia

Patients with pulmonary atresia and ventricular septal defect in whom diminutive central pulmonary arteries prohibit primary repair and who are, therefore, considered for right ventricular outflow tract patch palliation may be candidates for catheter based creation of right ventricle to pulmonary artery continuity using the procedures outlined above. Fre-

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Fig. 7. Right ventriculogram before (top) and after (bottom) radiofrequency valvotomy and balloon valvuloplasty in po lsterior proif xtion with 20” cranial anaulation and lateral .uroiection in a 4-day-old newborn (reproduced with permission from Am J I i966;77:1370-1372).

quently in these patients, the right ventricular infundibulum is significantly hypoplastic and often relatively short. Therefore, after canalization of the atretic segment, stent implantation across the outflow tract will be necessary in most cases to create a functional communication. Considering the typically longer atretic segments, procedural risks are greater. Feasibility has been demonstrated using the radiofrequency wire [15,31], but the created right ventricular outflow tracts were relatively small compared to transannular outflow patch placement. The technique is similar to the procedure described for pulmonary atresia with intact ventricular septum. If the right ventricular outflow tract is short, secure positioning of the guiding catheter or the steerable electrode catheter could be difficult. If secure positioning cannot be accomplished, the procedure should be abandoned. Especially with longer segment atresia and less

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secure guidance, a laser wire with laser energy emitted coaxially with known depth of penetration and minimal damage to adjacent tissue [23] would significantly improve safety and efficiency of the procedure. With only anecdotal experience mostly in older patients, any statement on efficacy and safety of this procedure would be speculative. Acknowledgements

The author would like to thank Ms. Karen Fleming for her secretarial assistance and word processing skills. References [ll

Radtke W, Keane JF, Fellows KE, Lang P, Lock JE. Percutaneous balloon valvotomy of congenital pulmonary stenosis using oversized balloons. J Am Co11 Cardiol 1986;8:909-915.

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