Catheterization interventions in the management of common arterial trunk

Progress in Pediatric Cardiology 15(2002) 73–80

1058-9813/02/$ - see front matter� 2002 Elsevier Science Ireland Ltd. All rights reserved.PII: S1058-9813Ž02.00011-5

Catheterization interventions in the management of common arterial trunk

Lee Benson *, Robert Freedoma,b, a,b

Department of Pediatrics, Division of Cardiology, The University of Toronto School of Medicine, Ontario, Toronto, Canadaa

Variety Club Cardiac Catheterization Laboratories, The University of Toronto School of Medicine, Ontario, Toronto, Canadab

Abstract

Over the past three decades, transcatheter interventions have become increasingly important in the treatment of patients withcongenital heart lesions. Many of these procedures have successfully been applied in the management of patients with commonarterial trunk, such as balloon angioplasty and stent implantation of pulmonary artery and conduit stenoses. Such therapeutictechniques combined with surgical algorithms have and will continue to improve patient outcomes.� 2002 Elsevier ScienceIreland Ltd. All rights reserved.

Keywords: Cardiac catheterization; Common arterial trunk; Interventional cardiology; Congenital heart disease

1. Introduction

Over the past three decades the functionality ofcardiac catheterization has changed dramatically from alaboratory of cardiovascular diagnosis to a site fortherapeutic interventionw1x. This is particularly so withthe development of high resolution echocardiographicdiagnosis and magnetic resonance imaging allowing fordetailed non-invasive anatomical and functional assess-ment w2x. This evolution in utility is manifest in themanagement algorithms as applied to infants and chil-dren with persistent common arterial trunk(persistenttruncus arteriosus). In this regard, the role of the cardiaccatheterization laboratory, if not in diagnosis, becomescrucial in planning primary and secondary surgicaltherapies. It has been more than 30 years since completecorrection of common arterial trunk(CAT) was firstperformed in an older child using the Rastelli techniquew3x. Although results continue to improvew4–8x, surgicalrepair remains challenging, especially in neonates. Thegoals of biventricular surgical repair include closure ofthe ventricular septal defect, removal of the pulmonaryarteries from the ascending portion of the single trunk,and restoration of continuity between the right ventricleand pulmonary arteries with either a valved or non-valved conduit. Other significant anomalies must be

*Corresponding author. The Hospital for Sick Children, 555 Uni-versity Avenue, Toronto, Ontario, Canada M5G 1X8. Tel.:q1-416-813-6141; fax:q1-416-813-7547.

E-mail address: [email protected](L. Benson).

repaired as well, such as anomalies of the coronaryarteries and obstructive lesions of the left ventricle andthe aorta such as severe truncal valve stenosis andyorregurgitation, coarctation of the aorta, and interruptionof the aortic arch(usually type B). All of this must beaccomplished with a low right ventricular pressure atthe conclusion of the repairw9–11x. Successful biventri-cular repair can be made more difficult in patients withother uncommon associated defects such as completeatrioventricular septal defect or total anomalous venousreturn, and it can be impossible in CAT patients withtricuspid atresia or hypoplastic left ventricle.Over the years the approach to surgical treatment has

evolved from palliative procedures(banding of the mainpulmonary artery, plication or creation of pulmonaryostial stenosis or bilateral pulmonary artery banding) toprimary surgical repair in the neonate, and particularlyin those with arch obstructionsw4,8,12,13x. Non-invasivepalliative or corrective interventions are useful in theimmediate perioperative period to manage residual prob-lems andyor during long-term follow-up when progres-sively acquired abnormalities can develop. As shown inTable 1 nearly all of the current interventional proce-dures have been used in the management of patientswith CAT.

2. Specific applications

2.1. Pulmonary artery branch stenosis

Pulmonary artery stenosis and hypoplasia can becongenital, acquired, and post-surgical and this obstruc-

74 L. Benson, R. Freedom / Progress in Pediatric Cardiology 15 (2002) 73–80

Table 1Interventional procedures applied in the management common arterialtrunk

Procedure Lesion

Valvuloplasty Truncal valve stenosisAngioplasty Pulmonary arterial stenosis,

recurrent coarctation,RV to PA conduit stenosis,ductal dilation

Stent implantation Pulmonary arterial stenosis,conduit stenosis

Occlusion device implantation Residual septal defects

Fig. 1. A chest radiogram of an infant after common arterial trunkrepair. Bilateral proximal pulmonary artery stenosis resulted in severeright heart failure shortly after surgery. Endovascular stents wererequired for palliation to improve cardiac output. Note the acute angletowards the bifurcation that the stents take outlining the proximalvessels.

tion often complicates the management of CAT. Assuch, pulmonary artery stenosis may lead to significantmaldistribution of pulmonary blood flow, right heartfailure and right ventricular hypertension, as well as toincreased resistance to flow across the total pulmonarybed. Branch pulmonary artery stenosis remains a diffi-cult problem. Stenosis beyond the hilum of the lung isdifficult to treat surgically, and incomplete relief of thisobstruction probably contributes to operative morbidityand mortality w14x. Pulmonary arterial hypoplasia andstenosis after surgical placement of a conduit is partic-ularly challenging because of the frequency of acuteposterior angulation at the distal conduit anastamosisproducing tenting and obstruction at the bifurcation(Fig.1).Balloon dilation of the obstructed pulmonary artery

is well tolerated clinically and should be considered asthe initial form of intervention. It is associated with alow morbidity risk and 1–2% mortalityw15x. In half ofthe patients a 50% increase in vessel diameter can beseen angiographically with a 20% decrease in the ratioof right ventricular to aortic systolic pressure) w15,16x,but restenosis occurs in 15–20% and long-term clinicalbenefit is achieved in-35% of patientsw16–18x.During the days to weeks after surgery the mechanism

of restenosis is rarely at the suture line(see below) andover distention of a balloon can result in suture disrup-tion and transmural tearing. In this situation stentimplantation has become the primary therapeutic option.As such, the observed stenosis is more often due toangulation of the vessel or to redundancy of patchmaterial used in the angioplasty. Two to 3 months aftersurgery conventional angioplasty appears to be safe(Fig. 2). Indeed, addressing these obstructive lesionssoon after surgery(within 6 months) has improved bothanatomical and hemodynamic results. In longer periodsof follow-up, lesions that are resistant to balloon dilationcan be enlarged using higher intra-balloon pressures,improving the overall success ratew19x. In addition torare fatal or non-fatal pulmonary perforation, complica-tions of balloon dilation have included aneurysm for-mation and rare occurrences of unilateral pulmonaryedemaw15–17,20,21x.

2.2. Endovascular stents

With all vascular dilation procedures recurrence ofthe lesion is of concern, either acutely due to recurrentdistensible elastic recoil or over longer periods of timedespite an adequate initial dilation. Various intravascularstent devices have been developed to provide a frame-work to resist the elastic recoil found in stenotic lesionsafter failed or recurrent balloon dilationw22,23x. Thereare two major types of stents, balloon expandable andself expanding(Fig. 3). In pediatric applications themost commonly used stent implant is a balloon expand-able stainless steel stent which retains its size and shapeafter balloon expansion and can be further enlarged withincreasing balloon diameters. Metal stents, providingsupport, rapidly become endothelialized(within 2–3months) when implanted against the vessel wall(Fig.4). Those portions of metal that are not apposed to thevessel wall remain uncovered, and side branches of thestented lumen remain patentw24x (Fig. 5). Hemolysishas not been reported when such portions of the stentremain free in the vessel lumen. Compromise or occlu-sion of side branches can occur but usually only if thebranch arises acutely from the main vessel or if theostium is caught by an end of the stent.The largest pediatric experience with stenting is in

the treatment of congenital or postoperative branchpulmonary artery stenosis. These lesions are difficult ifnot impossible to assess surgically, and restenosis iscommon after attempted surgical treatment. With stentimplantation, however, successful vessel enlargement is

75L. Benson, R. Freedom / Progress in Pediatric Cardiology 15 (2002) 73–80

Fig. 2. A patient with right pulmonary artery stenosis, some months after common arterial trunk repair. Note the excellent anatomical(andhemodynamic) relief after balloon dilation(lower panel).

close to 100% and the incidence of restenosis at inter-mediate follow-up is exceptionally low. In a multi-institutional study of 121 stent placements in 85 patientsthere was immediate hemodynamic improvement withsignificant reduction in pressure gradients in all patientswith substantial vessel enlargement and increase in bloodflow to the affected lung(Fig. 6). At mid-term follow-up restenosis was found in only one patient who has asuccessful repeat dilationw23x. Distal branch pulmonaryartery stenosis is also amenable to treatment with mul-tiple stent placements and stents can be overlapped inseries to afford support of long segment lesions. Suchapplications have been shown the most cost effectivemeans of treating branch pulmonary artery stenosisw25x.During the immediate period after surgical repair of

CAT, we have been reluctant to perform balloon dilationfor obstructed pulmonary arteries and have opted forstent implantation, even in the youngest of childrenw26,27x. These stenotic lesions are not due to the fibrousscar seen many months after surgery and are more oftenrelated to kinking, tenting, patch redundancy of external

compressionw28x (Fig. 7). As such, stent dilation ofpredefined diameters reduces the potential trauma to thefresh suture line in the first days after surgery. Indeed,such small implants can remain unobstructed for manyyears, until further surgery may be required, often totreat a stenotic right ventricle to pulmonary arteryconduit. At that time a longitudinal incision along thestent will allow enlargement of the patchw29x. Finally,transcatheter placement of stents has also been reportedin the patent ductus arteriosus for palliation of complexcongenital heart defectsw30,31x. Moreover, in the rareCAT infant with interruption of the aortic arch andprostaglandin resistance, stenting has been used to main-tain ductal patently before surgical repair of the archw32x.Potential complications of stent placement include

embolization or misplacement of stents, and rarely sidebranch narrowing or fracture of the stent strutsw32x. Alarge delivery sheath is required for implanting themajority of stent diameters and can result in vascularaccess compromise, but techniques to reduce placement


Fig. 3. Balloon expandable stent. These example is a 3-cm-long slotted stent that can expand to 15 mm in diameter, with 3 or 4 mm shortening.It requires 7 to 10 French introducer sheaths depending the diameter and profile of the dilating balloon.

Fig. 4. A scanning electromicrograph of normal endothelializationafter stent implantation to the pulmonary artery. Note in panel(A),how the endothelial layer stops at a side branch, and how the stentstrut lies across the branch ostium. As such, little or no flow reductionoccurs to the vessel.

profiles have limited such concerns. Furthermore, thestent, especially when implanted into small vessels andnot fully expanded may become obstructed from acutethrombosis(rare) or neointimal proliferation through thestent struts.The use of rigid stents in growing children has certain

limitations. Growth of the child and the great vesselproximal and distal to the fixed diameter rigid stent willultimately result in an acquired stenosis. Preferably thestents should be implanted to a size which will besufficient for the patient as an adult. However, re-expansion of a stent that has become incorporated intothe vessel wall is possiblew33x. New designs whichallow an implanted stent to open(break apart) uponredilation to larger diameters are also being evaluatedw34x.

2.3. Conduit stenosis

Over the last 30 years, the use of extracardiac valvedconduits between the subpulmonary ventricle and thepulmonary arteries has allowed for correction of anumber of complex congenital heart lesions. Despitevarious technical modifications and the availability ofdifferent types of valved conduits, this technique stillcommits the patients to multiple operations. A recentreport reviewing 405 conduits implanted between 1971and 1993, describes an overall conduit survival at 5, 10and 15 years of 84%, 58% and 31%, respectivelyw35x,with conduit obstruction the most frequent reason forsurgical reintervention w35,36x. Hemodynamic andimmunological mechanisms may be responsible for cal-cification and deterioration occurring at various levels

or diffusely throughout the conduitw36–38x. Indeed,second and subsequent conduits had shorter survivalthan the original implants. It is hypothesized that adhe-sions and calcifications present at reoperation make itmore difficult to obtain an ideal fit and flow character-istics at replacement.In the surgical repair of CAT, several different conduit

materials have been used with varying durabilityw11,39–42x. A number of studies have demonstratedthat percutaneous implantation of balloon-expandablestents offers a safe and effective palliation for obstructedconduitsw43–46x (Fig. 8). At a median interval of 2.4years after insertion of a conduit, we implanted stentsin 43 such obstructed conduits in patients at a medianage of 6 years. The mean systolic right ventricularpressures and conduit gradients decreased, respectively,from 71"18 mmHg and 48"19 mmHg before to


Fig. 5. A plastic cast of a balloon exponible stent previously placed in the left pulmonary artery of a pig. Note the side branches, widely patentthrough the open stent struts.

Fig. 6. Left pulmonary artery stenosis after common arterial trunk repair. A stent(3 cm in length) was placed to relieve the stenosis. Note howthe proximal portion of the stent remains in the main pulmonary artery, but allows unobstructed flow to the right lung(right panel).This patienthad the stent further enlarged with growth, until the time of conduit replacement when it was cut back to the ostium and patch enlarged.

48"15 mmHg and 19"13 mmHg after stenting. Fifteenpatients had a second transcatheter intervention either adilation or additional stenting, and two patients had athird intervention, allowing for postponement of surgeryin eight patients. A conduit was replaced surgically in20 of the 43 patients(47%). At a median of 1.9 yearsafter stent placement, 20 patients(47%) had surgicalreplacement of conduit. At follow-up of the other 22patients at a median interval of 2.2 years, 86% remained

unoperated at 1 year, 72% at 2 years and 47% at 4yearsw46x (Fig. 4).

3. Recurrent coarctation of the aorta

Interruption of the aortic arch or aortic coarctationare associated with CAT infrequently. With repair at thetime of intracardiac surgical correction, recurrence ratesof aortic obstruction are similar to those in CAT patients


Fig. 7. Left pulmonary artery stent implantation in a small child after common arterial trunk repair. A small 2 cm stent(dilation potential 10mm) was placed with the understanding and expectation, that the stent would palliated the stenosis longer than the conduit would last. Thus, atthe second surgery for conduit replacement, the stent could be patch enlarged.

Fig. 8. A lateral right ventriculogram after common arterial trunk repair defining a stenotic conduit(at the valve level), left panel; the obstructionpalliated with a stent implant. This reduced the right ventricular pressure to less than one-half systemic levels, and allowed 2–3 years furtherpalliation before the child outgrows the conduit.

without aortic obstructions. In pediatric patients balloondilation of the obstructions is the treatment of choiceand should be used in the initial form of interventionw47x.

4. Other interventions

Successful balloon dilation has been reported in onechild with a stenotic truncal valve and in another withan obstructive aortic homograft conduitw48,49x.

5. Summary

Over the past two decades transcatheter interventionshave become increasingly useful in the treatment ofpatients with a variety of congenital heart defect. Amongpatients with CAT balloon angioplasty and implantation

of stents have been especially effective in the treatmentof obstructed pulmonary arteries and right and leftventricular conduits. Use of these non-invasive thera-peutic alternatives to surgery will continue to improvepatient outcomes.

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Catheterization interventions in the management of common arterial trunk