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Key Questions in CONGENITAL CARDIAC SURGERY
c) biplane right ventricular angiogram that is performed to confirm
the site of the obstruction, to measure the pulmonary valve
annulus diameter (Figure 11) and to evaluate the function of
the right ventricle;
MPA
**
RVOT
220
RV
Figure 11. Angiographic evaluation of the pulmonary
valve annulus in the lateral projection after a right
ventricular angiogram demonstrating thickened
pulmonary valve leaflets with the valve doming
(asterisks). RV = right ventricle; RVOT = right ventricular
outflow tract; MPA = main pulmonary artery; A =
pulmonary valve annulus.
d) haemodynamic assessment of the pulmonary valve gradient;
e) selection of the appropriate balloon size. Accepted practice is
to use a balloon that is 1.2-1.4 times the diameter of the
pulmonary valve annulus. Longer balloons give more stability
during valvuloplasty, with 20mm-long balloons generally used
in neonates and infants, 30mm-long balloons in children and
40mm-long balloons in adolescents and adults.
Balloon pulmonary valvuloplasty is generally a safe and effective
•
procedure, with a low complication rate. Complications are more
6 Congenital angiography and catheter interventions
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common in neonates or infants with the most severe pulmonary valve
stenosis.
Rare complications include right bundle branch block, femoral
•
venous obstruction, injury to the tricuspid valve, pulmonary
regurgitation and balloon rupture.
A flow-directed catheter, such as a balloon wedge catheter, can be
•
used to cross the tricuspid valve and subsequently a soft-tipped wire
to cross the pulmonary valve prior to positioning the balloon
angioplasty catheter. Whilst this may be difficult or time consuming in
very small patients, the risk of not doing so could result in the
catheter and or wire passing through the chordae of the tricuspid
valve. This in turn may result in damage to these structures when the
balloon catheter is advanced or retrieved through the right ventricle.
14 What are the indications for pulmonary artery
angioplasty and stent placement?
Abnormalities of the pulmonary arteries are involved in a wide variety
•
of congenital heart defects. In the clinical setting, stenotic or
hypoplastic arteries may lead to a pressure burden on the right
ventricle.
Balloon angioplasty alone is indicated for both severe main
•
pulmonary artery and severe branch pulmonary artery stenosis,
particularly in very small patients or in those with pulmonary arteries
with very complicated anatomy in whom primary stent implantation is
not a viable option.
Significant stenosis is obvious when there is a:
•
221
a) measurable gradient of 20-30mmHg across the stenotic area;
b) elevation of the right ventricular or proximal main pulmonary
artery pressure > two thirds of systemic pressure, secondary
to more distal obstruction;
c) relative flow discrepancy between the two lungs of 35%/65%
or worse.
In low pulmonary flow situations, such as with Glenn shunts and a
•
Fontan circulation, the gradient in the pulmonary bed is an unreliable
determinant of the degree of stenosis.
A similar situation presents when there is decompression run-off to a
•
compliant contralateral artery. In this context, the pressure gradient
alone is not a good indicator of severity.
Pulmonary artery stents are indicated in main or branch pulmonary
•
artery stenosis that is not expected to have, or has not had, an
Key Questions in CONGENITAL CARDIAC SURGERY
adequate or persistent response to pulmonary artery balloon dilation
(Figure 12).
ABLPA post-stent
222
Figure 12. Lateral projection angiogram demonstrating: A) stenosis of the
left pulmonary artery (LPA)(arrow); and B) improvement of the LPA diameter
(arrow) following treatment with balloon angioplasty and stent placement.
It is ideal that the stents placed into the central branch pulmonary
•
arteries have adult-size potential. The use of smaller stents are
recognised as a palliative procedure and a commitment for surgical
removal or potential of enlargement at a future date.
The risks of pulmonary angioplasty and stent placement include
•
vessel perforation, arrhythmia during manipulation of the catheters
and wires, and bleeding.
The risks of the stents specifically include misplacement,
•
embolisation and jailing of the adjacent branch vessels. Embolisation
to the ventricle may require an emergent surgical approach for
removal of the stent.
Placement of a pulmonary artery stent can represent a significant
•
burden to subsequent surgical interventions, which can be indicated
by in-stent stenosis, or other surgical indications, such as pulmonary
valve interventions.
Stents placed beyond the bifurcation can produce complex branches
•
stenosis, including lobar bifurcations requiring extensive
reconstructions. The use of pulmonary artery branch stenting should
LPA stenosis
6 Congenital angiography and catheter interventions
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be discussed at a multidisciplinary team meeting, with both
interventional cardiology and surgical teams present.
15 What are the indications for pulmonary vein
angioplasty or stent placement?
Pulmonary vein stenosis can present as:
•
a) an isolated congenital lesion or in association with other
cardiac defects;
b) an acquired lesion after corrective surgery for anomalous
pulmonary venous connections;
c) a complication of extreme prematurity;
d) a complication of pulmonary vein isolation ablation in adult
patients with atrial fibrillation.
Comparison data of balloon angioplasty versus stent dilation suggest
•
that stents achieve better results and have longer patency rates. Final
stent diameter is an important factor, with a greater end diameter
being associated with a better outcome.
Paediatric pulmonary vein ballooning and stenting yields generally
•
poorer results in the mid to long term, as compared to vein
interventions in adults following ablation. Pulmonary vein
interventions in children with congenital, progressively obstructing
disease are rarely curative, with or without the addition of surgical
interventions.
Pulmonary artery wedge angiograms with follow through to the
•
levophase are useful in this diagnosis, if transseptal access to the
pulmonary veins is not available.
The angioplasty technique requires appropriate balloon diameter
•
selection. More recently, cutting and drug-eluting balloons have been
used.
Stent implantation can be considered if there is elastic recoil of the
•
lesion or if vessel dissection is noted. A variety of stents are available
but the goal is to place a stent which may be subsequently dilated
(Figure 13).
Complications are similar to angioplasty and stenting of other
•
vascular structures and include vessel dissection, stent malposition
or embolisation.
Pulmonary haemorrhage after intense intervention on the pulmonary
•
veins is not uncommon. Blood is cross-matched and available, and
very frequently patients are monitored in a critical care area after
intervention.
223
Key Questions in CONGENITAL CARDIAC SURGERY
AB
*
Figure 13. Angiographic images demonstrating: A) left pulmonary vein
stenosis at the site of the veno-atrial junction (arrow), and venous
collateralisation (asterisk); and B) unobstructed drainage in the atrial cavity
(arrow) following stent placement.
224
16 What are the indications for ductus arteriosus stent
placement?
Stenting of the ductus arteriosus has been used to establish a
•
reliable source of pulmonary blood flow for the palliation of:
a) cyanotic heart disease, notably patients with severe tetralogy
of Fallot and all forms of pulmonary atresia, as an alternative to
aortopulmonary surgical shunts;
b) neonates with hypoplastic left heart syndrome (HLHS), as part
of the hybrid procedure, in an alternative to the Norwood
procedure;
c) neonates with non-HLHS lesions, where a single-stage repair
may be contraindicated.
Current literature suggests that ductus stenting is most favourable in
•
neonates with a morphologically straight ductus (no more than one to
two bends), requiring a reliable palliation for 3-6 months.
In full-term neonates, a stent diameter of 3.5-4mm generally provides
•
adequate palliation of pulmonary blood flow without leading to
excessive pulmonary blood flow. In patients weighing less than 3kg,
a diameter of 3mm may be adequate.
Complications of the procedure include those associated with
•
cardiac catheterisation in neonates, particularly femoral vessel injury
or occlusion.
6 Congenital angiography and catheter interventions
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In patients with ductal-dependent pulmonary blood flow, there is a
•
risk of requiring extracorporeal membrane oxygenation or bypass in
cases of injury to the duct during manipulation or unexpected spasm
compromising adequate pulmonary blood flow.
Stent malposition or embolisation can occur, requiring surgical
•
intervention.
Hybrid procedures required in HLHS and non-HLHS patients involve
•
surgical placement of bilateral branch pulmonary artery bands and
stent delivery through a median sternotomy, normally performed
without cardiopulmonary bypass.
17 What are the general principles of patent ductus
arteriosus closure?
The indications for PDA occlusion vary depending on the
•
physiological context at the time of presentation.
In small and premature neonates (<2.4kg) with a low PVR and
•
persistent left-to-right shunt, duct closure is performed to control
pulmonary overcirculation, as well as prevention of endarteritis. Such
procedures are challenging but more favourable now, due to the
development of occlusion devices with a better profile for these
specific ducts.
In infants with a large PDA and elevated pulmonary vascular
•
resistance, a full haemodynamic study to assess vascular reactivity to
pulmonary vasodilator therapy prior to intervention is required. If
reactive, closure may be indicated.
In older patients who have developed Eisenmenger syndrome and
•
have a persistent right-to-left shunt, occlusion is contraindicated.
The PDA can be occluded with different devices, including:
•
225
a) coils — which are usually used to close a small PDA (<2mm).
The Flipper®Cook coil is the most frequently used controlled-
delivery coil and ranges from 3mm diameter by three loops to
8mm diameter by five loops. The Nit-Occlud®coil facilitates
closure of somewhat larger ducts and also has a controlled
release;
b) devices (Figure 14) — which include:
i) Amplatzer™ Duct Occluder;
ii) Amplatzer™ Duct Occluder II;
iii) Amplatzer™ Vascular Plug II;
iv) MVP™ microvascular plug (Medtronic).
226
Key Questions in CONGENITAL CARDIAC SURGERY
AB
C
Figure 14. Patent ductus arteriosus closure devices: A) Amplatzer™
Duct Occluder; B) Amplatzer™ Duct Occluder II; C) Amplatzer™
Vascular Plug II.
The device is selected based on the morphology (Figure 15) and
•
minimum diameter of the duct. See below for different types of PDA
morphology.
Serious complications of PDA occlusion are rare and include
•
inadvertent device embolisation into the pulmonary and systemic
circulation. Obstruction to aortic or pulmonary flow is a risk
particularly in small infants. Haemolysis secondary to residual shunt
is more commonly seen following coil occlusion.
Reproduced with permission from Abbott.
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AB
CD
227
Figure 15. Angiographical images demonstrating the different
morphologies of patent ductus arteriosus based on the Krichenko
classification: A) tubular; B) conical; C) saccular; and D) elongated.
18 What are the current recommendations for atrial
septostomy/stenting in congenital heart disease?
Balloon atrial septostomy is the longest established interventional
•
cardiac catheterisation procedure, first performed by Rashkind and
Miller in 1966 on a neonate with transposition of the great vessels
and severe desaturation.
Whenever possible, septostomy is performed at the bedside using
•
echocardiographic guidance, to minimise exposure to radiation.
Access is usually obtained from the femoral or umbilical vein. A
•
balloon is passed across the interatrial septum (the patent foramen
ovale if present), inflated and quickly pulled back in order to tear
the fossa ovalis membrane.
228
Key Questions in CONGENITAL CARDIAC SURGERY
In cases of a muscular septum and restrictive muscular
•
communication, a stent may be placed, under fluoroscopy guidance.
Indications for atrial septostomy include:
•
a) transposition of the great arteries with a restrictive or intact
atrial communication, requiring enhanced atrial mixing;
b) restriction to an obligatory left-to-right atrial shunt, such as in
mitral atresia and hypoplastic left heart syndrome, requiring
unrestrictive left-to-right shunting;
c) pulmonary atresia with intact ventricular septum, tricuspid
atresia or total anomalous pulmonary venous return, requiring
unrestrictive right-to-left shunting;
d) left atrial hypertension on extracorporeal membrane
oxygenation (ECMO) support requiring decompression.
19 What are the principles of transcatheter closure of a
secundum atrial septal defect?
Indications for transcatheter device closure of a secundum ASD
•
include:
a) right heart volume overload;
b) sequelae of paradoxical emboli, such as stroke or recurrent
transient ischaemic attacks;
c) symptomatic transient right-to-left shunting causing cyanosis,
where a communication to maintain adequate cardiac output is
not required (platypnoea-orthodeoxia).
Contraindications for transcatheter device closure of a secundum
•
ASD include:
a) advanced pulmonary vascular disease;
b) restrictive left heart physiology, usually in elderly patients with
impaired left ventricular function.
Echocardiography plays an important role in the guidance of these
•
procedures and assessment of the result. Either intracardiac or
transoesophageal echocardiography can be used.
The process of transcatheter device closure of the ASD includes:
•
a) adequate sizing of the defect using a compliant balloon that is
placed through the defect and inflated until flow across the
ASD stops, based on echocardiographic imaging;
b) measuring the waist of the balloon by echocardiography and/or
fluoroscopy;
6 Congenital angiography and catheter interventions
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c) selecting the ASD device based on this measurement.
The currently available devices include:
•
a) self-centring devices:
i) Abbott Amplatzer™ Septal Occluder (Figure 16A and
B);
ii) Occlutech Figulla Flex II®ASD device;
iii) CeraFlex™ ASD Occluder;
iv) Cardia Ultrasept™ atrial septal defect closure device;
v) GORE
b) non-self-centring devices:
i) GORE®Septal Occluder (Figure 16C and D);
ii) Occlutech, Cera and Abbott (Amplatzer™) produce a
®
CARDIOFORM ASD Occluder;
variant of their self-centring devices.
AB
C D
Figure 16. Commonly used devices for atrial septal defect closure: A)
Amplatzer™ Septal Occluder; and B) the same device after placement
under fluoroscopy and TOE guidance. Note the anteroposterior facing
position of the device in situ; C) GORE
device after placement under fluoroscopy and TOE guidance.
with permission from Abbott.
®
Septal Occluder; and D) the same
Reproduced
229
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