Glen shunt (BDG)

GENERAL PRINCIPLES OF SUPERIOR AND TOTAL
CAVOPULMONARY CONNECTIONS
 Goal =separate the systemic and pulmonary circuits, resulting in
normal or near normal oxygen saturation.
 Cavopulmonary connections -divert systemic venous return
directly into the pulmonary vascular bed, providing more
“effective” pulmonary blood flow and reducing the volume load
on the single ventricle.
GLENN SHUNT-A REVIEW

 After these procedures, the single ventricle ejects blood only to the
systemic circuit, with pulmonary blood flow derived by “passive
flow” into the pulmonary vascular bed at the expense of higher
central venous pressure.
 improve cyanosis and minimize ventricular work
 elevated PVR in the neonate precludes their use until
approximately 3 months of age

 The cavopulmonary connections -stage to the modified Fontan
1)BDG
2)Hemi-Fontan.
 Staging - high incidence of pleural effusions and low-output
myocardial failure when taken directly for fontan procedure..

Single left ventricle physiologies
 Tricuspid atresia with normally related great arteries
 Double-inlet left ventricle with normally related great arteries
 Transposition of the great arteries with PS
 Malaligned atrioventricular canal with hypoplastic right ventricle
 Pulmonary atresia with intact ventricular septum

TRICUSPID ATRESIA

Single right ventricle physiologies
 HLHS
 DORVwith mitral atresia
 Malaligned atrioventricular canal with hypoplastic left ventricle
 Heterotaxy syndromes

HYPOPLASTIC LEFT HEART SYNDROME

GOALS OF STAGE 1 PALLIATION
Unobstructed systemic blood flow
Limited PBF
Undistorted PA
Unobstructed PVreturn
Minimal AV valve regurgitation

 allows the neonate to survive into infancy
 not a stable anatomic or physiologic long-term solution.
 ultimately undergo some variation of the Fontan operation as their
final surgical palliation

Selecting Patients with Tricuspid Atresia for the
Fontan Procedure: The “Ten Commandments”
1. Minimum age, 4 years
2. Sinus rhythm
3. Normal caval drainage
4. Right atrium of normal volume
5. Mean pulmonary artery pressure ≤ 15 mm Hg
6. Pulmonary arterial resistance < 4 U/m2
7. Pulmonary-artery-to-aorta-diameter ratio ≥ 0.75
8. Normal ventricular functions (ejection fraction > 0.6)
9. Competent left atrioventricular valve
10. No impairing effects of previous shunts

 Glenn.
 unidirectional (classic) and bidirectional superior cavopulmonary
anastomoses and inferior cavopulmonary anastomosis (inferior
vena cava [IVC]-to-PA connection).
 Interim palliation with a BDG shunt - standard of care in infancy (4
to 9 months of age).

Timing of shunt
 decrease in PVR= superior cavopulmonary anastomoses by 3 to 6
months of age.
 Mahle - early ventricular unloading after neonatal single-
ventricle palliation improved aerobic exercise performance in
preadolescents with the Fontan palliation.
 early -opportunity to address distorted pulmonary arteries from
previous bands or shunts and to create a better distribution of
PA blood flow and growth of the pulmonary vascular bed.

Indications for early shunt procedure
 Cyanosis secondary to inadequate pulmonary blood flow after
neonatal palliation
CHF from an excessive volume load caused by severe
atrioventricular valve regurgitation or by an elevated Qp:Qs.

 early - weighed against the risks of elevated SVC pressure and
cyanosis.
 Bradley - younger than 3 months was associated with lower oxygen
saturation in the early postoperative period and a risk of PA
thrombosis.
 Some infants with severe ventricular dysfunction or
atrioventricular valve regurgitation - not be suitable for further
staged palliation and may require heart transplantation

Prerequisites before the procedure
 Echo
 cath
For anatomic and hemodynamic assessment of the
 PA
 Aortic arch
 Ventricular and AV valve function
 Caval anatomy-Presence of decompressing veins that may
result in cyanosis after superior cavopulmonary
anastomosis.

CLASSIC GLENN SHUNT
Dr. Glenn
anastomosis between the transected distal end of the right
pulmonary artery and the side of the SVC, which is ligated
distal to the anastomosis.
azygous vein is ligated to prevent its decompressing flow
from the SVC.

BIDIRECTIONAL GLENN SHUNT
median sternotomy
CPB
shunt is ligated with a vascular clip or ligature.
Preservation of the proper spatial orientation of the
SVC relative to the PA is essential
azygos vein is ligated but not divided
SVC is then divided, and the cardiac end is oversewn.
cephalic end is anastomosed end to side to the
ipsilateral PA.

 bi-directional - far less likely to engender Pulmonary vascular obstructive
disease compared with systemic-pulmonary shunts
 minimal Distortion of the pulmonary artery architecture.

Shunt between the Superior Vena Cava and Right Pulmonary Artery — Technic of Anastomosis.
Glenn WW. N Engl J Med 1958;259:117-120.

Angiogram Taken Two Months after Operation.

Arterial Oxygen Studies before and after the Shunt.*

Technique Without Cardiopulmonary Bypass
BDG
 Patients with sources of pulmonary blood flow that do not need
interruption as part of the cavopulmonary anastomosis
(antegrade flow through a stenotic pulmonary valve or banded
PA) and have no specific intracardiac pathology requiring
revision are candidates for cavopulmonary anastomosis without
CPB.
 HLHS -not candidates -pulmonary blood flow is shunt
dependent/ may require PA reconstruction and other
intracardiac procedures at the time of their superior
cavopulmonary anastomosis

HEMI FONTAN PROCEDURE

FONTAN PROCEDURE
d’Udekem Y et al. Circulation 2007;116:I-157-I-164
Copyright © American Heart Association, Inc. All rights reserved.

Postoperative Physiology
 circulation to the lungs is from the upper body systemic venous
return.
 pulmonary blood flow results from upper body blood flow, all SVC
return must pass through the lungs to reach the heart in the
absence of decompressing venous collaterals.

 early age - reduction of the volume work of the single ventricle and
a predictable Qp:Qs of a 0.6 to 0.7.
 This ratio is higher in young infants because of the relative size of
the head and the upper extremities in young infants as opposed to
those in older children, but in general, systemic arterial oxygen
saturations (SaO2) are 75% to 85%.

 immediate reduction in the volume load of the single ventricle by
removing the aortopulmonary shunt decreases the work of the
single ventricle and may improve long-term AV valve and
myocardial function.
 AV valve regurgitation resulting from physiologic rather than
structural abnormalities may decrease as the ventricular geometry
normalizes

 oxygen is delivered more efficiently to the body because only
deoxygenated blood from the SVC rather than admixed blood from
the ventricle is presented to the lungs for oxygen uptake.
 reduction in cardiac output needed to achieve a given tissue O2
delivery

DIASTOLIC DYSFUNCTION

 ventricular filling is not absolutely dependent on pulmonary
venous return, because IVC flow is still diverted directly to the
single ventricle and maintains preload.
 acute volume reduction noted after superior cavopulmonary
anastomosis is better tolerated than in the case of transitioning a
child from a neonatal palliation directly to the Fontan completion
without an intervening superior cavopulmonary anastomosis

 SaO2 - lower in very young younger than 3 months patients.
 as young as 4 weeks have had satisfactory BDG shunt creation
 patients younger than 3 months -early cyanosis, PA thrombosis, and
vascular congestion.
 delay of the procedure until the child is older than 3 months
 By age 6 months-mortality risk approaches 0

Postoperative Issues

Mechanical Ventilation
 Positive pressure ventilation with increased mean airway pressures
adversely affects PVR and ventricular filling
 Early institution of spontaneous ventilation improves
hemodynamics
 Spontaneous breathing also increases pco2, which will promote
increased cerebral blood flow and, thereby, increase pulmonary
blood flow.

 “Physiologic” (3 to 5 cm H2O) PEEP-well tolerated, does not
significantly affect PVR or CO, and may improve oxygenation by
reducing areas of microatelectasis, reestablishing functional
residual capacity, and improving ventilation/–perfusion matching.

Elevated Cavopulmonary Pressures
 minimize the transpulmonary gradient (PA mean pressure – common
atrium mean pressure) to allow passive PBFthrough the lungs and
back to the single ventricle.
 elevated transpulmonary gradient - pulmonary venous obstruction,
elevated PVR, or pleural effusion, hemothorax, or pneumothorax.
 Extubating - reduce the common atrial pressure and promote flow
through the lungs by creating a greater transthoracic gradient from
the extrathoracic space to the intrathoracic space.
 Diminished cavopulmonary blood flow will reduce systemic SaO2

 Elevation of PVR from the inflammatory effects of CPB may be
minimized with pulmonary vasodilators -nitric oxide at 5 to 20
parts per million in inspired gas.
 Mild facial edema after superior cavopulmonary anastomosis
may persist for up to 72 hours.
 Majority of pleural effusions - diminish over time with judicious
diuretic use and fluid restriction.

 aspirin (5 mg/kg/day) - reduce the risk of thrombosis of the
superior cavopulmonary circuit

 significantly elevated SVC pressure ,upper extremity plethora and
edema - obstruction at the cavopulmonary anastomosis, distal PA
distortion, or marked elevations in PVR.
 Significant elevations of pressure in the SVC may limit cerebral
blood flow.
 If the SVC pressure is more than 18 mm Hg- early catheterization

Hypertension and Bradycardia
 Transient postoperative hypertension and bradycardia -first 24
to 72 hours
 Hypertension - pain, catecholamine secretion, intracranial
hypertension
 acute elevation of the central venous pressure -reflex similar to
that seen in head trauma, such that systemic hypertension is
necessary to preserve adequate cerebral perfusion.
 aggressive lowering of the blood pressure may adversely affect
the cerebral perfusion pressure
 vasodilators =cautiously.

 Transient bradycardia =acute reduction of the volume load of the
single ventricle, or may be due to injury to the sinus node or its
arterial supply.

Low Cardiac Output
 preexisting ventricular dysfunction or severe atrio-ventricular valve
regurgitation- volume-loaded ventricles, which need high filling
pressures to generate adequate output, volume reduction and the
effects from CPB may significantly reduce cardiac output and
oxygen delivery to the tissues.

Cyanosis
 Excessive hypoxemia (SpO2 <75%) should be investigated promptly.
 pulmonary venous desaturation
 systemic venous desaturation
 decreased pulmonary blood flow.

Pulmonary venous desaturation
 Pleural effusion
 Pneumothorax
 Hemothorax
 Chylothorax
 Pulmonary edema
 Atelectasis
 Bacterial pneumonia/viral pneumonitis
 Arteriovenous malformation

Systemic venous desaturation/Decreased
oxygen delivery
 Anemia
 Low cardiac output
 Decreased ventricular function
 Severe AV valve regurgitation
 Pericardial tamponade

Increased oxygen consumption
 Sepsis
 Venovenous collateral from superior cavopulmonary circuit via the
systemic venous circuit to the systemic ventricle
 Baffle leak

Decreased pulmonary blood flow
 Pulmonary venous hypertension
 Restrictive atrial communication
 Decompressing vein

 Decreased pulmonary blood flow - decompressing venovenous
collaterals, an undiagnosed contralateral LSVC
 decompressing venous collaterals – MC IN bilateral superior vena
cava, a higher early postoperative transpulmonary gradient, and
elevated pressure in the SVC.

 A left SVC to coronary sinus- may re-canalize, resulting in
significant desaturation after superior cavopulmonary
anastomosis.
 Successful transcatheter coil embolization

PULMONARY AV MALFORMATIONS
 particularly in patients with heterotaxy syndrome.
 Diversion of normal hepatic venous flow from the pulmonary
circulation
 regress after incorporation of hepatic venous flow into the lungs.
 young age
 polysplenia (interrupted IVC with azygos continuation to the
SVC).

 gradual hypoxemia months to years
 pulsatile second source of pulmonary blood flow may minimize
the development
 malformations diminish or disappear completely after fontan
completion
 theoretic advantages exist to an ivc-pa cavopulmonary
anastomosis relative to the formation of pulmonary
arteriovenous malformations, the elevation in hepatic venous
pressure and the detrimental effects on liver function may be
prohibitive

 long-term aspirin (a cyclooxygenase inhibitor) = prevented the
development of cyanosis by preventing pulmonary AV fistula
formation.
 Transcatheter embolisation when feeding artery greater than 3mm.
 Surgery-Fistulectomy/Lobectomy

Glen shunt (BDG)

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