2. What is Single Ventricle/ Univentricular Heart
(UVH)?
Univentricular heart is a term used to describe a wide variety of structural cardiac abnormalities associated
with a functional single ventricular chamber.
The consensus of STS- and the European study group database proposed that the nomenclature of UVH
should include-
● Double inlet Left and Right Ventricles (DILV, DIRV)
● Absence of one AV connection (Tricuspid Atresia, Mitral Atresia)
● Common AV valves (unbalanced complete AV canal defect)
● Hearts with only one well developed ventricle and heterotaxy syndromes (single ventricle heterotaxy
syndrome)
5. The PBF is either derived from the pulmonary artery (PA) coming off of the single ventricle or from the level
of the great vessels (patent ductus arteriosus, surgically placed aorta-pulmonary artery shunt (or RV to PA
non-valved conduit), or aorto-pulmonary collateral vessels). The SBF is either unobstructed or obstructed.
Based on such a thought, these patients may be grouped into the following subsets:
This classification is helpful in determining the type of therapy that a given patient needs.
Group 1: Unobstructed Systemic Blood Flow
1A: Unobstructed SBF with unobstructed PBF
1B: Unobstructed SBF with moderately obstructed PBF
1C: Unobstructed SBF with severely obstructed (or atretic) PBF
Group 2: Obstructed Systemic Blood Flow
6. In summary, the systemic and pulmonary blood flow returns mix with each other with
consequent lower systemic oxygen saturations (75–85%—Normal 96%).
The systemic and pulmonary circuits work in-parallel rather than normal in-series
circulation.
Markedly increased PBF results in systemic hypo-perfusion and severely decreased PBF
creates severe hypoxemia.
Therefore, a delicate balance of the blood flows between the two circulations should be
preserved.
7. Management Strategies to Address the Single
Ventricle Defects
Since there is only one functioning ventricle, the overall objective is to allow the functioning ventricle
(whether morphologically right or left) to supply the systemic circulation and to connect the systemic veins
directly to the PAs (Fontan circulation—single ventricle repair).
This procedure can’t be done in the neonate since PA pressure and resistance are high.
Consequently, it is performed by staged procedures.
The types of procedures and their timing have evolved over the years.
8. Currently this is accomplished by staged total cavo-pulmonary connection (TCPC), devised by de
Leval and associates. This TCPC is undertaken in three stages: Stages I, II, and III.
Stage I—Management at the Time of Initial Presentation
The management at initial presentation, typically in the neonatal period, depends upon the
pathophysiology of the defect itself plus the associated cardiac abnormalities, namely the status of
PBF, the presence of obstruction to SBF, and other cardiac defects.
1. Status of Pulmonary Blood Flow
The PBF may be decreased, increased, or the PBF is adequate.
a. Reduced Pulmonary Blood Flow (Group 1C above)
In patients with reduced PBF, the ductus arteriosus should be kept patent by PGE1
infusion. Once the baby is stable, go towards a more stable way of increasing PBF i.e.
Modified BT Shunt.
9.
10. b) Increased Pulmonary Blood Flow (Group 1A above)
A markedly elevated PBF produces congestive heart failure (CHF). These infants are
initially stabilized with anticongestive therapy. This should be followed by banding of the
PA, irrespective of control of CHF
c) Adequate Pulmonary Blood Flow (Group 1B above)
Babies with a mildly increased or near normal PBF with O2 saturations in the low 80s do
not exhibit significant symptoms and, are less cyanotic than babies with pulmonary
oligemia and do not require any treatment and may be followed until Stage II.
11. 2. Obstructed Systemic Blood Flow (Group 2 above)
The majority of these babies belong to HLHS syndrome or its variants and require Norwood operation
with either Modified BT or Sano shunt
In some institutions, cardiac transplantation is employed to address this lesion
2. Other Cardiac Abnormalities
Some of the babies may have other cardiac abnormalities such as intra-cardiac obstruction, aortic
arch obstruction, or atrioventricular valve insufficiency at presentation or may develop such
abnormalities during the succeeding period.
These should be dealt with and both SBF and PBF should be maintained by various surgical
procedures and then should proceed for stage II.
12.
13. Stage II—Bidirectional Glenn
Independent of the nature of palliative intervention during the neonatal period,
bidirectional Glenn operation by anastomosis of the superior vena cava (SVC) to the
right PA, end-to-side is undertaken at an approximate age of six months.
If a prior BT or Sano shunt is present, it is ligated at the time of bidirectional Glenn.
While performing the procedure at six months is commonly accepted, the Glenn can be
performed as early as three months subject to demonstrating normal PA pressures and
anatomy.
14.
15. Stage III—Fontan/Kruetzer Procedure
The IVC blood flow is rerouted into the PA. At the same time a fenestration between the
conduit and the atrial mass is created.
Arbitrary division of these procedures into Stage IIIA (diversion of IVC into the PA) and Stage
IIIB (closure of the fenestration) may be undertaken.
Stage IIIA
In the Stage IIIA, the TCPC may be accomplished by redirecting the IVC blood flow into the PA
either by a lateral tunnel or by an extra-cardiac, non-valved conduit.
This surgery is typically carried out anytime from one to two years of age, frequently one year after
the bidirectional Glenn.
At the present time, the majority of surgeons favor an extra-cardiac conduit to achieve the final
stage of Fontan. It also appears that most surgeons create a fenestration, 4–6 mm in size, between
the conduit and the atria.
16. Stage IIIB
During the Stage IIIB, the fenestration is occluded by transcatheter methods usually 6–
12 months following Stage IIIA Fontan.
19. Evolution of surgery for Functionally UVH
The development in 1940s of the BT shunt and the original description in 1952 of the PA banding ushered in
an era of palliation for selected patients with single ventricle hearts who suffered from either a shortage or
an excess of pulmonary blood flow.
20. ● The Fontan procedure was first applied in 1968 for tricuspid atresia based on the
principle that the right atrium could be used as a pumping chamber for the
pulmonary circulation.
● The original description of the atriopulmonary connection included the insertion
of an aortic or pulmonary homograft valve at both the inflow and the outflow of
the right atrium as well as a classical Glenn anastomosis of the superior vena cava
to the right pulmonary artery.
● Kreutzer and colleagues described the use of the patient’s native pulmonary
valve between the right atrium and pulmonary artery.
● Bjork and coworkers were worried about the long-term durability of conduits and
valve prostheses and devised a valveless atrioventricular anastomosis whereby
the right atrial appendix is anastomosed to the right ventricle with the aid of an
autologous pericardial patch.
21. ● It soon became apparent that neither valves nor the rudimentary right ventricle needed to be
incorporated into the Fontan connection, so the Fontan procedure evolved into a direct
atriopulmonary connection with closure of the atrial communication for tricuspid atresia.
22. Lateral Tunnel Fontan (Total Cavopulmonary Connection)
● de Leval and colleagues revealed that the atriopulmonary connection performed poorly
in terms of flow energetics because of turbulence that was further exaggerated by
pulsation.
● In contrast, a cavopulmonary connection had mainly laminar flow patterns.
● In this design, the superior vena cava blood drains directly into the pulmonary artery,
and inferior vena cava blood is baffled through a straight intra-atrial conduit to the
pulmonary artery
● Additional theoretical advantages are a reduced risk of thrombosis because of less
blood stasis and exposure of only a limited portion of the right atrium to high venous
pressures, thus reducing the risk of arrhythmias.
● In addition, because the coronary sinus remains in the lower pressure pulmonary
venous atrium, myocardial venous drainage is unobstructed.
● This introduction of total cavopulmonary connection, coupled with an intermediate
stage of a bidirectional Glenn anastomosis or a hemi-Fontan procedure, greatly
improved clinical results with the Fontan procedure.
23.
24. ● The beginning of the operation may involve performing a bidirectional
cavopulmonary anastomosis, or this may already be in place.
● For cardiopulmonary bypass, a venous cannula is placed low down on the
inferior vena cava and a further cannula high up in the superior vena cava
near the junction with the innominate vein.
● The ascending aorta is cannulated.
● The operation is performed using moderate hypothermia.
● Any existing systemic to pulmonary artery shunts are taken down.
● The aorta is cross-clamped, and cold blood cardioplegia is infused. A needle
vent is placed in the ascending aorta.
● The main pulmonary artery is transected.
● To prevent bleeding or aneurysm formation after closure of the proximal
pulmonary artery stump, the suture line is reinforced with two small Teflon
felt strips and the pulmonary valve leaflets are included in the suture line.
● The distal main pulmonary artery is closed, taking care not to distort or
narrow the branch pulmonary arteries.
25. Procedure
A, The right atrium is opened along the crest of the septum. The atrial septal defect is enlarged if
necessary, and the size of the intra-atrial baffle is measured between the eustachian valve (EV) and
crista terminalis (CT).
B, Future site of baffle between the superior vena cava and inferior vena cava.
C, A Gore-Tex tube of at least 16-mm diameter is cut to size and opened longitudinally, and if
required, a 4- to 5-mm fenestration is cut.
D and E, The prosthetic baffle is sewn halfway around the junction of the inferior vena cava with the
right atrium, along the posterior wall of the atrial septum, along the CT, and halfway around the
junction with the superior vena cava. Care is taken to avoid injury to the sinus node.
F, The cardiac end of the transected superior vena cava is anastomosed in an end to- side manner
with the undersurface of the right pulmonary artery
26. Fontan Fenestration
● Another important clinical improvement was the creation of a fenestration in the
Fontan baffle, which allows systemic venous blood to shunt to the pulmonary venous
atrium, achieving better preload for the systemic ventricle at the cost of some systemic
arterial desaturation.
● Thus, cardiac output is maintained and systemic venous pressure is reduced.
● The fenestration can be closed later by a transcatheter approach.
● A retrospective study by Bridges and associates showed a significant decrease in
pleural effusions and hospital stay compared with nonfenestrated patients.
● Consequently, the fenestrated Fontan circuit has become the procedure of choice for
the high-risk population.
27. Lateral Tunnel versus
Extracardiac Conduit
● The extracardiac conduit initially was designed to avoid pulmonary and systemic venous
obstruction in patients with a small atrium.
● Its use has the additional advantage that it avoids extensive atrial suture lines that are
potentially arrhythmogenic.
● Thrombogenicity and lack of growth of the prosthetic conduit remain potential late problems.
28.
29.
30. ● The lateral tunnel Fontan optimizes flow dynamics in the pulmonary artery, leaves
the coronary sinus in the low pressure atrium, and has a low risk of damage to the
atrioventricular node. The same advantages can be attributed to the extracardiac
Fontan procedure.
● The extracardiac Fontan procedure has the additional advantage that no intra-
atrial access is required and thus can be done without aortic cross-clamping and, in
suitable cases, also without the use of cardiopulmonary bypass
31. Fontan for Biventricular Hearts
Certain cardiac defects with two well-formed ventricles are better served with a Fontan procedure.
Examples-
DORV with a remote VSD or a straddling atrioventricular valve, which would make a
biventricular repair problematic.
ccTGA
Unbalanced Atrioventricular septal defects.
