Flashcards in Single Ventricle Hypoplastic Left Heart Syndrome Hypoplastic Right Heart Syndrome Deck (88):
The term single ventricle refers
to any congenital cardiac anomaly in which one ventricle is hypoplastic or absent
significant hypoplasia of either ______ necessitates______
A-V valve, or apical portion of the LV or RV, necessitates single ventricle physiology.
Single Ventricle Type Defects
HypoplasticLeftHeartSyndrome HypoplasticRightHeartSyndrome DoubleOutletRightVentricle DoubleInletleftventricle Complete AVSD MitralValveAtresia TricuspidAtresia Pulmonary atresia
Single Ventricle Physiology -overview
Single functional pumping chamber Valves/Outflow tracts may be disrupted Goal: Must control/balance PA and Aortic flow
HLHS was first successfully treated in the
mid- 1980's by Dr. William Norwood, working out of Philadelphia Children’s Hospital under Dr. Aldo Castaneda.
HLHS fatality before surgery
HLHS had been nearly 100% fatal. Success rates were low, more of the infants were given a second chance at life through palliative surgeries.
Since these procedures were developed recently, the oldest patients are just reaching adulthood.
Dr. William Norwood reports 1st successful case in
HLHS PDA perfuses
most prominent case in HLHS
Baby Fae, the little girl who received the baboon heart transplant in 1984, is probably the most prominent case of HLHS
Prostaglandins (PGE1) - bought time to improve results
HLHS is a severe congenital heart defect in which
The left side of the heart does not develop.
Atretic, hypoplastic aorta and arch
Large PDA (only blood flow to body)
Small MV and/or AV
Hopefully, an ASD allowing blood returning from lungs to reach the single ventricle.
(ASD may be restrictive or non-restrictive)
Infants with HLHS who are born with a severely restricted or no inter-atrial communication (a rare occurrence) show
profound hypoxemia with increased LA/ PA pressures
pH 7.17 pO2 26 pCO2 58 BE-7.8
In infants with a large, unobstructed ASD, the blood flow
the LA to the RA increases (L->R).
is is the first attempt to balance the pulmonary and systemic circulations
Hypoplastic left heart syndrome (HLHS) is the most common
form of congenital heart disease that results in a functional single ventricle
It is estimated that HLHS occurs in
0.16 to 0.18 per 1000 live births. Males > Females No environmental risk factors have been identified
Without surgery, hypoplastic left heart syndrome
is uniformly fatal usually within the first 2 weeks of life.
The endocardial tube gets pinched shut in a region that becomes the future ventricle, hypoplastic heart syndrome will occur.
If the pinched part of the endocardial tube is the bulbus-cordis region
of the developing heart, hypoplastic RIGHT syndrome will occur.
If the pinched part of the endocardial tube is the ventricular region
it will be the LEFT side that is hypoplastic
Hypoplastic right heart syndrome (HRHS) refers to____ and causes_____
underdevelopment of the right sided structures of the heart.
These defects cause inadequate blood flow to the lungs and thus, a cyanotic infant.
The major problem with HRHS
pulmonary valve atresia
Secondary problems with HRHS include
hypoplastic RV A small TV A hypoplastic pulmonary artery.
survival rate of hrhs
he survival rate is predicted to be 15-30 years post-Fontan
This does NOT mean the child will die at this time. It MEANS that the heart function deteriorated and the child will be listed for transplant.
Other parents feel that ,with advances in medical techonology
still needing more work, they prefer to buy time for improvement by choosing the Fontan route.
The goal of surgical reconstruction is to relieve
obstruction to systemic flow, un-restrict blood flow from left to right atrium, and create a source of adequate pulmonary blood flow.
The ultimate goal is to create
parallel circulations and balance the pulmonary and systemic blood flow (Qp/Qs)
Immediate Palliation for HLHS/HRHS
Balloon Atrial Septostomy (Rashkind Procedure) Blade Septectomy (Hanlon Procedure) –not used much
The first stage, the Norwood procedure is typically performed
within the first week(s) of life.
The second stage, the Bi-directional Glenn or Hemi- Fontan, is typically performed
before the infant is 6 months old.
the Completion Fontan operation is completed at
18 months to two years old,
DHCA Procedure: on arrest, the surgeon does the following:
Enlarge aorta (create neo-aorta)
Add Systemic-PA shunt during warming Modified B-T (3.5 mm shunt size-average) Sano (5.0 mm shunt size-average)
The Sano Shunt showed improvement
in the survival of newborn babies with HLHS.
The Sano Shunt is constructed from
slightly larger Gortex tube graft than that used for the modified BT shunt. Generally a 5 mm tube graft is selected in contrast to the 3.5 mm graft.
Distally, the Sano graft is connected
to the main PA between the right and left pulmonary artery takeoffs. The proximal end of the shunt is connected to a limited infundibular incision in the RV.
MBTS (Subclavian-PA) charac.
May have preferential right PA flow
Smaller shunt that may clot post-op
Rocky course in the OR
More stable in the PICU post-op
More centrally located on PA
Higher pressure shunt Larger shunt More stable in the OR
Rocky course in the PICU
Survival rates with Norwood procedure
Today, about 90 percent of babies presenting with HLHS can be expected to survive their Norwood operation; truly a success given that 20+ years ago the outlook was hopeless.
OK, so now I have new pulmonary (MBTS) and systemic blood flow (Neo- aorta), how can I manage it?
By controlling PVR and SVR you can control the preferential flow of blood
Pressure = Flow x Resistance (in case you haven’t seen this before)
The surgery set the flow parameters (conduit size) Post-op manipulates the resistance (PVR/SVR)
In HLHS, total blood flow coming from the heart can be considered
to be a zero sum game.
Thus, when more blood is directed to one circulation, less is available for the competing circuit.
Sound a little like left heart bypass?
With parallel circulation, pulmonary and systemic blood flow is determined by the
ratio of Pulmonary vascular resistance (PVR) to Systemic vascular resistance (SVR).
Qp/Qs describes how the cardiac output from
the single ventricle is partitioned. If a marked discrepancy occurs in blood flow to the pulmonary and systemic circulations, rapid onset of hemodynamic instability will occur.
How do you think the (Qp/Qs) ratio will be altered if I increase the shunt size? Surgical Shunt (BT/Sano)
The BT shunt/Sano connecting the systemic circulation to the pulmonary circulation is the single largest component of resistance.
Surgical Shunt (BT/Sano) The proper shunt size for each patient is determined
initially by the patient’s size and is confirmed by hemodynamic data and oxygen saturations.
Surgical Shunt (BT/Sano) The Qp/Qs ratio is calculated after cardiopulmonary
bypass is discontinued.
As in preoperative management, the goal is to achieve aQ p/Qs ratio of 1.0.
(Qp/Qs) Post-operative Monitoring
Recent articles indicate the usefulness of mixed venous oxygen saturation (SvO2) monitoring to estimate pulmonary-to-systemic blood flow ratio (Qp/Qs) in perioperative management of the Norwood procedure
Increased PBF (Decreased PVR)
Although increased pulmonary blood flow results in higher oxygen saturation, systemic blood flow is decreased.
Perfusion becomes poor, and metabolic acidosis and oliguria may develop.
Decreased PBF (Increased PVR)
If PVR is significantly higher than SVR, systemic blood flow is increased at the expense of pulmonary blood flow.
This may result in profound hypoxemia
Pulmonary Vascular Resistance (PVR)
↓ FiO2 ↑ CO2 ↓ pH PEEP
Pulmonary Vascular Resistance (PVR) decrease
↑ FiO2 ↓ CO2 ↑ pH
iNO (inhaled nitric oxide)
Systemic Vascular Resistance (SVR) increase
↑ Ph ↑ FiO2 Vasoconstrictors
Systemic Vascular Resistance (SVR) decrease
↑ CO2* Vasodilators
Qp/Qs increasing PVR
PVR can also be increased by
y maintaining the hematocrit at greater than 40%, a state that optimizes oxygen-carrying capacity and increases the viscosity of the blood increased viscosity
Flow = ΔP x πr4 L x V x 8
Bidirectional Glenn (BDG) and Hemi-Fontan Procedures (HFP) - Stage II
Preformed at around
Cyanosis increasing between stages I and II
would shorten the duration of time between surgeries
Bidirectional Glenn (BDG) and Hemi-Fontan Procedures (HFP) - Stage II done with DHCA or off CPB
Take down systemic-PA shunt
Occlude SVC flow Anastamosis done right PA to the SVC
(Bi-directional Cavopulmonary Anastomosis) CHARACTERISTICS
Anastamosis PA/Right atrial appendage SVC is patched
Intracardiac Baffle Extracardiac Conduit
After a Fontan operation, the pressure in the veins will be higher than normal, to
overcome this resistance and maintain blood flow. (high CVP = 14-25+ mmHg)
In a Fontan circulation blood goes:
LV → aorta → organs
That CVP propels blood
capillaries → veins → RA → lungs
If PVR is high, the Fontan
cannot be performed.
A small amount of resistance will exist across the lungs. (pressure drop)
Hybrid Treatment (HLHS)
Hybrid Cath Lab/OR room
Palliation to ensure survival PDA stent
Atrial Septal Stent (Balloon if needed first) Bilateral PA Banding
Remember: Balancing and controlling the pulmonary and systemic flow is of utmost importance on these children
SUCCESS OF NORWOOD
The overall success following the hemi-Fontan procedure (stage II)
Success after completing the Fontan procedure (stage III)
Among low-risk patients who undergo staged reconstruction or transplantation,
actuarial survival at 5 years is approximately 70%.
What does that mean? Be careful with statistics.
75% alive after stage I (at hospital discharge) 95% alive after stage II (at hospital discharge) 90% alive after stage III (at hospital discharge)
This means: .75 x .95 x .9 = 64% overall survival
Ideal Post-op Blood Gases
PaCO2: pH: PaO2: SaO2:
35–45 mm Hg 7.35–7.40 30–45 mm Hg 70–85%
7.4 / 40 / 40 is key Hematocrit >40 % , SAO2 = 75%
To much shunt flow ? BLOOD GASES
PaCO2: 36 pH: 7.23 PaO2: 49 SaO2: 88% BE: -7.8
To little shunt flow ? ABG
PaCO2: 48 pH: 7.19 PaO2: 23 SaO2: 58% BE: -11.8
3 Tough cases Fragile OR and post-op course May need ECMO May need NOMO (ECMO with no oxygenator in line) May need a VAD Hemi- and Fontan are redo surgeries (femoral cannula?)
Due to the atretic aorta where are you going to cannulate for arterial? AND VENOUS HYPOTHERMIA CARDIOPLEGIA
Arterial: Pulmonary artery (what?)
Venous: Single atrial
Hypothermia: DHCA (possibly antegrade cerebral/retrograde cerebral perfusion)
Cardioplegia: One shot antegrade Thru arterial cannula Aortic root if possible
Pump Run: On → cool: 20 min → XC/CP/arrest → warm: on 23 min → off CPB →MUF 10 min
*(OnDHCA:letvenousexsanguinationoccurbeforeclampingthe venous line )
On → cool: 20 min → Arrest/XC/CP → warm: on 23 min → off CPB→MUF 10 min
Typical times: FOR PUMP RUN
CPB time = 43” XC time= 48 Arrest time= 45
What considerations do you need to make when you circulatory arrest first, then give CP down the aortic cannula?
Arterial and Venous Cannulation BDG
Arterial: Neo-aorta Venous: Single Atrial Hypothermia: Moderate – continuous CPB Cardioplegia: No cardioplegia
An extra-cardiac Fontan will follow this procedure
Arterial and Venous Cannulation Hemi Fontan
Arterial: Neo-aorta Venous: Single Atrial Hypothermia: DHCA Cardioplegia: With cardioplegia
A lateral tunnel Fontan will follow this procedure
Arterial and Venous Cannulation Fontan
Arterial: Neo-aorta Venous: Single atrial Hypothermia: Mild Cardioplegia: With or without cardioplegia
Physiology is tough with these kids (think in terms of QP/Qs)
Keep pump primed and ready (you may only be off temporarily)
Redo surgeries can take a while to get in (be ready to use emergent femoral cannulation)
And what if your patient can’t come off CPB?
ECMO NOMO Pediatric VAD
Mechanical circulatory support is expanding it’s role in congenital cardiac surgery.
Pediatric impella is available ECMO and centrifugal ventricular assist
devices are still the mainstay, New pulsatile, para-corporeal VAD’s designed for
pediatrics are being utilized.
In addition, several new, continuous flow devices are under development as fully implantable systems for adults, ultimately may be useful for pediatric patients.
BELIN HEART DRIVEN BY
is a pneumatically driven, pulsatile para-corporeal device that can offer either LVAD, RVAD or (BIVAD) support.
The pump sizes are BERLIN HEART
0, 25, 30, 50 and 60 mls, meaning that it can be used to support any size of child from 3-100 kg.
The LVAD drains blood from the
LV via a cannula inserted into the apex and returns it to the aorta
The RVAD drains from the
RA and returns blood to the PA