Single Ventricle Hypoplastic Left Heart Syndrome Hypoplastic Right Heart Syndrome Flashcards Preview

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Flashcards in Single Ventricle Hypoplastic Left Heart Syndrome Hypoplastic Right Heart Syndrome Deck (88):
1

The term single ventricle refers

to any congenital cardiac anomaly in which one ventricle is hypoplastic or absent

2

significant hypoplasia of either ______ necessitates______

A-V valve, or apical portion of the LV or RV, necessitates single ventricle physiology.

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Single Ventricle Type Defects

HypoplasticLeftHeartSyndrome  HypoplasticRightHeartSyndrome  DoubleOutletRightVentricle  DoubleInletleftventricle  Complete AVSD  MitralValveAtresia  TricuspidAtresia  Pulmonary atresia

4

Single Ventricle Physiology -overview

 Single functional pumping chamber  Valves/Outflow tracts may be disrupted  Goal: Must control/balance PA and Aortic flow

5

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.

6

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.

7

Dr. William Norwood reports 1st successful case in

1983

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HLHS PDA perfuses

the coronaries

9

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

10

Prostaglandins (PGE1) - bought time to improve results

1986

11

HLHS is a severe congenital heart defect in which

The left side of the heart does not develop.

12

HLHS Characteristics

 Atretic, hypoplastic aorta and arch
 Large PDA (only blood flow to body)
 Hypoplastic LV
 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)

13

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

14

In infants with a large, unobstructed ASD, the blood flow

from
the LA to the RA increases (L->R).

15

is is the first attempt to balance the pulmonary and systemic circulations

ASD. QP/QS=1

16

Hypoplastic left heart syndrome (HLHS) is the most common

form of congenital heart disease that results in a functional single ventricle

17

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

18

Without surgery, hypoplastic left heart syndrome

is uniformly fatal usually within the first 2 weeks of life.

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embryological cause

The endocardial tube gets pinched shut in a region that becomes the future ventricle, hypoplastic heart syndrome will occur.

20

If the pinched part of the endocardial tube is the bulbus-cordis region

of the developing heart, hypoplastic RIGHT syndrome will occur.

21

If the pinched part of the endocardial tube is the ventricular region

it will be the LEFT side that is hypoplastic

22

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.

23

The major problem with HRHS

pulmonary valve atresia

24

Secondary problems with HRHS include

hypoplastic RV  A small TV  A hypoplastic pulmonary artery.

25

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.

26

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.

27

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.

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The ultimate goal is to create

parallel circulations and balance the pulmonary and systemic blood flow (Qp/Qs)

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Immediate Palliation for HLHS/HRHS

 Balloon Atrial Septostomy (Rashkind Procedure)  Blade Septectomy (Hanlon Procedure) –not used much

30

The first stage, the Norwood procedure is typically performed

within the first week(s) of life.

31

The second stage, the Bi-directional Glenn or Hemi- Fontan, is typically performed

before the infant is 6 months old.

32

the Completion Fontan operation is completed at

18 months to two years old,

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DHCA Procedure: on arrest, the surgeon does the following:

 Close PDA
 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)

34

The Sano Shunt showed improvement

in the survival of newborn babies with HLHS.

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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.

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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.

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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

38

Sano (RV-PA)

 More centrally located on PA
 Higher pressure shunt  Larger shunt  More stable in the OR
 Rocky course in the PICU

39

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.

40

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)

41

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?

42

With parallel circulation, pulmonary and systemic blood flow is determined by the

ratio of Pulmonary vascular resistance (PVR) to Systemic vascular resistance (SVR).

43

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.

44

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.

45

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.

46

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.

47

(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

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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.

49

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

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Pulmonary Vascular Resistance (PVR)
Increase

↓ FiO2  ↑ CO2  ↓ pH  PEEP

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Pulmonary Vascular Resistance (PVR) decrease

 ↑ FiO2  ↓ CO2  ↑ pH
 iNO (inhaled nitric oxide)

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Systemic Vascular Resistance (SVR) increase

 ↑ Ph  ↑ FiO2  Vasoconstrictors

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Systemic Vascular Resistance (SVR) decrease

 ↑ CO2*  Vasodilators

54

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

55

Bidirectional Glenn (BDG) and Hemi-Fontan Procedures (HFP) - Stage II
 Preformed at around

6 months

56

Cyanosis increasing between stages I and II

would shorten the duration of time between surgeries

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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

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Hemi-Fontan Procedure
(Bi-directional Cavopulmonary Anastomosis) CHARACTERISTICS

 Anastamosis PA/Right atrial appendage  SVC is patched

59

Completion Fontan
(Stage III)
 Two choices:

 Intracardiac Baffle  Extracardiac Conduit

60

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)

61

In a Fontan circulation blood goes:

LV → aorta → organs

62

That CVP propels blood

capillaries → veins → RA → lungs

63

If PVR is high, the Fontan

cannot be performed.
 A small amount of resistance will exist across the lungs. (pressure drop)

64

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

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SUCCESS OF NORWOOD

75%.

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The overall success following the hemi-Fontan procedure (stage II)

approaches 95%.

67

Success after completing the Fontan procedure (stage III)

90%.

68

Among low-risk patients who undergo staged reconstruction or transplantation,

actuarial survival at 5 years is approximately 70%.

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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

70

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%

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To much shunt flow ? BLOOD GASES

 PaCO2: 36  pH: 7.23  PaO2: 49  SaO2: 88%  BE: -7.8

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To little shunt flow ? ABG

 PaCO2: 48  pH: 7.19  PaO2: 23  SaO2: 58%  BE: -11.8

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CPB Considerations

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?)

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 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

75

PUMP RUN

Pump Run: On → cool: 20 min → XC/CP/arrest → warm: on 23 min → off CPB →MUF 10 min
 *(OnDHCA:letvenousexsanguinationoccurbeforeclampingthe venous line )
OR
On → cool: 20 min → Arrest/XC/CP → warm: on 23 min → off CPB→MUF 10 min

76

 Typical times: FOR PUMP RUN

 CPB time = 43” XC time= 48 Arrest time= 45

77

What considerations do you need to make when you circulatory arrest first, then give CP down the aortic cannula?

?

78

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

79

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

80

Arterial and Venous Cannulation Fontan

 Arterial: Neo-aorta  Venous: Single atrial  Hypothermia: Mild  Cardioplegia: With or without cardioplegia

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CPB Notes

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)

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And what if your patient can’t come off CPB?

ECMO NOMO Pediatric VAD

83

Pediatric VADS

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.

84

BELIN HEART DRIVEN BY

is a pneumatically driven, pulsatile para-corporeal device that can offer either LVAD, RVAD or (BIVAD) support.

85

 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.

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The LVAD drains blood from the

LV via a cannula inserted into the apex and returns it to the aorta

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The RVAD drains from the

RA and returns blood to the PA

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Notes on Pediatric VADS

 Berlin Heart has a limited center usage  VADS can be time consuming to the staff (perfusion
may have to be in-house or bedside)
 Other VADS are used with a BSA > 0.7
 Most Peds centers have ECMO staffs that already are made to staff 24/7