Single Ventricles

What is a functional single ventricle?

A group of severe CHD that cannot maintain biventricular circulation, and there is only one type of surgery that works.

Why are these defects considered single ventricles?

Because of hypoplastic ventricles and lack of cardiac output.

Please list the 6 examples of functional single ventricle defects.

1. Hypoplastic left heart syndrome

2. Pulmonary atresia with an intact septum

3. Unbalanced AV septal defect

4. Mitral valve atresia

5. Tricuspid atresia

6. Double inlet ventricle

What should be analyzed when looking at AV connection?

The mode of AV connection.

Please list the 5 modes of AV connection.

• Two perforate valves

• Common AV valve

• One imperforate and one perforate valve

• AV valve straddling

• AV valve overriding

What happens to the atria in double inlet ventricle?

Both atria are connected to a dominant ventricle.

What can the inflow valve be in double inlet ventricle?

The inflow valve can be a common valve or two atrioventricular valves.

What is true about the inflow valves?

The inflow valves are in close proximity to each other.

What second chamber is usually present?

A second rudimentary chamber with no inflow communication.

How does blood flow move in double inlet ventricle?

Blood flow moves through an inlet VSD to the dominant ventricle.

What should be determined using morphologic features?

Whether the functional dominant chamber is a left ventricle or right ventricle.

Why may ventricle type be hard to identify?

We may not be able to identify the ventricle type.

What may be absent in double inlet ventricle?

There may not be a rudimentary ventricle.

What is the rudimentary ventricle actually described as?

The bulboventricular foramen, and it may shrink over time.

What does an inlet VSD lead to?

Straddling and overriding valves.

How is double inlet ventricle defined?

Double inlet ventricle is defined by >50% commitment of both AV valves to one dominant ventricle.

What does the asterisk indicate in the diagram?

The rudimentary chamber.

What term is used if there is <50% commitment of one AV valve to the contralateral ventricle?

VSD with overriding AV valve.

What great artery relationship do DILVs almost always have?

DILVs almost always have transposed great arteries.

How many DILVs have normally related great arteries?

Only 30–35% have normally related great arteries.

What is normally related great arteries in DILV called?

Holmes heart.

How common is double inlet ventricle among CHD?

It occurs in 1% of all CHD.

Are most cases sporadic or inherited?

Most cases are sporadic.

What factors are suspected in double inlet ventricle?

Abnormal chromosomal patterns or genetic factors are suspected.

What does family history of single-ventricle defects do to recurrence risk?

It increases recurrence risk to roughly 5% to 8% in the future.

What embryology issue causes DILV?

DILV stems from a lack in the widening and shifting of the embryonic atrioventricular (AV) canal.

Instead of aligning properly between the primitive left and right ventricles, where does the AV canal align?

It aligns strictly over the left ventricle.

What does this AV canal alignment problem misalign?

The IVS.

What does IVS misalignment cause?

Abnormal valve alignment.

Where do the developing mitral and tricuspid valves anchor?

Into the single morphological left ventricle.

What is the trabeculated right ventricle described as?

A small, rudimentary outlet chamber.

What happens because ventricular development and looping are disrupted?

The outflow tracts typically undergo transposition of the great arteries.

What does mixing of oxygen-rich and oxygen-poor blood cause in DILV?

It causes either severe cyanosis or pulmonary over-circulation, depending on the presence of outflow obstruction.

Please list the 7 single ventricle anomalies included due to “Y-type circulation.”

• Double inlet left ventricle

• Double inlet right ventricle

• Tricuspid atresia

• Hypoplastic left heart syndrome

• Straddling mitral or tricuspid valves

• Common AV canal defect (unbalanced)

• Heterotaxy syndromes

What great artery relationship do the majority of DILV cases have?

The majority of DILV cases have transposed great arteries.

In DILV with transposed great arteries, where does the aorta arise from?

The rudimentary right ventricle.

In DILV with transposed great arteries, where does the pulmonary artery arise from?

The main left ventricle.

What happens without pulmonary stenosis when PVR drops?

Excessive blood rushes to the lungs.

What does excessive pulmonary blood flow trigger?

Congestive heart failure, tachypnea, and failure to thrive.

What happens with pulmonary stenosis?

If outflow stenosis to the lungs is present, pulmonary blood flow becomes restricted.

What does restricted pulmonary blood flow cause?

Profound cyanosis.

Why is recognizing single ventricle physiology important?

It improves management of these CHD.

What is key in managing single ventricle physiology?

Protection of pulmonary vasculature, surveillance and treatment of outflow tract obstruction, and minimizing volume and pressure overload to the functional ventricle.

What does an infant with restricted pulmonary blood flow present with?

Cyanosis and a harsh systolic ejection murmur over the precordium.

Please list the 4 clinical signs/symptoms listed with restricted pulmonary blood flow.

• Tachypnea

• Dyspnea

• Paleness

• Poor pulses

Please list the 3 reasons this restricted-flow presentation happens.

• Restricted pulmonary blood flow from ductus arteriosus constriction

• May need PGE1 therapy

• Severe aortic obstruction, such as restrictive VSD or aortic arch obstruction

When do patients without obstruction present?

A few weeks later.

Patients without obstruction can present with what 4 findings?

• Congestive heart failure

• Pulmonary over-circulation

• Tachypnea

• Mild oxygen desaturation

Patients without obstruction present like what other defect?

Like a patient with a large VSD.

What does the ECG vary depending on?

The CHD.

Please list the 4 murmurs/sounds listed for DILV.

• Harsh systolic murmur

• Second heart sound

• Pulmonary flow murmur

• Gallop

Please list the 5 chest X-ray findings.

• Cardiomegaly (no pulmonary stenosis)

• Increased pulmonary vascularity

• Normal heart size

• Decreased pulmonary vasculature

• Narrow mediastinum

What approach should be used for echo interrogation?

Segmental approach.

Please list the 6 parts of the segmental approach.

• Atrial segments

• Atrioventricular connection

• Ventricular segments

• Ventricular arterial connection

• Arterial segments

• Venous connections

What is the best view for definition in DILV?

Subcostal 4C.

In subcostal 4C, please list the 9 things to define or evaluate.

• Visceral situs, atrial situs, and cardiac apex position

• Ventricular morphology

• Dominant and rudimentary ventricle

• Relationship of the great arteries

• Position and commitment of the AV valves

• Presence of an ASD/PFO

• IVC connection to the right atrium

• Pulmonary venous return

• Abdominal aorta flow

In heterotaxy syndromes, what IVC finding should be checked?

Interrupted IVC.

In subcostal SAX, what should be repeated?

The information obtained from subcostal 4C.

In subcostal SAX, what should be reviewed about the inflow valves?

The inflow valves should be reviewed in SAX to show the type of valve.

In PLAX sweeping to RV inflow, what should be shown?

Both inflows dedicated to the LV.

What valve issues should be noted in PLAX?

Any valve issues.

What should be noted about the great arteries in PLAX?

The great arteries and the ventricle they arise from.

What great artery finding suggests transposition?

Parallel great arteries.

What should be noted about the ventricles in PLAX?

The size of the ventricles.

What should be interrogated in PLAX?

Pulmonary stenosis.

In PSAX great artery level, what relationship should be shown?

In PSAX great artery level, what size discrepancy should be shown?

What arteries should be assessed in PSAX great artery level?

What pulmonary structures should be shown in PSAX great artery level?

The outflow valve relationship en face at 4 o’clock.

Any size discrepancy of the outflow valves, such as stenosis or atresia.

The coronary arteries.

The PA branches.

What should high parasternal be used for?

Presence and size of PDA.

In PSAX ventricular level, what should be shown about the inflow valves?

In PSAX ventricular level, what septal defect should be shown?

In PSAX ventricular level, what size difference should be shown?

What muscles should be shown in PSAX ventricular level?

What function should be shown in PSAX ventricular level?

The connection/commitment and morphology of the inflow valves.

Inlet VSD.

The size difference of the dominant versus rudimentary ventricle.

Papillary muscles.

Ventricular function.

What are apical views the best view to evaluate?

What VSD should be visualized in apical views?

What should be shown about the two inflow valves in apical views?

The crux of the heart.

The inlet VSD.

The commitment of the two inflow valves to the dominant ventricle.

Please list the 4 inflow valve abnormalities to look for in apical views.

• Straddling

• Overriding

• Stenosis

• Atresia

What regurgitation should be checked in apical views?

What should be determined about the ventricles in apical views?

What should be shown about the great arteries in apical views?

What should be evaluated in the outflow valves?

Inflow valve regurgitation.

The morphology, size, and function of the ventricles.

The relationship of the great arteries.

Obstruction to flow.

In SSN, what should be assessed about the aortic arch?

What should be shown about the aortic arch?

What ductal structure should be assessed?

What venous connection should be assessed?

Obstruction or hypoplasia.

Arch sidedness.

Presence of PDA.

Pulmonary venous connection.

Please list the 4 associated defects with double inlet ventricle.

• ASD

• VSD

• Coarctation of the aorta

• Sub and valvular pulmonary stenosis

Please list the 4 differentials for double inlet ventricle.

• Pulmonary atresia with an intact septum

• Tricuspid atresia

• Hypoplastic left heart syndrome

• Unbalanced AV canal defect

Is single ventricle physiology compatible with life without intervention?

No. Single ventricle physiology is not compatible with life without intervention.

How long may palliation of functional ventricles only be effective?

One to four decades of life.

What do most patients eventually require?

Transplantation or mechanical support

What is the main treatment/management procedure?

The modified Fontan procedure.

How many stages are in the modified Fontan procedure?

3 stages.

What is the modified Fontan designed to do?

Have all systemic venous return flow passively into the pulmonary circulation.

What does the palliative procedure change based on?

Whether there is excessive or restricted pulmonary blood flow.

What must be decided first before repair?

Whether there is stenosis or unrestricted flow.

In restricted pulmonary blood flow, what can happen to the PDA?

The PDA can constrict and the baby will be cyanotic.

What can reduce pulmonary blood flow besides PDA constriction?

Reduced flow through the VSD or pulmonary outflow tract with increased Doppler gradient.

What palliative treatment is used for restricted pulmonary blood flow?

A modified Blalock-Taussig (BT) shunt.

What type of shunt is a modified BT shunt?

A systemic-to-PA shunt.

What size conduit is used for the modified BT shunt?

A 3- to 4-mm conduit.

What does the modified BT shunt connect? What does this provide?

The subclavian or innominate artery to the right branch PA.

What does this provide; Unrestricted flow from the heart to the aorta.

What palliative treatment is used for unrestrictive pulmonary blood flow?

Pulmonary artery banding.

When is PA banding performed?

At 4 to 8 weeks of age.

What do pulmonary artery bands decrease?

Downstream PA pressure.

Why is downstream PA pressure decreased?

To prepare for second- and third-stage surgery and restrict pulmonary blood flow.

What can happen if PA bands migrate distally?

They may cause distortion of the branch PAs, typically the right PA.

What can a PA band distort?

The pulmonary valve.

What can pulmonary valve distortion cause?

Varying degrees of pulmonary valve regurgitation.

When is the second stage surgery performed?

At 4–6 months.

What surgery is performed in the second stage?

Bidirectional Glenn.

What does the bidirectional Glenn reduce?

The volume of blood in the heart.

What does the bidirectional Glenn help increase?

O2 saturations.

What is the third stage of surgery?

The Fontan procedure.