HLHS and IHSS (or HCM)

Question 1

What is hypoplastic left heart syndrome (HLHS)?

Answer 1

A rare and complex defect affecting approximately 1 in 4,000 births.
The LV does not develop due to abnormal folding of the heart tube resulting in the area that would become the LV getting pinched, compressed.

Question 2

Describe the physical appearance of the LV in HLHS:

Answer 2

The LV is a mass of myocardium with only a slit resembling a cavity.

Question 3

How does HLHS affect the MV and aortic root?

Answer 3

MV can be abnormal or stenotic.

Aortic root may be narrow and atretic.

Question 4

Name 6 characteristics of HLHS:

Answer 4

1) Hypoplastic LA 2) RVE, RVH 3) Hypoplastic LV may be filled with clot 4) Coronary perfusion is retrograde 5) Large PDA 6) ASD, VSD (probably perimembranous VSD)

Question 5

Describe the flow path for coronary perfusion in patients with HLHS:

Answer 5

Flow is retrograde, coming from the PA to the PDA, to the aortic root, to the coronary arteries.

Question 6

Name 6 medical care options for patients with HLHS:

Answer 6

1) Keep PDA open 2) Correct metabolic acidosis 3) Manipulate PVR 4) Intubation 5) Cardiac medication management 6) O2 supplement

Question 7

Why would it be important to keep the PDA open in patients with HLHS?

Answer 7

The PDA will be needed to get perfusion to the coronary arteries, the brain, and systemically.
Also, if the baby does not have an ASD, they will give it one.

Question 8

What is the most common course of treatment for patients born with HLHS?

Answer 8

The Norwood Procedure

Question 9

Describe stage 1 of the Norwood Procedure:

Answer 9

Stage 1 is palliative and is usually done in the first few days. Surgery involves constructing a “neo-aorta” by dividing the MPA and combining it with the aorta.
A B-T shunt establishes systemic to pulmonary flow by attaching the right subclavian artery to the right pulmonary artery.

Question 10

Describe stage 2 of the Norwood Procedure:

Answer 10

Stage 2, aka: Glenn procedure, is usually performed at 4-6 months of age. MD’s will remove the B-T shunt. They will establish a systemic to venous connection by detaching the SVC from the RA and attaching it to the RPA. This allows the single ventricle to do less work. The IVC is still in place.

Question 11

Describe stage 3 of the Norwood Procedure:

Answer 11

Stage 3, aka: Fontan completion, is usually performed at age 2-3 years. This will provide complete separation of systemic and pulmonary circulation. The IVC will be connected to the RPA via a tunnel through the RA, or via a conduit outside the RA.
A small, temporary fenestration may be made between the tunnel and RA or the conduit and RA to reduce pressure.

Question 12

What is Idiopathic Hypertrophic Subaortic Stenosis, also known as Hypertrophic Cardiomyopathy (HCM)?

Answer 12

A disease of the myocardium in which the myocardium is abnormally thickened (>4cm) without any obvious cause. It is the leading cause of sudden cardiac death in young athletes.

Question 13

Describe how IHSS (aka: HCM) affects they myocardium at the cellular level:

Answer 13

It is a genetic mutation of the myofibrils. The sarcomeres are abnormally thickened and are not aligned normally. This abnormal alignment is known as myocardial disarray.

Question 14

How does IHSS (aka: HCM) affect the LV shape and size?

Answer 14

The LV will be small, and there will be a change in its shape and contour.
There will also be a degree of LVOT obstruction.

Question 15

How does IHSS (aka: HCM) affect the LV function?

Answer 15

The LVED and LVES volumes will be small, and the EF will be approximately 75%-80%.
There will be cavity obliteration during contraction.

Question 16

How does IHSS (aka: HCM) affect the LV pressures?

Answer 16

There will be an abnormal resting gradient between the LV and Ao.
The LAP and LVEDP will be increased.
The outflow track obstruction will also affect pressures.

Question 17

What is systolic anterior motion of the mitral valve (SAM)?

Answer 17

The movement of the MV during systole anteriorly towards the LVOT.
It is believed the Venturi effect may elevate the MV and that drag forces may move it anteriorly.

Question 18

What is the Venturi effect?

Answer 18

Fluid pressure reduction at areas of stenosis, resulting from the need to increase the flow velocity.

Question 19

Name 4 classifications of Hypertrophic cardiomyopathies:

Answer 19

1) Obstructive or non-obstructive (obstructive refers to LVOT)
2) ASH: asymetrical septal hypertrophy
3) LVH: when patient has systemic HTN and AS and normal myocardium/myofibrils
4) HCM: if abnormal myocardium, decreased LV volume/area, no systemic HTN and no AS.

Question 20

If left untreated, IHSS leads to _______ and ____ _____.

Answer 20

LV systolic and diastolic failure.

Question 21

Can affects of HCM be reversed?

Answer 21

No, it can only be medically managed.

Question 22

Name some treatment or surgical options for IHSS:

Answer 22

1) Ethanol injection to reduce outflow track obstruction.
2) Myotomy/myectomy 3)Pacemaker if needed
4) MV repair 5) TV ring: put in annulus to reduce size of annulus and alleviate TR. 6) Prophylactic antibiotics to reduce risk of SBE.