Aortic Coarctation

Question 1

What is “true” coarctation of the aorta?

Answer 1

A distinct, shelf-like thickening or infolding of the aortic media into the lumen of the aorta. It is distinct from hypoplasia of the aortic isthmus.

Question 2

What is aortic hypoplasia?

Answer 2

Defined as a narrowed diameter of an aortic segment with a normal aortic media. This is distinct from true aortic coarctation which involves a thickened or folded aortic media.

Question 3

What is an atretic aortic arch?

Answer 3

Refers to two patent ends with an interposed ligamentous strand.

Question 4

What is almost always associated with an atretic aortic arch?

Answer 4

VSD (and the patent ductus arteriosus provides blood flow to the distal aorta.

Question 5

What is the life expectancy of someone with uncorrected coarctation of the aorta?

Answer 5

30 years

Question 6

What is the male to female ratio of aortic coarctation?

Answer 6

males:females = 3:2

Question 7

What is aortic coarctation syndrome?

Answer 7

Coarctation plus hypoplasia of the aortic isthmus and intracardiac defects.

Question 8

What is the definition of aortic isthmus hypoplasia?

Answer 8

When the isthmus is less than 40% of the diameter of the ascending aorta.

Question 9

What is the definition of proximal transverse aortic arch hypoplasia?

Answer 9

When the diameter is 60% of the ascending aorta.

Question 10

What is the definition of hypoplasia of the distal transverse aortic arch?

Answer 10

When the diameter is 50% of the ascending aorta.

Question 11

What are the two historical classifications of aortic coarctation?

Answer 11

Adult (post-ductal) which was actually a discrete juxtaductal narrowing, and Infantile (preductal) which involved a more diffuse narrowing of an aortic segment in addition to the juxtaductal narrowing.

Question 12

What is the modern classification system of aortic coarctation?

Answer 12

It involves three categories:

1) isolated coarctation
2) coarctation with VSD
3) coarctation with complex intracardiac anomaly

Question 13

What are the cardiovascular anomalies COMMONLY associated with coarctation of the aorta?

Answer 13

VSD
Bicuspid Ao valve
Various mitral anomalies
PDA
Ao hypoplasia

Question 14

What is Shone’s syndrome?

Answer 14

It is the combination of 1) Ao Coarctation, 2) supravalvular mitral stenosis, 3) parachute mitral valve, 4) sub-aortic stenosis

Question 15

What is the association of low pulmonary blood flow cardiac lesions/syndromes with coarctation of the aorta?

Answer 15

They are rarely associated with coarctation of the aorta.

Question 16

What life-threatening extra-cardiac, extra-aortic anomaly is associated with aortic coarctation?

Answer 16

Intracranial aneurysms

Question 17

Name three chromosomal abnormalities in which aortic coarctation is relatively common.

Answer 17

Trisomy 13
Trisomy 18
Turner’s

Question 18

What is one theory that explains why aortic coarctation occurs so close to the ductus arteriosus?

Answer 18

Some investigators suggest that ductal tissue spreads into the aorta and subsequently causes constriction after birth. Normally, ductal tissue invades up to 1/3 of the aorta’s circumference, but in local coarctation sometimes completely encircles the aortic lumen.

Question 19

What is thought to be the cause of aortic coarctation in Turner’s syndrome?

Answer 19

Lymphatic obstruction resulting in distended thoracic ducts that compress the ascending aorta, alter intracardiac blood flow, and cause neck webbing.

Question 20

In Turner’s syndrome, what common external physical finding is associated with coarctation of the aorta?

Answer 20

Neck webbing. Turner’s patients with neck webbing are eight times more likely to have coarctation of the aorta than those without neck webbing. NOTE: other syndromes with webbed necks such as Noonan’s and fetal hydantoin do not demonstrate this association.

Question 21

What are common physical exam findings in an infant < 3 months old with aortic coarctation?

Answer 21

Ejection murmur along the left sternal border and in the left subscapular area.
Prominent precordial impulse often with systolic thrill.
Hepatomegaly and gallop rhythm if CHF is present.
Commonly femoral pulses are diminished.

Question 22

Describe the pressures measured in the lower extremities as compared to the upper extremities in patients with aortic coarctation.

Answer 22

Classically, there is a large gradient between the two measurements in which the upper extremities have a markedly higher blood pressure than the lower; however, in the setting of a PDA the pressures in the lower extremities may be equal to or even higher than those in the upper.

Question 23

What anatomic and physiologic findings can explain the absence of a systolic pressure gradient in patient with CoA?

Answer 23

1) The RV may provide flow to the lower body via a PDA
2) LV function may be so poor that systemic hypotension makes it impossible to detect a gradient
3) Rarely, the right subclavian artery has an aberrant origin distal to the coarctation.

Question 24

If a patient with CoA lacks a systemic gradient between upper and lower extremities, how might pulse oximetry reveal the reason why?

Answer 24

If the patient has a PDA and relies on the RV for systemic blood flow, there may be a differential cyanosis with lower SpO2 recorded from the toe than the preductal hand.

Question 25

Describe the classic murmur heard in a patient with CoA.

Answer 25

Systolic, at least III/VI, best heard in the LUSB, crescendo-decrescendo, apical diastolic rumble

Question 26

What is the common ECG finding in an infant with CoA?

Answer 26

RVH

Question 27

What is the most common ECG finding in older children with CoA?

Answer 27

LVH

Question 28

What causes the rib notching seen on CXR in patient with CoA?

Answer 28

tortuous collaterals which correlate directly with age and inversely with the diameter of the coarctation.

Question 29

When did PGE1 become available clinically?

Answer 29

late 1970s

Question 30

How long does it take to get maximal response to PGE1 administration to a neonate?

Answer 30

15 minutes to 4 hours after the start of the infusion.

Question 31

What age of neonate can benefit from PGE1 administration in the setting of CoA?

Answer 31

14 days and younger (assuming the ductus has not already closed)

Question 32

What is associated with a dose of PGE1 in excess of 0.05 mcg/kg/min?

Answer 32

An increased risk of NEC.

Question 33

What dose of PGE1 is associated with increased risk for NEC?

Answer 33

> = 0.05 mcg/kg/min

Question 34

What are side effects and complications of PGE1 administration to neonates?

Answer 34

Cutaneous vasodilation
hypotension
cardiac dysrhythmias/conduction abnormalities
jitteriness/seizure activity
fever
respiratory depression
increased infection
diarrhea
metabolic derangements
rarely, coagulopathy

Question 35

How should mechanical ventilation be approached in a patient with CoA and VSD?

Answer 35

These patients often have Qp > Qs and in order to restore that closer to a 1:1 ratio, permissive hypoxemia to SaO2 85% and permissive hypercarbia to pCO2 40 - 50 mmHg should be standard goals.

Question 36

Does CoA repair require an a-line?

Answer 36

Yes, in the right radial artery to monitor BP response to aortic cross-clamp. (Unless the patient has an anomalous RSCA origin distal to the coarctation in which case one may cannulate the temporal artery or the surgeon can transduce in the proximal aorta with a needle or one may simply forgo proximal pressure monitoring).

Question 37

What is the utility of a post-ductal arterial line in CoA repair?

Answer 37

It can be used to evaluate the adequacy of the repair

Question 38

What is the operative mortalitiy for CoA repair?

Answer 38

2 - 3% in patient older than 1 year

7% in infants

Question 39

What is the mortality of CoA repair in neonates?

Answer 39

2% in isolated CoA

17% in those with complex intracardiac lesions

Question 40

What are the four common operative procedures for repair of CoA?

Answer 40

1) resection of the stenosis with end-to-end aortic anastomosis
2) patch augmentation
3) subclavian flap aortoplasty
4) extended resection with primary anastomosis

Question 41

What is the surgical approach commonly used for simple end-to-end anastomosis repair of CoA in the neonate?

Answer 41

left thoracotomy

Question 42

When is extended end-to-end anastomosis for CoA repair in the neonate indicated?

Answer 42

When there is some degree of hypoplasia of the aortic arch as well as extensive ductal tissue in the periductal aorta. This approach may decrease the incidence of recurrent coarctation although tension on this anastomosis can lead to restenosis itself.

Question 43

What is the surgical approach to an extended end-to-end anastomosis for CoA repair in the neonate?

Answer 43

Usually left thoracotomy but can be performed via a median sternotomy on CPB with associated defects are repaired at the same setting.

Question 44

What is the unique benefit of patch aortoplasty for CoA repair in the neonate?

Answer 44

It can be performed without ligating the PDA and thus, may be of benefit to patients in which there is relative hypoplasia of the LV because the RV can help support the systemic circulation via a R–>L shunt across the PDA maintained with PGE1. Once the shunt reverses to L–>R (indicating improvement in LV function) PGE1 can be shut off.

Question 45

What is the association of aortic cross-clamp time and spinal cord ischemic injury?

Answer 45

There is no association.

Question 46

What mean arterial pressure distal to the cross-clamp of the aorta is considered minimally adequate to prevent spinal cord ischemia?

Answer 46

50 mmHg

Question 47

What complications may follow CoA repair?

Answer 47

Hemorrhage
Anastomotic stenosis
Recurrent laryngeal nerve injury
thoracic duct injury
Paraplegia
Arm ischemia if subclavian flap aortoplasty performed

Question 48

What age group is at greatest risk for pulmonary compromise in the event of unilateral recurrent laryngeal nerve injury and why?

Answer 48

Neonates and infants because the compliant chest wall retracts during partially obstructed inspiration and poor lung expansion may result.

Question 49

What is the physiology behind post-CoA-repair hypertension?

Answer 49

Surgical stimulation of sympathetic nerve fibers located between the media and adventitia of the aortic isthmus resulting in marked elevations of NE and also of renin release by JG cells in the first 12 hours after surgery. These responses can be avoided by infiltration of the aortic wall with lidocaine.

Question 50

What is postcoarctectomy syndrome?

Answer 50

Severe abdominal pain accompanied by HTN, fever, abdominal tenderness, vomiting, ileus, melena, and leukocytosis all occurring 2 - 3 days after surgery. It is rare in neonates.

Question 51

What is thought to be the physiology behind postcoarctectomy syndrome?

Answer 51

The sudden increase in BP to vessels below the CoA results in necrotizing arteritis of the small arteries of the mesentery and small intestine. Alternatively, the increased renin levels postop might cause “steal” and shunt blood away from mesenteric vessels.