Rush Center for Congenital
and Structural Heart Disease

Definition

 

Narrowing of the aortic arch, typically at the around the origin of the left subclavian artery and PDA.  This narrowing will cause the blood pressure in the left ventricle and ascending aorta to be elevated.  Prolonged or severe coarctation leads to left ventricular hypertrophy, dilation and eventually failure.

 

Incidence

 

4th most common congenital heart disease, although in one series it was the 7th most common congenital heart disease and its repair is the 5th most common surgery in congenital heart disease. Coarctation is present in 9% of all congenital heart diseases, and it is the predominant feature in 0.2-0.6/1,000 live births.

 

 

 

 

Embryology

 

The following table shows aortic arch arteries origin of some of the major systemic arterial vessels.

The first pair of aortic arches is formed by the curving of the ventral aorta to meet the dorsal aorta, these will eventually contribute to the external carotid arteries.

The second pair of aortic arch arteries appear in week four. These regress rapidly and only portion is left which forms the stapedial and hyoid arteries.

The third pair of the aortic arch arteries appear around the end of the fourth week. these will give rise to the common carotid arteries and proximal portion of the internal carotid arteries. The distal portion of the internal carotid arteries are formed by the cranial portions of the dorsal aorta.

 

Aortic Arches Arterial Vessels 
I external carotid arteries
II regress rapidly and only portion is left which forms the stapedial and hyoid arteries
III common carotid arteries and proximal portion of the internal carotid arteries
IV On the left side, it persists, connecting the ventral aorta to the dorsal aorta,
forming the aortic arch. On the right it forms the proximal portion of the right subclavian artery.
V are rudimentary and do not develop into any known vessels, this pair of aortic arch arteries are not seen in many embryo specimens
VI The proximal portions develop into the right and left pulmonary arteries, while the distal portion of the left aortic arch artery develop into the ductus arteriosus
 
The fourth aortic arch arteries develop soon after the third arch arteries. Their development differ on the left from that on the right. On the left side, it persists, connecting the ventral aorta to the dorsal aorta, forming the aortic arch. On the right it forms the proximal portion of the right subclavian artery.

The fifth pair of aortic arch arteries are rudimentary and do not develop into any known vessels, this pair of aortic arch arteries are not seen in many embryo specimens.

The sixth aortic arch arteries develop in the middle of the fifth week. The proximal portions develop into the right and left pulmonary arteries, while the distal portion of the left aortic arch artery develop into the ductus arteriosus.

 

Pathology

 

Embryology: One theory suggests decreased blood flow in the aorta leading to coarctation, another theory proposes that coarctation is the result of a lasso ring of ductal tissue surrounding the aortic arch, consequently restricting after birth leading to coarctation of the aorta. Or coarctation of the LPA in patients with pulmonary atresia or critical pulmonary stenosis with in-utero left-to-right shunting at the PDA due to ductal tissue which may lasso the LPA leading to LPA stenosis after birth.  

Coarctation of the aorta could be associated with multiple stenotic lesions of the left heart as seen in Shones syndrome.

Narrowing could be proximal or distal to the PDA. As the narrowing becomes significant more and more collaterals develop. The amount of collaterals may be so large that it will decrease any pressure gradient across the coarctation and lower extremity blood pressures will be close to the upper extremity blood pressures. Pressure gradient across the coarctation may be more than the difference between the upper and lower extremity blood pressure due to collateral vessels bypassing the area of coarctation.

 

 

Pathophysiology

 

 

 

 

Clinical Manifestations

 

The incidence in males is higher than in females.

Usually asymptomatic except in severe coarctation in the newborn, these children present with congestive heart failure and metabolic acidosis. Incidental findings usually uncover coarctation, for example, hypertension of upper extremities, decreased femoral pulsations, murmur heard over the precordium and back (left of interscapular space). The murmur is systolic but due to the fact that systolic flow at the site of coarctation is slightly after systole ends, i.e., closure of the aortic and pulmonary valves. The murmur appears to spill over into diastole because systole and diastole is marked by a valve closure.

Blood pressure in lower extremities equal or just below that in the upper extremities may indicate coarctation since systolic pressure in femoral arteries is approximately 20 mm Hg higher than that of arm blood pressure.

Associated lesions should be sought for example bicuspid aortic valve and this should be suspected when there is a systolic click or mitral stenosis which may present with diastolic rumble murmur or aortic stenosis.

 
 

 

ECG

 

In the neonatal period , the ECG may reflect RVH rather than LVH.  This is because the right ventricle in-utero is the dominant ventricle, and through the PDA pumps blood to the descending aorta.  Therefore, coarctation of the aorta may cause an increase in the afterload of the RV as it will cause narrowing of the aortic arch-descending aorta junction.

This ECG, shows rsR' pattern in the right chest leads indicating RVH.  In addition there are deep S waves in the left chest leads.

 

Later in infancy, the expected LVH pattern (tall R waves in left chest leads & deep S waves in right chest leads) become evident:

 

CXR

 

Cardiomegaly, with evidence of LVH and rib notching could be seen.  Indented aorta is occasionally noted.

 

 

Echocardiography

 

Echocardiography shows the narrowing of the aortic arch by 2-D as well as the pressure gradient by Doppler flow velocity. In a neonate an aortic arch measuring less than 4 mm will cause a pressure gradient. In measuring the pressure gradient across the aortic arch the Doppler flow velocity prior to the point of coarctation should be taken into consideration and when calculating the pressure gradient otherwise the pressure difference would be exaggerated. Normally, flow in the descending aorta has a rapid upstroke in systole and brief retrograde flow in early diastole while in coarctation the systolic upstroke is reduced with continuous forward flow in diastole.
 
 
 
 

 

Cardiac Catheterization

 

Cardiac catheterization is performed in coarctation of the aorta not only for diagnosis, but also for therapeutic purposes.
Angiography demonstrates the cardiac anatomy and extent of stenosis of the aortic arch.  Balloon dilation, with or without stenting may be attempted in native coarctation as well as recoarctation.  In the latter it tends to be safer as the scarring surrounding the aortic arch from previous surgery or balloon dilation lessens the chance of aortic rupture.
 

 

 

Treatment

 

Surgical repair is the standard of care in native coarctation of the aorta with end-to-end anastomosis with or without use of subclavian artery flap. Patients with small pressure gradients across the coarctation are at high risk to develop spinal cord injury due to ischemia resulting from aortic cross-clamping because they do not have well developed collaterals.

Post coarcectomy hypertension is seen which affects both upper and lower extremities. This may be caused by:

Small arterial bed in the postcoarctation systemic arterial circulation

High rennin levels

Abnormal baro receptors

Abnormal catecholamine production

Balloon angioplasty for a native coarctation is done at some centers, however, long-term results are not clear.  Older children and adults with coarctation of the aorta respond well to balloon dilation with stent placement to prevent re-coractation.

Untreated adults tend to die early with increased incidents of arteriosclerotic changes and cerebral vascular accidents.

Recoarctation post-operatively occurs regardless of the procedure performed. However, it tends to occur earlier in patients with early repair.

Balloon dilatation of recoarctation of the aorta either due to surgical repair or due to initial balloon dilatation of native coarctation appears to be helpful. If there is only a mild pressure gradient across the coarctation, however, there is hypertension particularly with exercise then anti hypertensive medication should be used.

The balloon size chosen should be 2-1/2 to 3 times the narrowest diameter of the coarctation, or the diameter of the aorta just before or after the coarctation.

Discrete coarctation post-operatively appears to respond to balloon dilatation much better than long segment narrowing of the aortic arch post-operatively.

 
 
Angiogram of coarctation of aorta.

Angiogram of balloon (stent) dilation of coarctation of aorta.

Angiogram, post-balloon dilation and stent placement of coarctation of aorta.

 

   

 

   
Neonatal Coarctation of the Aorta with Intact Ventricular Septum

 

These babies present in acute congestive heart failure and appear very ill. This is due to left ventricular failure. The left ventricle is burdened in normal heart by labor and delivery (assuming systemic ventricle status), this will be aggravated by coarctation leading to high left atrial pressure and high pulmonary vascular resistance leading into right ventricular failure as well.

Prostaglandin improves condition because of opening of patent ductus arteriosus or the ampulla at the aortic end and will improve perfusion to the lower extremities and reduce the pressure overload on the left ventricle.

Electrocardiography shows right ventricular hypertrophy in the first six months and after that left ventricular hypertrophy. Typically left ventricular hypertrophy is not seen in the first six months of life.

Echocardiography shows the lesion and its extent. It is important to rule out other lesions such as ventricular septal defect, bicuspid aortic valve, aortic stenosis, mitral valve abnormalities, patent ductus arteriosus or atrial septal defect. These lesions could be associated with coarctation of the aorta.

Cardiac catheterization is done only when anatomy is complex. Balloon dilatation may be performed if there is added risk to surgery.

Surgery is the treatment of choice and the earlier it is done the better. Rate of recurrence is 9-24%.

In surgery the left subclavian artery is frequently sacrificed. In fact, complications from such a procedure is rare. Recoarctation is treated with balloon valvuloplasty. 9% of simple coarctations tend to recoarctation, 12% of coarctations with VSD develop recoarctation and 24% of patients with interrupted aortic arch develop recoarctation.

 

 

Coarctation of the Aorta with Ventricular Septal Defect

40% of babies with coarctation have ventricular septal defects.

Almost all present in the neonatal period. Because of ventricular septal defect an increased left-to-right shunting results in congestive heart failure.

Chest x-ray shows signs of congestive heart failure and increased pulmonary blood flow.

The ventricular septal defect could be anywhere and no specific type is more common with coarctation of the aorta.

Treatment is surgical by repairing the coarctation and either main pulmonary artery banding, both could be performed from a lateral thoracotomy. Occasionally the ventricular septal defect could also be repaired.

 

 

Coarctation of the Aorta with Mitral Valve Abnormalities

 

Mitral valve abnormalities are seen in 25% of patients with coarctation. 2% of patients have severe abnormalities and 10% of patients also have mitral regurgitation. Incidence of mitral stenosis is higher with ventricular septal defect and coarctation as compared with coarctation alone.

Mitral stenosis may be secondary to parachute mitral valve or hypoplasia of the mitral valve ring or supravalvar ring. Pressure gradient across the mitral valve may be exaggerated by a ventricular septal defect due to left-to-right shunting and increased blood flow across the mitral valve. Therefore, ventricular septal defect closure may; decrease the pressure gradient. Mitral regurgitation even mild may not be tolerated because of the already high pulmonary venous pressure.

 

 

Coarctation of the Aorta with Aortic Stenosis

 

21% of patients with coarctation have a normal aortic valve but only 2% are severe enough requiring surgery. 5% of all critically ill infants with coarctation also have aortic stenosis.

Aortic stenosis could be valvar or subvalvar. Aortic stenosis leads to decreased cardiac output with poor pulses in all extremities masking upper and lower extremity pulse difference.

Treatment may be by repairing coarctation first and balloon valvoplasty of the aortic valve.

Coarctation of the aorta may occur with complex cyanotic congenital heart disease. However, it is not known to occur with tetralogy of Fallot.

 

 

Interrupted Aortic Arch

 

0.019 Per 1,000 live births. 1.3% of all critically ill neonates present in 5% of all patients with aortic obstruction.

Types:

  • Type A is when the interruption is distal to the left subclavian.
  • Type B is when the interruption is between the left subclavian and left carotid artery
  • Type C is when the interruption is between the left and right carotid arteries

Aortic valve deformities are present in 60% of cases. VSD is very common. Anomalous subclavian artery is very common especially with Type B interruption. DiGeorge syndrome is reported in 48% of cases.

Interrupted aortic arch presents like severe coarctations but usually earlier in life.

Treatment:

Surgical end-to-end anastomosis or by using graft.

Abdominal coarctation is seen with unusual site of coarctation, Williamís syndrome, Takayasuís disease and neurofibromatosis.

 

 

Post-Coarcectomy Syndrome

 

Fever and abdominal pain. This is more common in males than females and usually in children less than 5 years of age. It is very rare.

Etiology:

Increased circulating rennin and catecholamines leading to mesenteric arteries spasm.

Symptoms and signs:

Fever, abdominal pain, leukocytosis, melena, abdominal x-ray shows bowel distention.

Treatment:

NPO, IV fluid and hyperalimentation and intra-lipid nutrition. Surgery if no improvement.

 

 

Post-Coarcectomy Hypertension

Hypertension in upper and lower extremities immediately post-operatively. This may last for 1-3 weeks. Dorsalis pedis pulses are palpated well. More common in youngster children.

Etiology:

Combination of poorly developed vasculature distal to coarctation, hyperkinetic heart, hyperreninemia and fluid overload.

Treatment:

Nitroprusside drip, Labetolol drip and then boluses, Hydralazine, Esmolol and chlorthiazide may be used.