Chapter 28

 

COARCTATION OF THE AORTA

    Narrowing of the vessel usually located in the initial aspect of the descending aorta, determining an impediment to the normal blood flow of different magnitude, depending upon the severity of the narrowing, its location in relation to the ductus arteriosus and possible associated vascular malformations.

ANATOMY

    The lesion is located beyond the left subdavian artery.
    It may be distal or proximal in relation to ductus arteriosus. In other instances, it may be located in front of such anatomical structure.
    The narrowing results from alteration of the media of the artery which produces an indentation on the external wall of the artery.
    In certain cases, the area of narrowing is more extensive, involving the whole contour of the aorta and extends for one to several centimeters (hypoplasia segmentaria).
    There is a collateral circulation connecting the proximal and distal aspects of the vessel which will be more or less developed depending upon the relation of the coarctation with the ductus arteriosus.

IF THE COAROTATION IS PROXIMAL TO THE DUCTUS, COLLATERAL CIRCULATION WILL DEVELOP POORLY DURING INTRAUTERINE LIFE

    If the coarctation is distal to the ductus, the collateral circulation will be better developed at the time of birth.
    Regardless of the type of coarctation and if the patient survives, the collateral circulation will continue to progressively develop with time.
    The collateral circulation will develop mainly by branches from both subdavian arteries, scapular, internal thoracic and intercostal arteries.
    As a consequence of the blood impediment, left ventricular hypertrophy will develop and aneurysms in the aortic arch and circle of Willis are not infrequent.
    In case of post ductal coarctation the ductus may be closed (65%) or may be patent (35%). In the last case a left to right shunt will be present with right ventricular diastolic overload and different degrees of pulmonary hypertension and right ventricular hypertrophy.
    In case of preductal coarctation the ductus is almost always patent with right ventricular hypertrophy and aortic and left ventricular hypoplasia. Right to left shunt at the level of PDA will occur.
    If the ductus closes with time in this second category of patients the left ventricular overload is much worse than in the post ductal variety.
    Frequent associated cardiovascular malformations are seen such as:

  1. Bicuspid aortic valve (85% of cases of coarctation of aorta)
  2. Aortic insufficiency
  3. PDA
  4. VSD
  5. Sub-aortic stenosis and aortic stenosis
  6. ASD
  7. Endocardiac fibroelastosis
  8. Anomalies of the right or left subdavian arteries
  9. Complete transposition of the great arteries

PHYSIOLOGY

    From the physiopathologic point of view a major classification is necessary.

  1. Preductal coarctation
  2. Postductal coarctation

    The other major aspect to consider is the condition of the ductus arteriosus, which results in a final classification:

  1. With closed ductus arteriosus
    1. Postductal
    2. Preductal with good collateral circulation
  2. With patent ductus arteriosus
    1. With left to right shunt
      • Postductal
      • Preductal (small PDA and good collateral circulation)
    2. With right to left shunt
      • Postductal (with pulmonary hypertension)
      • Preductal (large PDA and poor collateral circulation)

    Depending on the severity of the coarctation and presence of closed or patent ductus the patient will present with:

  1. Arterial hypertension due to renal and mechanical factors with systolic overload of the left ventricle and cerebral circulation.Both the right and left heart. In terminal cases of pulmonary hypertension, the shunt may change to right to left type.
  2. Distal arterial hypotension beyond the area of aortic coarctation with relative blood deficit and visceral and muscular ischemia.
  3. Local blood turbulence at the coarctation level with post stenotic dilatation and easy implantation of SBE.
  4. In case of preductal coarctation pulmonary hypertension with right ventricular hypertrophy will be accompanied by aortic and left ventricular hypoplasia.

CLINICAL PICTURE

    The diagnosis of coarctation can be made in the majority of patients only by pressure determination and careful physical examination.

Dyspnea
Angina pectoris
Congestive Heart Failure 		    Due to left ventricular systolic overload
Headache
Cerebral hemorrhage
Hypertensive encephalopathy 		    Due to cerebral circulation systolic overload
Aortic dissection
SBE
Aortic aneurysm 		    Mechanical consequences of the abnormal hemodynamic conditions
Dyspnea
SBE
Cyanosis
Right ventricular failuire		    If large PDA is present and pulmonary hypertension develops

    In the postductal variety, the newborn usually has a good collateral circulation at birth.
    The evolution is much more benign than in the preductal type.
    If the ductus remains open, the patient will develop a left to right shunt. If this shunt is large they will evolve toward pulmonary hypertension and eventually Eisenmenger Syndrome, which may further complicate the basic problems secondary to the coarctation.
    If the ductus is closed the picture and clinical symptoms will only depend on the severity of the stenosis and the degree of development of the collateral circulation.
    In the preductal variety, the newborn usually has a very poor collateral circulation at birth, and blood will continue to circulate from pulmonary artery to aorta through a PDA.
    Pulmonary hypertension is almost the rule with right ventricular hypertrophy in these cases.
    Preductal coarctation is probably one of the most common causes of heart failure in newborns and most of these patients will die in the first few months of life.

PHYSICAL EXAMINATION

  1. Arterial hypertension localized in both arms (This is a sign which may be absent in infancy and may appear in the early teens).
  2. Lower systolic and diastolic blood pressure in both legs than in arms.
  3. Pulsus parvus in the femoral arteries.
  4. Intercostal arteries pulsations.
  5. Cyanosis in the inferior limbs and inferior part of the body of patients with PDA and right to left shunt.
  6. Physical signs of LVH due to hypertension.
  7. Systolic murmur in the interscapular area, radiated downward and toward the frontal chest wall. If the stenosis is only moderate, a continuous murmur can be heard.
  8. Superficial murmurs in the collateral circulation are also frequently present.
  9. Systolic ejection murmurs due to aortic bicuspid valve (in 50% of these patients).
  10. If pulmonary hypertension develops, the proper physical findings of the entity will appear.

ELECTROCARDIOGRAM

  1. Postductal coarctation with closed ductus:
      Normal EKG or LVH (systolic overload pattern).
  2. Postductal coarctation with PDA:
      Biventricular hypertrophy. Possible signs of marked RV
      systolic overload in case of pulmonary hypertension.
  3. Preductal coarctation with PDA:
      LVH if the ductus is very small (systolic overload pattern).
      Biventricular hypertrophy if large PDA and progressive
      changes of pulmonary hypertension develops with late
      marked right ventricular systolic overload.

ROENTGENOGRAM

    LVH since early infancy. Many times the LVH diminishes with age due to a larger collateral circulation.
    Small ascending aorta.
    The frequent malformations at the left subdavian artery may alter the left superior contour of the aortic arch.
    Rib notching (Rossler sign) due to the collateral circulation. (More often in 3rd to 8th rib) are seen more often after 4 yrs. of age.

CARDIAC CATHETERIZATION AND ANGIOGRAPHY

    Right and left catheterization is to be done for evaluation of pulmonary pressure and to exclude associated malformations.
    Aortogram is essential for localization and evaluation of extension of the coarctation as pre and post stenotic dilatations.

TREATMENT

    Prophylaxis of bacterial endocarditis.
    Treatment of CHF.
    Surgery is indicated optionally, when the patient is 15 or older and the aorta is fully developed.
    If CHF supervenes in early infancy and no proper control is obtainable with medical treatment, surgery must be considered regardless of the patient's age as an emergency.
    The surgical treatment consists of resection of coarctation with end to end anastomosis in 90% of patients. If extensive hypoplasia is present and end to end anastomosis is not possible, and a Dacron tubular prosthesis should be used. If the patient's aorta presents many degenerative lesions and resection is hazardous, a prosthetic bypass, leaving the coarctation in place, is the option.


Coarctation of aorta at level of patent ductus arteriosus.


Coarctation of Aorta in a 19 year-old black patient showing a small ascending aorta and typical rib notching (Rossler sign)


Aortic Coarctation, adult type. There is also a question of mild stenosis at the origin of the left internal carotid artery.