Aortic Regurgitation, Pediatric

Basics

Description

Incompetence of the aortic valve causes leakage of blood into the LV during diastole. �

Epidemiology

Incidence

Aortic regurgitation occurs in ~5% of non-Asians and up to 50% of Asians with ventricular septal defect (VSD). The latter group has VSDs in the subpulmonary position.
Aortic incompetence is also associated with various forms of LV outflow abnormalities and numerous other entities. Aortic insufficiency also may be the result of rheumatic fever.

Risk Factors

Genetics
Isolated congenital aortic regurgitation is a rare congenital malformation. �

Pathophysiology

A regurgitant jet of 20% of the aortic valve orifice area can double LV output and work.
In severe cases, the diastolic regurgitant fraction can be as much as 60% of the LV stroke volume.
The increase in LV end-diastolic volume and compensatory reflex peripheral vasodilation results in an increase in total stroke volume.
With the exhaustion of compensatory mechanisms and possible myocardial ischemia, LV failure will ensue.

Etiology

Bicuspid aortic valve (congenital)
Rheumatic
Other forms of congenitally abnormal aortic valve
Aneurysm of the sinus of Valsalva
VSD with prolapsing aortic cusp
Marfan syndrome
Ehlers-Danlos syndrome
Osteogenesis imperfecta
Aortic regurgitation may also occur in association with discrete subaortic stenosis.
Aortic regurgitation may occur as a result of interventions for aortic valve stenosis (catheter or surgical) and other cardiac interventions.

Associated Conditions

VSD
Rheumatic heart disease
Connective tissue disease
Other congenital cardiac defects

Diagnosis

History

Natural history: �

Natural history data are available for adult patients only:
- In patients who are asymptomatic and have normal LV function, the rate of development of symptoms or LV dysfunction averages 4.3%/yr.
- Average mortality rate is <0.2%/yr. Conversely, 25% of the patients who die or develop systolic dysfunction do so before the onset of warning symptoms.
- No recent data regarding natural history of symptomatic patients since onset of symptoms generally accepted as indication for surgery.
- Variables identified as being associated with higher risk for the development of future symptoms, systolic dysfunction, or death include age, LV end-diastolic dimension, and end-systolic dimension.
- On serial longitudinal studies, rate of increase in LV end-systolic dimension and decrease in ejection fraction are reported as independent predictors of outcome.
- Adult criteria are not similarly defined for pediatric patients.
Chronic aortic regurgitation is better tolerated than acute and less likely to have symptoms associated with a given amount of regurgitation. Cardiac awareness may result because of the large stroke volume.
Excessive sweating and heat intolerance due to vasodilation may be an early symptom.
Chest pain may occur with exertion.
Symptoms associated with LV failure include dyspnea, shortness of breath, fatigue.

Physical Exam

Characteristic peripheral signs are produced by a combination of large pulse volume and vasodilation:
- With more severe disease, the systolic pressure increases and the diastolic pressure decreases.
- A sharp increase in the pulse gives it a "water hammer quality."�
Apical impulse may be displaced inferiorly and laterally with an apical diastolic thrust.
Systolic thrill may be palpable over the base.
Heart sounds are usually normal.
The typical murmur of aortic regurgitation is heard in early diastole, characterized as a high-pitched decrescendo beginning with the 2nd heart sound and maximally along the left midsternal borders with radiation to the apex:
- An ejection murmur is often heard at the base due to increased blood flow across the aortic valve.
- With moderate or severe regurgitation, a mid-diastolic rumble (Austin-Flint murmur) may be audible over the mitral area. This is due to the regurgitant jet impeding opening of the mitral valve anterior leaflet.

Tests

EKG: �

Normal in mild aortic regurgitation and at times in severe disease
Severe cases display increased QRS voltage in the left precordial leads with tall and upright T waves
An ST and T wave strain pattern may ensue
Left bundle branch block
Large Q waves in left precordial leads
In selected patients, exercise and radionuclide studies may be useful.

Imaging

CXR:
- LV enlargement in an inferior and leftward direction
- Aortic root is dilated.
- Pulmonary venous congestion may be seen in association with LV failure.
- Echo 2-dimensional imaging is useful in assessing potential etiology of aortic regurgitation, including:
  - Acquired AI
  - VSD with aortic cusp prolapse
  - Bicuspid aortic valve
  - Subaortic stenosis
  - Dilation of the aortic root and mitral valve prolapse in Marfan syndrome.
Doppler imaging:
- Assesses the presence and severity of aortic regurgitation
- Holodiastolic reversal of flow can be seen in the descending aorta in patients with moderate or severe regurgitation.
- Color Doppler flow mapping of the jet using jet width and area is useful.
M-Mode imaging:
- Useful in the evaluation of secondary changes of the LV resulting from aortic regurgitation, such as dilatation, hypertrophy, and diminished function
- Serial evaluation of LV cavity size and function is important for management decisions.

Surgery
Cardiac catheterization: �

No longer indicated for the diagnosis of aortic regurgitation
Occasionally indicated in the management, when questions remain unanswered regarding severity, hemodynamics, LV function, or associated lesions

Differential Diagnosis

Other causes of aortic runoff with basilar diastolic murmurs and wide pulse pressure include: �

Patent ductus arteriosus
Ruptured sinus of Valsalva
Coronary arteriovenous fistula
Aorta-to-LV tunnel and aorticopulmonary window
The diastolic murmur of pulmonary regurgitation in the presence of pulmonary HTN (Graham Steel murmur) is medium-pitched, but may be higher pitched similar to aortic regurgitation in the presence of pulmonary HTN.

Treatment

Medication

Digoxin and diuretic therapy for patients in CHF
Vasodilator therapy:
- Nipride, hydralazine, nifedipine, and ACE inhibitors have been shown to reduce systemic vascular resistance, augment forward stroke volume, and reduce regurgitant volume in adults. Standards for children are not available.
- Criteria for the use of chronic vasodilator therapy in the pediatric patients with mild to moderate aortic insufficiency have not been established. No specific data exist showing long-term benefit in children.
- Data in asymptomatic patients with severe aortic regurgitation and normal LV function indicated no beneficial effect from nifedipine or enalapril in reduction or delay of surgery, reduction of regurgitant volume, decrease in size of LV, or improvement of LV function.

Additional Treatment

General Measures

Management depends on the cause, duration, secondary cardiac changes (ventricular dilation and function), and associated symptoms.
Significant symptoms and findings of preoperative LV systolic dysfunction are major indicators of decreased likelihood for optimal postoperative outcome.
Ideal timing of surgery for aortic regurgitation balances the risk of surgery with the possible prevention of LV dysfunction. The age and size of the patient is an important consideration.

Surgery

Aortic valvuloplasty if possible in selected cases.
Pulmonary autograft procedure (Ross operation):
- The patient's pulmonary valve replaces the aortic valve in the LV outflow tract.
- A homograft is used on the right side of the heart.
- Intermediate follow-up shows excellent durability of the pulmonary valve in the aortic position in most patients.
- Growth of the pulmonary valve has been demonstrated in children. There is no need for anticoagulation postoperatively.
- Good results demonstrated in a population of infants and toddlers, some of whom had aortic regurgitation prior to the pulmonary autograft procedure following earlier intervention for congenital LV outflow tract obstruction.
- Procedure of choice in this subset of very young pediatric patients.
Aortic valve replacement with a mechanical prosthesis:
- Bi-leaflet mechanical valves such as St. Jude or Carbomedics are durable with excellent function but will need replacement when used in pediatric patients.
- Anticoagulation is necessary to minimize the risk of thrombosis.
Aortic valve repair:
- In select patients, this is preferable.
Aortic valve replacement with bioprosthesis:
- A significant risk of valve degeneration and calcification over time requiring replacement
- These complications are more common in children and adolescents.
Asymptomatic patients with normal ventricular function:
- Precise timing of surgery in this group of patients may be difficult to determine.
- Patients with LV dysfunction require valve replacement with or without symptoms.
- Surgery may be recommended in asymptomatic patients with LV end diastolic dimension >75 mm or LV systolic dimension >55 mm; specific data are not available for infants and children.
- Patients with significant aortic insufficiency should be followed closely with serial studies.
- Because of inherent variability in testing, no decision should be made on single measurements.
Aortic regurgitation with ventricular septal defect:
- Surgery for aortic regurgitation in association with ventricular septal defect and prolapsing aortic cusp is performed earlier than in most other situations.
- Although controversy exists as to the precise timing, all would agree that regurgitation that progresses to moderately severe as assessed by both Doppler ECG and physical exam warrants surgical repair.
Aortic regurgitation with Marfan syndrome or bicuspid aortic valve:
- Timing of surgery is more likely to be determined by the finding of aortic root dilation.
Aortic regurgitation with discrete subaortic stenosis:
- Timing of surgery for subaortic stenosis varies with age and severity.
- Aggressive approach is to resect a subaortic membrane when Doppler ECG evidence of severe obstruction. Mild aortic regurgitation may be noted after surgery.
- Many patients exist with mild subaortic stenosis in whom there is no progression of LV outflow tract obstruction with conservative management.
- Aortic regurgitation is not a primary indication for surgery since it is rarely severe.

Ongoing Care

Follow-Up Recommendations

Patient Monitoring

Serial ECGs after surgery for aortic insufficiency to assess results and serve as a baseline for late follow-up.
Approximately 80% of the overall reduction in volume occurs within the 1st 10-14 days postoperatively.
The magnitude in reduction correlates with the improvement in function:
- Patients with persistent LV dilation should be treated similar to other patients with ventricular dysfunction, including therapy with ACE inhibitors.
- Repeat clinical evaluation along with echo, if there is significant residual aortic regurgitation, will determine necessity for repeat surgical intervention.

Additional Reading

1Bonow ACC/AHA Task Force Report. J Am Coll Cardiol. 1998;32:1486-1588.2Evangelista �A. Long-term vasodilator therapy in patients with severe aortic regurgitation. N Engl J Med. 2005;353:1342-1349. �[View Abstract]3Hasaniya �N. Outcome of aortic valve repair in children with congenital aortic valve insufficiency. J Thor Cardiovasc Surg. 2004;127(4):970-974. �[View Abstract]4Kanu �C. 2008 Focused Update Incorporated Into the ACC/AHA 2006 Guidelines for the Management of Patients With Valvular Heart Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Management of Patients With Valvular Heart Disease: Endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Circulation. 2008;118:e523-e661.5Scognamiglio �R. Nifedipine in asymptomatic patients with severe aortic regurgitation and normal left ventricular function. N Engl J Med. 1994;331:689-694. �[View Abstract]6Williams �I. Ross procedure in infants and toddlers followed into childhood. Circulation. 2005;112[Suppl I]:I-390-I-395.

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