Patent Ductus Arteriousus and A/P Septal Defect

3. Ductal Closure
8 weeks - 88% closed
If delayed - prolonged patency
If failed - persistent patency

4. PDA as coexistent anomaly
Ductus delivers 55% of combined output to descending aorta - angle of insertion acute
Duct dependant circulation - angle of insertion obtuse (R) sided arch - Left sided PDA more common
PDA from aortic diverticulum / aberrant subclavian artery (L) vascular ring formed

5. Aneurysms of the Ductus (Rare)
2 Types

6. Clinical Features
Essentially consequence of (L) to (R) shunting
Magnitude of shunt
Size of PDA
PVR
Presentation - shunt magnitude

7. Operation - Persistent patency

Vessel Orientation

8. PDA in premature infants

9. Aortopulmonary Septal Defect
AP Window

10. Associations : (30-50% have associated abnormality)

12. Operative intervention
Routine CPB (snare RPA and LPA)
Patch closure of defect
Correction of associated defects

Origin of the right or left pulmonary artery from the ascending aorta

13. Morphologic Considerations

14. Clinical Features and Diagnostic Criteria

15. Natural History and Operative Results
Anomaly rare
Lethal without operation
When an isolated lesion, can be low-risk procedure

PERSISTENT PDA
-this term applied if fails to close by 3 months of age (88% are closed by 8 weeks)
-1/2000 infants
-twice as common in females as in males
-other factors: high altitudes, hypoxia, RDS, maternal rubella(affects the development of elastic and fibrous tissue), inheritance, low gestational age, associated cardiac malformations
-Premature infant
-approximately 30% overall > 30 weeks; 28-30 weeks ~ 80%
-ductus not as sensitive to O2 and more sensitive to prostaglandins which are increased in prematurity
-often these patients have RDS

ANATOMY
-as stated, it is an extension of the main PA joining the aorta a few millimeters from the origin of the subclavian artery—segment of aorta between subclavian artery and ductal junction is termed the isthmus
-recurrent laryngeal nerve separates from the vagus lateral to the ductus, curves caudally underneath, and then courses medially and superiorly toward the tracheo-esophageal groove
-variations possible from the pulmonary or arterial end

-Tetrology of Fallot: usually absent ductus—may originate from a varied arterial site and enter the pulmonary circulation via branch pulmonary arteries
-aneurysms are rare
infantile—spontaneous regression-usually resolve without therapy; usually involve the central portion; pulmonary end closed with marked narrowing of the aortic end
childhood—aortic end patent; potential for rupture and death

PRESENTATION
-based on the size of the shunt
small ductus may be discovered incidentally
moderate size ductus will present with heart failure/pulmonary infection
-physical findings-related to LV volume overload and increased pulmonary blood flow
hyperactive precordium with an increased LV impulse
upper left sternal border thrill
bounding peripheral pulses
hepatomegaly / JVD
“machinery” murmur
-EKG—LV hypertrophy
-CXR—cardiac enlargement, increased pulmonary vascular markings
-Echocardiography—method of choice for evaluation
-Cardiac catheterization—usually reserved for patients suspected of having increased PVR (If PVR equals SVR, flow across the ductus may be minimal and color flow echocardiography may not describe it well) or if findings suggest pulmonary hypertension. In most patients there will be normal right heart pressures and a step up in oxygen saturation at the pulmonary artery level.
-MRI—If echo inconclusive may employ this modality (patient usually large)

NATURAL HISTORY
-spontaneous closure is rare in term infants, but common in premature infants
-SBE occurs primarily in children with a small PDA; it used to be responsible for 50% of the deaths in the pre-antibiotic era—now, deaths are rare due to this
-respiratory infections are common
-increased blood flow can lead to pulmonary endothelial injury—pulmonary HTN results; Eisenmenger’s syndrome can result in as short as 12 months
-CHF accounts for 30% of deaths in children with an untreated PDA; death from heart failure in patients with a moderate sized ductus and chronic volume overload occur most often in the third and fourth decade of life

TREATMENT
-Initial tx is focused on symptoms:
digoxin
diuretics
vetillatory support—if necessary
inotropes—if necessary
antibiotics if presenting symptom is endocarditis
-Premature infant—indomethacin 0.1-0.2 mg/kg Q8H for 3 doses; may be repeated one or two more times. Contraindicated in the presence of renal dysfunction, hyperbilirubinemia, and bleeding disorders. In addition, the presence of severe CHF, sepsis, inadequate tissue perfusion, or organ failure is a strong relative contraindication to indomethacin.

SURGERY
-a PDA in and of itself is an indication for closure—a term infant > 3 months old should be electively closed; if symptomatic, control symptoms with medication and then close
-a small ductus in a premature infant can be followed; if CHF develops, the ductus should be closed promptly
-surgical risk is <1%--those at higher risk are generally older with chronic heart and/or lung disease, or an older fragile PDA. Should not be closed in those with severe pulmonary hypertension and cyanosis due to reversal of flow.
-technique
Left posterolateral thorocotomy
3rd/4th intercostal space
identify vagus, phrenic, LPA, LSA
expose the ductus (vagus and recurrent laryngeal lie just medial to the pleura)
Hemoclip (premature infants) or ligatation (older infants)
Older infants are ligated/divided to prevent the risk of recanalization
-open method—usually reserved for adults with calcified/friable ducts.
Patch or direct closure of the duct using CPB
-thorocoscopic closure
-transarterial catheter closure
Rashkin PDA occluder/Lock clamshell device/gianturco coils
Best results if <3mm; up to 10mm acceptable
-complications:
left vocal cord paralysis
phrenic nerve injury
Horner’s syndrome
Chylothorax

Recanalization—may be as high as 23% in single ligature/hemoclip techniques
False aneurysm formation

AORTOPULMONARY SEPTAL DEFECT
-AP window is a defect of conotruncal development in which there is incomplete separation of the aorta and pulmonary arteries—there is a direct communication (“window”) between the two great vessels.
-rare ~ 0.2% of CHD
-L to R shunt>>increased pulmonary blood flow>>LV volume overload and failure; most defects are large and allow equalization of pressures between the aorta and PA
-presentation is much like a PDA and depends on size of the defect, the PVR, and other associated malformations. Cyanosis is frequently absent unless severe pulmonary disease has developed; failure to thrive and frequent respiratory infections are common.
-diagnostic study of choice is echo; cardiac cath also helpful to evaluate associated abnormalities
-systolic murmur on examination

Type I defects are simple, nearly circular between the proximal ascending aorta and the main pulmonary artery; they begin in/near the sinus of Valsalva and end before the origin of the RPA; Right or Left coronary arteries (more often the Right) may be associated with the proximal rim of the defect.
Type II defects are helicoid in shape and extend in a more cephalad direction; frequently extend to the origin of the RPA
Type III defects often have no discernible posterior rim and can extend to involve the RPA and the posterior wall of the ascending aorta; RPA may seem to arise from the aorta

Associated defects
-isolated lesion
-PDA, ASD, right aortic arch-10% of patients
-Interruption of the aortic arch (Type A), hypoplastic arch, coarctation--30-50% of patients.
Aortic arch obstruction impedes systemic blood flow and promotes shunting to the pulmonary system, causing further hemodynamic embarrassment; usually aortic interruption is associated with a more complicated type of AP septal defects involving the RPA, and the size of the aorta may decrease abruptly above the defect

Management
-medical stabilization
diuretics and digoxin
transfusion and antibiotics as necessary
prostaglandins if a coincident aortic arch obstruction exists avoid oxygen
-closure undertaken at the time of diagnosis because of the risk of developing pulmonary vascular disease—patients with a large APW will not survive infancy uncorrected
-surgical technique

median sternotomy and cardiopulmonary bypass
control of pulmonary arteries necesssary
defect is exposed through an aortotomy(Type II/III) or ?transpulmonary(Type I) approach
closed with a patch which avoids the coronary ostia
-usually a routine post op course, in some cases sudden, severe pulmonary hypertension may occur—increased PA pressures, hypoxia, hypotension. Tx with high dose O2/possibly ECMO
-mortality 10%--outcome generally depends on the PVR at the time of repair