1. Patent Ductus Arteriosus
Dr. K. Vanderdonck
Cardiothoracic Surgery
Charlotte Maxeke Johannesburg Academic Hospital
& UNIVERSITY OF THE WITWATERSRAND
Hannes Meyer Registrar Symposium 3-5 June 2011

2. Classification of Congenital Cardiac Lesions
Anomalies
Charateristics
Acyanotic
LR Shunt
= ↑ PBF
Triad:
FFT
Chest infections
CCF
PDA
ASD
VSD
A-V Canal
2. Obstructive
Often asymptomatic
Coarctation
Aortic stenosis
Pulmonary stenosis
Cyanotic
3. Decreased PBF
Cyanosis
Child well,
asymptomatic
Tetralogy
Pulmonary atresia
Tricusp atresia a,b
TGV + PS
4. Increased PBF
FTT
Truncus
TAPVC
Tricuspid atresia c
TGV
Failure to thrive (FFT); congestive cardiac failure (CCF); pulmonary blood flow (PBF)

3. Pathophysiology of LR shunts
Clinical importance of pulmonary vascular resistance:
Neonatal pulmonary artery pressure (PAP) greater than that of adults
Reaches adult levels by 2-3 months of age
If PAP remains elevated in presence of a shunt, development of pulmonary vascular obstructive disease (PVOD)

4. Patent Ductus Arteriosus Definition
Also called ductus of Botalli
Normal vascular structure in foetal life
Extracardiac lesion
Directly connects pulmonary and systemic arterial systems
Persistence of ductus after 3 months in postnatal period abnormal

5. Patent Ductus Arteriosus Definition
4 distinct clinical forms:
Isolated PDA in otherwise healthy child
Isolated PDA in premature baby
Associated with more significant cardiac defects
As a life sustaining structure in cyanotic or left-sided obstructive lesions (ductal-dependent)

6. Patent Ductus Arteriosus Historical Background
Ductus arteriosus & its postnatal closure described by Galen in 131 AD
Physiologic importance of ductus arteriosus elucidated by Harvey in 1628
1938 Robert Gross at Boston Children’s Hospital = first successful ligation
1967 Portsmann used polyvinyl alcohol plug placed with catheter to close PDA
Indomethacin introduced by Heymann in 1976
1991 Laborde performed first VATS closure PDA

7. Patent Ductus Arteriosus Embryology
Derived from distal aspect of the embryological left 6th arch
By 6th week of gestation, ductus arteriosus carries between 55 and 60% of the combined ventricular output

8. Patent Ductus Arteriosus Embryology
Diverts blood away from high resistance pulmonary circulation to descending aorta and low pressure umbilical placental circulation where gas exchange occurs
Ductal flow directly from PA into descending aorta  ductus equal in width to descending aorta and appears as direct extension of PA into descending aorta

9. Patent Ductus Arteriosus Foetal Physiology
Maintenance of foetal ductal patency:
High levels of circulating and locally produced prostaglandins (PGE 2 & PGE 1)
As foetus matures, ductal smooth muscle becomes more sensitive to vasoconstricting effect of pO2, but low pO2 maintains duct patency
pH + other factors play role
RV & LV function in parallel + Share systemic and placental circulations

10. Patent Ductus Arteriosus Histology
The wall of the ductus differs from the surrounding vascular structures:
Media deficient in elastic fibres
Composed primarily of poorly organized smooth muscle cells in a spiral configuration
Intima thick with increased number of mucoid-filled structures
Smooth muscle sensitive to environmental factors (vasodilating effect of prostaglandins and vasoconstricting effect of pO2)

11. Patent Ductus Arteriosus Postnatal Events
At birth, rapid circulatory changes
RV & LV function in series
Lung ventilation  PVR drops and pulmonary blood flow increases
Due to increased pulmonary venous return, LA pressure rises and PFO closes
PDA closes:
Initially functional and reversible
Later anatomical and irreversible = ligamentum

12. Patent Ductus Arteriosus Postnatal Ductal Closure
Postnatal closure occurs in 2 stages:
Functional or reversible closure: contraction of medial smooth muscle Occurs within hours after birth in full term neonates
Anatomic or irreversible closure: Connective tissue formation with fibrosis  produces ligamentum arteriosus Completed by 2-3 weeks

13. Patent Ductus Arteriosus Mechanisms of Ductal Closure
Contraction of smooth muscle cells due to:
Increased pO2 following lung ventilation
Decreased PG levels:
Removal placenta = source of circulating PG
Blood flow to lungs removed PG from circulation
Contraction of smooth muscle greatest at pulmonary end, extends to aortic end
Closure may be incomplete at aortic end (ductal ampulla or ductal bump)

14. Patent Ductus Arteriosus Premature Babies
In preterm babies
Overall incidence 30%
Histologically normal ductus but immature
Less sensitive to vasoconstricting effects of pO2,
More sensitive to vasodilating effects of PG
Less likely to respond to postnatal conditions of closure
Trial of Indocid
Early surgery if Indocid fails

15. Patent Ductus Arteriosus Term Infants
In term infants:
Histology different from normal ductus:
Media contains elastic lamina similar to aortic wall
Smooth muscle organized in fine helocoid spiral fashion
Intima thick with a complete internal elastic lamina
Variable mucoid deposits, lie mostly in media
Is considered a congenital malformation

16. Patent Ductus Arteriosus Anatomy
PDA = extension of MPA
Curves under the aortic arch
Joins descending aorta at acute angle a few mm beyond origin of LSCA
Recurrent laryngeal nerve curves around PDA
Anatomic variations

17. Patent Ductus Arteriosus Diagnosis
History
Physical Examination
CXR: Heart
Lungs
ECG
Echocardiography (ECHO) + colour Doppler
Often diagnostic of the anatomy
Many operations done on ECHO data only
Chest Xray (CXR); Electrocardiogram (ECG); Echocardiography (ECHO)

18. Patent Ductus Arteriosus Diagnosis
Cardiac catheterization and angiography
To assess PAP + PVR and response to oxygen on pulmonary vasculature
To assess operability
PVR > 8 Wood units in 100% O2 constitutes a contra-indication to surgery ( x 80 to convert to dynes-sec/cm-5 )
Interventional cardiology
MRI

19. Patent Ductus Arteriosus Echocardiography

20. Patent Ductus Arteriosus Angiography

21. Patent Ductus Arteriosus Pathophysiology
Dependant on 2 factors:
Size of shunt
Difference between SVR and PVR
At birth, PVR elevated  little flow regardless of size
As PVR drops, LtRt shunt increases dependent of size of PDA
Persistent foetal circulation

22. Patent Ductus Arteriosus Physiological Classification
Physiological Classification: depends
On the size of the PDA
On the degree of pulmonary hypertension and the pulmonary vascular resistance
Important in terms of surgical indication
Classified as small, moderate or large

23. Patent Ductus Arteriosus Physiological Classification
Small PDA
Qp:Qs < 1.5:1
Normal PA pressure / normal PVR
Asymptomatic in childhood
Life long risk of infective endocarditis
SBE on PDA − PV − AoV − mycotic aneurysm of descending aorta
Surgery on infected PDA risky
Interventional cardiolgy / transcatheter closure

24. Patent Ductus Arteriosus Physiological Classification
Moderate size PDA:
Moderate pulmonary hypertension
Do not develop Eisenmenger syndrome
Mild symptoms: some growth retardation, fatigue on effort
May be asymtomatic
Presence of loud murmur with diastolic spillover + thrill

25. Patent Ductus Arteriosus Physiological Classification
Large PDA
Direct large communication between MPA and Aorta
PA pressure equal to systemic
Qp:Qs increased to a degree dependent on PVR
Can develop Eisenmenger syndrome
CCF – FTT – Chest infections
Systolic murmur

26. Patent Ductus Arteriosus Physiological Classification
Eisenmenger syndrome:
Severe pulmonary vascular obstructive disease which is irreversible
Presence of suprasystemic PA pressures and PVR with shunt reversal (Rt  Lt shunt)
Increasing cyanosis
Death

27. Patent Ductus Arteriosus Incidence
5-10% of all congenital cardiac defects
M/F ratio = 1 : 2
1 in term live births
Incidence higher in preterm babies = 20-30%
Spontaneous closure
Common in premature babies
Rare in term infants

28. Patent Ductus Arteriosus Incidence
Duct not closing postnatally = pathological
From partial closure to wide open
Factors:
Hypoxia
High altitude
Respiratory distress syndrome
Maternal rubella in 1st trimestre
Low gestational age
Associated cardiac malformations

29. Patent Ductus Arteriosus Complications
Death in infancy high due to CCF for large PDA
Death in early, middle adulthood
CCF in moderate size PDA
PVOD + Eisenmenger in large PDA
SBE = complication of small PDA
Respiratory tract infections

30. Patent Ductus Arteriosus Complications
Ductal aneurysms
Dilatation of the PDA or remaining ductal tissue
Spontaneous or postoperative
Spontaneous = true aneurysms
Postoperative after PDA ligation
Often false aneurysm
Can be true aneurysm

31. Patent Ductus Arteriosus Complications
Ductal aneurysms
Spontaneous infantile ductal aneurysm
Present at birth or shortly thereafter
Often regress spontaneously
Second type develops in childhood or adulthood
Due to patency at aortic end
Greater tendency for progressive dilatation and rupture

32. Patent Ductus Arteriosus Treatment
Medical therapy:
Depending on symptoms:
Antifailure treatment
Inotropes
Ventilation
Antibiotics
Pharmacological treatment: Indocid
Surgery or intervention: presence of a duct is an indication for closure, except if pulmonary vascular obstructive disease

33. Patent Ductus Arteriosus Treatment
Premature babies:
Presence of large PDA associated with organ hypoperfusion + do not tolerate LV overload well
Trial of Indomethacin = inhibitor of prostaglandin synthetase
0.1 – 0.2 mg / kg hourly x 3 doses
Associated with hepatic, renal, platelet dysfunction
Inefficient in term babies

34. Patent Ductus Arteriosus Surgical Technique
General anesthetic + ventilation
Invasive monitoring
Risk of hypothermia
Patient on right side
Left postero-lateral thoracotomy in 4th intercostal space
Latissimus dorsi incision

35. Patent Ductus Arteriosus Surgical Technique
Mediastinal pleura opened along descending aorta, to origin of LSCA
Superior intercostal vein
Care taken to avoid vagus nerve
Recurrent laryngeal nerve defines PDA, but don’t go looking for it

36. Patent Ductus Arteriosus Surgical Technique
PDA dissected with blunt angled instrument until completely free

37. Patent Ductus Arteriosus Surgical Technique
Dissect under aorta on both sides PDA

38. Patent Ductus Arteriosus Surgical Technique
Substraction Technique
When large PDA + PHT

39. Patent Ductus Arteriosus Surgical Technique
PDA ligation

40. Patent Ductus Arteriosus Surgical Technique
PDA division

41. Patent Ductus Arteriosus Surgical Technique
Mediastinal pleura is closed: if bleeding, closure will tamponade bleeding and allow exploration
One single pleural drain for 24 hours
In small infants: intercostal muscles approximated with a continuous suture
In older children: 1 or 2 pericostal sutures placed
Patient usually extubated postop

42. Patent Ductus Arteriosus Surgical Technique
In premature baby
Sick: communication with anaesthetist essential
Hand-bagging
Need to release the lung to allow ventilation
Proper dissection essential
Clip
Single ligation

43. Patent Ductus Arteriosus Surgical Technique
PDA with severe reversible PHT
PDA with single pulmonary artery
Need cardiac cath and evaluation PVR
Presence PFO
Partial ligation PDA
Restudy later + Interventional closure PDA

44. Patent Ductus Arteriosus Surgical Technique
Surgery in adult ductus:
More difficult – surgical risk higher than in children
Duct may be calcified
Consider median sternotomy and CPB

45. Patent Ductus Arteriosus Postoperative Complications
Accidental ligation LPA or aorta in small babies – importance of proper dissection
Recanalisation of ductus: rare even with ligation if properly done
Left vocal cord paralysis – phrenic nerve paralysis uncommon
Chylothorax: rare
Bleeding
Aneurysm of PDA

46. Patent Ductus Arteriosus Postoperative Complications

47. Patent Ductus Arteriosus Other Therapeutic Modalities
Interventional cardiology
VATS

48. Patent Ductus Arteriosus Transcatheter Closure

49. Patent Ductus Arteriosus Transcatheter Closure

50. Patent Ductus Arteriosus Transcatheter Closure