Definition

  • Ductus patent after 3 months of birth in a term baby.

Incidence

  • 10% of all congenital heart disease.
  • Twice more common in females
  • More in
    • Preterm
    • Low birth weight
    • High altitude
    • Rubella syndrome

Embryology

  • From left sixth aortic arch
  • Starts functioning in sixth week
  • Connects proximal left pulmonary artery artery to aorta just distal to left subclavian artery
  • Right aortic arch- right sided ductus also may be present
  • Length in neonate is 1 cm
  • Width in fetus is same as that of descending aorta. In neonate, half.
  • Persistent ductus in neonate which is as wide as descending aorta- window ductus.
  • Closure starts at pulmonary end- conical shape with ampulla.
  • Mechanisms of closure-
    • Increased oxygen
    • Decreased prostaglandin
  • Types of closure-
    • Functional-
      • Starts at 12 hours and completes at 24 hours
      • Sometimes delayed upto 3 months
    • Anatomical-
      • Migration of smooth muscle to intima followed by necrosis of intima followed by fibrosis.

Hemodynamics

  • Size of shunt (based on Qp/Qs)
    • Small- less than 1.5
    • Moderate- 1.5 to 2.5
    • Large- more than 2.5
  • Consequence of shunt
    • Small- nil
    • Moderate-
      • Increased pulmonary blood flow
      • Volume overload of LA & LV- leads to LV failure
    • Large-
      • Increased pulmonary blood flow
      • Volume overload of LA & LV- leads to LV failure
      • Systemic pressure transmitted to pulmonary artery and hence RV
  • PVOD (pulmonary vascular obstructive disease)
    • Occurs in moderate and large shunts, especially in the latter
    • Shunt may or may not be reversed
  • Heart failure
    • Occurs in moderate and large shunts, especially in the latter
  • Preterm
    • Develop heart failure with even small shunts due to
      • Less sympathetic innervation of myocardium
      • Low calcium
      • Increased fetal Hb
      • Subendocardial ischemia due to low oxygen content
    • PDA can cause ARDS

Clinical features

  • Small PDA
    • Asymptomatic
    • Continuous murmur in children
    • Systolic murmur in infants
    • Murmur may not be audible (Doppler PDA)
  • Moderate and large PDA
    • HF after first week of life
    • Most infants survive HF
    • Increased respiratory infections
    • PVOD
    • Continuous murmur before going into PVOD when it becomes systolic
  • Before PVOD-
    • High volume pulse with wide pulse pressure
    • Hyperdynamic LV apex
    • Systolic or continuous thrill
    • S2 drowned in murmur (actually paradoxically split due to increased LVET and early pulmonary closure due to pressure of shunted blood)
    • LV S3
    • Eddie sounds are heard within the continuous murmur
      • Mechanism is collision of shunted ductal blood with RV outflow into PA
    • Continuous murmur
      • Left infraclavicular area, upper left sterna border, upper axilla, upper left side of the back
      • Crescendo decrescendo murmur peaking at S2
      • High pitched
      • Harsh or rasping
      • Increased in supine posture
      • Increased with inspiration due to fall in PVR
      • Diastolic part is longer in small PDA than in moderate or large PDA
      • Synonyms- Gibson’s murmur, machinery murmur, train in tunnel murmur, cartwheel murmur, humming top murmur, churning murmur, mill wheel murmur.
    • MDM at apex
  • After PVOD-
    • Differential cyanosis and clubbing, sometimes left upper limb also involved
    • RV apex
    • S2- normal split with loud P2
    • PES
    • Systolic murmur
    • No LV S3 or apical MDM
    • PR, TR
  • Preterm
    • Systolic murmur
    • HF
      • In first week of life itself
      • HF presents as bradycardia, apnoea and hypercarbia. Liver enlarges after some weeks.

ECG

  • Before PVOD-
    • LAE
    • LVH with volume overload pattern
  • After PVOD-
    • RAE
    • RVH
    • Right axis deviation

Chest X-ray

  • Before PVOD-
    • MPA dilation- earliest sign- called cap of Zinn
    • Increased pulmonary vascularity, sometimes more on right
    • LAE
    • LV type cardiomegaly
    • Prominent aortic knuckle
    • Ductal hump between aortic knuckle and MPA- especially seen in infants
  • After PVOD-
    • Prominent MPA with peripheral pruning
    • Ductal calcification in elderly

Echocardiography

  • Systolic and diastolic gradients
  • PDA size
  • PR and TR pressures
  • LA and LV dimensions, especially LA to aorta ratio
  • Qp/Qs by continuity equation

Cath study

  • Oxygen step up of 5% from RV to PA
  • Angiographic appearance of ductus- 5 groups (A to E)

Complications

  • HF
  • Respiratory infections
  • PVOD
  • Infective endarteritis
    • In adolescents and adults
    • Vegetations at pulmonary end of ductus
  • Ductal aneurysm
    • In infants and children
    • At aortic end
    • May rupture
    • Falcon and Perloff classification
      • Patent at both ends
      • Closed at pulmonary end
      • Post-operative
      • Spontaneous rupture

PDA with other congenital heart diseases

  • PDA is desirable- ductus dependent
    • Totally dependent- pulmonary atresia with intact ventricular septum, mitral atresia, aortic atresia, interrupted aortic arch
    • Partially dependent- tricuspid atresia, pulmonary atresia with VSD, TOF with PS, TGA with PS
  • PDA is undesirable-
    • ASD, VSD, AVCD

Management

  • Preterm
    • Medical closure
  • Any audible PDA needs closure. Small PDA is closed for fear of developing infective endarteritis.
  • Catheter closure can be done for PDA of less than 6 mm diameter.
  • Surgery is ligation and division.