Heart pearls!

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.