Patent Ductus AteriosisPDA

Muhammad Syed MD

Heart

Low vascular resistance of the placenta

High vascular resistance of the fluid-filled fetal lung

Right-to-left shunts

Two right-to-left shunts occur in the fetus• Foramen ovale — Blood shunted from the right

to left atrium • Ductus arteriosus — Blood shunted from the

pulmonary artery to the aorta

Ductus Arteriosus

ForamenOvale

Two right-to-left shunts occur in the fetus

• Foramen ovale — Blood shunted from the right to left atrium

• Ductus arteriosus — Blood shunted from the pulmonary artery to the aorta

TRANSITION AT DELIVERY 

• Alveolar fluid clearance

• Lung expansion

• Circulatory changes

Circulatory changes

• clamping of the umbilical cord, • rise in neonatal systemic blood pressure. • lung expansion reduces both pulmonary vascular

resistance and the pulmonary artery pressure.

• increased pulmonary arterial blood flow • raises pulmonary venous return to the left atrium and left

atrial pressure. • As the left atrial pressure increases and the right atrial

pressure falls, right-to-left shunting across the foramen ovale decreases.

Patent Foramen Ovale

If the flap forms incompletely or does not completely seal close, then deoxygenated blood can pass from the right atrium to the left atrium. A patient with an open or patent foramen ovale will have a heart murmur. Unfortunately, this heart murmur maybe undetectable and the patient will exhibit no other obvious symptoms.

If the ductus arteriosus remains open after birth and fails to close it is referred to as a patent ductus arteriosus.

Patent Ductus Arteriosus

• PDA occurs commonly in premature infants, especially in those with respiratory distress syndrome

• Among very low birth weight (VLBW) infants (birth weight below 1500 g) PDA occurred in 30 percent

Because of the large volume of blood flow, the ductus becomes a large vessel with a diameter similar to that of the descending aorta

Patency of the ductus

Mainly on Low arterial oxygen content

Also is influenced by dilators,

• prostaglandins

• nitric oxide

HYDROCORTISONE

Facilitates ductal constriction

Hydrocortisone treatment decreases the

sensitivity of the ductus to the dilating action

of PGE2

CLOSURE

Constrictors (Increased O2)

PGE2, a vasodilator

Anatomic closure usually is complete within one to three months.

Gestational age

In term infants, functional closure after birth

24 hours 50 %48 hours in 90 %72 hours in virtually all

In preterm infants, ductal closure can bedelayed and the ductus can reopen followingconstriction.

Delayed closureOccurs especially when accompanying respiratory disease is present.

Severe respiratory distress syndrome; in ill infants less than 30 Wgestation, PDA persists on the fourth day in approximately 65 %

Two other factors may be important:

• Contractile capacity in ductal tissue is less in immature

• Ductus in preterm infants continues to dilate in response to PGE2 and NO, in contrast to term infants whose ductus loses responsiveness shortly after birth

Reopening

•  The histological changes following constriction of the ductus occur rapidly in term infants and prevent subsequent reopening.

• Reopening may occur because the effects of ductal constriction on events that lead to anatomic closure are influenced by immaturity.

• In one study, for example, constriction resulted in hypoxia, cell death, VEGF expression, endothelial proliferation, and intimal mound formation in the ductus of term but not preterm baboons

Shunting of blood flow through a PDA in prematures is essentially all left-to-right

Excessive flow through the pulmonary circulation

Pulmonary edema 

Pulmonary hemorrhage 

Bronchopulmonary dysplasia 

Systemic and cerebral blood flow effects 

Preterm animals and infants with a PDA

increase their cardiac output. However,

postductal blood flow is reduced, which may

lead to organ dysfunction.

NEC

IVH

CLINICAL FEATURES 

• Machinery Murmur ( infraclavicular region and upper left sternal border)

• Prominent left ventricular impulse

• Bounding pulses,

• and widened pulse pressure (greater than 25 mmHg)

• "silent," especially in the first three days

(deterioration of respiratory status )

Diagnosis

• ECHO

• A transductal diameter that exceeds 1.5 mm is the most commonly used definition of a significant PDA

PDA closure indications

• Significant left-to-right shunt + symptomatic

• Evidence of left-sided volume overload (ie,

left atrial or ventricular enlargement),• reversible pulmonary arterial hypertension

• PDA closure is not recommended in patients with severe and irreversible PAH

Small PDA  Recommend closure of a small audible PDAeven in the absence of a significant L-to-Rright shunt

Silent PDA Never have hemodynamic consequencesRisk Of endocarditis

Infants with a persistent PDA had a four-fold increased risk of death compared to infants who never had a significant PDA

Management

• Supportive therapy — During evaluation and treatment, supportive measures are applied.

• A neutral thermal environment and adequate oxygenation minimize demands on left ventricular output.

• Positive end-expiratory pressure (PEEP) may improve gas exchange in infants with respiratory compromise.

• Maintaining the hematocrit at 35 to 40 percent may increase pulmonary vascular resistance and reduce the left-to-right shunt

• Not recommend routine use of furosemide or any other loop diuretic, which stimulates renal synthesis of PGE2.

THERAPEUTIC INTERVENTIONS

Interventions for PDA closure include:

• Pharmacologic therapy, which is used exclusively in premature infants

• Surgical ligation

• Percutaneous catheter occlusion

 

Pharmacologic therapy

Inhibitors of prostaglandin synthesis, such

as indomethacin and ibuprofen, are used as

the initial interventions for PDA closure in

preterm infants.

Indomethacin has proven to be ineffective in

term infants and older patients with a PDA.

Thank you