PATENT DUCTUS ARTERIOSUS- clinical features and pathophysiology

a congenital heart defect caused by problems during the development of heart
PDA or Patent ductus arteriosus is an opening between two major blood vessels leading from the heart( aorta and pulmonary arteries)

1. PATENT DUCTUS ARTERIOSUS Dr PRANOY DEY, PROFESSOR, DEPARTMENT OF PAEDIATRICS, ASSAM MEDICAL COLLEGE AND HOSPITAL

2. INTRODUCTION Patent Ductus arteriosus is a communication between the pulmonary artery and aorta. The aortic attachment of the ductus arteriosus is just distal to the left subclavian artery. The ductus arteriosus closes functionally and anatomically soon after birth; its persistence is called patent ductus arteriosus.

3. INCIDENCE PDA occurs approximately 1 of 2,000 live births, but it is relatively uncommon among the adult population. In infants, it accounts for 10% to 12% of all congenital heart disease. PDA s twice as common in female infants as in male infants. In Rubella syndrome, male female are equally affected.

4. RISK FACTORS Maternal rubella infection Birth at high altitude Premature birth Female sex, and Genetic factors In infants born at <28 weeks of gestation, there is a 60% incidence of PDA.

5. THE FETAL CIRCULATION The presence of the ductus arteriosus in the fetal circulation is essential to allow right to left shunting of nutrient rich, oxygenated blood from the placenta to the fetal systemic circulation, thereby passing the fetal pulmonary circuit. In fetus, the ductus arteriosus is kept open by 1. low arterial oxygen content. 2. placental prostaglandin E2 (PGE2)

6. BIRTH Several changes occur at birth to initiate normal closure of the ductus arteriosus within the first 15 to 18 hrs of life. Spontaneous respirations result in increased blood oxygen content. Prostaglandin levels decrease because of placental ligation and increased metabolism of prostaglandins within the pulmonary circulation by prostaglandin dehydrogenase. Generally, the ductus arteriosus is hemodynamically insignificant within 15hrs and completely closed by 2 to 3 weeks.

7. NATURAL HISTORY Unlike PDA in premature infants, spontaneous closure of a PDA is rare in full term infants and children. This is because the PDA in term infants results from a structural abnormality of the ductal smooth muscle rather than a decreased responsiveness of the ductal smooth muscle to oxygen. CHF or recurrent pneumonia develops if the shunt is large. Pulmonary vascular obstructive disease may develop if a large PDA with pulmonary hypertension is left untreated. Although rare, an aneurysm of PDA may develop and possibly rupture in adult life.

8. HEMODYNAMICS PDA results in a left to right shunt from aorta to the pulmonary artery. Flow occurs both during both systole and diastole as pressure gradient is present throughout the cardiac cycle between the two great arteries (if the pulmonary artery pressure is normal). The flow of blood results in a murmur that starts in systole, after the first sound, and reaches a peak at the second sound. The murmur then diminishes in intensity and is audible during only a part of the diastole - Continuous murmur. Due to PDA, it results in a systolic as well as diastolic overload of pulmonary artery.

9. 5. Increased flow after passing through lungs reaches the left atrium. To accommodate the flow, the left atrium enlarges in size. The increased volume of blood reaching the left atrium enters the left ventricle in diastole, across the normal mitral valve. The passage of this increased flow across the mitral valve results in an and accentuated first sound and mitral delayed diastolic murmur. 6. The large volume of blood in the left ventricle causes prolongation of the left ventricular systole and an increase in the size of left ventricle to accommodate the extra volume. The prolonged left ventricular systole results in delayed closure of the aortic valve and a late A2. With large left to right shunts, the S2 may be paradoxically split.

10. 7. The large left ventricular volume ejected into the aorta results in dilatation of the ascending aorta. A dilated ascending aorta results in aortic ejection click and precedes the start of the CONTINUOUS MURMUR. 8. Aortic ejection systolic murmur in bedside, drowned by the loud continuous murmur and is usually not made out as separate murmur

11. CLINICAL MANIFESTATIONS: 1. HISTORY Patients are usually asymptomatic when the ductus is small. A large shunt PDA may cause a lower respiratory tract infection, atelectesis , and CHF ( accompanied by tachypnea and poor weight gain, poor feeding). Exertional dyspnea may be present in children with a large shunt PDA. May become symptomatic in early life and develop congestive cardiac failure around 6-10 weeks of age.

12. 2.PHYSICAL EXAMINATION Tachycardia and tachypnea may be present in infants with CHF. Bounding peripheral pulses with wide pulse pressure ( with elevated systolic pressure and lower diastolic pressure) are characteristic findings of a large PDA. With a small shunt these findings do not occur. With a large shunt, the precordium is hyperactive. A systolic thrill may be present at the upper left sternal border. The P2 is usually normal, but its intensity may be accentuated if pulmonary hypertension is present .

13. MURMURS - 1.Continuous murmur (machinery) is best audible at the left infraclavicular area or upper left sternal border. 2. Flow Murmurs- (a) Mitral delayed diastolic (b) aortic ejection systolic (drowned) SOUNDS- (a)Accentuated first heart sound (b)Narrowly or paradoxically split second sound (large shunts) Differential cyanosis and clubbing present in shunt reversal if pulmonary vascular obstructive disease develops, a right to left ductal shunt results in cyanosis of only lower half of the body

14. INVESTIGATION

15. Colour and pulsed Doppler. Cardiac catheterisation.

16. ASSESSMENT OF SEVERITY Heart size Third sound and diastolic murmur Pulse pressure

17. COURSE Ejection systolic murmur at birth( due to pulmonary hypertension) ------- continuous murmur after a few weeks. Development of pulmonary arterial hypertension ------- diastolic component lost -----------ejection systolic murmur Severe PAH ----- Right to left shunt ------- disappearance of the murmur and appearance of differential cyanosis.

18. COMPLICATIONS Cardiac failure Infective endocarditis Eisenmenger Rare complications- Aneurysmal dilatation of the pulmonary artery or the ductus Calcification of the ductus Non infective thrombosis of the ductus with embolization Paradoxical emboli

19. DIFFERENTIAL DIAGNOSIS Aortico -pulmonary defect. Ruptured sinus of valsalva aneurysm. Coronary arterio- venous fistulas Aberrant left coronary with massive collaterals from the right Truncus arteriosus VSD with aortic insufficiency Peripheral pulmonic stenosis Venous hum in TAPVC

20. TREATMENT Indomethacin or ibuprofen is effective before the age of two weeks in preterm and unlikely in term newborns. Dose of indomethacin----0.2 mg/kg/dose orally every 12-24 hrs for three doses. (second and third doses are 0.1 mg/kg/dose for <48 hrs and 0.25mg/ kg/dose for>7days) Newborns not responding may require surgical ligation. Catheter based treatment (occlusive devices or coils) is used In term infants PDA may close spontaneously as late as 1 month after birth.

21. THANK YOU.