Patent ductus arteriosus physical examination
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- Brisk upstroke pulse: Bounding arterial pulses are present due to the continuous runoff of blood from the aorta into the pulmonary artery during diastole.
- Pulmonary to systemic flow ratio <1.5 to 1
- Normal precordial activity
- Murmur may be present. Its nature may be different for neonates and older patient. This is so because of the relative difference in pulmonary and systemic vascular resistance in them.
- In the newborn, the pressure during systole is greater in aorta compared to pulmonary circulation. However, this gradient between aortic and pulmonary circulation is not so prominent in diastole. Due to this the murmur may only be audible during the systole.
- The pulmonary artery pressure falls after the newborn period. Due to this the pressure in aorta is higher than pulmonary artery both in systole and in diastole. This in turn leads to the characteristic continuous, machinery murmur or Gibson's murmur (both during systole and diastole).
- Features of machinery murmur are:
- Pulmonary to systemic flow ratio between 1.5 and 2.2 to 1
- As a result of the runoff from the aorta, there are bounding pulses, and the pulse pressure widens.
- A continuous thrill may be present in the first or second left intercostal space.
- Displaced apex (indicating left ventricular overload)
- Continuous murmur (may be grade 2,3 and occasionally 4)
- The features of murmur are very similar to that seen with small ducts, however, they are louder than that associated with small PDA.
- Pulmonary to systemic flow ratio >2.2 to 1
- Dynamic left ventricular impulse
- Left ventricular thrill
- S1 is normal, S2 may be split with an accentuated pulmonary component. The continuous machinery murmurs with similar features as seen in moderate and small sized ducts but with louder intensity (4/6 grade) could be heard.
- An apical diastolic rumble due to increased flow across the mitral valve may be present.
- A third heart sound may be present.
- If there is no reduction in the size of ductus, after age 2, progressive obstructive disease develops in these patients:
- Signs of heart failure develop
- The JVP may be elevated due to RV failure. Prominent "a wave" due to diminished RV compliance and RVH.
- Signs of pulmonary hypertension associated with right-to-left shunt start appearing.
- As the pulmonary hypertension increases, left to right flow across the duct decreases and there is no audible murmur. A murmur of pulmonic insufficiency may be noted (Graham-Steell murmur) due to dilation of the pulmonic valve ring resulting from pulmonary hypertension. Flow into a dilated pulmonary trunk causes a pulmonic ejection sound and pulmonic ejection murmur. The second pulmonic heart sound is closely split or not split.
- Differential cyanosis i.e. cyanosis is more pronounced in lower extremities compared to upper.This is so because the ductus originates distal to the left subclavian artery. The left subclavian artery mainly supplies the upper extremities which escapes the shunting of blood.
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