Which cardiac findings suggest patent ductus arteriosus (PDA)?

Updated: Nov 20, 2018
  • Author: Luke K Kim, MD; Chief Editor: Stuart Berger, MD  more...
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In neonates, a heart murmur is discovered within the first few days or weeks of life. The murmur is usually recognized as systolic rather than continuous in the first weeks of life and can mimic a benign systolic murmur.

Findings upon cardiac examination include the following:

  • If the left-to-right shunt is large, precordial activity is increased, with the magnitude of increased activity related to the magnitude of left-to-right shunt

  • The apical impulse is laterally displaced; a thrill may be present in the suprasternal notch or in the left infraclavicular region

  • The first heart sound (S1) is typically normal, and the second heart sound (S2) is often obscured by the murmur; phonocardiographic data from the past suggested the occurrence of paradoxical splitting of S2 related to premature closure of the pulmonary valve and a prolonged ejection period across the aortic valve

  • The murmur may be only a systolic ejection murmur, or it may be a crescendo/decrescendo systolic murmur that extends into diastole

  • Occasionally, auscultation of the patent ductus arteriosus (PDA) reveals numerous clicks or noises resembling shaking dice or a bag of rocks

In 1898, Gibson described the classic murmur. Subsequently, the hallmark physical finding of patent ductus arteriosus (PDA) has been referred to as a machinery murmur, which is continuous. The murmur may be accentuated in systole. Typically, the murmur is loudest at the left upper chest. If the pulmonary-to-systemic blood ratio approaches or exceeds 2:1, an apical flow rumble, caused by high flow into the left ventricle, is frequently present. Also, because flow through the left ventricle into the aorta is increased, an aortic ejection murmur may be present. If the patent ductus arteriosus (PDA) is small, the amplitude of the murmur may increase with inspiration as pulmonary impedance drops.

The peripheral pulses are often referred to as bounding. This is related to the high left ventricular stroke volume, which may cause systolic hypertension. The phenomenon of bounding pulses also is caused by the low diastolic pressure in the systemic circulation as blood runs off from the aorta into the pulmonary circulation.

Low birth weight premature infant

In the low birth weight premature infant, diagnosing a patent ductus arteriosus (PDA) on auscultation may be difficult. Babies that have a more severe clinical course of hyaline membrane disease (HMD) may have a higher prevalence of patent ductus arteriosus (PDA). The exact reason for this is unclear.

In the low birth weight premature infant, the classic signs of a patent ductus arteriosus (PDA) are usually absent. The classic continuous murmur is rarely heard. A rough systolic murmur may be present along the left sternal border, but a small baby with a large patent ductus arteriosus (PDA) and significant pulmonary overcirculation may have no murmur. In that case, typically, precordial activity is increased and peripheral pulses are bounding. The increased precordial activity is caused by the large left ventricular stroke volume. Bounding pulses are caused by the relatively low systemic arterial blood pressure due to the continuous runoff of blood from the aorta into the pulmonary artery.

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