Persistent ductus botalli

Galen already described a persistent botallic duct in the 2nd century. Further records of this can be found in the 17th century by Botallo. Frey succeeded in performing the first surgical treatment of the ductus in Düsseldorf in 1937 (Häring 1986).

The persistent ductus botalli (PDA) is a persistent vascular connection between the descending thoracic aorta and the pulmonary artery that remains unobstructed for more than 3 months postpartum (Herold 2023). The normally physiological closure of the fetal ductus does not occur (Cesnjevar 2016).

The persistent ductus botalli is a physiological phenomenon in premature infants (Kindler 2017).

A distinction is made between a:

- Small PDA:

There is no significant enlargement of the left heart. There is a left-right shunt during the entire cardiac cycle. The pulmonary time volume (Qp) / body time volume (Qs) is < 1.5: 1. The ratio of pulmonary artery pressure to systemic pressure is normal (Herold 2023).

- Medium sized PDA:

There is a volume load on the left atrium, the left ventricle and the pulmonary vessels. The pulmonary time volume (Qp) / body time volume (Qs) is 1.5 - 2: 1. The pressure separation between the two circuits is PAP / SP ≤ 0.5. The pulmonary vascular resistance is not yet significantly increased (Herold 2023).

- Large PDA

With a large PDA, the lung time volume (Qp) / body time volume (Qs) is > 2: 1. There is almost no pressure separation between the two circuits, i.e. a pulmonary vascular disease (the so-called Eisenmenger reaction) has occurred with a largely irreversible increase in pulmonary vascular resistance to the systemic resistance and there is now a shunt reversal with a right-to-left shunt (Herold 2023).

PDA is present in approx. 10 % of all congenital heart defects (Herold 2023). This makes PDA the most common congenital angiopathy (Christ 2022). The gender ratio of males to females is 1:2 to even 1:3 (Herold 2023).

PDA occurs significantly more frequently in premature babies (Christ 2022).

After a rubella infection during pregnancy, the risk of developing PDA in the unborn child increases (Christ 2022). Immaturity of the newborn and postpartum hypoxia also play a role (Vogel 2022).

However, the exact reasons why the ductus does not close in some children are not yet known (Christ 2022).

During pregnancy, the duct is kept open by high levels of circulating prostaglandins and by the non-ventilated lungs. Postprandially, with the separation of the umbilical cord from the placenta, the high prostaglandin levels fall. The lungs expand rapidly with the first breaths and the lung resistance falls as a result. All these factors lead to a contraction of the smooth muscles in the area of the ductus wall and the ductus is permanently closed no later than 3 days after birth (Cesnjevar 2016).

If the ductus does not close, the postnatal drop in pulmonary vascular resistance results in an aortopulmonary systolic-diastolic left-right shunt (Cesnjevar 2016).

A PDA is usually localized on the left side. Only patients with a right-sided aortic arch may have a right-sided or even bilateral ductus (Cesnjevar 2016).

With a large PDA, the following may already be present in infancy: (Herold 2023)

- Signs of severe heart failure

- dyspnea

- tachypnea

- failure to thrive

- Hepatomegaly (Cesnjevar 2016)

- Differential cyanosis (the oxygen saturation in the lower half of the body is lower than in the upper half [Kasper 2015])

- Eisenmenger reaction: The Eisenmenger reaction usually occurs after the age of 3 years (Herold 2023)

With a medium-sized PDA, the first symptoms usually only appear in the 3rd decade. An Eisenmenger's reaction can occur between the 2nd and 4th decade of life (Herold 2023).

In addition to the physical examination, auscultation, blood pressure measurement and measurement of oxygen saturation in both arms and legs, an echo / color Doppler and an MRI should be performed. If pulmonary hypertension is suspected, a cardiac catheterization is also indicated (Herold 2023). In the case of a very small ductus, angiography is recommended (Christ 2022).

Palpation:

- Widened apex of the heart displaced laterally and caudally

- Buzzing above the 2nd ICR left parasternal palpable (Christ 2022).

Auscultation:

In the neonatal period there is a systolic murmur in the left infraclavicular region. This later develops into a continuous systolic-diastolic murmur - also known as a "machine murmur" - in the left infraclavicular region (Cesnjevar 2016). The larger the PDA, the weaker the murmur can be auscultated (Christ 2022).

If the patent ductus botalli is very small and haemodynamically irrelevant, the auscultation is unremarkable. In this case, one speaks of a so-called "silent duct" (Cesnjevar 2016).

Blood pressure:

A large blood pressure amplitude is typical for the PDA (Cesnjevar 2016).

Echocardiography:

This allows the ductus to be assessed very well in terms of its size and dynamic relevance (Cesnjevar 2016).

ECG:

The ECG shows signs of left heart strain. If there is also evidence of right heart hypertrophy, this should be interpreted as a sign of a significant increase in pulmonary pressure (Cesnjevar 2016).

MRI:

An MRI is indicated for a:

- Auscultatory silent ductus

- Small, haemodynamically insignificant ductus

- Hemodynamically relevant duct with systolic-diastolic auscultatory murmur

- Very large duct with pulmonary hypertension (Cesnjevar 2016)

Angiography:

Angiography is the most sensitive detection for a small PDA (Christ 2022).

Chest X-ray

This usually shows cardiomegaly and more or less pronounced signs of pulmonary hyperemia (Cesnjevar 2016).

- Eisenmenger reaction: This occurs in severe PDA in the 3rd year of life, in moderate PDA between the 2nd and 4th decade of life (Herold 2023)

- Dissociated cyanosis, i.e. cyanosis of the lower part of the body. This occurs with the onset of shunt reversal (Christ 2022)

With a pronounced left-right shunt above the PDA, a relevant steal phenomenon can also occur in the systemic circulation in premature infants with:

- Necrotizing enterocolitis (NEC)

- Cerebral ischemia with secondary hemorrhages (Cesnjevar 2016)

With a small PDA, there is a risk of:

- Endarteritis

- Septic embolisms

- Lung abscesses (Herold 2023)

- Endocarditis (Vogel 2022).

Older patients may experience:

- Pulmonary arterial hypertension

- Calcifications of the ductus

- Aneurysms (Herold 2023)

A PDA can still close spontaneously up to the 4th month of life. Conservative treatment with medication is also possible in newborns (for more information, see "Internal therapy" (Christ 2022).

An asymptomatic ductus does not necessarily need to be treated, but it does represent a significantly increased risk of endocarditis (Vogel 2022).

Occasionally, some newborns experience closure of the ductus after administration of intravenous prostaglandin synthesis inhibitors such as indomethacin or ibuprofen (Christ 2022) or closure is also possible as a result of treatment with acetylsalicylic acid (Lohr 2002).

Surgical closure of the ductus should be performed as early as possible (Christ 2022), i.e. in premature infants with respiratory distress syndrome and children with cardiorespiratory insufficiency immediately after diagnosis, and in mature newborns within the first 3 months of life (Vogel 2022).

The risk of the procedure is < 1% (Christ 2022).

Surgical treatment of a PDA can consist of:

- Interventional catheter occlusion

The procedures of choice here include various occluder systems or coils (Herold 2023). Nowadays, most PDAs are closed by interventional therapy. The success rate is now over 90 % (Vogel 2022).

- Surgical therapy

If interventional closure is not possible due to the size of the shunt or for technical reasons, surgical closure is indicated (Herold 2023). This is also performed in symptomatic premature infants and in the presence of complex cardiac vitiation (Vogel 2022).

Spontaneous closure is possible with PDA (Herold 2023).

Causes of death from untreated PDA are:

- Heart failure

- Pulmovascular disease (so-called Eisenmenger reaction)

- Complications of endarteritis (Herold 2023)

- Infective endocarditis (Kasper 2015)

1. Cesnjevar R, Dittrich S (2016) S2k guideline: Persistent ductus arteriosus in childhood and adolescence. Bavarian Medical Journal 640 - 645
2. Christ J (2022) Cardiology: Basics. Elsevier Urban and Fischer Publishers 115 - 116
3. Häring R, Zilch H (1986) Lehrbuch Chirurgie mit Repetitorium. Walter de Gruyter Berlin / New York 347
4. Herold G et al. (2023) Internal Medicine. Herold Publishing House 193 - 194
5. Kasper D L, Fauci A S, Hauser S L, Longo D L, Jameson J L, Loscalzo J et al. (2015) Harrison's Principles of Internal Medicine. Mc Graw Hill Education 1523
6. Kindler A, Seipolt B, Heilmann A, Range U, Rüdiger M, Hofmann S R (2017) Development of a Diagnostic Clinical Score for Hemodynamically Significant Patent Ductus Arteriosus. Front Pediatr. Sec. Neonatology (5) 280 https://doi.org/10.3389/fped.2017.00280
7. Lohr M (2002) Original exam questions with commentary: GK 2 Pathophysiology, Pathobiochemistry. Georg Thieme Verlag Stuttgart / New York 194
8. Vogel A (2022) Surgery in question and answer. Elsevier Urban and Fischer Publishers 120