Congenital heart defects with right-left shunt

Nils Stensen first described tetralogy of Fallot in 1571 (Apitz 2015) and the clinical picture was described anatomically and pathologically by Sir Thomas Bevill Peacock in 1866 (Chopra 2013). The French pathologist Etienne Louis Arthur Fallot, after whom the tetralogy of Fallot was ultimately named, coined the term "tetralogy" in 1888 (Chopra 2013).

The first open heart surgeries with the heart-lung machine have been possible since 1953 (Schmaltz 1998).

A right-to-left shunt is the transfer of venous, deoxygenated blood into the systemic circulation, also referred to as Qp < Qs. This always leads to central cyanosis (Blum 2016).

Congenital right-left shunts are among the cyanotic heart defects. These include:

- Truncus arteriosus

- Tetralogy of Fallot (occurs in approx. 5.5 % [Menche 2020])

- Tricuspid atresia

- Transposition of the great arteries

- Pulmonary atresia

- Total pulmonary vein malformation (Herold 2023)

- Univentricular heart

- Aortic atresia

- Ebstein anomaly

- Cor triatriatum (Hombach 2001)

The strength of the right-left shunt is measured in Qp / Qs. If this value is < 1, it is a right-to-left shunt (DGfK 2022).

Cyanotic shunt vitis is significantly rarer than acyanotic shunt vitis (Kröner 2010).

A right-to-left shunt is caused by a combination of a defect in the septum and an increase in pressure in the right heart (Hansis 1998).

The shunt usually exists at the ventricular or atrial level. If the blood flow in the pulmonary circulation is also severely obstructed, a right-to-left shunt occurs. This means that the blood cannot be sufficiently oxygenated. Cyanosis occurs when > than 3 g % hemoglobin is no longer sufficiently loaded with oxygen. This also explains the more rapid onset of cyanosis in polyglobulia and the less rapid onset of cyanosis in the presence of anemia (Kröner 2010).

The typical symptom of a right-left shunt is central mixed cyanosis (Hombach 2001). Depending on the severity of the defect, the following may occur:

- dyspnoea

- cyanosis

- Reduced performance

- failure to thrive in children

- Angina pectoris

- Hypoxic seizures

- Syncope

- Typical is the squatting position of the children to improve the oxygen supply (Menche 2020)

Postnatal diagnostics include auscultation, ECG, chest X-ray and measurement of oxygen saturation as well as non-invasive imaging such as echocardiography, cardiac MRI and angio-CT. Invasive diagnostics include cardiac catheterization (Blum 2016).

Shunts can be assessed well by echocardiography, otherwise shunts and most congenital heart diseases can be optimally assessed by CMR (Kasper 2015).

In the context of central cyanosis, poor oxygenation can lead to damage to the heart muscles. This reduces the heart's pumping capacity and can even lead to cell necrosis (Blum 2016).

The oxygen deficit can lead to:

- Increased production of erythropoietin

- polyglobulia

- A sharp increase in HKT (≥ 65 %). The critical limit here is a HCT of > 75 % and an oxygen saturation of < 65 %.

- Increased thrombus formation

- Embolization of the thrombi in the systemic circulation with cerebral infarctions and brain abscesses (Blum 2016)

- Iron deficiency anemia

- Drum flail fingers

- Watch glass nails

- Excessive growth of the gums (Blum 2016)

Surgical correction of the respective malformation as early as possible (Hombach 2001).

1. Apitz J et al. (2002) Pediatric cardiology: diseases of the heart in newborns, infants, children and adolescents. Steinkopff Publishers 389 - 404
2. Blum U, Meyer H, Beerbaum P (2016) Compendium of congenital heart defects in children: diagnosis and treatment. Springer Verlag Berlin / Heidelberg 21
3. Chopra H K et al. (2013) Textbook of Cardiology: A Clinical and Historical Perspective. Jaypee Brothers Medical Publishers 273 - 274
4. German Society for Cardiotechnology e. V. (DGfK) (2022) Formulary
5. Hansis M (1998) Basic knowledge of surgery. Springer Verlag Berlin / Heidelberg 142
6. Herold G et al. (2022) Internal medicine. Herold Verlag 181
7. Hombach V (2001) Interventional Cardiology, Angiology and Cardiovascular Surgery: Technique - Clinic - Therapy. Schattauer Verlag Stuttgart / New York 576, 584
8. 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 47, 270e- 25 - 270e- 26, 1519 - 1553
9. Kröner C, Koletzko B (2010) Basic knowledge of pediatrics. Springer Verlag Berlin / Heidelberg 212
10. Menche N (2020) White Series: Internal Medicine. Elsevier Urban and Fischer Publishers Germany 50 - 51
11. Schmaltz A A, Apitz J, Singer H, Wagner G (1998) Congenital heart defects with predominantly left-to-right shunt. In: Apitz J Pediatric Cardiology. Steinkopff Verlag Heidelberg Chapter 7 doi: https://doi.org/10.1007/978-3-642-53754-7_7