Cardiovascular (cardiac) shunts are abnormal connections between the pulmonary and systemic circulations. Most commonly they are the result of congenital heart disease.
Blood can either be shunted from the systemic circulation to pulmonary circulation (i.e. 'left-to-right shunt') or between the pulmonary circulation and systemic circulation (i.e. 'right-to-left shunt') 1-4. Rarely, the shunted blood returns to the same cardiac chamber without traversing a capillary bed, termed a 'circular shunt' 5-7.
In a left-to-right shunt oxygenated blood flows directly from the systemic circulation to the pulmonary circulation, which results in decreased tissue oxygenation through reduced cardiac output 1-4. Causes include 1-4:
- vascular pulmonary shunts
In a right-to-left shunt deoxygenated blood flows directly from the pulmonary circulation to the systemic circulation, decreasing tissue oxygenation by reducing the oxygen content of systemic arterial blood 1-4. Causes include 1-4:
- vascular pulmonary shunts
- parenchymal intrapulmonary shunts
A useful mnemonic to remember some of the cardiac causes of a right-to-left shunt can be found here.
In most left-to-right or right-to-left cardiovascular shunts, shunted blood returns to the same chamber after traversing a capillary bed (either pulmonary or peripheral), if this does not occur then the term 'circular shunt' can be employed 5. Such shunts are generally present in complex congenital heart defects 5-7.
Examples that have been described in the literature include:
- a ventricular septal defect, pulmonary stenosis, tricuspid regurgitation, and a patent foramen ovale 5: some blood moves from the left atrium to the left ventricle, shunts to the right ventricle, regurgitates into the right atrium, and shunts back to the left atrium without traversing a capillary bed
- a patent foramen ovale, pulmonary atresia, and a Gerbode defect 6: some blood shunts from the right atrium to the left atrium, to the left ventricle, and shunts back to the right atrium without traversing a capillary bed
- a communication between a pulmonary artery and the right atrium 7: some blood moves from the right atrium to the right ventricle, to the pulmonary artery, and communicates back to the right atrium without traversing a capillary bed
Imaging findings vary depending on the underlying etiology, please see articles listed above for further details.
- 1. Rajiah P, Kanne JP. Cardiac MRI: Part 1, cardiovascular shunts. AJR Am J Roentgenol. 2011;197 (4): W603-20. doi:10.2214/AJR.10.7257 - Pubmed citation
- 2. Lange S, Walsh G. Radiology of Chest Diseases. TIS. ISBN:B005UG7V10. Read it at Google Books - Find it at Amazon
- 3. Provenzale JM, Nelson RC, Vinson EN. Radiology Case Review. Lippincott Williams & Wilkins. ISBN:0781778603. Read it at Google Books - Find it at Amazon
- 4. Sommer RJ, Hijazi ZM, Rhodes JF. Pathophysiology of congenital heart disease in the adult: part I: Shunt lesions. Circulation. 2008;117 (8): 1090-9. doi:10.1161/CIRCULATIONAHA.107.714402 - Pubmed citation
- 5. Shone JD, Anderson RC, Elliott LP, Amplatz K, Lillehei CW, Edwards JE. “Circular” shunt resulting from co-existent ventricular septal defect, pulmonary valvular stenosis, congenital tricuspid insufficiency, and patent foramen ovale. (1962) Am Heart J. 64:547–55.
- 6. Jue KL, Noren G, Edwards JE. Pulmonary atresia with left ventricular-right atrial communication: basis for circular shunt. (1966) Thorax. 21 (1): 83-90. Pubmed
- 7. Singhi AK, Sivakumar K. Circular shunt in a pulmonary artery to right atrial tunnel, an anomaly unreported so far. (2014) Annals of Pediatric Cardiology. 7 (2): 155. doi:10.4103/0974-2069.132504 - Pubmed
Related Radiopaedia articles
Congenital heart disease
There is more than one way to present the variety of congenital heart diseases. Whichever way they are categorized, it is helpful to have a working understanding of normal and fetal circulation, as well as an understanding of the segmental approach to imaging in congenital heart disease.
congenital heart disease
- normal relationship between chambers and valves
- atrioventricular valves
- outflow tract
- great vessels
- venous inflow
- anomalous valves
- abnormal relationship of chambers and valves
- atrioventricular abnormality
- great vessel connection abnormality
- conotruncal cardiac anomalies
- pentalogy of Cantrell
- Shone syndrome
- congenital heart disease - chest x-ray approach
surgical repairs (mnemonic)
- arterial switch procedure
- Blalock-Taussig shunt
- double switch procedure
- Fontan procedure
- Glenn procedure
- Mustard repair
- Norwood procedure
- Pott shunt
- pulmonary artery banding
- Rastelli procedure
- Sano shunt
- Senning repair
- total repair of tetralogy of Fallot (TOF)
- unifocalisation procedure
- Waterston shunt