right-to-left shunt


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shunt

 [shunt]
1. to turn to one side; to divert; to bypass.
2. a passage or anastomosis between two natural channels, especially between blood vessels. Such structures may be formed physiologically (e.g., to bypass a thrombosis), or they may be structural anomalies.
3. a surgical anastomosis.
arteriovenous shunt a U-shaped plastic tube inserted between an artery and a vein (usually between the radial artery and cephalic vein), bypassing the capillary network, a formerly common means of arteriovenous access.
cardiovascular shunt an abnormality of the blood flow between the sides of the heart or between the systemic and pulmonary circulation; see left-to-right shunt and right-to-left shunt.
jejunoileal shunt an intestinal bypass performed to control obesity.
left-to-right shunt diversion of blood from the left side of the heart to the right side, or from the systemic to the pulmonary circulation through an anomalous opening such as a septal defect or patent ductus arteriosus.
LeVeen shunt peritoneovenous shunt.
mesocaval shunt a portosystemic shunt between the superior mesenteric vein and the inferior vena cava to reduce portal hypertension.
peritoneovenous shunt a device whose purpose is to remove excess ascitic fluid from the peritoneal cavity and return it to the venous system; called also LeVeen shunt.



The shunt consists of a peritoneal tube, a one-way valve, and a tube leading to a large vein, usually the superior vena cava or the jugular vein. The perforated peritoneal tube is placed in the peritoneal cavity and attached to the one-way valve which opens at a pressure of 3 cm H2O. The valve controls the direction of the flow of ascitic fluid and prevents a backflow of blood from the vein. A tube leading from the valve empties into the venous system.

The shunt is triggered into action by the patient's breathing. Upon inspiration, the diaphragm descends toward the abdominal cavity and causes a rise in fluid pressure in the thoracic superior vena cava. The difference in pressure, usually about 5 cm H2O, opens the shunt valve, allowing the flow of ascitic fluid into the large vein. The action of the shunt can be enhanced by the patient's inspiring against pressure, as when using a blow bottle.

A disadvantage of the shunt is dilution of the blood and a resultant drop in hematocrit, which necessitates transfusion of packed cells and perhaps a slowing of the rate of flow of ascitic fluid into the venous system. Other inherent risks are infection, leakage of ascitic fluid from the operative site, elevated bilirubin, gastrointestinal bleeding, and disseminated intravascular coagulation.
Peritoneovenous (LeVeen) shunt for chronic ascites moves fluid from the peritoneal (abdominal) cavity into the superior vena cava. From Ignatavicius and Workman, 2000.
portacaval shunt a portosystemic shunt between the portal vein and the vena cava.
portosystemic shunt a surgically created shunt that connects the portal and systemic circulations, such as a mesocaval, portacaval, or splenorenal shunt.
postcaval shunt portacaval shunt.
pulmonary shunt an anomaly in which blood moves from the venous circulation to the arterial circulation without participating in gas exchange, resulting in hypoxemia.
reversed shunt right-to-left shunt.
right-to-left shunt diversion of blood from the right side of the heart to the left side or from the pulmonary to the systemic circulation through an anomalous opening such as septal defect or patent ductus arteriosus.
splenorenal shunt an anastomosis of the splenic vein and the left renal vein, created to lower portal hypertension following splenectomy.
ventriculoatrial shunt the surgical creation of a communication between a cerebral ventricle and a cardiac atrium by means of a plastic tube; done for relief of hydrocephalus.
ventriculoperitoneal shunt a communication between a cerebral ventricle and the peritoneum by means of plastic tubing; done for the relief of hydrocephalus.
ventriculovenous shunt a communication between a lateral ventricle and the venous system by means of a plastic tube; done for relief of hydrocephalus.

right-·to-·left shunt

the passage of blood from the right side of the heart into the left (as through a septal defect), or from the pulmonary artery into the aorta (as through a patent ductus arteriosus); such a shunt can occur only when the pressure on the right side exceeds that in the left, as in advanced pulmonic stenosis, or when the pulmonary artery pressure exceeds aortic pressure, as in one form of Eisenmenger syndrome or in tricuspid atresia.

right-to-left shunt

Etymology: ME, shunten
a shunt in which unoxygenated venous blood bypasses the lungs and directly enters the arterial system, as in the tetralogy of Fallot and other conditions.

right-to-left shunt

(rīt-left shŭnt)
The passage of blood from the right side of the heart into the left (as through a septal defect), or from the pulmonary artery into the aorta (as through a patent ductus arteriosus); such a shunt can occur only when the pressure on the right side exceeds that in the left.

shunt

1. to turn to one side; to divert; to bypass.
2. a passage or anastomosis between two natural channels, especially between blood vessels. Such structures may be formed physiologically (e.g. to bypass a thrombosis), or they may be structural anomalies.
3. a surgical anastomosis.

arteriovenous (A-V) shunt
a U-shaped or straight tube inserted between an artery and a vein (usually between the radial artery and cephalic vein), bypassing the capillary network; commonly done to allow repeated access to the arterial system for the purpose of hemodialysis.
cardiovascular shunt
an abnormality of the blood flow between the sides of the heart or between the systemic and pulmonary circulation; see left-to-right shunt (below) and right-to-left shunt (below).
left-to-right shunt
diversion of blood from the left side of the heart to the right side, or from the systemic to the pulmonary circulation through an anomalous opening such as a septal defect or patent ductus arteriosus.
LeVeen shunt
a device whose purpose is to remove excess ascitic fluid from the peritoneal cavity and return it to the venous system. Called also peritoneal-venous shunt.
peritoneal-venous shunt
see LeVeen shunt (above).
pleuroperitoneal shunt
a catheter placed to transfer pleural fluid into the peritoneal cavity; requires manual pumping.
portacaval shunt, postcaval shunt
see portacaval shunt.
reversed shunt
right-to-left shunt.
right-to-left shunt
diversion of blood from the right side of the heart to the left side or from the pulmonary to the systemic circulation through an anomalous opening such as septal defect or patent ductus arteriosus.
ventriculovenous shunt
a surgical procedure used in the treatment of hydrocephalus.
References in periodicals archive ?
Patients with large right-to-left shunts scored higher on one of seven tests of cognitive efficiency and attention, but overall there seemed to be no significant difference between groups in this category.
However, the source of the right-to-left shunts has not yet been confirmed by echocardiography as perhaps being due to a patent foramen ovale, she said.
They act as direct right-to-left shunts, resulting in central cyanosis, clubbing, exceptional dyspnea, and polycythemia, when the shunt is large.
Articles cover topics such as diagnosis criteria for recurrent headaches in childhood and adolescence, auditory event-related potentials, the clinical research application of transcranial magnetic and direct current stimulation, transcranial Doppler ultrasound, cardiac and pulmonary right-to-left shunts, contact points, adaptive mechanisms, and the injection of drugs using acupuncture techniques.
Effect on migraine of closure of cardiac right-to-left shunts to prevent recurrence of decompression illness or stroke or for haemodynamic reasons.
Of these cases, only 7% had large right-to-left shunts, compared with 20% having small shunts.
Residual right-to-left shunts pose a high rise of thromboembolism even in patients on warfarin who have a therapeutic anti-coagulation level.