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

(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.
References in periodicals archive ?
Preclosure right-to-left shunt was severe in 95% of patients, as summarized in Table 2.
Unfortunately, c-TCD is unable to differentiate cardiac from pulmonary right-to-left shunts and provides no data on the shape and size of the defect [7].
Another possible cause of paradoxical air embolism is a pulmonary right-to-left shunt, which may occur with an arterial-venous malformation (AVM).
In the Comorbidities Associated With Migraine and Patent Foramen Ovale (CAMP) study, 20 patients with large right-to-left: shunts scored significantly lower on measures of auditory and verbal memory and learning than did 20 patients with no right-to-left shunt. There was a significant inverse relationship between test scores and the number of embolic tracks detected on transcranial Doppler sonography, Jill Jesurum, Ph.D., and her associates reported at the meeting.
In your case, the concern is a right-to-left shunt, meaning that a blood clot could travel from the right to the left side of the heart, and then on to the brain and cause a stroke.
Thus, the volume of the left-to-right shunt across the defect far exceeded that of the right-to-left shunt. The patient was referred for surgical repair of his sinus venosus atrial septal defect.
Furthermore, in localised forms of bronchoalveolar carcinoma, hypoxaemia may be due to intrapulmonary right-to-left shunt (4,5).
A right-to-left shunt through a persistent foramen ovale (PFO) may produce a significant desaturation of arterial blood when the patient changes from decubitus to a sitting or standing position [2].
Refractory hypoxemia unexplained by CXR findings and with a structurally normal heart by echocardiography should strongly raise the suspicion for an extracardiac right-to-left shunt such as pulmonary AVM.
Lung perfusion scan with Tc-99m MAA was performed and showed focal tracer uptake at the region of the brain, stomach, and both kidneys indicating right-to-left shunt (Figure 2).
A cryptogenic stroke in the context of a PFO is thought to be caused by a transient right-to-left shunt, enabling development of a paradoxical embolus.
After injection of agitated saline into an upper extremity vein was not detected right-to-left shunt by transthoracic contrast echocardiography.