Doppler Evaluation of TIPS Shunts

Summary

In this educational lecture, Professor Mark Cleaver from the University of Wisconsin discusses the Doppler examination of TIPS (Transjugular Intrahepatic Portosystemic Shunts) used to treat portal hypertension in patients with cirrhosis. He explains the importance of TIPS in managing complications, the procedure's success rate, and the role of Doppler surveillance in maintaining shunt patency. The talk also covers complications, surveillance principles, and potential pitfalls in Doppler imaging, emphasizing the need for standardized protocols for accurate diagnosis and intervention.

Takeaways

• 🏥 Professor Mark Cleaver discusses Doppler examination of TIPS (Transjugular Intrahepatic Portosystemic Shunts), a common procedure in the treatment of portal hypertension.
• 📈 Portal hypertension is often caused by liver disease, particularly cirrhosis, which can be due to alcohol, viral infection, or other causes, with viral causes being more prominent worldwide.
• 🌡 The condition is diagnosed when portal pressure exceeds 12 mm Hg and can lead to complications like ascites, variceal bleeding, and hepatic encephalopathy.
• 🛠️ TIPS shunts are used to address these complications, with significant improvements in quality of life and effectiveness compared to other treatments.
• 🔍 The placement of TIPS involves creating a conduit between the portal system and the right hepatic vein, with a technical success rate over 90%.
• 🔒 Doppler surveillance is crucial for maintaining the patency of TIPS shunts, with a 1-year patency rate of 85% when monitored, compared to only 25% without surveillance.
• 🚑 Complications of TIPS shunts include stent thrombosis, stent stenosis, and occlusion, which can be treated with interventional techniques such as balloon angioplasty.
• 📊 Doppler sonography is highly sensitive and specific for detecting complete TIPS shunt occlusion, with sensitivities and specificities exceeding 95%.
• 📏 Identifying TIPS stenosis is more challenging, with eight different parameters proposed to assess shunt function, including flow direction, collateral vein reappearance, and velocity changes.
• 📉 The Venous Pulsatility Index (VPI) is a newer index suggested for evaluating TIPS dysfunction, but it has not been widely adopted due to inconsistent results.
• 🚫 Doppler artifacts can occur at the edges of shunts, mimicking flow, which can be misleading without proper spectral Doppler confirmation.
• 💡 The script emphasizes the importance of standardizing Doppler protocols and considering factors like patient position and respiratory state when measuring velocities in TIPS shunts.

Q & A

What is the main subject of the lecture by Mark Cleaver?

The main subject of the lecture is the Doppler examination of TIPS (Transjugular Intrahepatic Portosystemic Shunts), covering aspects of portal hypertension, TIPS placement and maintenance, Doppler surveillance principles, and potential issues encountered during ultrasound of these devices.

Why are most TIPS shunts placed in the United States?

Most TIPS shunts are placed in people with cirrhosis, which is predominantly caused by either alcoholic or viral etiology in the United States.

What is the definition of portal hypertension?

Portal hypertension is defined as a condition where the portal pressure exceeds 12 millimeters mercury, occurring when liver disease impedes blood flow through the liver, leading to increased portal venous pressure and the development of portal systemic collaterals.

What are the three main complications of portal hypertension?

The three main complications of portal hypertension are intractable ascites, variceal bleeding, and hepatic encephalopathy.

How have TIPS shunts performed in addressing complications of portal hypertension?

TIPS shunts have performed remarkably well, significantly improving the quality of life of recipients and performing as well or better than other treatment methods for variceal bleeding and ascites.

What does TIPS stand for and how are they typically placed?

TIPS stands for Transjugular Intrahepatic Portosystemic Shunt. They are typically placed through the jugular vein into the right hepatic vein, establishing a conduit between the portal system and the right hepatic vein.

Why is Doppler surveillance important for TIPS shunts?

Doppler surveillance is important because it helps maintain the patency of the shunt. Without surveillance, the 1-year patency rate can be as low as 25%, but with Doppler surveillance, it can be maintained at about 85%.

What are some complications associated with TIPS shunts that Doppler surveillance aims to detect?

Complications that Doppler surveillance aims to detect include stent thrombosis, stent stenosis, stenosis of the draining hepatic vein, and complete occlusion of the shunt.

What is the significance of reversed flow in the portal venous branches post-TIPS placement?

Reversed flow in the portal venous branches post-TIPS placement indicates that the shunt is functioning correctly, as it shows that blood is being diverted away from the liver and towards the shunt, reducing portal pressure.

How does the Venous Pulsatility Index (VPI) help in assessing TIPS shunt dysfunction?

The Venous Pulsatility Index (VPI) measures the dampening of cardiac pulsation in the hepatic vein due to shunt stenosis. A VPI value of 0.16 or less indicates shunt dysfunction, as it suggests a flatline waveform which is considered bad.

What are some pitfalls to be aware of when performing Doppler examinations of TIPS shunts?

Some pitfalls include abnormal hemodynamics immediately after shunt placement, Doppler artifacts at the edges of shunts that can mimic flow, and variations in velocities within the shunt dependent on the phase of respiration.

Why is it important to standardize Doppler protocols when measuring velocities within TIPS shunts?

Standardizing Doppler protocols is important to ensure consistent and comparable measurements. Variations in patient position and respiratory state can significantly affect velocity readings, so it's crucial to perform measurements in the same way each time or to note the conditions for subsequent studies.