The hemodynamics of transjugular intrahepatic portosystemic shunts: investigations with Doppler sonography and development of an in vitro model

Transmitted cardiac pulsations as an indicator of transjugular intrahepatic portosystemic shunt function: initial observations

PURPOSE

To determine if cardiac pulsations are visible and quantifiable on spectral waveforms during Doppler ultrasonographic (US) evaluation of transjugular intrahepatic portosystemic shunts (TIPS), and if so, whether their magnitude declines with shunt dysfunction.

MATERIALS AND METHODS

Baseline and pre-revision US images obtained in 15 patients with venographically confirmed TIPS malfunction were retrospectively examined for spectral waveform pulsation. Cardiac pulsatility was quantified by using the venous pulsatility index (VPI), the venous equivalent of resistive index. VPIs were obtained at four locations from the main portal vein to the stent-hepatic venous junction. Baseline and follow-up examination results in 11 patients with functional TIPS acted as controls and were evaluated similarly. Baseline and follow-up mean VPIs at all four locations were compared for both sets of patients by using the Newman-Keuls pairwise multiple sample comparison test. The chi(2) test was used to determine if a VPI threshold that would result in an acceptable sensitivity and specificity for shunt dysfunction existed.

RESULTS

One hundred twenty mean VPIs were obtained in the study group, and 88 mean VPIs were obtained in the control group. Pre-revision VPIs at each location were significantly lower (P <.01) than all baseline values and than the follow-up values in the control group. A VPI less than 0.16 was 94% sensitive and 87% specific for shunt dysfunction.

CONCLUSION

The VPI, a quantitative measure of cardiac pulsation obtained with Doppler US, may be a useful parameter for assessing TIPS function.

Color and pulsed Doppler ultrasound findings in normally functioning transjugular intrahepatic portosystemic shunts

OBJECTIVE

To evaluate blood flow changes inside normally functioning transjugular intrahepatic portosystemic shunts (TIPS), using color Doppler ultrasound (CDUS) and pulsed Doppler ultrasound (PDUS).

METHODS

A total of 72 patients (mean age 54, range 36-78 years) underwent TIPS placement, portal angiography, CDUS and PDUS examinations. Measurements inside the stent were taken at the portal side, at the central part and at the venous end of the TIPS.

RESULTS

In well functioning TIPS the mean peak velocity (PV) on the portal side was 37 m/s (range 22-65 cm/s), in the area of the incoming intrahepatic portal branch the mean PV was 59 cm/s (range 40-95 cm/s) and at the side of the incoming hepatic vein the mean PV was 135 cm/s (range 88-220 cm/s). In the punctured hepatic and portal veins the mean PV was 25 cm/s (range 15-30 cm/s) and 18 cm/s (10-22 cm/s), respectively. The flow increase from the portal to the mid part (P less than or = 0.001) and to the venous side was statistically significant (P less than or = 0.001).

CONCLUSION

A velocity gradient between the portal and the venous side of a TIPS is a normal finding caused by branches of the portal and hepatic vein joining the TIPS from the side and it is characteristic of a normally functioning TIPS.

Transjugular intrahepatic portosystemic shunts (TIPS): effects of respiratory state and patient position on the measurement of Doppler velocities

OBJECTIVE

The purpose of this prospective study was to examine the effects of patient position and respiratory state on the measurements of Doppler velocities in transjugular intrahepatic portosystemic shunts.

SUBJECTS AND METHODS

Thirty-eight transjugular intrahepatic portosystemic shunts in 34 consecutive patients were studied using Doppler sonography. Peak velocities were measured in the mid shunt with the patient in three positions (supine, sitting upright, and left lateral decubitus) and two respiratory states (deep inspiration and quiet respiration). A mixed linear regression model was used to assess statistically significant differences among the six velocity measurements.

RESULTS

Peak velocities in the mid stent averaged 22 cm/sec greater in quiet respiration than in deep inspiration, which was a significant difference (p < 0.00001). Differences in velocities in the three patient positions were not significant (p = 0.53). Using 90-190 cm/sec as the normal range, the peak velocity shifted from normal to abnormal levels by changing respiratory state in 17 (45%) of 38 studies. Using 60 cm/sec as the lower normal limit, the peak velocity fell below the normal range with inspiration in 10 (26%) of 38 studies. In 12 (32%) of 38 studies, a decline in peak velocity exceeding 50 cm/sec could be induced by inspiration.

CONCLUSION

Peak systolic velocity in transjugular intrahepatic portosystemic shunts is substantially altered by the respiratory state of the patient at the time of the measurement, but not by the patient position. Respiratory state must be taken into account in the interpretation of peak velocity for shunt stenosis.

The first decade of the transjugular intrahepatic portosystemic shunt (TIPS): state of the art

The transjugular intrahepatic portosystemic shunt (TIPS) is an interventional treatment resulting in decompression of the portal system by creation of a side-to-side portosystemic anastomosis. Since its introduction 10 years ago, more than 500 publications have appeared demonstrating rapid acceptance and increasing clinical use. This review summarizes the present knowledge of technical aspects and complications, follow-up of patients, and indications. With respect to the technique, the TIPS procedure is probably one of the most difficult interventions and, therefore, technical success and complications clearly depend on the skills of the operator. Thus, the number and kind of complications reported in this review do not necessarily relate to the procedural complications of an experienced center. The follow-up of the TIPS patient has to assess shunt patency, liver function and hepatic encephalopathy. Shunt patency can best be monitored by duplex-sonography. Routine radiological revision seems not to be helpful and does not improve results, i.e., rebleeding and survival. Short term patency may be improved by anticoagulation, while such a treatment does not influence long-term patency. With respect to the indications of TIPS, much is known about treatment of variceal bleeding. The nine randomized studies that are available to date show that survival is comparable between patients receiving TIPS or endoscopic treatment. The second group of patients is the group with refractory ascites and related complications, such as hepatorenal syndrome and hepatic hydrothorax. It has been demonstrated that TIPS improves these complications, but randomized studies are still lacking. In addition, TIPS has been applied successfully to patients with Budd-Chiari syndrome, portal vein thrombosis, before liver transplantation, and for the treatment of ectopic portal hypertensive bleeding.

Long-term follow-up after TIPS: use of Doppler velocity criteria for detecting elevation of the portosystemic gradient

PURPOSE

To evaluate the performance of Doppler ultrasound as a screening test for detecting elevated portosystemic gradients in failing transjugular intrahepatic portosystemic shunts (TIPS).

MATERIALS AND METHODS

Twenty-seven of 61 patients who underwent TIPS creation between November 1991 and March 1996 were studied. At routine intervals, angle-corrected velocity measurements of portal venous and intrashunt blood flow (at the portal venous, middle, and hepatic venous levels of the shunt) were obtained. These were compared with portal hemodynamics for diagnostic accuracy in predicting clinically significant elevation of the portosystemic gradient. Venographic and manometric correlations were obtained on all patients available for follow-up and were not limited to those with symptoms or "abnormal" Doppler studies. Receiver-operating characteristic (ROC) curves were done. Linear regression was done to study correlation of shunt velocities with portal pressure, and logistic regression was done to predict shunt stenosis with use of shunt velocities.

RESULTS

The most accurate location for shunt velocity measurement was the main portal vein, but this had an area under the ROC curve of only 0.70. Accuracy of any velocity threshold (including maximum shunt velocity) was no greater than 70%. Maximum shunt velocity of less than 60 cm/sec was 93% specific for detecting shunt restenosis, but only 25% sensitive, for an overall accuracy of 64%. High sensitivity (90%) could only be achieved with poor specificity (< 33%). Linear regression revealed poor correlation between shunt or portal vein velocity measurements and portal pressure (/r/ < 0.23 for all).

CONCLUSIONS

Intrashunt and portal venous Doppler velocities alone do not accurately predict elevation of the portosystemic gradient on long-term follow-up after TIPS.