Hemodynamic changes in hepatic artery after glucose ingestion in healthy subjects and patients with cirrhosis

Effect of ingesting a meal and orthostasis on the regulation of splanchnic and systemic hemodynamics and the responsiveness of cardiovascular α1-adrenoceptors

Postprandial orthostasis activates mechanisms of cardiovascular homeostasis to maintain normal blood pressure (BP) and adequate blood flow to vital organs. The underlying mechanisms of cardiovascular homeostasis in postprandial orthostasis still require elucidation. Fourteen healthy volunteers were recruited to investigate the effect of an orthostatic challenge (60°-head-up-tilt for 20 min) on splanchnic and systemic hemodynamics before and after ingesting an 800-kcal composite meal. The splanchnic circulation was assessed by ultrasonography of the superior mesenteric and hepatic arteries and portal vein. Systemic hemodynamics were assessed noninvasively by continuous monitoring of BP, heart rate (HR), cardiac output (CO), and the pressor response to an intravenous infusion on increasing doses of phenylephrine, an α₁-adrenoceptor agonist. Neurohumoral regulation was assessed by spectral analysis of HR and BP, plasma catecholamine and aldosterone levels and plasma renin activity. Postprandial mesenteric hyperemia was associated with an increase in CO, a decrease in SVR and cardiac vagal tone, and reduction in baroreflex sensitivity with no change in sympathetic tone. Arterial α₁-adrenoceptor responsiveness was preserved and reduced in hepatic sinusoids. Postprandial orthostasis was associated with a shift of 500 mL of blood from mesenteric to systemic circulation with preserved sympathetic-mediated vasoconstriction. Meal ingestion provokes cardiovascular hyperdynamism, cardiac vagolysis, and resetting of the baroreflex without activation of the sympathetic nervous system. Meal ingestion also alters α₁-adrenoceptor responsiveness in the hepatic sinusoids and participates in the redistribution of blood volume from the mesenteric to the systemic circulation to maintain a normal BP during orthostasis.NEW & NOTEWORTHY A unique integrated investigation on the effect of meal on neurohumoral mechanisms and blood flow redistribution of the mesenteric circulation during orthostasis was investigated. Food ingestion results in cardiovascular hyperdynamism, reduction in cardiac vagal tone, and baroreflex sensitivity and causes a decrease in α₁-adrenoceptor responsiveness only in the venous intrahepatic sinusoids. About 500-mL blood shifts from the mesenteric to the systemic circulation during orthostasis. Accordingly, the orthostatic homeostatic mechanisms are better understood.

Correlation of hepatic vein Doppler waveform and hepatic artery resistance index with the severity of nonalcoholic fatty liver disease

PURPOSE

The study was conducted to evaluate the effect of various degrees of fatty infiltration in patients with nonalcoholic fatty liver disease on hepatic artery resistance index and hepatic vein waveform patterns.

METHODS

After identification and grading of fatty infiltration, 60 patients and 20 normal healthy subjects were examined using color and spectral Doppler sonography. The level of fatty liver infiltration was ascertained and graded by biopsy in patients and excluded by MRI in controls. The patients were allocated to four study groups consecutively, until the required number was reached, according to infiltration level as follows: normal (group A), mild (group B), moderate (group C), and severe (group D). The hepatic vein waveforms were classified into the three following groups: triphasic, biphasic, and monophasic waveform. The hepatic artery resistance index was calculated as the mean of three different measurements.

RESULTS

The incidence of monophasic and biphasic hepatic vein waveform was 2 (10%) for group B, 11 (55%) for group C, 16 (80%) for group D, and none for group A. The difference in the distribution of triphasic Doppler waveform pattern between the patients and the control group was significant (p < 0.001). Hepatic artery resistance index was 0.81 (+ or - 0.02), 0.78 (+ or - 0.03), 0.73 (+ or - 0.03), and 0.68 (+ or - 0.05), respectively, in groups A, B, C, and D and was significantly different between groups (p < 0.001).

CONCLUSION

As the severity of nonalcoholic fatty infiltration increases, the incidence of abnormal hepatic vein waveforms increases and hepatic artery resistance index decreases.

Doppler vibrometry: assessment of arterial stenosis by using perivascular tissue vibrations without lumen visualization

PURPOSE

To correlate vibration frequency and duration at Doppler vibrometry with stenosis severity determined at catheter angiography.

MATERIALS AND METHODS

Sixteen patients (eight women) scheduled to undergo abdominal or pelvic angiography were recruited after providing informed consent. An ultrasonography (US) scanner was customized to acquire raw echo data before conventional Doppler processing. Data were acquired from perivascular tissue regions proximal to stenoses, close to the most narrow lumen, and distal to stenoses in the renal, hepatic, common iliac, and superior mesenteric arteries. The data were processed to quantify vibration frequency and duration. The minimum lumen diameter and the pre- and poststenotic lumen diameters were quantified from angiograms. One patient with a hepatic artery stenosis did not yield measurable vibrometry data due to significant bowel gas.

RESULTS

Stenoses (diameter reduction, 43%-91%) were angiographically measured in the six renal arteries, four hepatic arteries, three iliac arteries, and one superior mesenteric artery yielding vibrometry data. Three iliac arteries were normal (<30% diameter reduction at angiography). For these 17 arteries, the vibration frequency was higher with a greater percentage of stenosis [Pearson r = .75; P < .001) and a smaller minimum lumen diameter (r = .72; P < .001). The vibration duration increased with a greater percentage of stenosis (r = .7; P < .001).

CONCLUSIONS

Preliminary results indicate that the vibration frequency and duration can be used to quantitatively estimate stenosis severity. Doppler vibrometry is complementary to duplex US and does not require lumen visualization.

Effect of diffuse fatty infiltration of the liver on hepatic artery resistance index

PURPOSE

This study was conducted to evaluate the effect of various degrees of diffuse fatty infiltration of the liver on the hepatic artery resistance index.

METHODS

One-hundred forty subjects were examined using standard color and spectral Doppler sonography protocols. Fatty infiltration of the liver was identified and graded sonographically. The patients were grouped (n = 35 in each of 4 groups) according to the degree of diffuse fatty infiltration of the liver as follows: normal (group 1), mild (group 2), moderate (group 3), and severe (group 4). The resistance index calculated for each patient was the mean of 3 measurements. Mean resistance index of the hepatic artery was then calculated for each group.

RESULTS

The mean resistance index was 0.81 +/- 0.04 for group 1, 0.79 +/- 0.06 for group 2, 0.75 +/- 0.05 for group 3, and 0.73 +/- 0.05 for group 4. We found a statistically significant (p < 0.05) decrease in resistance index when comparing groups 3 and 4 with groups 1 and 2 separately.

CONCLUSIONS

Hepatic artery resistance index decreases as the severity of diffuse fatty infiltration increases.

Intrahepatic spontaneous retrograde portal flow in patients with cirrhosis of the liver: reversal by food intake

OBJECTIVE

The purpose of our study was to assess whether intrahepatic spontaneous retrograde portal flow in patients with cirrhosis of the liver can be reversed to a normal portal venous flow by food intake.

CONCLUSION

Of the 18 cirrhotic patients with intrahepatic spontaneous retrograde portal flow, 16 (89%) showed a marked change in portal flow direction after food intake. This evidence strongly suggests that intrahepatic spontaneous retrograde portal flow may be reversible. Furthermore, this finding implies that regular food intake may be important in the maintenance of effective hepatic blood flow in cirrhotic patients.

Correlation between hepatic tumor index on color Doppler sonography and tumor vessels on arteriography in large hepatocellular carcinomas

We assessed a possible correlation between the hepatic tumor index (as the ratio of the tumoral peak systolic velocity to the peak systolic velocity of the right or left hepatic artery) and grade of tumor vessel in large hepatocellular carcinomas (HCCs). Color Doppler sonographic findings were evaluated and compared with selective hepatic arteriographic findings in 78 patients with 93 hepatocellular carcinomas larger than 2.0 cm in diameter. Pulsatile color flow images were obtained in 78 of 93 lesions. The hepatic tumor index was equal to or greater than 1.0 in 57 of 78 lesions. These lesions were revealed arteriographically to have distinct tumor vessels and/or arteriovenous shunting. When this index was 1.0 or greater, we calculated 90% accuracy in distinguishing HCCs with distinct tumor vessels from those without distinct tumor vessels. The hepatic tumor index correlated with the grade of tumor vessels and the presence of arteriovenous shunting.

Hepatic arterial resistance after mixed-meal ingestion in healthy subjects and patients with chronic liver disease

PURPOSE

This study investigated hemodynamic changes in the resistance index of the hepatic artery after mixed-meal ingestion.

METHODS

We used color Doppler sonography to measure hemodynamic changes in the right hepatic artery in response to mixed-meal ingestion (225 ml, 69 g, 300 kcal) in 9 healthy subjects, 15 patients with chronic hepatitis with low-grade fibrosis (no bridging), 10 patients with chronic hepatitis with moderate-grade (bridging) fibrosis, and 18 patients with cirrhosis.

RESULTS

After mixed-meal ingestion, the mean (+/-standard error) maximum increase in the resistance index of the right hepatic artery in healthy subjects was 31+/-2%. These changes were significantly greater than those in patients with chronic hepatitis with low-grade fibrosis (22+/-2%; p<0.05), patients with chronic hepatitis with moderate-grade fibrosis (11+/-2%; p<0.01), and cirrhotic patients (5+/-2%; p<0.01). Mixed-meal ingestion produced significantly smaller increases in the resistance index in cirrhotic patients than in patients with chronic hepatitis with low-grade fibrosis (p<0.01). A postprandial increase in the resistance index of 15% or less was associated with 100% sensitivity, 72% specificity, and 84% accuracy in distinguishing patients with cirrhosis from patients with chronic hepatitis.

CONCLUSIONS

The response of the resistance index after mixed-meal ingestion decreases as the severity of hepatic fibrosis increases. Doppler evaluation of postprandial increases in the resistance index of the right hepatic artery may be useful in differentiating between patients with chronic hepatitis and those with cirrhosis.