Azygos Flow Research Articles

Hemodynamic changes in women with symptoms of supine hypotensive syndrome.

Supine positioning during late pregnancy causes the gravid uterus to compress the inferior vena cava, resulting in dramatic hemodynamic changes. The maintenance of placental perfusion requires maternal circulatory and autonomic adaptations. Women with supine hypotensive syndrome (defined as a drop in systolic blood pressure of anything between 15 and 30mmHg or an increase in heart rate of 20 bpm, with or without symptoms) may have reduced ability to compensate for the effects of supine positioning. Twelve womenwith uncomplicated pregnancies and no symptoms of supine hypotension (normal) and 10 women withuncomplicated pregnancies who reportedsymptoms of supine hypotension between 34 and 38weeks' gestation underwent magnetic resonance imaging in the supine and left lateral positions. Phase contrast images were evaluated to measure blood flow through the aorta, inferior vena cava, superior vena cava and azygos vein. Women with symptoms of supine hypotension showed significant reductions in azygos venous flow rate compared with the normal group (-0.15 (-0.30 to -0.01)L/min). Those with symptoms showed no statistically significant compensatory changes in heart rate compared with the normal group (heart rate change 4.5 (-3.1 to 12.1) bpm).Hemodynamic changes in response to positioning were similar across both groups including: a reduction in inferior vena cava blood flow, reduction in cardiac output and an increase in azygos blood flow. Maternal hemodynamic adaptations were found to be consistent across groups irrespective of whether the women had symptoms of supine hypotension. In both groups a reduction in blood flow through the inferior vena cava occurred in the supine position with a subsequent reduction in cardiac output. Both groups showed a compensatory increase in blood flow through the azygos vein in order to partially compensate for this. Taking into account the effect of maternal position, women with symptoms were found to have reduced azygos flow compared with asymptomatic women. There was a significant increase in heart rate when the women were supine than when they were in the left lateral position.

Four-dimensional Flow MRI as a Marker for Risk Stratification of Gastroesophageal Varices in Patients with Liver Cirrhosis.

Purpose To assess the feasibility of four-dimensional (4D) flow MRI as a noninvasive imaging marker for stratifying the risk of variceal bleeding in patients with liver cirrhosis. Materials and Methods This study recruited participants scheduled for both liver MRI and gastroesophageal endoscopy. Risk of variceal bleeding was assessed at endoscopy by using a three-point scale: no varices, low risk, and high risk requiring treatment. Four-dimensional flow MRI was used to create angiograms for evaluating visibility of varices and to measure flow volumes in main portal vein (PV), superior mesenteric vein, splenic vein (SV), and azygos vein. Fractional flow changes in PV and SV were calculated to quantify shunting (outflow) from PV and SV into varices. Logistic analysis was used to identify the independent indicator of high-risk varices. Results There were 23 participants (mean age, 52.3 years; age range, 25-75 years), including 14 men (mean age, 51.7 years; age range, 25-75 years) and nine women (mean age, 53.2 years; age range, 31-72 years) with no varices (n = 8), low-risk varices (n = 8), and high-risk varices (n = 7) determined at endoscopy. Four-dimensional flow MRI-based angiography helped radiologists to view varices in four of 15 participants with varices. Independent indicators of high-risk varices were flow volume in the azygos vein greater than 0.1 L/min (P = .034; 100% sensitivity [seven of seven] and 62% specificity [10 of 16]) and fractional flow change in PV of less than 0 (P < .001; 100% sensitivity [seven of seven] and 94% specificity [15 of 16]). Conclusion Azygos flow greater than 0.1 L/min and portal venous flow less than the sum of splenic and superior mesenteric vein flow are useful markers to stratify the risk of gastroesophageal varices bleeding in patients with liver cirrhosis. © RSNA, 2018 Online supplemental material is available for this article.

Portal hypertension in patients with cirrhosis: indirect assessment of hepatic venous pressure gradient by measuring azygos flow with 2D-cine phase-contrast magnetic resonance imaging.

To measure azygos, portal and aortic flow by two-dimensional cine phase-contrast magnetic resonance imaging (2D-cine PC MRI), and to compare the MRI values to hepatic venous pressure gradient (HVPG) measurements, in patients with cirrhosis. Sixty-nine patients with cirrhosis were prospectively included. All patients underwent HVPG measurements, upper gastrointestinal endoscopy and 2D-cine PC MRI measurements of azygos, portal and aortic blood flow. Univariate and multivariate regression analyses were used to evaluate the correlation between the blood flow and HVPG. The performance of 2D-cine PC MRI to diagnose severe portal hypertension (HVPG ≥ 16mmHg) was determined by receiver operating characteristic curve (ROC) analysis, and area under the curves (AUC) were compared. Azygos and aortic flow values were associated with HVPG in univariate linear regression model. Azygos flow (p < 10(-3)), aortic flow (p = 0.001), age (p = 0.001) and presence of varices (p < 10(-3)) were independently associated with HVPG. Azygos flow (AUC = 0.96 (95% CI [0.91-1.00]) had significantly higher AUC than aortic (AUC = 0.64 (95% CI [0.51-0.77]) or portal blood flow (AUC = 0.40 (95% CI [0.25-0.54]). 2D-cine PC MRI is a promising technique to evaluate significant portal hypertension in patients with cirrhosis. • Noninvasive HVPG assessment can be performed with MRI azygos flow. • Azygos MRI flow is an easy-to-measure marker to detect significant portal hypertension. • MRI flow is more specific that varice grade to detect portal hypertension.

Endovascular Treatment of Superior Vena Cava Obstruction After Surgical Correction of Intracardiac Total Anomalous Pulmonary Venous Connection

A three-month-old infant operated for obstructed intracardiac total anomalous pulmonary venous connection was readmitted because of sinus bradycardia and superior vena cava syndrome. Cardiac catheterization revealed a stenosis at the superior vena cava-right atrial junction with retrograde azygos flow. Following balloon dilatation of the stenotic area and stent implantation, the superior vena cava syndrome was rapidly relieved. At six months, an echocardiogram confirmed unobstructed flow from the superior vena cava to the right atrium.

Collateral Flow Measurement by Phase-contrast Magnetic Resonance Imaging for the Assessment of Systemic Venous Baffle Patency After Atrial Switch Repair for Transposition of the Great Arteries

We aimed to describe and compare azygos vein flow patterns of patients with obstructed and unobstructed systemic venous baffle after atrial switch repair for d-transposition of the great arteries (TGA). We hypothesized that phase-contrast magnetic resonance imaging would enable characterization of retrograde collateral flow across the azygos vein in cases of systemic venous baffle obstruction. This is a retrospective, cross-sectional study. Twelve patients with atrial switch repair for TGA were examined. Azygos flow index was measured with phase-contrast magnetic resonance imaging; comparison was made between patients with documented systemic venous baffle obstruction (n=3) and a control group of patients without baffle obstruction (n=9). Patients with systemic venous baffle obstruction had a distinctive azygos flow pattern that was retrograde and an increased amount of azygos flow compared with patients without obstruction [median (range), -436 (-455/-399) vs. 103 (51/125) mL/min/m2; P=0.01]. Patients with systemic venous baffle obstruction have a characteristic collateral flow across the azygos vein. Azygos vein flow measurement may be used for the assessment of baffle patency in patients after atrial switch repair for TGA. However, diagnostic accuracy needs to be tested in a larger population.

Chronic Liver Disease: Systemic and Splanchnic Venous Flow Mapping with Optimized Cine Phase-Contrast MR Imaging Validated in a Phantom Model and Prospectively Evaluated in Patients1

To validate magnetic resonance (MR) imaging cine phase-contrast blood flow mapping in vitro and in patients with chronic liver disease, with or without portal hypertension, and to assess the accuracy of azygos, splanchnic, and systemic blood flow measured with MR imaging in the detection of high-risk esophageal varices and compare these measurements with endoscopic evaluation, the reference standard. The local ethics committee approved this study. Patients gave written informed consent. Two phantoms were used to validate the MR imaging phase-contrast flow sequence. Patients with liver cirrhosis (n = 59), chronic liver disease without cirrhosis (n = 12), and nodular regenerative hyperplasia (NRH) (n = 11), and healthy control subjects with no liver disease (n = 25) were included. The patients underwent upper digestive system endoscopy. Mean abdominal aorta, portal venous, and azygos blood flow was measured on MR images, which were reviewed by two blinded observers to determine the presence and grade of esophageal varices. The reproducibility and intra- and interobserver variability of the blood flow measurements were assessed with intraclass correlation coefficients (ICCs). The performance of the MR blood flow measurements in staging high-risk varices was determined with receiver operating characteristic curve analysis. The correlation between MR visual analysis and endoscopic grading was assessed by using κ statistics. MR flow rate measurements had excellent correlations with actual flow values in vitro (ICC > 0.990 for phantoms 1 and 2). Mean aortic flow was significantly higher in patients with cirrhosis than in control subjects (P < .001). Mean azygos flow was significantly higher in patients with cirrhosis than in patients with chronic liver disease without cirrhosis (P = .005) and control subjects (P < .001). Low intra- and interobserver variability (ICC > 0.990 for each blood flow type) and high reproducibility (ICC > 0.850 for each blood flow type) were demonstrated. The optimal cutoff mean azygos flow value was 2.3 mL/sec for varices with grades of 2 or higher. MR imaging azygos flow measurement appears to be a promising technique for detecting high-risk esophageal varices in patients with portal hypertension.

Review article: a critical comparison of drug therapies in currently used therapeutic strategies for variceal haemorrhage.

Vasoactive drugs are safe and easy to administer, and universal treatment is the first-line approach for all patients with suspected variceal bleeding. There are strong arguments that the combination of vasoactive drugs, started as soon as possible, and endotherapy later on is the best therapeutic option, particularly in cases of ongoing bleeding at the time of endoscopy. The main action of vasoactive drugs is to reduce variceal pressure. This can be achieved by diminishing the variceal blood flow and/or by increasing resistance to variceal blood flow inside the varices. Changes in variceal pressure parallel changes in portal pressure. Drugs for the treatment of variceal bleeding can therefore be assessed by measuring the changes in portal pressure, azygos blood flow and variceal pressure. Vasoactive drugs can be divided into two categories: terlipressin (Glypressin), and somatostatin and its analogues, especially octreotide. Terlipressin significantly reduces portal and variceal pressure and azygos flow, is superior to placebo in the control of variceal haemorrhage and improves mortality. It is beneficial when combined with sclerotherapy. It also has the advantage that it might preserve renal function, one of the most important factors affecting the outcome of cirrhosis. As such, terlipressin is the most potent of the various vasoactive drugs. Somatostatin significantly reduces portal and variceal pressure and azygos flow, is superior to placebo in controlling variceal haemorrhage, and improves the success of sclerotherapy. The effect of octreotide is well established for preventing the increase in portal pressure after a meal (similar to blood in the intestines) though the effect of ocreotide on variceal pressure is controversial.

Time profile of the haemodynamic effects of terlipressin in portal hypertension

Background/Aims: Terlipressin is a long-acting vasopressin analogue that has been proved useful in the treatment of varicel haemorrhage. This study investigates the time profile of the haemodynamic effects of terlipressin on portal hypertension as well as the efficacy in decreasing portal pressure and collateral blood flow of reduced doses, suitable for longer therapy to prevent early rebleeding. Methods: Splanchnic and systemic haemodynamics were measured in 23 patients with cirrhosis and portal hypertension in baseline conditions and at 30 min, 1, 2, 3 and/or 4 h after the double-blind administration of a single intravenous injection of 1 mg ( n=8) or 2 mg ( n=8) of terlipressin, or placebo ( n=7). Results: Placebo caused no significant effects. At 30 min of terlipressin administration, the hepatic venous pressure gradient (1 mg: −16±9%, 2 mg: −21±11%; p<0.01) and azygos blood flow (1 mg: −19±13%, 2 mg: −25±17%; p<0.05) were significantly reduced. These effects were still significant at 4 h (2 mg) or 3 h (1 mg). Both doses moderately increased arterial pressure at 1 h. At 4 h, neither arterial pressure nor peripheral vascular resistance was significantly modified by either dose of terlipressin. Terlipressin caused no significant changes in hepatic blood flow. Conclusions: In patients with cirrhosis, a single injection of 2 mg of terlipressin significantly and markedly reduces portal pressure and azygos flow for up to 4 h. The effects of a reduced dose (1 mg) were almost as pronounced and prolonged, suggesting that after the initial control of variceal bleeding, terlipressin therapy could be maintained for several days at low dosage to reduce the risk of early rebleeding.

Azygos blood flow: Phase contrast quantitation in volunteers and patients with portal hypertension pre- and postintrahepatic shunt placement

Flow volume in the azygos venous system was quantitated with Cine-phase contrast (PC) velocity mapping in volunteers and compared with patients with known portal hypertension, who were referred for transjugular intrahepatic portosystemic shunt (TIPS) placement. Subsequently, the TIPS-induced hemodynamic effects on portal and azygos flow were analyzed. To assess intra- and intersubject variability, flow in the azygos veins was measured in each of 10 normal subjects at three different times. Subsequently, portal and azygos flow was quantitated in 20 patients with portal hypertension, before and after TIPS placement. All imaging was performed on a 1.5-tesla magnetic resonance imaging (MRI) system. Azygos flow was measured transaxially at the midthoracic level. Cine-PC flow measurements of the main portal vein followed morphological evaluation of the portal venous system with axial and coronal breath-held magnet resonance angiogram. Azygos flow in normal subjects was characterized by high inter- and low intrasubject variability. Azygos flow in patients with portal hypertension was significantly higher (P < .001). Following successful TIPS placement in 18 patients, Cine-PC revealed a mean decrease in azygos flow of 46.3% (P < .001) and a 134% (P < .001) increase of portal flow. Reflecting the complexity of portal hemodynamics, there was no correlation between the changes in the portal and azygos systems. In 2 patients with early occlusion of TIPS, documented invasively, portal and azygos flow values remained largely unchanged. Cine-PC enables the noninvasive, quantitative assessment of flow within the azygos venous system. Azygos flow was found to be markedly elevated in patients with portal hypertension. Combined portal and azygos PC flow measurements quantitate the therapeutic effect of TIPS placement. (Hepatology 1996 Nov;24(5):1109-15)

Azygos blood flow: phase contrast quantitation in volunteers and patients with portal hypertension pre- and postintrahepatic shunt placement.

Flow volume in the azygos venous system was quantitated with Cine-phase contrast (PC) velocity mapping in volunteers and compared with patients with known portal hypertension, who were referred for transjugular intrahepatic portosystemic shunt (TIPS) placement. Subsequently, the TIPS-induced hemodynamic effects on portal and azygos flow were analyzed. To assess intra- and intersubject variability, flow in the azygos veins was measured in each of 10 normal subjects at three different times. Subsequently, portal and azygos flow was quantitated in 20 patients with portal hypertension, before and after TIPS placement. All imaging was performed on a 1.5-tesla magnetic resonance imaging (MRI) system. Azygos flow was measured transaxially at the midthoracic level. Cine-PC flow measurements of the main portal vein followed morphological evaluation of the portal venous system with axial and coronal breath-held magnet resonance angiogram. Azygos flow in normal subjects was characterized by high inter- and low intrasubject variability. Azygos flow in patients with portal hypertension was significantly higher (P < .001). Following successful TIPS placement in 18 patients, Cine-PC revealed a mean decrease in azygos flow of 46.3% (P < .001) and a 134% (P < .001) increase of portal flow. Reflecting the complexity of portal hemodynamics, there was no correlation between the changes in the portal and azygos systems. In 2 patients with early occlusion of TIPS, documented invasively, portal and azygos flow values remained largely unchanged. Cine-PC enables the noninvasive, quantitative assessment of flow within the azygos venous system. Azygos flow was found to be markedly elevated in patients with portal hypertension. Combined portal and azygos PC flow measurements quantitate the therapeutic effect of TIPS placement.

The acute and chronic effects of isosorbide-5-mononitrate on portal haemodynamics in cirrhosis

The effects of acute and chronic administration of isosorbide-5-mononitrate on portal and systemic circulation was studied in patients with cirrhosis and portal hypertension. Acute administration reduced the mean arterial pressure and hepatic venous pressure gradient (18.4 +/- 0.9 to 16.5 +/- 0.9 mmHg), whilst having a variable effect on azygos blood flow. The hepatic venous pressure gradient fell consistently only in patients in whom the azygos blood flow increased acutely. With chronic administration no reduction in mean arterial and hepatic venous pressure gradient was identified before rechallenge, despite a marked and consistent reduction in azygos flow (540 +/- 89 to 306 +/- 60 ml/min). Rechallenge with isosorbide-5-mononitrate in patients on chronic nitrate therapy reproduced the haemodynamic effects identified with acute administration, lowering mean arterial and hepatic venous pressure gradient (19 +/- 1.5 to 16.0 +/- 1.8 mmHg) with a variable effect on azygos flow. The wedged hepatic venous pressure was significantly lower than pretreatment values (19.9 +/- 1.6 compared with 23.4 +/- 2.1 mmHg). We conclude that acute nitrate administration lowers the hepatic venous pressure gradient, either by reducing portal venous inflow or by reducing portal-collateral resistance. Chronic administration reduces portal-collateral flow without consistently lowering the hepatic venous pressure gradient. No evidence of nitrate tolerance or tachyphylaxis was observed.

A Pitfall in Azygos Vein Cannulation in Cirrhotic Patients: Mistaken Cannulation of the Mammary Vein

Azygos venous flow can be measured by a thermodilution catheter in patients with cirrhosis. This is a useful technique since azygos flow is thought to reflect the superior portosystemic collateral flow in these patients. The authors report 3 cases in which mistaken internal mammary vein cannulation mimicked azygos vein cannulation in the supine fluoroscopic view. A lateral fluoroscopic view confirmed internal mammary cannulation. They suggest that if the azygos arch is unpronounced or flow measurements are unexpectedly low in patients with portal hypertension due to cirrhosis, a lateral view be performed to rule out internal mammary vein cannulation.

Glucagon selectively increases splanchnic blood flow in patients with well-compensated cirrhosis.

To delineate the circulatory effects of glucagon in cirrhosis, we infused two moderately supraphysiological doses of this hormone into 19 patients with cirrhosis and determined hemodynamic responses. Patients were divided into a group with good liver function (Pugh Class A, n = 8) and poorer function (Pugh Class B and C, n = 11). All patients received glucagon at 10 ng per kg per min for 20 min, then 20 ng per kg per min for a further 20 min. These doses raised serum glucagon levels to a similar degree in both groups of patients. Serum glucose levels also rose in both groups but to a lesser degree in Class BC patients. Serum noradrenaline and adrenaline remained unchanged in both groups. Heart rate, mean arterial pressure, cardiac index, systemic vascular resistance, hepatic venous pressure gradient and hepatic blood flow were measured basally and during the second glucagon infusion. None of these measurements significantly changed in either group of patients. Azygos and renal venous blood flow were measured basally and during the first and second infusions. Azygos flow increased significantly only in Group A patients: basal, 0.32 +/- 0.03 liter per min; first infusion, 0.40 +/- 0.06 liter per min; second infusion, 0.49 +/- 0.07 liter per min. Corresponding values in Group BC patients were: 0.54 +/- 0.08, 0.54 +/- 0.08 and 0.52 +/- 0.08 liter per min. Renal blood flow did not change significantly. One patient with a portacaval shunt increased superior mesenteric venous flow from 0.78 liter per min to 0.95 liter per min with glucagon.(ABSTRACT TRUNCATED AT 250 WORDS)

The First Open-Heart Repairs of Ventricular Septal Defect, Atrioventricular Communis, and Tetralogy of Fallot Using Extracorporeal Circulation by Cross-Circulation: A 30-Year Follow-up

From March 26, 1954, to July 19, 1955, 45 patients with major cardiac malformations not previously correctable underwent open repair utilizing cross-circulation between patient and donor without donor deaths. All operations were carried out at normothermia with lowered flow rates based on azygos flow studies. Twenty-seven patients, more than half of them infants, had ventricular septal defects closed. There were 8 hospital deaths, and there have been only 2 late deaths in 30 years. Fourteen (87.5%) of 16 who underwent recatheterization have closed defects. The 17 30-year-survivors are all in New York Heart Association Functional Class I. Five patients 4 months to 10 years old were operated on for atrioventricular canal (complete form). All had intractable failure, and 4 had pulmonary hypertension. Two of the 3 hospital deaths were due to heart block. The long-term survivor, a 15-month-old infant at the time of operation (severe pulmonary hypertension, 90/50 mm Hg), underwent repair 31 years ago and is now married with 3 children. Recatheterization disclosed normal pulmonary pressure (20/4 mm Hg), no shunts, and mild mitral regurgitation. Ten cyanotic tetrads 13 months to 14 years old were operated on with 5 hospital deaths. Of the 3 late deaths, 1 was accidental at 17 years, 1 occurred suddenly at home 13 years after operation in infancy for atresia, and the third occurred at reoperation 10 years later. The 2 remaining patients (1 the first patient operated on) are in excellent health. The surgical methods used and the physiological advantages of cross-circulation (temporary placenta) that made these results possible at a time when surgical knowledge was primitive are described.

In Vitro Oxygenation of Fresh Whole Blood for Arterial Perfusion

With the elucidation of the "azygos flow factor" by Andreason and Watson,¹it was established that a markedly reduced venous return and cardiac output were compatible with prolonged survival in dogs. Lillehei²has demonstrated that with caval occlusion produced at normal body temperature azygos vein flow into the right atrium is compatible with survival for periods of 30 to 60 minutes. In dogs this flow amounted to 8 to 14 ml. per kilogram of body weight per minute and was less than 10% of the basal cardiac output. The clinical application of this principle resulted in "cross circulation procedures." with blood flow between donor and patient regulated in the range of 20 to 25 ml. per kilogram per minute. This technique permitted open right cardiotomy and the surgical repair of congenital defects of the interatrial and interventricular septa. Recently, in many laboratories, pump oxygenators have been developed to