Lee JH, Denault AY, Beaubien-Souligny W, Cho SA, Ji SH, Jang YE, Kim EH, Kim HS, Kim JT.J Cardiothorac Vasc Anesth. 2023 Aug;37(8):1456-1468. doi: 10.1053/j.jvca.2023.04.010. Epub 2023 Apr 13.PMID: 37183119
Guest Editor:
Zhe Amy Fang, MD MPH
Ann & Robert H. Lurie Children’s Hospital of Chicago
Take-Home Points
What is already known:
- In adults, increased portal vein pulsatility is related to right heart failure, and in the perioperative setting, it is associated with acute kidney injury after cardiac surgery
- Very limited data on portal and splenic venous flow patterns in children with congenital heart disease
What this study adds:
- The portal, splenic, and hepatic vein flow patterns of children differ between different types of congenital heart disease
- Portal vein pulsatility decreased in children with biventricular physiology after surgical repair
- Patients with pulmonary hypertension had significantly higher portal vein pulsatility index compared to those without
- Maximum portal vein velocity is lower in those with Fontan physiology
Introduction
Increased central venous pressure is known to lead to worsening kidney function in patients with decompensated heart failure1. Elevated right sided pressures is transmitted to the inferior vena cava and through the venous system into end-organs leading to congestive organ dysfunction. Portal vein and splenic venous pulsatility and flow patterns is a measure of venous congestion and has shown promise in adults in predicting acute kidney injury in post-operative cardiac surgical patients2. Portal vein pulsatility index (PVPI) is an attractive potential marker as it can be easily obtained at bedside using ultrasound and may thus be used to guide patient management.
Adult studies have shown increased portal vein pulsatility index after cardiopulmonary bypass is associated with longer duration intensive care unit stay, longer need for vasopressor support, and increased incidence of post-operative complications in patients who are at high risk undergoing cardiac surgery3. However, there is a paucity of data examining the portal venous flow patterns in pediatric patients with congenital heart disease. Adult PVPI data does not translate directly into the pediatric population because pediatric patients with congenital heart disease have diverse circulations that range from single to biventricular circulations and it is unknown what effects the different lesions may have on venous flow. Lee et al examined 323 patients with a variety of congenital heart defects and presented their findings on the venous flow patterns of the various lesions4.
Summary of Study
The authors conducted a prospective observational study charactering splanchnic venous flow patterns in 323 pediatric patients with congenital heart disease. Patients received a preoperative transthoracic (TTE) or transesophageal echocardiography (TEE) after induction of anesthesia and a second examination after chest closure. Pulsatility index was calculated as (maximal velocity – minimal velocity)/maximal velocity.
Patients were divided into single ventricle or biventricular group. The biventricular group had 246 patients and included patients who had atrial septal defect (ASD), ventricular septal defect (VSD), and pulmonary stenosis (PS). The single ventricle group had 77 patients and included patients who had Blalock-Taussig-Thomas (BTT) shunt, Glenn or Fontan circulation.
In the biventricular group, the mean PVPI decreased significantly from 38.8% to 25.5% (p < 0.001) after correction of cardiac defects. The splenic venous pulsatility index also decreased significantly after surgery. The portal vein and splanchnic pulsatility indices correlated with each other. Right ventricular (RV) systolic pressure was associated with both portal and splenic vein pulsatility index but were not associated with left ventricular ejection fraction. The hepatic atrial reversal (AR) velocity decreased from 20.1 cm/s to 9.6 cm/s in the biventricular group after surgical repair. The estimated RV pressure was associated with atrial reversal – systole (AR-S) ratio. There were 93 patients with pulmonary hypertension in the biventricular group, and in those with pulmonary hypertension, the PVPI was significantly higher than those without pulmonary hypertension (43.3% vs. 27.7%, p < 0.001). A preoperative PVPI of >32% was predictive of pulmonary hypertension with a sensitivity of 72% and specificity of 76% (AUC 0.769).
In the single ventricle group, the maximum portal vein and hepatic vein flow velocities were significantly lower in those with Fontan physiology compared to those with BTT shunt or Glenn (13.5 cm/s vs. 19.7 cm/s vs. 23.1 cm/s vs., p < 0.001). In both Fontan and Glenn patients, the cardiac index was inversely correlated to the PVPI but not in the BTT shunt patients. There were high interindividual variability in portal and splenic vein pulsatility indices amongst patients with single ventricle physiology. In patients who underwent Fontan procedure without fenestration, the hepatic vein flow had a monophasic flow pattern without atrial reversal flow. Portal vein pulsatility was significantly associated with splenic vein pulsatility and the absolute hepatic atrial reversal velocity.
Opinion
This is the first study that looked at the portal and splanchnic vein flow patterns in pediatric patients with a variety of congenital heart disease. In the adult population, increased PVPI is a marker of venous congestion and associated with AKI after cardiac surgery. Not unexpectedly, patients with pulmonary hypertension had higher portal vein pulsatility index. Furthermore, the biventricular lesions the authors examined in this study, ASD, VSD, and PS are all associated either venous congestion and/or elevated right sided pressures preoperatively. Postoperatively with surgical correction, there was a significant decrease in portal vein pulsatility index.
Patients with single ventricle physiology had significant differences in venous flow patterns compared to those with biventricular circulation. Particularly, patients with Fontan physiology had decreased maximal portal vein velocity. As the single ventricle must provide the mechanical energy required for both the systemic and pulmonary circulation, the portal vein flow velocities would be lower.
Previous studies have examined venous flow patterns in specific lesions. Kutty et al, studied portal vein flow in 20 patients with Glenn circulation and compared to 20 healthy controls5. They found that Glenn patients had higher PVPI (0.55 + 0.18 vs. 0.35 + 0.15, p = 0.001) and lower portal vein flow (137.3 + 77.0 vs 215.7 + 91.4, p = 0.036) compared to controls. Aggarwal et al, investigated the utility of portal vein pulsatility index in 52 patients who underwent tetralogy of Fallot repair6. The authors found PVPI increased to 50% from 35% on the first post-operative day. Furthermore, patients with higher PVPI had longer ICU length of stay, duration of mechanical ventilation and mortality.
The major limitation of this study is the small size of patients in the single ventricle group. There were only 16 patients with BTT shunts, and 22 patients with Fontan physiology. Patients in the biventricular group also had simple lesions. It would of interest to investigate more complex lesions and their effect on venous flow patterns. Furthermore, the measurements of venous flow patterns were measured in the immediate postoperative period, and it would be of interest to see how these patterns change with patient recovery.
Conclusion
Lee, et al provided a descriptive study of portal, splenic and hepatic vein flows patterns in children undergoing congenital cardiac surgery. The authors found that for those with biventricular circulation, the PVPI decreases significantly after corrective surgery. A portal vein pulsatility index of > 32% is predictive pulmonary hypertension with an AUC of 0.769 in patients with two ventricles. In patients with Fontan physiology, the portal vein and hepatic vein flow velocities were significantly lower compared to those with Glenn or BTT shunt physiology. As this is the first study of its kind, it would be of interest to relate portal vein pulsatility index to outcomes after congenital cardiac surgery in the future.
References
1. Mullens, W. et al. Importance of venous congestion for worsening of renal function in advanced decompensated heart failure. J Am Coll Cardiol 53, 589–596 (2009).
2. Beaubien-Souligny, W. et al. Alterations in Portal Vein Flow and Intrarenal Venous Flow Are Associated with Acute Kidney Injury After Cardiac Surgery: A Prospective Observational Cohort Study. J Am Heart Assoc 7, e009961 (2018).
3. Denault, A. et al. Perioperative Doppler ultrasound assessment of portal vein flow pulsatility in high-risk cardiac surgery patients: a multicentre prospective cohort study. Br J Anaesth 129, 659–669 (2022).
4. Lee, J.-H. et al. Evaluation of Portal, Splenic, and Hepatic Vein Flows in Children Undergoing Congenital Heart Surgery. J Cardiothorac Vasc Anesth 37, 1456–1468 (2023).
5. Kutty, S. S. et al. Hepatic stiffness in the bidirectional cavopulmonary circulation: The Liver Adult-Pediatric-Congenital-Heart-Disease Dysfunction Study group. J Thorac Cardiovasc Surg 151, 678–684 (2016).
6. Aggarwal, H. et al. Utility of portal vein pulsatility fraction in patients undergoing corrective surgery for tetralogy of Fallot. Cardiol Young 33, 2357–2362 (2023).
