Exercise capacity in the Bidirectional Glenn physiology: Coupling cardiac index, ventricular function and oxygen extraction ratio

Clinical Interventions and Hemodynamic Monitoring in the Setting of Left Ventricular Systolic Heart Failure in Children: Insights From a Physiologic Simulator

BACKGROUND

In pediatric critical care, vasoactive/inotropic support is widely used in patients with heart failure, but it remains controversial because the influence of multiple medications and the interplay between their inotropic and vasoactive effects on a given patient are hard to predict. Robust evidence supporting their use and quantifying their effects in this group of patients is scarce.

STUDY QUESTION

The aim of this study was to characterize the effect of vasoactive medications on various cardiovascular parameters in pediatric patient with decreased ejection fraction.

STUDY DESIGN

Clinical-data based physiologic simulator study.

MEASURE AND OUTCOMES

We used a physics-based computer simulator for quantifying the response of cardiovascular parameters to the administration of various types of vasoactive/inotropic medications in pediatric patients with decreased ejection fraction. The simulator allowed us to study the impact of increasing medication dosage and the simultaneous administration of some vasoactive agents. Correlation and linear regression analyses yielded the quantified effects on the vasoactive/inotropic support.

RESULTS

Cardiac output and systemic venous saturation significantly increased with the administration of dobutamine and milrinone in isolation, and combination of milrinone with dobutamine, dopamine, or epinephrine. Both parameters decreased with the administration of epinephrine and norepinephrine in isolation. No significant change in these hemodynamic parameters was observed with the administration of dopamine in isolation.

CONCLUSIONS

Milrinone and dobutamine were the only vasoactive medications that, when used in isolation, improved systemic oxygen delivery. Milrinone in combination with dobutamine, dopamine, or epinephrine also increased systemic oxygen delivery. The induced increment on afterload can negatively affect systemic oxygen delivery.

Hemodynamic performance of tissue-engineered vascular grafts in Fontan patients

In the field of congenital heart surgery, tissue-engineered vascular grafts (TEVGs) are a promising alternative to traditionally used synthetic grafts. Our group has pioneered the use of TEVGs as a conduit between the inferior vena cava and the pulmonary arteries in the Fontan operation. The natural history of graft remodeling and its effect on hemodynamic performance has not been well characterized. In this study, we provide a detailed analysis of the first U.S. clinical trial evaluating TEVGs in the treatment of congenital heart disease. We show two distinct phases of graft remodeling: an early phase distinguished by rapid changes in graft geometry and a second phase of sustained growth and decreased graft stiffness. Using clinically informed and patient-specific computational fluid dynamics (CFD) simulations, we demonstrate how changes to TEVG geometry, thickness, and stiffness affect patient hemodynamics. We show that metrics of patient hemodynamics remain within normal ranges despite clinically observed levels of graft narrowing. These insights strengthen the continued clinical evaluation of this technology while supporting recent indications that reversible graft narrowing can be well tolerated, thus suggesting caution before intervening clinically.

Fontan procedure in patients with preoperative mean pulmonary artery pressure over 15 mmHg

BACKGROUND

Several factors affect the long-term outcome of Fontan procedure, but a high pulmonary artery pressure is still one of the most important limitation for proceeding to a Fontan circulation. Herein, we present our experience in Fontan patients with high preoperative pulmonary artery pressures.

METHODS

A retrospective analysis was performed to evaluate Fontan patients with a preoperative pulmonary artery pressure >15 mmHg between 2009 and 2020. Sixteen patients were operated on with a mean preoperative pulmonary artery pressure of 17.5 ± 2.1 mmHg.

RESULTS

Mean age at the time of Fontan procedure was 7.8 ± 5.6 years. All the patients had stage 2 cavopulmonary anastomosis before Fontan completion, with a mean interstage period of 4 ± 2.6 years. Fontan completion was achieved with a polytetrafluorethylene tubular conduit, two of which were intra-extracardiac. Fenestration was performed in five (31%) cases. Postoperative pulmonary artery pressures and arterial oxygen saturation levels were 11.2 ± 2.8 and 97.8 ± 2 mmHg, respectively. Mean duration of pleural drainage was 3.9 ± 5.3 days. Any morbidity and mortality were not encountered during a mean follow-up period of 4.8 ± 7.7 years.

CONCLUSIONS

The midterm results of stage 3 Fontan completion in patients with pulmonary artery >15 mmHg are encouraging. Not only the mean pulmonary artery pressure but also the pulmonary vascular resistance may be helpful in order to identify the high risk patients before Fontan completion.

A computational study of the Fontan circulation with fenestration or hepatic vein exclusion

Fontan patients may undergo additional surgical modifications to mitigate complications like protein-losing enteropathy, liver cirrhosis, and other issues in their splanchnic circulation. Recent case reports show promise for several types of modifications, but the subtle effects of these surgeries on the circulation are not well understood. In this paper, we employ mathematical modeling of blood flow to systematically quantify the impact of these surgical changes on extracardiac Fontan hemodynamics. We investigate two modifications: (1) the fenestrated Fontan and (2) the Fontan with hepatic vein exclusion. Closed-loop hemodynamic models are used, which consist of one-dimensional networks for the major vessels and zero-dimensional models for the heart and organ beds. Numerical results suggest the hepatic vein exclusion has the greatest overall impact on the hemodynamics, followed by the largest sized fenestration. In particular, the hepatic vein exclusion drastically lowers portal venous pressure while the fenestration decreases pulmonary artery pressure. Both modifications increase flow to the intestines, a finding consistent with their utility in clinical practice for combating complications in the splanchnic circulation.