Time course of endothelin-1 and adrenomedullin after the Fontan procedure

Unique Pulmonary Hypertensive Vascular Diseases Associated with Heart and Lung Developmental Defects

Although pediatric pulmonary hypertension (PH) shares features and mechanisms with adult PH, there are also some significant differences between the two conditions. Segmental PH is a unique pediatric subtype of PH with unclear and/or multifactorial pathophysiological mechanisms, and is often associated with complex congenital heart disease (CHD), pulmonary atresia with ventricular septal defect, and aortopulmonary collateral arteries. Some cases of complex CHD, associated with a single ventricle after Fontan operation, show pathological changes in the small peripheral pulmonary arteries and pulmonary vascular resistance similar to those observed in pulmonary arterial hypertension (PAH). This condition is termed as the pediatric pulmonary hypertensive vascular disease (PPHVD). Recent advances in genetics have identified the genes responsible for PAH associated with developmental defects of the heart and lungs, such as TBX4 and SOX17. Targeted therapies for PAH have been developed; however, their effects on PH associated with developmental heart and lung defects remain to be established. Real-world data analyses on the anatomy, pathophysiology, genetics, and molecular biology of unique PPHVD cases associated with developmental defects of the heart and lungs, using nationwide and/or international registries, should be conducted in order to improve the treatments and prognosis of patients with these types of pediatric PH.

Design and rationale of re-energize fontan: Randomized exercise intervention designed to maximize fitness in fontan patients

In this manuscript, we describe the design and rationale of a randomized controlled trial in pediatric Fontan patients to test the hypothesis that a live-video-supervised exercise (aerobic+resistance) intervention will improve cardiac and physical capacity; muscle mass, strength, and function; and endothelial function. Survival of children with single ventricles beyond the neonatal period has increased dramatically with the staged Fontan palliation. Yet, long-term morbidity remains high. By age 40, 50% of Fontan patients will have died or undergone heart transplantation. Factors that contribute to onset and progression of heart failure in Fontan patients remain incompletely understood. However, it is established that Fontan patients have poor exercise capacity which is associated with a greater risk of morbidity and mortality. Furthermore, decreased muscle mass, abnormal muscle function, and endothelial dysfunction in this patient population is known to contribute to disease progression. In adult patients with 2 ventricles and heart failure, reduced exercise capacity, muscle mass, and muscle strength are powerful predictors of poor outcomes, and exercise interventions can not only improve exercise capacity and muscle mass, but also reverse endothelial dysfunction. Despite these known benefits of exercise, pediatric Fontan patients do not exercise routinely due to their chronic condition, perceived restrictions to exercise, and parental overprotection. Limited exercise interventions in children with congenital heart disease have demonstrated that exercise is safe and effective; however, these studies have been conducted in small, heterogeneous groups, and most had few Fontan patients. Critically, adherence is a major limitation in pediatric exercise interventions delivered on-site, with adherence rates as low as 10%, due to distance from site, transportation difficulties, and missed school or workdays. To overcome these challenges, we utilize live-video conferencing to deliver the supervised exercise sessions. Our multidisciplinary team of experts will assess the effectiveness of a live-video-supervised exercise intervention, rigorously designed to maximize adherence, and improve key and novel measures of health in pediatric Fontan patients associated with poor long-term outcomes. Our ultimate goal is the translation of this model to clinical application as an "exercise prescription" to intervene early in pediatric Fontan patients and decrease long-term morbidity and mortality.

A Review of Adrenomedullin in Pediatric Patients: A Useful Biomarker

Adrenomedullin has several properties. It acts as a potent vasodilator, has natriuretic effects, and reduces endothelial permeability. It also plays a role in initiating the early hyperdynamic phase of sepsis. Since its discovery, many articles have been published studying the uses and benefits of this biomarker. The aim of this review is to determine the usefulness of adrenomedullin in pediatric patients. Relevant studies covering adrenomedullin in pediatrics (<18 years) and published up until August 2021 were identified through a search of MEDLINE, PubMed, Embase, Web of Science, Scopus, and Cochrane. Seventy studies were included in the present review, most of them with a low level of evidence (IV to VI). Research on adrenomedullin has primarily been related to infection and the cardiovascular field. The performance of adrenomedullin to quantify infection in children seems satisfactory, especially in sepsis. In congenital heart disease, this biomarker seems to be a useful indicator before, during, and after cardiopulmonary bypass. Adrenomedullin seems to be useful in the pediatric population for a large variety of pathologies, especially regarding infection and cardiovascular conditions. However, it should be used in combination with other biomarkers and clinical or analytical variables, rather than as a single tool.

Increased Circulating Endothelin 1 Is Associated With Postoperative Hypoxemia in Infants With Single-Ventricle Heart Disease Undergoing Superior Cavopulmonary Anastomosis

Background Inadequate pulmonary vascular growth results in morbidity for many children with single-ventricle heart disease (SVHD). Endothelin 1 (ET1) is a potent vasoconstrictor and stimulator of pulmonary artery smooth muscle proliferation. Circulating ET1 levels and their association with outcomes have not been studied during early SVHD palliation. We aimed to define circulating levels of ET1 in patients with SVHD undergoing stage 2 palliation and evaluate their relationship to postoperative hypoxemia. We hypothesized that patients with SVHD with higher ET1 concentration would have a greater post-stage 2 hypoxemia. Methods and Results Prospective cohort study of 55 subjects with SVHD undergoing stage 2 palliation and 50 controls. Samples for ET1 analysis were collected at preoperation (systemic and pulmonary vein) and 2, 24, and 48 hours postoperation for cases and a single time point for controls. The primary outcome was percentage of first 48 postoperative hours with clinically significant hypoxemia (saturation, <70%). ET1 concentration was lower in preoperative cases than controls (2.2 versus 2.7 pg/mL; P=0.0015) and in the pulmonary vein than systemic vein (1.7 versus 2.2 pg/mL; P<0.001). ET1 level increased by 2 hours postoperation and trended back to baseline by 48 hours. Higher preoperative pulmonary vein ET1 and 2 hours postoperative ET1 were associated with larger hypoxemia burden (10.6% versus 2.7% [P=0.0081]; and 7.6% versus 3.2% [P=0.01], respectively). Multivariable testing demonstrated ET1 concentration and cardiopulmonary bypass time were associated with hypoxemia, whereas catheterization measurements and clinical variables were not. Conclusions Infants with SVHD with higher perioperative ET1 concentration experience more post-stage 2 hypoxemia. ET1 activity may be a modifiable risk factor of pulmonary vascular inadequacy for stage 2 palliation.

Pulmonary vascular disease in Fontan circulation-is there a rationale for pulmonary vasodilator therapies?

The Fontan circulation is a palliative concept for patients with univentricular hearts. The central veins are connected directly to the pulmonary arteries (cavo-pulmonary connection) to separate the pulmonary and the systemic circulation. There is no sub-pulmonary ventricle that generates pressure to drive blood through the pulmonary arteries. Pulmonary blood flow is determined by central venous pressure (CVP) and pulmonary vascular resistance (PVR). The capability of the Fontan circulation to compensate for alterations in PVR is limited, as CVP can only be increased within narrow ranges without adverse clinical consequences. Consequently, systemic ventricular preload and cardiac output are dependent on a healthy lung with low PVR. Failure of the Fontan circulation is relatively common. In addition to ventricular dysfunction, maladaptive pulmonary vascular remodeling resulting in increased pulmonary resistance may play a key role. The pathophysiology of the maladaptive vascular processes remains largely unclear and diagnosis of an increased PVR is challenging in Fontan circulation as accurate measurement of pulmonary arterial blood flow is difficult. In the absence of a sub-pulmonary ventricle, pulmonary artery pressure will almost never reach the threshold conventionally used to define pulmonary arterial hypertension. There is a need for markers of pulmonary vascular disease complementary to invasive hemodynamic data in Fontan patients. In order to treat or prevent failure of the Fontan circulation, pathophysiological considerations support the use of pulmonary vasodilators to augment pulmonary blood flow and systemic ventricular preload and lower CVP. However, to date the available trial data have neither yielded enough evidence to support routine use of pulmonary vasodilators in every Fontan patient nor have they been helpful in defining subgroups of patients that might benefit from such therapies. This review discusses potential pathomechanisms of pulmonary vascular disease; it summarizes the current knowledge of the effects and efficacy of pulmonary vasodilator therapy in Fontan patients and tries to outline areas of potential future research on the diagnosis and treatment of pulmonary vascular disease and Fontan failure.

Impact of Nesiritide Infusion on Early Postoperative Recovery After Total Cavopulmonary Connection Surgery

OBJECTIVE

The purpose of the study is to compare the effects of nesiritide on the discharge time and pleural effusion in children with total cavopulmonary connection (TCPC), and to provide a more reasonable clinical method for these children.

METHODS

Forty-four who children underwent cavopulmonary connection between January 2016 and 2017 were retrospectively collected, and 5 children were excluded from analysis due to postoperative thrombosis or second Fontan surgery due to high pulmonary hypertension. Thirteen children received nesiritide (3-11 days) plus conventional treatment as the nesiritide group, continuous infusion of nesiritide with the dose of 0.01 ug kg^-1 min^-1. Twenty-six children with the conventional treatment as the conventional treatment group. The length of stay in hospital and the retention time of chest drainage tube were compared between two groups.

RESULTS

There were no significant differences in the time of cardiopulmonary bypass, postoperative ventilation time, ICU time, and vasoactive inotropic drug scores in the two groups. There were no hospital deaths in two groups. The median hospital stay was 20 days in the nesiritide group (11-56 days, means 25 days), and the median length of hospital stay was 28 days in the routine treatment group (9-95 days, means 34 days). There is no statistically significant difference between two groups with regard to the length of stay in hospital (P = 0.281). Regarding the thoracic drainage duration, the median was 17 days (9-55 days, means 22 days) in the nesiritide group and 23 days in the conventional treatment group (7-91 days, means 31 days) (P = 0.294). All the patients had no severe complications such as excessive fluid load, intractable hypotension, and liver or kidney injury.

CONCLUSION

Nesiritide is safe in children who underwent cavopulmonary connection surgery. Compared with the conventional treatment group, postoperative nesiritide is not associated with improved early clinical outcomes after TCPC surgery.

Endothelin-1 may play an important role in the Fontan circulation

OBJECTIVES

Our goal was to evaluate whether endothlin-1 (ET-1) plays an important role in the Fontan circulation.

METHODS

Thirteen patients with single-ventricle physiology (Glenn circulation, n = 7; Fontan circulation, n = 6) were evaluated using lung histopathological and immunohistochemical studies and then compared with the normal autopsied controls without congenital heart disease (n = 13). We evaluated the medial thickness of the small pulmonary arteries. For 10 of these patients, quantitative real-time polymerase chain reaction analyses of ET-1, endothelin receptors Type A and Type B, endothelin-converting enzyme-1 and endothelial nitric oxide synthase were performed.

RESULTS

The medial thickness of the small pulmonary arteries in patients with single-ventricle physiology was greater than that of those in the control group (P = 0.0341). Severe medial hypertrophy of the pulmonary arteries was observed in patients who had poor outcomes. Immunohistochemical studies revealed that the marked expression of ET-1 was observed in the endothelium and media of their pulmonary arteries. In these patients, the messenger RNA expression of ET-1 was also increased. Two patients showed high levels of expression of ETAR and ETBR, although these 2 cases maintain good Fontan circulation.

CONCLUSIONS

Medial hypertrophy and the overexpression of ET-1 in the pulmonary arteries were observed in some patients in whom the Fontan circulation failed. Our data suggest that ET-1 may play an important role in maintaining the Fontan circulation.

Endothelin-1 activation in pediatric patients undergoing surgical coarctation of the aorta repair

AIM

To determine endothelin-1 (ET-1) concentration before and after surgical coarctectomy and evaluate its association with left ventricular geometric change.

METHODS

A prospective, cohort study of 24 patients aged 2 d to 10 years with coarctation of the aorta undergoing surgical repair. A sub-cohort of patients with age < 1 mo was classified as “neonates”. Echocardiograms were performed just prior to surgery and in the immediate post-op period to assess left ventricle mass index and relative wall thickness (RWT). Plasma ET-1 levels were assessed at both time points. Association between ET-1 levels and ventricular remodeling was assessed.

RESULTS

Patients < 1 year demonstrated higher pre-op ET-1 than post-op (2.8 pg/mL vs 1.9 pg/mL, P = 0.02). Conversely, patients > 1 year had no change in ET-1 concentration before and after surgery (1.1 vs 1.4, NS). Pre-op, patients < 1 year demonstrated significantly higher ET-1 than older children (2.8 vs 1.1, P = 0.001). Post-op there was no difference between the age groups (1.9 vs 1.4, NS). Neither RWT nor left ventricle mass index (LVMI) varied from pre-op to post-op. The subset of neonates showed a strong positive correlation between pre-op ET-1 and RWT (r = 0.92, P = 0.001). Patients with ET-1 > 2 pg/mL pre-op demonstrated higher LVMI (65.7 g/m^2.7vs 38.5 g/m^2.7, P = 0.004) and a trend towards higher RWT (45% vs 39%, P = 0.07) prior to repair than those with lower ET-1 concentration.

CONCLUSION

ET-1 concentration is significantly variable in the peri-operative period surrounding coarctectomy. Older children and infants have different responses to surgical repair suggesting different mechanisms of activation.

The Pulmonary Circulation in the Single Ventricle Patient

In recent decades, survival of children with complex congenital heart disease has improved considerably. Specifically, children with a variety of congenital heart defects resulting in ‘single ventricle’ physiology can now undergo palliative surgery that allows survival beyond the neonatal period, and in many cases into adulthood, despite having a single functional ventricular pumping chamber supplying both the pulmonary and systemic circulation. Our growing understanding of the functionally univentricular heart has resulted in freedom from Fontan failure of >50% at 25 years post-Fontan. Yet there is still a fair amount of knowledge to be gained, specifically as it relates to the pulmonary circulation in this group of patients. Knowledge gaps relate not only to the pulmonary circulation after Fontan operation, but also at each stage of the single ventricle surgical palliation, including the native physiology prior to any intervention. The pulmonary circulation is affected by multiple issues related to the single ventricle, including specific details of the anatomy unique to each patient, any intervention(s) undertaken, and potential complications such as aortopulmonary collaterals, protein losing enteropathy, plastic bronchitis, venovenous collaterals, pulmonary arteriovenous fistulae, ventricular dysfunction, pulmonary venous stenosis, and more. This chapter will review the current knowledge with regard to the pulmonary circulation in the single ventricle patient, primarily after the Fontan operation. Additionally, it is our hope to help the practitioner assess the pulmonary circulation in the single ventricle patient; we will also discuss the evidence behind and approach to treatment strategies in order to optimize the pulmonary circulation in this complex group of patients.

Pulmonary vasodilator therapy in the failing Fontan circulation: rationale and efficacy

The Fontan operation is the final step of palliation for patients with a functionally single ventricle. Since its introduction in the 1970s, the Fontan surgery has become part of a successful surgical strategy that has improved single ventricle mortality. In recent years, we have become more aware of the limitations and long-term consequences of the Fontan physiology. Pulmonary vascular resistance plays an important role in total cavopulmonary circulation, and has been identified as a potential therapeutic target to mitigate Fontan sequelae. In this review, we will discuss the results of different pulmonary vasodilator trials and the use of pulmonary vasodilators as a treatment strategy for Fontan patients.

Pulmonary vasodilator therapy and early postoperative outcome after modified Fontan operation

Although mortality is low after the modified Fontan procedure, there is a significant percentage of patients with prolonged postoperative recovery. The objective of this study is to evaluate the usefulness of postoperative administration of oral sildenafil and inhaled nitric oxide on early postoperative outcome. A prospective interventional and comparison study with a historical cohort was conducted. Between January, 2010 and March, 2013, 16 patients received oral sildenafil during immediate modified Fontan postoperative period. Inhaled nitric oxide was also administered if the patient was kept intubated 12 hours after surgery. Early postoperative outcome was compared with a historical cohort of 32 patients on whom the modified Fontan procedure was performed between March, 2000 and December, 2009. Postoperative administration of sildenafil and nitric oxide had no influence on early postoperative outcome after the modified Fontan procedure in terms of duration of pleural effusions, mechanical ventilation time, length of stay in the ICU, and length of hospital stay.

Impact of Empiric Nesiritide or Milrinone Infusion on Early Postoperative Recovery After Fontan Surgery

Background—

We sought to determine whether empirical nesiritide or milrinone would improve the early postoperative course after Fontan surgery. We hypothesized that compared with milrinone or placebo, patients assigned to receive nesiritide would have improved early postoperative outcomes.

Methods and Results—

In a single-center, randomized, double-blinded, placebo-controlled, multi-arm parallel-group clinical trial, patients undergoing primary Fontan surgery were assigned to receive nesiritide, milrinone, or placebo. A loading dose of study drug was administered on cardiopulmonary bypass followed by a continuous infusion for ≥12 hours and ≤5 days after cardiac intensive care unit admission. The primary outcome was days alive and out of the hospital within 30 days of surgery. Secondary outcomes included measures of cardiovascular function, renal function, resource use, and adverse events. Among 106 enrolled subjects, 35, 36, and 35 were randomized to the nesiritide, milrinone, and placebo groups, respectively, and all were analyzed based on intention to treat. Demographics, patient characteristics, and operative factors were similar among treatment groups. No significant treatment group differences were found for median days alive and out of the hospital within 30 days of surgery (nesiritide, 20 [minimum to maximum, 0–24]; milrinone, 18 [0–23]; placebo, 20 [0–23]; P =0.38). Treatment groups did not significantly differ in cardiac index, arrhythmias, peak lactate, inotropic scores, urine output, duration of mechanical ventilation, intensive care or chest tube drainage, or adverse events.

Conclusions—

Compared with placebo, empirical perioperative nesiritide or milrinone infusions are not associated with improved early clinical outcomes after Fontan surgery.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00543309.

Long-term Issues After the Fontan Procedure

The Fontan procedure is used to treat various serious congenital heart defects. Although many people who have had the procedure live productively into adulthood, as they age, they face several health issues due to the physiology of the Fontan circulation. This article reviews the 4 types of Fontan procedures and the changes caused by the surgery, including single-ventricle physiology, nonpulsatile pulmonary perfusion, systemic venous hypertension, and intracardiac scarring, as well as their sequelae. Key nursing assessment items and possible treatment strategies are reviewed. Additional topics, including pregnancy in patients who have undergone the procedure, infective endocarditis prophylaxis, and health-related quality of life, are briefly discussed. Options for Fontan failure, including Fontan conversion or transplantation, are presented. Potential future solutions are outlined.

Modulation of pulmonary vascular resistance as a target for therapeutic interventions in Fontan patients: focus on phosphodiesterase inhibitors

Despite advancements in surgical techniques over the past 20 years, Fontan patients have decreased exercise capacity as a consequence of an inherent inability to adequately increase cardiac output during exercise. They are also affected by several complications that are associated with considerable morbidity and mortality. As the systemic and pulmonary circulations are placed in series without a subpulmonary ventricle propelling blood through the pulmonary vasculature, the systemic venous pressure and the respiratory mechanics are the only forces driving pulmonary blood flow. In Fontan circulation, pulmonary vascular resistance is the single most important factor involved in the limitation of cardiac output and treatments able to decrease pulmonary vascular resistance might conversely improve cardiac output and exercise capacity. In this article we discuss the initial experience with the use of sildenafil in Fontan patients and we discuss the possible mechanisms through which sildenafil might positively act in Fontan circulation.

Possible role of adrenomedullin in the regulation of Fontan circulation: Mature form of plasma adrenomedullin is extracted in the lung in patients with Fontan procedure

OBJECTIVE

We investigated the pathophysiological significance of molecular forms of adrenomedullin (AM) in patients after the Fontan procedure.

METHODS

Plasma concentrations of mature AM (AM-m), an active form, glycine-extended AM (AM-Gly), an inactive form, and total AM (AM-T: AM-m+AM-Gly) were measured by specific immunoradiometric assay in the femoral vein, pulmonary artery and femoral artery of 29 consecutive patients after the Fontan procedure. The eleven patients who had history of Kawasaki disease and have normal coronary and hemodynamics served as control.

RESULTS

Patients who underwent Fontan procedure had significantly higher venous concentrations of AM-T, AM-Gly, and AM-m than age-matched normal controls (AM-T, 12.0+/-3.3 vs. 9.6+/-2.0; AM-Gly, 10.4+/-3.0 vs. 8.5+/-1.6; AM-m, 1.6+/-0.7 vs. 1.0+/-0.6 pmol/l, each p<0.05). In patients with Fontan procedure, there were no differences in plasma AM-T, AM-Gly or AM-m levels between the femoral vein and pulmonary artery, however, there was a significant step-down in the AM-m levels, but not in plasma AM-T or AM-Gly levels, between the pulmonary artery and femoral artery (1.3+/-0.6 to 1.0+/-0.6, p<0.05). The venous concentrations of AM-m correlated negatively with systemic blood flow (cardiac output) (r=-0.46, p<0.05).

CONCLUSIONS

Results suggest that in Fontan circulation plasma AM-m is increased in parallel with those of AM-T and AM-Gly and that AM-m is extracted in the lung. Extracted AM-m may be involved in the regulation of pulmonary arterial tonus, although further studies are necessary to elucidate the exact role of AM in Fontan circulation.

Increased plasma concentrations of the mature form of adrenomedullin during cardiac surgery and hepatosplanchnic hypoperfusion

Adrenomedullin is a potent vasodilatory peptide. Plasma adrenomedullin (AM) concentrations increase during and after cardiopulmonary bypass (CPB). However, the cause of this increase and its site of production have not been identified. We investigated the role of the hepatosplanchnic and cerebral circulations in the increase of plasma AM and investigated whether tissue hypoxygenation is a cause of the AM increase seen during CPB. We measured plasma total AM (AM-T) and the biologically active form of AM, mature AM (AM-m), in seven patients undergoing CPB. Both plasma AM-T and AM-m concentrations increased significantly 60 min after weaning from CPB. At this time point, arterial AM-T and AM-m concentrations were 18-fold and 10-fold larger, respectively, than baseline values measured after the induction of anesthesia. The plasma AM-m concentration and the ratio of AM-m/AM-T in blood from the hepatic vein were significantly larger than those from the radial artery or jugular bulb. The AM-m/AM-T ratio decreased during CPB, suggesting that production of the intermediate form of AM, AM-glycine, is more than that of AM-m. The oxygen tension of the hepatic venous blood (PhvO2) was significantly less during CPB. Plasma AM-m concentrations sampled from the hepatic vein showed a significant negative correlation with PhvO2 at 10 min (r = 0.824; P < 0.02) and 60 min (r = 0.828; P < 0.02) after the onset of CPB. These data suggest that the hepatosplanchnic circulation is an important source of AM-m during CPB. Furthermore, hypoxygenation of the hepatosplanchnic region may be an important cause of this AM-m increase.

Myocyte endothelin exposure during cardioplegic arrest exacerbates contractile dysfunction after reperfusion

Transient left ventricular (LV) dysfunction can occur after cardioplegic arrest. The contributory mechanisms for this phenomenon are not completely understood. We tested the hypothesis that exposure of LV myocytes to endothelin (ET) during simulated cardioplegic arrest would have direct effects on contractile processes with subsequent reperfusion. LV porcine myocytes were randomly assigned to three groups: 1) CONTROL: normothermic (37 degrees C) cell media (n = 204); 2) Cardioplegia: simulated cardioplegic arrest (K(+) 24 mEq/L, 4 degrees C x 2 h) followed by reperfusion and rewarming with cell media (n = 164); and 3) Cardioplegia/ ET: simulated cardioplegic arrest in the presence of ET (200 pM) followed by reperfusion with cell media containing ET (n = 171). Myocyte contractility was measured by computer-assisted video microscopy. In a subset of experiments, myocyte intracellular calcium was determined after Fluo-3 (Molecular Probes, Eugene, OR) loading by digital fluorescence image analysis. Myocyte shortening velocity was reduced after cardioplegic arrest compared with controls (52 +/- 2 vs 84 +/- 3 microm/s, respectively; P < 0.05) and was further reduced with cardioplegic arrest and ET exposure (43 +/- 2 microm/s, P < 0.05). Intracellular calcium was significantly increased in myocytes exposed to cardioplegia compared with normothermic control myocytes and was further augmented by cardioplegia with ET supplementation (P < 0.05). Exposure of the LV myocyte to ET during cardioplegic arrest directly contributed to contractile dysfunction after reperfusion. Moreover, alterations in intracellular calcium may play a role in potentiating the myocyte contractile dysfunction associated with ET exposure during cardioplegic arrest.