Contemporary Outcomes of Children With Acute Fulminant Myocarditis Supported With Peripheral Extracorporeal Membrane Oxygenation

Despite extracorporeal membrane oxygenation (ECMO) utilization in nearly 20% of cases, there are limited data in children with acute fulminant myocarditis (AFM) requiring ECMO. Herein we identify risk factors for death or heart transplant (HT) in children with AFM supported with ECMO, describe our experience with left atrial (LA) decompression, and depict long-term outcomes of survivors. We performed a retrospective cohort of patients <18 years with AFM (≤14 days of symptoms, rapid cardiogenic shock, and normal left ventricular [LV] size on presentation) supported with ECMO admitted to a single intensive care unit from 1997 to 2021. Among 28 patients (median age 9 years), 21 (75%) survived to discharge without HT. Patients were supported on ECMO for a median of 6 days. Three patients were bridged to HT with durable ventricular assist devices (VAD). Four patients died, two of whom were supported with VAD. At presentation, seven (25%) patients had high grade or complete atrioventricular block and eight (29%) had ventricular tachycardia. Before ECMO cannulation, 21 (75%) patients received CPR. The death/HT group had higher peak troponin levels (12.5 vs . 1.0 ng/ml, p = 0.02) and initial mean LA or pulmonary capillary wedge pressure (27 vs . 18 mm Hg, p = 0.03). Left atrial decompression was performed in 22 patients (79%). Twenty-two (79%) had acute myocarditis on endomyocardial biopsy. Among transplant-free survivors, 18 (86%) had normalization in LV function (median 7 days); the remaining three patients had persistent mild LV dysfunction at last follow-up (median 842 days). Transplant-free survival of pediatric patients with AFM supported on ECMO was 75% and associated with lower initial LA pressure and lower peak troponin. Recovery in ventricular function among survivors was rapid and durable.

Impact of a positive crossmatch on pediatric heart transplant outcomes

BACKGROUND

Pediatric heart transplant (HT) candidates experience high waitlist mortality due to a limited donor pool that is constrained in part by anti-HLA sensitization. We evaluated the impact of CDC and Flow donor-specific crossmatch (XM) results on pediatric HT outcomes.

METHODS

All pediatric HTs between 1999 and 2019 in the OPTN database were included. Donor-specific XM results were sub-categorized based on CDC and Flow results. Primary outcomes were treated rejection in the first year and time to death or allograft loss. Propensity scores were utilized to adjust for differences in baseline characteristics.

RESULTS

A total of 4,695 pediatric HT patients with T-cell XM data were included. After propensity score adjustment, a positive T-cell CDC-XM was associated with 2 times higher odds of treated rejection (OR 2.29 (1.56, 3.37)) and shorter time to death/allograft loss (HR 1.50 (1.19, 1.88)) compared to a negative Flow-XM. HT recipients who were Flow-XM positive with negative/unknown CDC-XM did not have higher odds of rejection or shorter time to death/allograft loss. An isolated positive B-cell XM was also not associated with worse outcomes. Over the study period XM testing shifted from CDC- to Flow-based assays.

CONCLUSIONS

A positive donor-specific T-cell CDC-XM was associated with rejection and death/allograft loss following pediatric HT. This association was not observed with a positive T-cell Flow-XM or B-cell XM result alone. The shift away from performing the CDC-XM may result in loss of important prognostic information unless the clinical relevance of quantitative Flow-XM results on heart transplant outcomes is systematically studied.

Use of apixaban in children awaiting heart transplantation

BACKGROUND

The use of apixaban in the pediatric cardiac population is expanding. We describe our apixaban dosing and monitoring strategy in children and young adults awaiting heart transplantation, along with outcomes related to bleeding and thrombosis during wait-list and early post-transplant periods.

METHODS

This study is a retrospective, single-center analysis of all patients receiving apixaban while awaiting cardiac transplantation. Weight-based dosing was monitored with peak drug-specific anti-Xa chromogenic analysis. Significant post-operative bleeding defined by chest tube output or need for surgical intervention.

RESULTS

From September 2020 to December 2022, 19 patients, median age 13.5 years (6.1, 15.8 years), weighing 48.9 kg (15.4, 67.6) received apixaban while awaiting transplant. Indication for apixaban was prophylaxis (n = 18, 3 with ventricular assist devices) and treatment of thrombus (n = 1). There were no clinically relevant non-major or major bleeding, nor thrombotic events while awaiting transplant. The median time from last apixaban dose to arrival in the operating room was 23.2 h (15.6-33.8), with median random apixaban level of 37 ng/mL (28.3, 59), 6.3 h (4.8, 8.4) prior to arrival in the operating room. In this study, 32% of patients had significant post-operative bleeding based on chest tube output post-transplant or need for intervention. No patients meeting criteria for significant post-operative bleeding were thought to be attributable to apixaban.

CONCLUSIONS

Careful use of apixaban can be safe and effective while awaiting heart transplant. There was no appreciable increase in peri-operative bleeding. The use of apixaban is promising in providing safe, predictable and efficacious anticoagulation while avoiding additional patient stressors.

Nucleated Red Blood Cells Are Predictive of In-Hospital Mortality for Pediatric Patients

PURPOSE

We sought to establish whether nucleated red blood cells (NRBCs) are predictive of disposition, morbidity, and mortality for pediatric patients presenting to the emergency department (ED).

METHODS

A single-center retrospective cohort study examining all ED encounters from patients aged younger than 19 years between January 2016 and March 2020, during which a complete blood count was obtained. Univariate analysis and multivariable logistic regression were used to test the presence of NRBCs as an independent predictor of patient-related outcomes.

RESULTS

The prevalence of NRBCs was 8.9% (4195/46,991 patient encounters). Patient with NRBCs were younger (median age 4.58 vs 8.23 years; P < 0.001). Those with NRBCs had higher rates of in-hospital mortality (30/2465 [1.22%] vs 65/21,741 [0.30%]; P < 0.001), sepsis (19% vs 12%; P < 0.001), shock (7% vs 4%; P < 0.001), and cardiopulmonary resuscitation (CPR) (0.62% vs 0.09%; P < 0.001). They were more likely to be admitted (59% vs 51%; P < 0.001), have longer median hospital length of stay {1.3 (interquartile range [IQR], 0.22-4.14) vs 0.8 days (IQR, 0.23-2.64); P < 0.001}, and median intensive care unit (ICU) length of stay (3.9 [IQR, 1.87-8.72] vs 2.6 days [IQR, 1.27-5.83]; P < 0.001). Multivariable regression revealed presence of NRBCs as an independent predictor for in-hospital mortality (adjusted odds ratio [aOR], 2.21; 95% confidence interval [CI], 1.38-3.53; P < 0.001), ICU admission (aOR, 1.30; 95% CI, 1.11-1.51; P < 0.001), CPR (aOR, 3.83; 95% CI, 2.33-6.30; P < 0.001), and 30-day return to the ED (aOR, 1.15; 95% CI, 1.15-1.26; P < 0.001).

CONCLUSIONS

The presence of NRBCs is an independent predictor for mortality, including in-hospital mortality, ICU admission, CPR, and readmission within 30 days for children presenting to the ED.

Contemporary outcomes of pediatric cardiac transplantation with a positive retrospective crossmatch

BACKGROUND

A positive crossmatch (+ XM) has traditionally been associated with adverse outcomes following pediatric heart transplantation. However, more recent studies suggest that favorable intermediate-term outcomes may be achieved despite a + XM. This study's hypothesis is that children with a + XM have similar long-term survival, but higher rate of complications such as rejection, coronary allograft vasculopathy (CAV), and infection, compared to patients with a negative (-) XM.

METHODS

The Pediatric Heart Transplant Society Registry (PHTS) database was queried from 2010-2021 for all patients <18 years of age with a known XM. Baseline demographics were compared between + XM and - XM groups using appropriate parametric and non-parametric group comparisons. Cox Proportional Hazards Modeling was used to identify risk factors for post-transplant graft loss, rejection, and CAV.

RESULTS

Of 4599 pediatric heart transplants during the study period, XM results were available for 3914 (85%), of which 373 (9.5%) had a + XM. Univariate analysis showed lower 10-year survival for patients with + XM (HR = 1.3, p = .04). Multivariate analyses revealed no significant difference in 10-year survival in the 2 groups; however, time to first rejection (p = .0001) remained significantly shorter in the + XM group.

CONCLUSIONS

Pediatric patients transplanted across a + XM experience earlier rejection; however, after multivariate adjustment, + XM is not independently associated with intermediate-term graft loss. The risk of heart transplantation against a + XM must be balanced with the ongoing risk of waitlist mortality.

Apixaban Anticoagulation in Children and Young Adults Supported With the HeartMate 3 Ventricular Assist Device

There is a growing population of pediatric and adult patients supported with the HeartMate 3 ventricular assist device (HM3 VAD) all of whom require anticoagulation. Apixaban is an anticoagulant requiring less testing than warfarin which has been shown to be effective in other indications. We report five pediatric and young adult patients managed on HM3 VAD with apixaban anticoagulation for 1589 days of VAD support between January 6, 2019 and January 7, 2022. The median age was 17 years and the weight was 69 kg. Four patients had congenital heart disease (2 single-ventricle Fontan circulation, and 2 biventricular circulations) and one had dilated cardiomyopathy. Apixaban was initiated at a median of 7 days postoperatively and doses were titrated based on peak apixaban-specific anti-Xa chromogenic analysis levels (goal 150-250 ng/ml). All patients received aspirin 81 mg daily. There was one major hemocompatibility-related event observed (outflow graft thrombus in the setting of medication nonadherence and chronic VAD infection); there was no major bleeding, death, or stroke. Three patients underwent heart transplantation and two remain on VAD support. In this limited series, apixaban paired with a level-based dosing regimen and low-dose aspirin provided safe and effective antithrombosis with only one hemocompatibility-related event related to medication non-adherence.

Initial multicenter experience with ventricular assist devices in children and young adults with muscular dystrophy: An ACTION registry analysis

PURPOSE

Cardiac disease results in significant morbidity and mortality in patients with muscular dystrophy (MD). Single centers have reported their ventricular assist device (VAD) experience in specific MDs and in limited numbers. This study sought to describe the outcomes associated with VAD therapy in an unselected population across multiple centers.

METHODS

We examined outcomes of patients with MD and dilated cardiomyopathy implanted with a VAD at Advanced Cardiac Therapies Improving Outcomes Network (ACTION) centers from 9/2012 to 9/2020.

RESULTS

A total of 19 VADs were implanted in 18 patients across 12 sites. The majority of patients had dystrophinopathy (66%) and the median age at implant was 17.2 years (range 11.7-29.5). Eleven patients were non-ambulatory (61%) and 6 (33%) were on respiratory support pre-VAD. Five (28%) patients were implanted as a bridge to transplant, 4 of whom survived to transplant. Of 13 patients implanted as bridge to decision or destination therapy, 77% were alive at 1 year and 69% at 2 years. The overall frequencies of positive outcome (transplanted or alive on device) at 1 year and 2 years were 84% and 78%, respectively. Two patients suffered a stroke, 2 developed sepsis, 1 required tracheostomy, and 1 experienced severe right heart failure requiring right-sided VAD.

CONCLUSIONS

This study demonstrates the potential utility of VAD therapies in patients with muscular dystrophy. Further research is needed to further improve outcomes and better determine which patients may benefit most from VAD therapy in terms of survival and quality of life.

The Surprise Question as a Trigger for Primary Palliative Care Interventions for Children with Advanced Heart Disease

There is significant uncertainty in describing prognosis and a lack of reliable entry criteria for palliative care studies in children with advanced heart disease (AHD). This study evaluates the utility of the surprise question-"Would you be surprised if this child died within the next year?"-to predict one-year mortality in children with AHD and assess its utility as entry criteria for future trials. This is a prospective cohort study of physicians and nurses caring for children (1 month-19 years) with AHD hospitalized ≥ 7 days. AHD was defined as single ventricle physiology, pulmonary vein stenosis or pulmonary hypertension, or any cardiac diagnosis with signs of advanced disease. Primary physicians were asked the surprise question and medical record review was performed. Forty-nine physicians responded to the surprise question for 152 patients. Physicians responded "No, I would not be surprised if this patient died" for 54 (36%) patients, 20 (37%) of whom died within 1 year, predicting one-year mortality with 77% sensitivity, 73% specificity, 37% positive predictive value, and 94% negative predictive value. Patients who received a "No" response had an increased 1-year risk of death (hazard ratio 7.25, p < 0.001). Physician years of experience, subspecialty, and self-rated competency were not associated with the accuracy of the surprise question. The surprise question offers promise as a bedside screening tool to identify children with AHD at high risk for mortality and help physicians identify patients who may benefit from palliative care and advance care planning discussions.

Pediatric heart transplant waiting times in the United States since the 2016 allocation policy change

We describe waiting times for pediatric heart transplant (HT) candidates after the 2016 revision to the US allocation policy. The OPTN database was queried for pediatric HT candidates listed between 7/2016 and 4/2019. Of the 1789 included candidates, 65% underwent HT, 14% died/deteriorated, 8% were removed for improvement, and 13% were still waiting at the end of follow-up. Most candidates were status 1A at HT (81%). Median wait times differ substantially by listing status, blood type, and recipient weight. The likelihood of HT was lower in candidates <25 kg and in those with blood type O; The <25 kg, blood type O subgroup experiences longer wait times and higher wait list mortality. For status 1A candidates, median wait times were 108 days (≤25 kg, blood type O), 80 days (≤25 kg, non-O), 47 days (>25 kg, O), and 24 days (>25 kg, non-O). We found that centers with more selective organ acceptance practices, based on a lower median Pediatric Heart Donor Assessment Tool (PH-DAT) score for completed transplants, experience longer status 1A wait times for their listed patients. These data can be used to counsel families and to select appropriate advanced heart failure therapies to support patients to transplant.

Current Practices in Treating Cardiomyopathy and Heart Failure in Duchenne Muscular Dystrophy (DMD): Understanding Care Practices in Order to Optimize DMD Heart Failure Through ACTION

Cardiac disease has emerged as a leading cause of mortality in Duchenne muscular dystrophy in the current era. This survey sought to identify the diagnostic and therapeutic approach to DMD among pediatric cardiologists in Advanced Cardiac Therapies Improving Outcomes Network. Pediatric cardiology providers within ACTION (a multi-center pediatric heart failure learning network) were surveyed regarding their approaches to cardiac care in DMD. Thirty-one providers from 23 centers responded. Cardiac MRI and Holter monitoring are routinely obtained, but the frequency of use and indications for ordering these tests varied widely. Angiotensin converting enzyme inhibitor and aldosterone antagonist are generally initiated prior to onset of systolic dysfunction, while the indications for initiating beta-blocker therapy vary more widely. Seventeen (55%) providers report their center has placed an implantable cardioverter defibrillator in at least 1 DMD patient, while 11 providers (35%) would not place an ICD for primary prevention in a DMD patient. Twenty-three providers (74%) would consider placement of a ventricular assist device (VAD) as destination therapy (n = 23, 74%) and three providers (10%) would consider a VAD only as bridge to transplant. Five providers (16%) would not consider VAD at their institution. Cardiac diagnostic and therapeutic approaches vary among ACTION centers, with notable variation present regarding the use of advanced therapies (ICD and VAD). The network is currently working to harmonize medical practices and optimize clinical care in an era of rapidly evolving outcomes and cardiac/skeletal muscle therapies.

Coagulation profiles and viscoelastic testing in multisystem inflammatory syndrome in children

OBJECTIVE

To characterize viscoelastic testing profiles of children with multisystem inflammatory syndrome in children (MIS-C).

METHODS

This single-center retrospective review included 30 patients diagnosed with MIS-C from March 1 to September 1, 2020. Thromboelastography (TEG) with platelet mapping was performed in 19 (63%) patients and compared to age- and sex-matched controls prior to cardiac surgery. Relationships between TEG parameters and inflammatory markers were assessed using correlation.

RESULTS

Patients with MIS-C had abnormal TEG results compared to controls, including decreased kinetic (K) time (1.1 vs. 1.7 minutes, p < .01), increased alpha angle (75.0° vs. 65.7°, p < .01), increased maximum amplitude (70.8 vs. 58.3 mm, p < .01), and decreased lysis in 30 minutes (Ly30) (1.1% vs. 3.7%, p = .03); consistent with increased clot formation rate and strength, and reduced fibrinolysis. TEG maximum amplitude was moderately correlated with erythrocyte sedimentation rate (ESR) (r = 0.60, p = .02), initial platelet count (r = 0.67, p < .01), and peak platelet count (r = 0.51, p = .03). TEG alpha angle was moderately correlated with peak platelet count (r = 0.54, p = .02). Seventeen (57%) patients received aspirin (ASA) and anticoagulation, five (17%) received only ASA, and three (10%) received only anticoagulation. No patients had a symptomatic thrombotic event. Six (20%) patients had a bleeding event, none of which was major.

CONCLUSIONS

Patients with MIS-C had evidence of hypercoagulability on TEG. Increased ESR and platelets were associated with higher clot strength. Patients were prophylactically treated with ASA or anticoagulation with no symptomatic thrombosis or major bleeding. Further multicenter study is required to characterize the rate of thrombosis and optimal thromboprophylaxis algorithm in this patient population.

Rehabilitation in Pediatric Heart Failure and Heart Transplant

Survival of pediatric patients with heart failure has improved due to medical and surgical advances over the past decades. The complexity of pediatric heart transplant patients has increased as medical and surgical management for patients with congenital heart disease continues to improve. Quality of life in patients with heart failure and transplant might be affected by the impact on functional status that heart failure, heart failure complications or treatment might have. Functional areas affected might be motor, exercise capacity, feeding, speech and/or cognition. The goal of rehabilitation is to enhance and restore functional ability and quality of life to those with physical impairments or disabilities. Some of these rehabilitation interventions such as exercise training have been extensively evaluated in adults with heart failure. Literature in the pediatric population is limited yet promising. The use of additional rehabilitation interventions geared toward specific complications experienced by patients with heart failure or heart transplant are potentially helpful. The use of individualized multidisciplinary rehabilitation program that includes medical management, rehabilitation equipment and the use of physical, occupational, speech and feeding therapies can help improve the quality of life of patients with heart failure and transplant.

The epigenetic modifier ubiquitin-specific protease 22 (USP22) regulates embryonic stem cell differentiation via transcriptional repression of sex-determining region Y-box 2 (SOX2)

Pluripotent embryonic stem cells (ESCs) undergo self-renewal until stimulated to differentiate along specific lineage pathways. Many of the transcriptional networks that drive reprogramming of a self-renewing ESC to a differentiating cell have been identified. However, fundamental questions remain unanswered about the epigenetic programs that control these changes in gene expression. Here we report that the histone ubiquitin hydrolase ubiquitin-specific protease 22 (USP22) is a critical epigenetic modifier that controls this transition from self-renewal to differentiation. USP22 is induced as ESCs differentiate and is necessary for differentiation into all three germ layers. We further report that USP22 is a transcriptional repressor of the locus encoding the core pluripotency factor sex-determining region Y-box 2 (SOX2) in ESCs, and this repression is required for efficient differentiation. USP22 occupies the Sox2 promoter and hydrolyzes monoubiquitin from ubiquitylated histone H2B and blocks transcription of the Sox2 locus. Our study reveals an epigenetic mechanism that represses the core pluripotency transcriptional network in ESCs, allowing ESCs to transition from a state of self-renewal into lineage-specific differentiation programs.

Optimization of direct fibroblast reprogramming to cardiomyocytes using calcium activity as a functional measure of success

Direct conversion of fibroblasts to induced cardiomyocytes (iCMs) has great potential for regenerative medicine. Recent publications have reported significant progress, but the evaluation of reprogramming has relied upon non-functional measures such as flow cytometry for cardiomyocyte markers or GFP expression driven by a cardiomyocyte-specific promoter. The issue is one of practicality: the most stringent measures - electrophysiology to detect cell excitation and the presence of spontaneously contracting myocytes - are not readily quantifiable in the large numbers of cells screened in reprogramming experiments. However, excitation and contraction are linked by a third functional characteristic of cardiomyocytes: the rhythmic oscillation of intracellular calcium levels. We set out to optimize direct conversion of fibroblasts to iCMs with a quantifiable calcium reporter to rapidly assess functional transdifferentiation. We constructed a reporter system in which the calcium indicator GCaMP is driven by the cardiomyocyte-specific Troponin T promoter. Using calcium activity as our primary outcome measure, we compared several published combinations of transcription factors along with novel combinations in mouse embryonic fibroblasts. The most effective combination consisted of Hand2, Nkx2.5, Gata4, Mef2c, and Tbx5 (HNGMT). This combination is >50-fold more efficient than GMT alone and produces iCMs with cardiomyocyte marker expression, robust calcium oscillation, and spontaneous beating that persist for weeks following inactivation of reprogramming factors. HNGMT is also significantly more effective than previously published factor combinations for the transdifferentiation of adult mouse cardiac fibroblasts to iCMs. Quantification of calcium function is a convenient and effective means for the identification and evaluation of cardiomyocytes generated by direct reprogramming. Using this stringent outcome measure, we conclude that HNGMT produces iCMs more efficiently than previously published methods.

The association between refractive cutoffs for spectacle provision and visual improvement among school-aged children in South Africa

OBJECTIVES

To evaluate different refractive cutoffs for spectacle provision with regards to their impact on visual improvement and spectacle compliance.

DESIGN

Prospective study of visual improvement and spectacle compliance.

PARTICIPANTS

South African school children aged 6-19 years receiving free spectacles in a programme supported by Helen Keller International.

METHODS

Refractive error, age, gender, urban versus rural residence, presenting and best-corrected vision were recorded for participants. Spectacle wear was observed directly at an unannounced follow-up examination 4-11 months after initial provision of spectacles. The association between five proposed refractive cutoff protocols and visual improvement and spectacle compliance were examined in separate multivariate models.

MAIN OUTCOMES

Refractive cutoffs for spectacle distribution which would effectively identify children with improved vision, and those more likely to comply with spectacle wear.

RESULTS

Among 8520 children screened, 810 (9.5%) received spectacles, of whom 636 (79%) were aged 10-14 years, 530 (65%) were girls, 324 (40%) had vision improvement > or = 3 lines, and 483 (60%) were examined 6.4+/-1.5 (range 4.6 to 10.9) months after spectacle dispensing. Among examined children, 149 (31%) were wearing or carrying their glasses. Children meeting cutoffs < or = -0.75 D of myopia, > or = +1.00 D of hyperopia and > or = +0.75 D of astigmatism had significantly greater improvement in vision than children failing to meet these criteria, when adjusting for age, gender and urban versus rural residence. None of the proposed refractive protocols discriminated between children wearing and not wearing spectacles. Presenting vision and improvement in vision were unassociated with subsequent spectacle wear, but girls (p < or = 0.0006 for all models) were more likely to be wearing glasses than were boys.

CONCLUSIONS

To the best of our knowledge, this is the first suggested refractive cutoff for glasses dispensing validated with respect to key programme outcomes. The lack of association between spectacle retention and either refractive error or vision may have been due to the relatively modest degree of refractive error in this African population.

Factors associated with spectacle-wear compliance in school-aged Mexican children

PURPOSE

To study the prevalence and determinants of compliance with spectacle wear among school-age children in Oaxaca, Mexico, who were provided spectacles free of charge.

METHODS

A cohort of 493 children aged 5 to 18 years chosen by random cluster sampling from primary and secondary schools in Oaxaca, Mexico, all of whom had received free spectacles through a local program, underwent unannounced, direct examination to determine compliance with spectacle wear within 18 months after initial provision of spectacles. Potential determinants of spectacle wear including age, gender, urban versus rural residence, presenting visual acuity, refractive error, and time since dispensing of the spectacles were examined in univariate and multivariate regression models. Children not currently wearing their spectacles were asked to select the reason from a list of possibilities, and reasons for noncompliance were analyzed within different demographic groups.

RESULTS

Among this sample of children with a mean age of 10.4 +/- 2.6 years, the majority (74.5%) of whom were myopic (spherical equivalent [SE] < or = -0.50 D), 13.4% (66/493) were wearing their spectacles at the time of examination. An additional 34% (169/493) had the spectacles with them but were not wearing them. In regression models, the odds of spectacle wear were significantly higher among younger (OR = 1.19 per year of age; 95% CI, 1.05-1.33) rural (OR = 10.6; 95% CI, 5.3-21.0) children and those with myopia < or = -1.25 D (OR = 3.97; 95% CI, 1.98-7.94). The oldest children and children in urban-suburban areas were significantly more likely to list concerns about the appearance of the glasses or about being teased than were younger, rurally resident children.

CONCLUSIONS

Compliance with spectacle wear may be very low, even when spectacles are provided free of charge, particularly among older, urban children, who have been shown in many populations to have the highest prevalence of myopia. As screening programs for refractive error become increasingly common throughout the world, new strategies are needed to improve compliance if program resources are to be maximized.