Spotlight Cover: Atrioventricular accessory pathways (APs) can cause profound electrical disturbances due to abnormal atrioventricular connections. Traditional approaches are insufficient for studying AP formation during late fetal stages. This study presents an isolated embryonic chick heart model to overcome existing limitations and provide in-depth electrophysiological insights into AP development. https://doi.org/10.1152/ajpheart.00115.2024.
Preeclampsia (PE) is a multisystemic disorder of pregnancy that not only causes perinatal mortality and morbidity but also has a long-term toll on the maternal and fetal cardiovascular system. Women diagnosed with PE are at greater risk for the subsequent development of hypertension, ischemic heart disease, cardiomyopathy, cerebral edema, seizures, and end-stage renal disease. Although PE is considered heterogeneous, inefficient extravillous trophoblast (EVT) migration leading to deficient spiral artery remodeling and increased uteroplacental vascular resistance is the likely initiation of the disease. The principal pathophysiology is placental hypoxia, causing subsequent oxidative stress, leading to mitochondrial dysfunction, mitophagy, and immunological imbalance. The damage imposed on the placenta in turn results in the “stress response” categorized by the dysfunctional release of vasoactive components including oxidative stressors, proinflammatory factors, and cytokines into the maternal circulation. These bioactive factors have deleterious effects on systemic endothelial cells and coagulation leading to generalized vascular dysfunction and hypercoagulability. A better understanding of these metabolic factors may lead to novel therapeutic approaches to prevent and treat this multisystemic disorder. In this review, we connect the hypoxic-oxidative stress and inflammation involved in the pathophysiology of PE to the resulting persistent cardiovascular complications in patients with preeclampsia.
The prevalence of hypertension in non-Hispanic black (BL) individuals is the greatest of any racial/ethnic group. Whereas women generally display lower rates of hypertension than men of the same background, BL women display a similar if not greater burden of hypertension compared with BL men. The risk for cardiovascular disease and related events is also highest in BL individuals. Given the importance of the sympathetic nervous system for the regulation of the cardiovascular system, a growing body of literature has investigated sympathetic function in BL and non-Hispanic white (WH) individuals. Here, we are focused on emerging evidence indicating that sympathetic function may be altered in BL individuals, with particular emphasis on the process by which bursts of muscle sympathetic nerve activity (MSNA) are transduced into vasoconstriction and increases in blood pressure (sympathetic vascular transduction). To synthesize this growing body of literature we discuss sex and race differences in 1) sympathetic outflow, 2) sympathetic vascular transduction, and 3) adrenergic receptor sensitivity. Sex differences are discussed foremost, to set the stage for new data indicating a sex dimorphism in sympathetic regulation in BL individuals. Specifically, we highlight evidence for a potential neurogenic phenotype including greater adiposity-independent sympathetic outflow and enhanced sympathetic vascular transduction in BL men that is not observed in BL women. The implications of these findings for the greater hypertension and cardiovascular disease risk in BL adults are discussed along with areas that require further investigation.
Cardiac fibroblasts play a pivotal role in maintaining heart homeostasis by depositing extracellular matrix (ECM) to provide structural support for the myocardium, vasculature, and neuronal network and by contributing to essential physiological processes. In response to injury such as myocardial infarction or pressure overload, fibroblasts become activated, leading to increased ECM production that can ultimately drive left ventricular remodeling and progress to heart failure. Recently, the American Journal of Physiology-Heart and Circulatory Physiology issued a call for papers on cardiac fibroblasts that yielded articles with topics spanning fibroblast physiology, technical considerations, signaling pathways, and interactions with other cell types. This mini-review summarizes those articles and places the new findings in the context of what is currently known for cardiac fibroblasts and what future directions remain.
https://doi.org/10.1152/ajpheart.00726.2023
Nighttime blood pressure (BP) and BP dipping (daytime–nighttime BP) are prognostic for cardiovascular disease. When compared with other racial/ethnic groups, Black Americans exhibit elevated nighttime BP and attenuated BP dipping. Neighborhood deprivation may contribute to disparities in cardiovascular health, but its effects on resting and ambulatory BP patterns in young adults are unclear. Therefore, we examined associations between neighborhood deprivation with resting and nighttime BP and BP dipping in young Black and White adults. We recruited 19 Black and 28 White participants (23 males/24 females, 21 ± 1 yr, body mass index: 26 ± 4 kg/m2) for 24-h ambulatory BP monitoring. We assessed resting BP, nighttime BP, and BP dipping (absolute dip and nighttime:daytime BP ratio). We used the area deprivation index (ADI) to assess average neighborhood deprivation during early and mid-childhood and adolescence. When compared with White participants, Black participants exhibited higher resting systolic and diastolic BP (Ps ≤ 0.029), nighttime systolic BP (114 ± 9 vs. 108 ± 9 mmHg, P = 0.049), diastolic BP (63 ± 8 vs. 57 ± 7 mmHg, P = 0.010), and attenuated absolute systolic BP dipping (12 ± 5 vs. 9 ± 7 mmHg, P = 0.050). Black participants experienced greater average ADI scores compared with White participants [110 (10) vs. 97 (22), P = 0.002], and select ADI scores correlated with resting BP and some ambulatory BP measures. Within each race, select ADI scores correlated with some BP measures for Black participants, but there were no ADI and BP correlations for White participants. In conclusion, our findings suggest that neighborhood deprivation may contribute to higher resting BP and impaired ambulatory BP patterns in young adults warranting further investigation in larger cohorts.NEW & NOTEWORTHY We demonstrate that young Black adults exhibit higher resting blood pressure, nighttime blood pressure, and attenuated systolic blood pressure dipping compared with young White adults. Black adults were exposed to greater neighborhood deprivation, which demonstrated some associations with resting and ambulatory blood pressure. Our findings add to a growing body of literature indicating that neighborhood deprivation may contribute to increased blood pressure.
https://doi.org/10.1152/ajpheart.00548.2023
Maternal major depressive disorder with peripartum onset presents health risks to the mother and the developing fetus. Using a rat model of chronic mild stress, we previously reported on the neurodevelopmental impact of maternal perinatal stress on their offspring. This study examined the cardiovascular impact of maternal perinatal stress on their offspring. The cardiovascular impact was assessed in terms of blood pressure and echocardiographic parameters. The results examined by a three-way ANOVA showed a significant association of cardiovascular parameters with maternal perinatal stress and offspring sex and age. Increased blood pressure was observed in adolescent female and adult male offspring of stress-exposed dams. Echocardiography showed an increase in left atrial dimension and a reduction in left ventricular systolic function in adolescent stress-exposed female offspring. Increased interventricular septum thickness at end-diastole and left ventricular diastolic dysfunction were observed in adult stress-exposed male offspring. The underlying mechanisms of cardiovascular impact were examined in stress-exposed adult offspring by assessing the levels of neurotransmitters and their metabolites in the medulla oblongata using high-performance liquid chromatography. A significant decrease in homovanillic acid, a dopamine metabolite and indicator of dopaminergic activity, was observed in adult stress-exposed female offspring. These results suggest a significant sex- and age-dependent impact of maternal stress during the peripartum period on the cardiovascular system in the offspring that extends to adulthood and suggests a multigenerational effect. The presented data urgently need follow-up to confirm their potential clinical and public health relevance.NEW & NOTEWORTHY We demonstrate that maternal perinatal stress is associated with sex- and age-dependent impact on the cardiovascular system in their offspring. The effect was most significant in adolescent female and adult male offspring. Observed changes in hemodynamic parameters and dopaminergic activity of the medulla oblongata are novel results relevant to understanding the cardiovascular impact of maternal perinatal stress on the offspring. The cardiovascular changes observed in adult offspring suggest a potential long-term, multigenerational impact of maternal perinatal stress.
https://doi.org/10.1152/ajpheart.00332.2024
Understanding the characteristics and behavior of low-density lipoprotein (LDL) particles provides insights into the atherogenic risk of elevated LDL cholesterol in hypercholesterolemia, cardiovascular disease risks. Studying LDL particles helps identify specific LDL subtypes [e.g., small dense LDL particles (sdLDL)] that may be atherogenic and, consequently, potential targets for therapeutics. This study cohort consists of African Americans (AAs), a population disproportionately affected by cardiovascular diseases, thereby accentuating the importance of the investigation. Differential expression (DE) analysis was undertaken using a dataset comprising 17,947 protein-coding mRNAs from the whole blood transcriptomes of 416 samples to identify mRNAs associated with low-density lipoprotein cholesterol (LDL-C) and sdLDL plasma levels. Subsequently, mediation analyses were used to investigate the mediating role of sdLDL particles on the relationship between LDL-C levels and mRNA expression. Finally, pathway enrichment analysis was conducted to identify pathways involving mRNAs whose relationship with LDL-C is mediated by sdLDL. DE analysis revealed 1,048 and 284 mRNA transcripts differentially expressed by LDL-C and sdLDL levels, respectively. Mediation analysis revealed that the associations between LDL-C and 33 mRNAs were mediated by sdLDL. Of the 33 mRNAs mediated by sdLDL, 18 were mediated in both males and females. Nine mRNAs were mediated only in females, and six were mediated only in males. Pathway analysis showed that 33 mRNAs are involved in pathways associated with the immune system, inflammatory response, metabolism, and cardiovascular disease (CVD) risk. In conclusion, our study provides valuable insights into the complex interplay between LDL-C, sdLDL, and mRNA expression in a large sample of AAs. The results underscore the importance of incorporating sdLDL measurement alongside LDL-C levels to improve the accuracy of managing hypercholesterolemia and effectively stratify the risk of CVD. This is essential as differences in sdLDL modulate atherogenic properties at the transcriptome level.NEW & NOTEWORTHY The study investigated the interplay between LDL-C and mRNA expression, focusing on the role of small dense LDL (sdLDL) particles and sex differences. Differential expression analysis identified 1,048 and 284 mRNAs associated with LDL-C and sdLDL levels, respectively. Mediation analysis revealed that sdLDL mediates the relationship between LDL-C and 33 mRNAs involved in immune, inflammatory, and metabolic pathways. These findings highlight the significance of sdLDL in cardiovascular disease risk assessment and underscore sex-specific differences in lipid metabolism.
https://doi.org/10.1152/ajpheart.00181.2024
Delta-9-tetrahydrocannabinol (THC), the psychoactive component of cannabis, remains a schedule I substance, thus safety data regarding the effects on the cardiovascular and prenatal health are limited. Importantly, there is evidence showing prenatal cannabis exposure can negatively impact fetal organ development, including the cardiovascular system. THC can cross the placenta and bind to cannabinoid receptors expressed in the developing fetus, including on endothelial cells. To understand the impact of prenatal THC exposure on the fetal cardiovascular system, we used our rhesus macaque model of prenatal daily edible THC consumption. Before conception, animals were acclimated to THC (2.5 mg/7 kg/day, equivalent to a heavy medical cannabis dose) and maintained on this dose daily throughout pregnancy. Fetal tissue samples were collected at gestational day 155 (full term is 168 days). Our model showed that in utero THC exposure was associated with a decreased heart weight-to-body weight ratio in offspring, warranting further mechanistic investigation. Histological examination of the fetal cardiac and vascular tissues did not reveal any significant effect of THC exposure on the maturity of collagen within the fetal heart or the aorta. Total collagen III expression and elastin production and organization were unchanged. However, bulk RNA-sequencing of vascular cells in the umbilical vein, umbilical artery, and fetal aorta demonstrated that THC alters the fetal vascular transcriptome and is associated with upregulated expression of genes involved in carbohydrate metabolism and inflammation. The long-term consequences of these findings are unknown but suggest that prenatal THC exposure may affect cardiovascular development in offspring.NEW & NOTEWORTHY Prenatal cannabis use is increasing and despite the public health relevance, there is limited safety data regarding its impact on offspring cardiovascular health outcomes. We used a translational, nonhuman primate model of daily edible Δ-9-tetrahydrocannabinol (THC) consumption during pregnancy to assess its effects on the fetal cardiovascular system. THC-exposed fetal vascular tissues displayed upregulation of genes involved in cellular metabolism and inflammation, suggesting that prenatal THC exposure may impact fetal vascular tissues.
https://doi.org/10.1152/ajpheart.00110.2024
Hypertension, a disease with known sexual dimorphism, accelerates aging-associated arterial stiffening, partly because of the activation of matrix remodeling caused by increased biomechanical load. In this study, we tested the effect of biological sex and the role of the matrix remodeling enzyme lysyl oxidase-like 2 (LOXL2) in hypertension-induced arterial stiffening. Hypertension was induced by angiotensin II (ANG II) infusion via osmotic minipumps in 12- to 14-wk-old male and female mice. Blood pressure and pulse wave velocity (PWV) were measured noninvasively. Wire myography and uniaxial tensile testing were used to test aortic vasoreactivity and mechanical properties. Aortic wall composition was examined by histology and Western blotting. Uniaxial stretch of cultured cells was used to evaluate the effect of biomechanical strain. LOXL2’s catalytic function was examined using knockout and inhibition. ANG II infusion-induced hypertension in both genotypes and sexes. Wild-type (WT) males exhibited arterial stiffening in vivo and ex vivo. Aortic remodeling with increased wall thickness, intralamellar distance, higher LOXL2, and collagen I and IV content was noted in WT males. Female mice did not exhibit increased PWV despite the onset of hypertension. LOXL2 depletion improved vascular reactivity and mechanics in hypertensive males. LOXL2 depletion improved aortic mechanics but worsened hypercontractility in females. Hypertensive cyclic strain contributed to LOXL2 upregulation in the cell-derived matrix in vascular smooth muscle cells (VSMCs) but not endothelial cells. LOXL2’s catalytic function facilitated VSMC alignment in response to biomechanical strain. In conclusion, in males, arterial stiffening in hypertension is driven both by VSMC response and matrix remodeling. Females are protected from PWV elevation in hypertension. LOXL2 depletion is protective in males with improved mechanical and functional aortic properties. VSMCs are the primary source of LOXL2 in the aorta, and hypertension increases LOXL2 processing and shifts to collagen I accumulation. Overall, LOXL2 depletion offers protection in young hypertensive males and females.NEW & NOTEWORTHY We examined the effect of sex on the evolution of angiotensin II (ANG II)-induced hypertension and the role of lysyl oxidase-like 2 (LOXL2), an enzyme that catalyzes matrix cross linking. While ANG II led to hypertension and worsening vascular reactivity in both sexes, aortic remodeling and stiffening occurred only in males. LOXL2 depletion improved outcomes in males but not females. Thus males and females exhibit a distinct etiology of hypertension and LOXL2 is an effective target in males.
https://doi.org/10.1152/ajpheart.00115.2024
Atrioventricular (AV) accessory pathways (APs) provide additional electrical connections between the atria and ventricles, resulting in severe electrical disturbances. It is generally accepted that APs originate in the altered annulus fibrosus maturation in the late prenatal and perinatal period. However, current experimental methods cannot address their development in specific locations around the annulus fibrosus because of the inaccessibility of late fetal hearts for electrophysiological investigation under physiological conditions. In this study, we describe an approach for optical mapping of the retrogradely perfused chick heart in the last third of the incubation period. This system showed stability for electrophysiological measurement for several hours. This feature allowed analysis of the number and functionality of the APs separately in each clinically relevant position. Under physiological conditions, we also recorded the shortening of the AV delay with annulus fibrosus maturation and analyzed ventricular activation patterns after conduction through APs at specific locations. We observed a gradual regression of AP with an area-specific rate (left-sided APs disappeared first). The results also revealed a sudden drop in the number of active APs between embryonic days 16 and 18. Accessory myocardial AV connections were histologically documented in all positions around the annulus fibrosus even after hatching. The fact that no electrically active AP was present at this stage highlights the necessity of electrophysiological evaluation of accessory atrioventricular connections in studying AP formation.NEW & NOTEWORTHY We present the use of retrograde perfusion and optical mapping to investigate, for the first time, the regression of accessory pathways during annulus fibrosus maturation, separately examining each clinically relevant location. The system enables measurements under physiological conditions and demonstrates long-lasting stability compared with other approaches. This study offers applications of the model to investigate electrical and/or functional development in late embryonic development without concern about heart viability.
https://doi.org/10.1152/ajpheart.00144.2024
GelBox is open-source software that was developed with the goal of enhancing rigor, reproducibility, and transparency when analyzing gels and immunoblots. It combines image adjustments (cropping, rotation, brightness, and contrast), background correction, and band-fitting in a single application. Users can also associate each lane in an image with metadata (for example, sample type). GelBox data files integrate the raw data, supplied metadata, image adjustments, and band-level analyses in a single file to improve traceability. GelBox has a user-friendly interface and was developed using MATLAB. The software, installation instructions, and tutorials, are available at https://campbell-muscle-lab.github.io/GelBox/.NEW & NOTEWORTHY GelBox is open-source software that was developed to enhance rigor, reproducibility, and transparency when analyzing gels and immunoblots. It combines image adjustments (cropping, rotation, brightness, and contrast), background correction, and band-fitting in a single application. Users can also associate each lane in an image with metadata (for example, sample type).
https://doi.org/10.1152/ajpheart.00397.2024
Detailed heart rate (HR) response patterns during exercise in patients with heart failure (HF) and sinus rhythm remain uncertain. We screened consecutive patients with HF who underwent cardiopulmonary exercise tests at a large academic center from November 2013 to July 2023. HR response during exercise was statistically classified using logistic differential equation models. A total of 99 patients were included. Of them, 75 patients were assigned to “sigmoidal pattern” and the other 24 to “exponential pattern.” Patients with the sigmoidal pattern were older and exhibited higher plasma B-type natriuretic peptide levels. Increases in HR and oxygen consumption (V̇o2)/kg up to the anaerobic threshold level were not different between both patterns. However, beyond the threshold, the sigmoidal pattern group showed no further increase in HR and significantly lower V̇o2/kg than their counterparts (interactions for P < 0.001). HR response during exercise in patients with heart failure and sinus rhythm was categorized into two unique groups: sigmoidal and exponential patterns. More detailed clarification of the sigmoidal pattern, potentially indicating sinus node dysfunction, should offer new clinical insights for chronotropic incompetence.NEW & NOTEWORTHY Heart rate response patterns can be classified into two groups among patients with chronic heart failure reaching maximal exertion: sigmoidal and exponential.
https://doi.org/10.1152/ajpheart.00398.2024
Chondroitin sulfate proteoglycans (CSPGs) inhibit sympathetic reinnervation in rodent hearts post-myocardial infarction (MI), causing regional hypoinnervation that is associated with supersensitivity of β-adrenergic receptors and increased arrhythmia susceptibility. To investigate the role of CSPGs and hypoinnervation in the heart of larger mammals, we used a rabbit model of reperfused MI and tested electrophysiological responses to sympathetic nerve stimulation (SNS). Innervated hearts from MI and sham rabbits were optically mapped using voltage and Ca2+-sensitive dyes. SNS was performed with electrical stimulation of the spinal cord, and β-adrenergic responsiveness was tested using isoproterenol. Sympathetic nerve density and CSPG expression were evaluated using immunohistochemistry. CSPGs were robustly expressed in the infarct region of all MI hearts, and the presence of CSPGs was associated with reduced sympathetic nerve density in the infarct versus remote region. Action potential duration (APD) dispersion and tendency for induction of ventricular tachycardia/fibrillation (VT/VF) were increased with SNS in MI but not sham hearts. SNS decreased APD at 80% repolarization (APD80) in MI but not sham hearts, whereas isoproterenol decreased APD80 in both groups. Isoproterenol also shortened Ca2+ transient duration at 80% repolarization in both groups but to a greater extent in MI hearts. Our data suggest that sympathetic remodeling post-MI is similar between rodents and rabbits, with CSPGs associated with sympathetic hypoinnervation. Despite a reduction in sympathetic nerve density, the infarct region of MI hearts remained responsive to both physiological SNS and isoproterenol, potentially through preserved or elevated β-adrenergic responsiveness, which may underlie increased APD dispersion and tendency for VT/VF.NEW & NOTEWORTHY Here, we show that CSPGs are present in the infarcts of rabbit hearts with reperfused MI, where they are associated with reduced sympathetic nerve density. Despite hypoinnervation, sympathetic responsiveness is maintained or enhanced in MI rabbit hearts, which also demonstrate increased APD dispersion and tendency for arrhythmias following sympathetic modulation. Together, this study indicates that the mechanisms of sympathetic remodeling post-MI are similar between rodents and rabbits, with hypoinnervation likely associated with enhanced β-adrenergic sensitivity.
https://doi.org/10.1152/ajpheart.00464.2024
Endothelial function declines with aging and independently predicts future cardiovascular disease (CVD) events. Diving also impairs endothelial function in humans. Yet, dolphins, being long-lived mammals adapted to diving, undergo repetitive cycles of tissue hypoxia-reoxygenation and disturbed shear stress without manifesting any apparent detrimental effects, as CVD is essentially nonexistent in these animals. Thus, dolphins may be a unique model of healthy arterial aging and may provide insights into strategies for clinical medicine. Emerging evidence shows that the circulating milieu (bioactive factors in the blood) is at least partially responsible for transducing reductions in age-related endothelial function. To assess whether dolphins have preserved endothelial function with aging because of a protected circulating milieu, we tested if the serum (pool of the circulating milieu) of bottlenose dolphins (Tursiops truncatus) induces the same arterial aging phenotype as the serum of age-equivalent humans. We incubated conduit arteries from young and old mice with dolphin and human serum and measured endothelial function ex vivo via endothelium-dependent dilation to acetylcholine. Although young arteries incubated with serum from midlife/older adult human serum had lower endothelial function, those incubated with dolphin serum consistently maintained high endothelial function regardless of the age of the donor. Thus, studying the arterial health of dolphins could lead to potential novel therapeutic strategies to improve age-related endothelial dysfunction in humans.NEW & NOTEWORTHY We demonstrate that, unlike serum of midlife/older adult humans, age-matched dolphin serum elicits higher endothelial function ex vivo in young mouse carotid arteries, suggesting that the circulating milieu of bottlenose dolphins may be geroprotective. We propose that dolphins are a novel model to investigate potential novel therapeutic strategies to mitigate age-related endothelial dysfunction in humans.
https://doi.org/10.1152/ajpheart.00425.2024
Chronic heart failure is associated with adverse remodeling of the heart that is typically characterized by cardiomyocyte hypertrophy. This requires the formation of new capillaries to maintain oxygen supply. Insufficient angiogenesis promotes the transition from compensated hypertrophy into heart failure. The aim of this study was to identify angiogenesis-related gene networks and corresponding regulatory hubs in endothelial cells from failing human hearts. We isolated left ventricular endothelial cells from patients with advanced heart failure undergoing left ventricular assist device surgery (n = 15) and healthy organ donors (n = 2) and performed RNA sequencing. Subgroup analysis revealed no impact of comorbidities on gene expression. In a weighted gene coexpression network analysis, we found 26 gene clusters, of which 9 clusters showed a significant positive or negative correlation with the presence of heart failure. We identified the transcription factors CASZ1 (castor zinc finger 1), ZNF523 (zinc finger protein 523), and NFE2L1 (nuclear factor erythroid 2-related factor 1) as hub genes of a cluster related to angiogenesis. Knockdown of CASZ1, ZNF523, or NFE2L1 in human umbilical vein endothelial cells led to a downregulation of genes from the respective cluster, including CD34 and platelet-derived growth factor-β, confirming their regulatory function. In conclusion, we assessed gene networks in endothelial cells and identified transcription factors CASZ1, ZNF532, and NFE2L1 as potential regulators of angiogenesis in failing human hearts. Our study provides insights into the transcriptional regulation of angiogenesis beyond the classical vascular endothelial growth factor signaling pathway.NEW & NOTEWORTHY Gene coexpression network analysis defined 26 gene clusters expressed in endothelial cells from failing human hearts. Transcription factors CASZ1, ZNF523, and NFE2L1 were identified as hub genes of a cluster related to angiogenesis. Knockdown of CASZ1, ZNF523, or NFE2L1 in human umbilical vein endothelial cells led to a downregulation of genes from the respective cluster, confirming their regulatory function. This provides insights into the transcriptional regulation of angiogenesis in heart failure beyond classical signaling pathways.
https://doi.org/10.1152/ajpheart.00375.2024
Dexamethasone is frequently prescribed for preterm infants to wean from respiratory support and/or to facilitate extubation. This pre-/postintervention prospective study ascertained the impact on clinical (respiratory support) and echocardiographic parameters after dexamethasone therapy in preterm fetal growth restriction (FGR) infants compared with appropriate for gestational age (AGA) infants. Echocardiography was performed within 24 h before the start and after completion of 10-day therapy. Parameters assessed included those reflecting pulmonary vascular resistance and right ventricular output. Seventeen FGR infants (birth gestation and birth weight, 25.2 ± 1.1 wk and 497 ± 92 g, respectively) were compared with 22 AGA infants (gestation and birth weight, 24.5 ± 0.8 and 663 ± 100 g, respectively). Baseline respiratory severity score (mean airway pressure × fractional inspired oxygen) was comparable between the groups, (median [interquartile range] FGR, 10 [6, 13] vs. AGA, 8 ± 2.8, P = 0.08). Pre-dexamethasone parameters of pulmonary vascular resistance (FGR, 0.19 ± 0.03 vs. AGA, 0.2 ± 0.03, P = 0.16) and right ventricular output (FGR, 171 ± 20 vs. 174 ± 17 mL/kg/min, P = 0.6) were statistically comparable. At post-dexamethasone assessments, the decrease in the respiratory severity score was significantly greater in AGA infants (median [interquartile range] FGR, 10 [6, 13] to 9 [2.6, 13.5], P = 0.009 vs. AGA, 8 ± 2.8 to 3 ± 1, P < 0.0001). Improvement in measures of pulmonary vascular resistance (ratio of time to peak velocity to right ventricular ejection time) was greater in AGA infants (FGR, 0.19 ± 0.03 to 0.2 ± 0.03, P = 0.13 vs. AGA 0.2 ± 0.03 to 0.25 ± 0.03, P < 0.0001). The improvement in right ventricular output was significantly greater in AGA infants (171 ± 20 to 190 ± 21, P = 0.014 vs. 174 ± 17 to 203 ± 22, P < 0.0001). This highlights differential cardiorespiratory responsiveness to dexamethasone in extremely preterm FGR infants, which may reflect the in utero maladaptive state.NEW & NOTEWORTHY Dexamethasone (DEX) is frequently used in preterm infants dependent on ventilator support. Differences in vascular structure and function that may have developed prenatally arising from the chronic intrauterine hypoxemia in FGR infants may adversely affect responsiveness. The clinical efficacy of DEX was significantly less in FGR (birth weight < 10th centile) infants, compared with appropriate for gestational age (AGA) infants. Echocardiography showed significantly less improvement in pulmonary vascular resistance in FGR, compared with AGA infants.
Spotlight Cover: Atrioventricular accessory pathways (APs) can cause profound electrical disturbances due to abnormal atrioventricular connections. Traditional approaches are insufficient for studying AP formation during late fetal stages. This study presents an isolated embryonic chick heart model to overcome existing limitations and provide in-depth electrophysiological insights into AP development. https://doi.org/10.1152/ajpheart.00115.2024.