BACKGROUND:Donor-derived cell-free DNA (dd-cfDNA), a noninvasive biomarker for heart allograft rejection, was initially developed based on the percent of total cfDNA. A two-threshold algorithm (2TA) was recently developed, assigning high risk of rejection if dd-cfDNA was ≥0.26% or donor-quantity score (DQS) was ≥18 copies/mL based on histologic biopsy assessment. The present study evaluated 2TA for its performance in detecting molecular rejection using the Molecular Microscope Diagnostic System (MMDx). METHODS:We assessed endomyocardial biopsies with matched dd-cfDNA assessments from the multicenter, prospective Trifecta-Heart study (ClinicalTrials.gov, NCT04707872). RESULTS:Among 366 biopsy-matched samples from 236 patients, MMDx classified 108 biopsies as rejection and 258 as no rejection. Median dd-cfDNA% and DQS were significantly higher in rejection vs non-rejection (0.67% vs 0.07%; 44 vs 1 copies/mL; p<0.001 for both) and were higher in antibody-mediated, T cell-mediated, and mixed rejection. Compared to the previous 0.15% dd-cfDNA cutoff, 2TA provided higher specificity (83.7% vs 76.7%) but similar sensitivity (83.3% vs 82.4%), reducing false positives by 30% with AUC of 0.87, a net reclassification index of 7.23%, and detecting molecular rejection better than histologic rejection. Each 0.05% increase in dd-cfDNA% and 5-copy/ml increase in DQS raised the odds of MMDx rejection by 14% and 20%, respectively. CONCLUSIONS:Using dd-cfDNA% with DQS for heart transplant rejection improves specificity and AUC compared to the previous cutoff, predicting molecular rejection better than histologic rejection.

BACKGROUND:Obesity is a major risk factor for atrial fibrillation and heart failure. We aimed to characterize left atrial (LA) structural and functional changes across body mass index (BMI) strata in patients with atrial fibrillation referred for catheter ablation. METHODS:We studied 1040 consecutive patients (67% male; mean age, 62 years; 71% in sinus rhythm). Participants were stratified by BMI (<25.0, 25-29.9, 30-34.9, and ≥35 kg/m2). Comprehensive echocardiographic assessment of LA structure and function was integrated with invasive LA pressure measurements obtained via transseptal access during the ablation procedure. Associations across BMI strata were evaluated using regression analyses. RESULTS:Patients with higher BMI had larger estimated total blood and plasma volumes along with higher LA volumes and pressures, greater cyclic wall stress, and a rightward shift of the estimated LA pressure-volume relationship. Conversely, estimated operant LA stiffness did not differ across BMI strata. BMI-related differences in LA volume were attenuated by body surface area indexing but preserved with height-based indexing. Conventional volumetric indices of LA phasic function were similar across BMI strata, whereas available LA strain indices (n=107) were lower with greater adiposity, consistent with worse LA phasic function. Compared with patients without heart failure, those with heart failure exhibited more pronounced structural, functional, and hemodynamic atrial remodeling, consistent with a more advanced atrial myopathy phenotype. CONCLUSIONS:In patients undergoing atrial fibrillation ablation, higher BMI is associated with a predominantly load-related pattern of LA remodeling, characterized by larger LA volume and pressures, greater cyclic wall stress, and a rightward shift of the estimated pressure-volume relationship. BMI-associated early atrial remodeling may precede overt atrial dysfunction, potentially contributing to the link between excess adiposity, atrial fibrillation, and heart failure with preserved ejection fraction.

IntroductionChronic inflammation is increasingly recognized as a key contributor to the development and progression of heart failure (HF), with epicardial adipose tissue (EAT) emerging as an important local immunomodulatory organ. This study examined lymphocyte populations in EAT and subcutaneous adipose tissue (SAT) across different stages of HF and compared them with individuals without HF to clarify their potential role in HF progression.MethodsLymphocyte subsets in EAT, SAT, and peripheral blood were analyzed by flow cytometry in subjects with HF stage D, HF stage C, and subjects without HF. Circulating hormones and inflammatory proteins were quantified using ELISA and Luminex assays.ResultsSubjects with HF stage D exhibited a reduction in T helper (Th), cytotoxic T (Tc), natural killer T (NKT), and B cells in EAT compared with both HF stage C subjects and subjects without HF, alongside changes observed in the circulation. In contrast, HF stage C was characterized by a significantly increased presence of Th2 and Th17 lymphocytes in EAT, indicating active immune remodeling during intermediate stages of HF. This stage was also associated with elevated circulating levels of Intracellular Adhesion Molecule-1, suggesting enhanced lymphocyte trafficking into adipose tissue. Across all study groups, EAT consistently contained a higher proportion of pro-inflammatory lymphocytes compared with SAT.ConclusionTogether, these findings demonstrate that HF progression is accompanied by dynamic and stage-dependent changes in lymphocyte composition within adipose tissue, supporting the concept that a progressively pro-inflammatory EAT microenvironment may contribute to myocardial inflammation dysfunction-associated HF progression.

We investigated how inflammatory fibroblasts (IFs) contribute to acute viral myocarditis, a dangerous inflammatory heart disease often caused by infections like coxsackievirus B3 (CVB3). Using CCL2-mCherry reporter mice, we tracked IF kinetics during CVB3 infection and discovered that their activity peaks on day 3 of myocarditis and is characterized by the production of Th1, Th2, and Th17 chemokines rather than typical profibrotic genes. We identified IL-1β as the most potent activator of this inflammatory state. We generated PDGFRαcreIL1r1fl/fl mice to specifically delete IL-1 signaling in fibroblasts. This targeted deletion reduced total cardiac inflammation by 45%-specifically lowering monocytes, T cells, and NK cells-without affecting viral clearance. By confirming the presence of IFs in endomyocardial biopsies from human patients, we have shown that fibroblast-specific IL-1 signaling is a critical driver of disease and a potential therapeutic target.

Chronic volume overload due to high-output heart failure profoundly alters pulmonary hemodynamics, yet its impact on the segmental distribution of pulmonary vascular resistance (PVR) is poorly defined. We hypothesized that long-term volume overload from an aortocaval fistula (ACF) induces compensatory reductions in microvascular and venous resistance while preserving vasoregulatory responsiveness. ACF was surgically induced in 8-week-old male Sprague-Dawley rats (n = 6); sham-operated controls (n = 6) underwent the same procedure without fistula creation. Six months later, isolated perfused and ventilated lungs were studied ex vivo. Hemodynamic parameters were recorded at controlled perfusion flow (40.0 ml/min/kg BW), and pressure–flow relationships were analyzed. Pulmonary artery, venous, and double-occlusion techniques were applied to partition total PVR into arterial, capillary, and venous segments. Hypoxic ventilation, angiotensin II, and norepinephrine were used to assess vasoreactivity. At matched flow, the ACF group exhibited a significantly lower total PVR, assessed as the slope of the pressure–flow relationship (0.05 ± 0.01 vs. 0.09 ± 0.04 mmHg·min·ml - ¹·kg, P < 0.05), which was accompanied by reduced baseline perfusion pressure (6.1 ± 1.5 vs. 8.0 ± 1.4 mmHg, P = 0.05). Segmental analysis revealed a trend toward reduced arterial pressure drop (1.7 ± 1.0 vs. 2.9 ± 1.1 mmHg, P = 0.07) and marked declines in capillary (0.8 ± 0.7 vs. 3.1 ± 1.1 mmHg, P < 0.05) and venous pressure drop (0.7 ± 1.5 vs. 2.8 ± 1.2 mmHg, P < 0.05). These changes were preserved during hypoxic pulmonary vasoconstriction. Lung wet weight tended to be higher (P = 0.07), but dry weight was significantly increased in ACF lungs (0.13 ± 0.02 vs. 0.10 ± 0.01 g, P = 0.01), indicating structural remodeling. Hypoxic and angiotensin II responses were preserved, while the norepinephrine response was augmented. These findings demonstrate a robust adaptation to chronic volume overload characterized by segment-specific post-arteriolar remodeling with preserved vasoreactivity. This structural adjustment likely mitigates pulmonary capillary hydrostatic pressure, suggesting that clinical pulmonary hypertension in high-output states is driven by excessive flow and preload rather than intrinsic vascular disease. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

BACKGROUND:This study aimed to explore the association of long-term left ventricular assist device (LVAD) support with changes in inflammation and cardiac remodelling in subjects with advanced heart failure (HF). METHODS:A single-centre prospective observational trial was conducted in 16 consecutive subjects with advanced HF who were indicated for implantation of HeartMate 3 LVAD. Blood samples were collected both during the procedure (V1) and 12 months postoperatively (V2) for comprehensive analysis. Additionally, in a subgroup of seven LVAD subjects listed for heart transplantation (HTx), a histological examination was performed on myocardial samples obtained during LVAD implantation and from the explanted heart following HTx. RESULTS:LVAD implantation was associated with reductions in brain natriuretic peptide (324.7±47.0 vs 124.6±50.3 pg/mL) and C reactive protein (15.2±3.8 vs 6.0±1.3 mg/L) levels. Decreased inflammation markers coincided with reduced levels of lymphocyte- and macrophage-derived cytokines and their stimulating factors. LVAD implantation was associated with modulation of circulating biomarkers related to negative cardiac remodelling processes, including reductions in fibrosis- and remodelling-associated mediators (Extracellular Matrix Metalloproteinase Inducer, fibroblast growth factor (FGF)-2, FGF-19, receptor for advanced glycation endproducts, suppression of tumourigenicity 2, interleukin 27) and angiogenesis-related factors (stromal cell-derived factor-1α, growth differentiation factor (GDF)-15, somatotropin, vascular endothelial growth factor, angiopoietin 1, hepatocyte growth factor). In parallel, markers of metabolism and systemic catabolic state were significantly modulated, with decreases in GDF-15, somatotropin, trefoil factor 3 and resistin and increases in leptin levels. Histological analysis of myocardial samples available from a subgroup of subjects showed reduced macrophage infiltration following LVAD implantation. CONCLUSIONS:Long-term LVAD support was associated with improved biochemical and haematological profiles and with coordinated changes in circulating markers of inflammation, metabolism and cardiac remodelling. These exploratory findings provide further insight into the biological changes associated with durable mechanical unloading in subjects with advanced HF.

Aims:Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have demonstrated cardioprotective effects in heart failure (HF), yet the molecular mechanisms underlying these benefits remain incompletely understood. This study aimed to characterize cardioprotective effects of SGLT2i, changes of circulating growth and inflammatory factors, as well as adipose tissue gene expression, in subjects with advanced HF (stage D). Methods:27 subjects with HF undergoing cardiovascular surgery were included, comprising 17 subjects treated with SGLT2i and 10 untreated controls. Soluble factors were analysed using Luminex assay, and mRNA expression in subcutaneous (SAT) and epicardial adipose tissue (EAT) was assessed. Results:Subjects receiving SGLT2i exhibited a non-significant trend toward lower BNP concentrations (329.1 ± 78.7 vs. 514.2 ± 103.8 pmol/L, p = 0.079) and increased circulatory levels of anti-inflammatory IL-10 (7.2 ± 0.4 vs. 5.8 ± 0.7 pg/mL, p = 0.025) and cardioprotective TGF-α (3.5 ± 0.3 vs. 2.7 ± 0.4 pg/mL, p = 0.039). sVEGFR3 levels (82.3 ± 4.7 vs. 63.3 ± 3.9 pg/mL, p = 0.010) were higher in SGLT2i, suggesting altered lymphangiogenic signalling. Transcriptomic analysis showed lower expression of genes associated with inflammation (IL6, CCL2, CXCL2), cardiac hypertrophy (PKFP, NAMPT), fibrosis (TNC, TNFAIP3), and cellular senescence (ICAM1, CDKN1A), predominantly in SAT. Conclusions:SGLT2i therapy in advanced HF was associated with higher circulating IL-10, TGF-α and sVEGFR3 levels and with a more favourable adipose tissue gene expression profile characterized by lower expression of genes related to inflammation, fibrosis, and cellular senescence. These findings identify molecular pathways associated with SGLT2i therapy that warrant further mechanistic investigation.

Human atrial chambers derive from distinct embryonic anlagens, the original embryonic atria gradually transforming into the so-called auricles, or atrial appendages. This study quantifies macroscopic variations in pectinate muscle architecture in human atrial appendages and evaluates their visualization using clinical imaging modalities. We examined 153 cadaveric donor hearts (103 specified sex: 61 female, 42 male; plus 50 unspecified), employing gross dissection, ex vivo micro-CT, histology, and in vivo clinical imaging (CT angiography, MRI, and transthoracic/transesophageal echocardiography). Left atrial appendage (LAA) morphologies (Wang classification) comprised chicken-wing (41%), cactus (23%), cauliflower (22%), and windsock (14%) types, with 11 ± 4 (mean ± SD) main pectinate muscles (length: 47 ± 16 mm). Right atrial appendage (RAA) pectinate muscle arrangements (Loukas classification) were dominated by type IV (41%), followed by types I/II (22%/20%), with 17 ± 4 muscles (length: 75 ± 17 mm); the RAAs were larger (p < 0.001) but showed lower muscle density (p = 0.007) than the LAAs. All modalities resolved main pectinate bundles, with angio-CT providing superior LAA detail; transesophageal echocardiography excelled for both sides. Precise atrial appendage morphology informs catheter ablation, pacing, and stroke risk stratification, bridging anatomical and clinical perspectives.

BACKGROUND:Heart failure with preserved ejection fraction (HFpEF) is causally related to obesity. Adipose tissue accumulates when energy intake exceeds expenditure. Resting metabolic rate (RMR) is a key determinant of energy expenditure, but it has not been evaluated in HFpEF. METHODS:Patients with HFpEF undergoing invasive hemodynamic exercise testing were categorized into lower- or higher-than-expected measured RMR groups based on the difference between directly measured RMR, calculated using the Weir equation (indirect calorimetry) and predicted RMR, estimated using the Mifflin-St. Jeor equation. RESULTS:Of 472 patients with HFpEF, 212 had lower-than-expected RMRs, and 260 had higher-than-expected RMRs. Compared with patients with lower-than-expected RMRs, those with higher-than-expected RMRs were older (69 ± 10 vs 65 ± 11 years; P < 0.001), more commonly women (66.2% vs 43.9%; P <0.001), and less likely to be obese (53.9% vs 75.0%; P < 0.001). At rest, patients with higher-than-expected RMRs displayed hemodynamic adaptations consistent with increased metabolic demand, including left ventricular dilation, higher stroke work and stroke volume index, and vasodilation. However, during exercise, patients with higher-than-expected RMRs displayed blunted augmentation in cardiac performance and inadequate vasodilation, indicating impaired cardiovascular reserve. Over a median follow-up of 4.6 (2.2, 6.4) years, patients with higher-than-expected RMRs had greater risks of cardiovascular death or hospitalization due to HF compared with those with lower-than-expected RMRs (HR 2.66 [95% CI 1.43-4.94]; P = 0.002). CONCLUSIONS:Patients with HFpEF and lower-than-expected RMRs have a greater prevalence of obesity, and those with higher-than-expected RMRs display circulatory adaptations to heightened metabolic demand at rest, which are coupled with blunted reserve capacity during exercise and increased risk for adverse clinical outcomes. Further studies are warranted to elucidate the underlying mechanisms by which RMRs contribute to the pathophysiology of HFpEF and to clarify its potential use in therapeutic strategies.

BACKGROUND:No large registries of patients with acute eosinophilic myocarditis (EM) are available. However, EM is perceived as a cardiac disease with high mortality, affecting mainly young and middle-aged adults according to small series and case reports. Awareness of the clinical presentation, associated systemic conditions, treatments, and outcomes of this uncommon condition is an unmet need. METHODS:In this international, multicenter, retrospective cohort study, 53 centers screened 193 patients with histologically proven acute EM between 1992 and 2023. After the exclusion of patients with insufficient data (n=10), symptoms lasting >30 days (n=19), or histological diagnosis not confirmed after review (n=8), 156 patients were included. RESULTS:Median age at presentation was 48 years (first to third quartile, 34-59 years) with male predominance (67.3%), and only 2 were pediatric cases (≤16 years of age; 1.3%). The main signs and symptoms at presentation were dyspnea (75.6%), fever (61.3%), and chest pain (53.2%). Unexpectedly, peripheral eosinophilia was reported in only 57.4% of cases, with a median cell count of 630 eosinophils/μL. The median left ventricular ejection fraction at presentation was 32% (first to third quartile, 25%-48%). The disorders most frequently associated with EM were eosinophilic granulomatosis with polyangiitis (22.4% of cases) and hypersensitivity forms (14.1%). Idiopathic/undefined forms accounted for 44.9% of cases, and miscellaneous causes accounted for 18.6%. In-hospital death or need for heart transplantation (HTx) occurred in 23 patients (14.7%; 22 deaths and 1 HTx), despite 43.6% being treated with temporary mechanical circulatory support and 92.9% being treated with immunosuppressive agents. Estimated rates of death or HTx at 1 and 3 years were 19.0% and 23.8%. Increased age, decreased left ventricular ejection fraction on admission, and no immunosuppressive therapy during hospitalization were independent predictors of death or HTx. A nonsignificant higher occurrence of deaths or HTx was observed in the hypersensitivity form (46.1%) compared with the eosinophilic granulomatosis with polyangiitis-associated form (13.1%) at 3 years (P=0.15). CONCLUSIONS:Acute EM can often present without peripheral eosinophilia, and rates of in-hospital and midterm mortality or HTx are high. Endomyocardial biopsy is required to reach the final diagnosis of EM because relying on peripheral eosinophilia can lead to missing diagnosis. In-hospital immunosuppression is associated with HTx-free survival, although tailored immunosuppressive therapies are needed to improve outcomes. REGISTRATION:URL: https://www.clinicaltrials.gov; Unique identifier: NCT06447935.

Type 2 diabetes is associated with small vessels dysfunction. This study assessed whether type 2 diabetes is associated with changes in the myocardial capillary pattern in two-dimensional histological sections as an indirect proxy for the three-dimensional network in the myocardium. We used myocardial samples from the left and right ventricles harvested during cardiac surgery (N = 53; 44 without and 9 with type 2 diabetes). We prepared histological sections with CD34-immunostained endothelium. We used cross-sections through the small vessels as points for two methods of point-pattern analysis: Voronoi-based analysis and fractal-based analysis. We were unable to detect differences in the microvascular pattern on myocardial sections of participants with and without type 2 diabetes.

Ischemic cardiomyopathy (ICM) is a major cause of cardiovascular morbidity and mortality, characterized by a complex pathophysiological substrate and heterogeneous clinical trajectories. Despite decades of investigation, its diagnosis and management remain challenging, particularly regarding the role of coronary revascularization in addition to optimal medical therapy. Recent advances in pharmacotherapy, device-based interventions, and percutaneous techniques have expanded treatment options, but important evidence gaps persist. This state-of-the-art review critically appraises the contemporary diagnosis and management of ICM. Particular emphasis is placed on the integration of multimodality non-invasive imaging into clinical decision-making, the reinterpretation of myocardial viability and revascularization in light of recent randomized evidence, and the interface between chronic coronary syndrome guidance and heart failure with reduced ejection fraction care in patients with ischemic LV dysfunction. By integrating these domains, the review supports a management approach in which guideline-directed medical and device therapy remain foundational, whereas revascularization is individualized according to myocardial substrate, coronary anatomy, symptoms, comorbidities, procedural risk, and multidisciplinary Heart Team assessment.

BACKGROUND:Antibody-mediated rejection (ABMR) in heart transplants is often negative for donor-specific antibody (DSA). We explored potential molecular differences between DSA-negative and DSA-positive molecular ABMR in 212 heart endomyocardial biopsies from the prospective Trifecta-Heart study (NCT04707872). METHODS:We characterized rejection in biopsies by the Molecular Microscope Diagnostic System (MMDx) and by histology, and at the time of biopsy, measured donor-derived cell-free DNA (dd-cfDNA, the Prospera test, Natera, Inc) and central plasma DSA (One Lambda Inc, assessed by L.G.H.). RESULTS:MMDx ABMR was 53% (33/63) DSA-positive and 79% (50/63) dd-cfDNA positive. DSA-negative (N = 33) and DSA-positive (N = 30) molecular ABMR were similar in days post-transplant (861 vs 1,119), percent dd-cfDNA as a fraction of total cfDNA positivity (76% vs 83%), and mean left ventricular ejection fraction (LVEF) (58.5 vs 56.5); DSA-negative ABMR had lower mean molecular ABMR activity (ABMRProb score 0.55 vs 0.70, p = 0.02). Gene expression profiles were essentially identical between DSA-negative and DSA-positive molecular ABMR, including interferon-gamma (IFNG)-inducible genes (e.g., CXCL11, CXCL9, and IDO1) and NK-expressed genes (e.g., KLRD1 and GNLY), compatible with a role for natural killer (NK) cells in both DSA-negative and DSA-positive ABMR. CONCLUSIONS:Molecular features of heart transplant biopsies with DSA-negative ABMR are virtually identical to those with DSA-positive ABMR and both are associated with high plasma dd-cfDNA.

AIMS:Chronic kidney disease (CKD) is common in patients with heart failure (HF) with preserved ejection fraction (HFpEF), and its presence is associated with more severe echocardiographic abnormalities and poorer outcomes through unclear mechanisms. CKD-associated endothelial dysfunction, inflammation, and activation of profibrotic pathways could worsen pulmonary vascular disease (PVD) in HFpEF, but such relationships have not been explored. METHODS:Consecutively evaluated patients with HFpEF undergoing invasive hemodynamic cardiopulmonary exercise testing were stratified by baseline kidney function to characterize potential differences in pulmonary vascular loading, hemodynamics, cardiopulmonary reserve, and outcomes based upon the presence and severity of kidney dysfunction. RESULTS:Of 925 patients with HFpEF, 319 (34.5%) had eGFR < 60 ml/min/1.73 m2. Patients with more severe kidney dysfunction were older and more likely to have diabetes, atrial fibrillation, and hypertension.. At rest, reduced kidney function was associated with lower hemoglobin, higher biventricular filling pressures, and lower cardiac output, but the severity of kidney dysfunction was most conspicuously associated with worsening PVD, evidenced by increasing pulmonary arterial (PA) pressures due to marked increases in pulmonary vascular resistance (PVR) as kidney dysfunction progressed (median [IQR] 1.3 [0.86, 1.88] to 2.8 [2.0, 3.8] WU from eGFR ≥ 90 to eGFR < 30, p<0.001), along with progressively lower PA compliance (PAC, 4.7 [3.6, 5.8] to 2.2 [1.8, 3.4] ml/mmHg from eGFR ≥ 90 to eGFR < 30, p<0.001). With exercise, differences in the severity of PVD became even more striking, with more severe elevation in PA pressures and PVR, and lower PA compliance, leading to lower transmural left-sided distending pressures, with no difference in exertional PA wedge pressure. Patients with worse kidney dysfunction displayed the most dramatic cardiac output limitations with exercise, which along with more severe anemia and markedly reduced O2 delivery, caused marked impairment in aerobic capacity. Worsening kidney function was associated with a striking gradient of increased risk of a composite of all-cause death and HF hospitalization [ranging from HR 2.38 (95% CI 1.01-5.59) for eGFR 60-90 to HR 16.77 (95% CI 6.65-42.28) for eGFR < 30 (vs. reference eGFR ≥ 90)]. CONCLUSIONS:Kidney dysfunction in patients with HFpEF is characterized by more severe pulmonary vascular disease at rest and with exercise, leading to reduced cardiac output reserve, impaired exercise capacity, and increased risk for adverse events. Further study is warranted to better understand causal relationships between CKD and PVD, and determine whether novel therapies to improve kidney function might target these impairments to improve clinical status.