Effect of left bundle branch pacing on right ventricular function: A 3-dimensional echocardiography study.

BACKGROUND: The effect of left bundle branch pacing (LBBP) on right ventricular (RV) function is not well known, and there is conflicting evidence regarding whether cardiac resynchronization therapy improves RV function. OBJECTIVES: The study aimed to investigate the effect of LBBP on RV function and to evaluate the response of RV dysfunction (RVD) to LBBP. METHODS: Sixty-five LBBP candidates were prospectively included in the study and underwent echocardiography at baseline and 6-month follow-up. LBBP response was left ventricular (LV) reverse remodeling, defined as a reduction in LV end-systolic volume of ≥15% at follow-up. RESULTS: Patients were assigned to 2 subgroups on the basis of 3-dimensional echocardiography-derived RV ejection fraction (EF) before LBBP implantation: 30 patients (46%) in the no RVD group and 35 patients (54%) in the RVD group. The RVD group was characterized by higher N-terminal pro-brain natriuretic peptide levels, New York Heart Association functional class, and larger LV/RV size. LBBP induced a significant reduction in QRS duration, LV size, and improvement in LVEF and mechanical dyssynchrony in both the no RVD and RVD groups, and a significant improvement in RV volumes and RVEF in the RVD group (all P<.01). LBBP resulted in a similar percentage reduction in QRS duration, LV dimensions, LV volumes, and percentage improvement in LVEF in RVD and no RVD groups (all P＞.05). LV reverse remodeling (29 of 35 patients vs 27 of 30 patients; P = .323) in the RVD group was similar to that in the no RVD group after LBBP. CONCLUSION: LBBP induces excellent electrical and mechanical resynchronization, with a significant improvement in RV volumes and function. RVD did not diminish the beneficial effects on LV reverse remodeling after LBBP.

Three-dimensional echocardiography reveals early mitral valve alterations in hypertrophic cardiomyopathy genetic mutation carriers.

BACKGROUND: The mitral valve undergoes structural modifications in response to cardiac functional changes, often predating cardiac decompensation and overt clinical signs. Our study assessed the potential of mitral valve morphological changes as early indicators for detecting carriers of hypertrophic cardiomyopathy (HCM)-associated gene mutations. METHODS: We studied 505 participants: 189 without the pathogenic gene mutations and left ventricular hypertrophy (G-/LVH-), 149 carriers without LV hypertrophy (G+/LVH-), and 167 manifest HCM patients (G+/LVH+). We juxtaposed the mitral valve morphology and associated metrics across these groups, emphasizing those carrying MYH7 and MYBPC3 mutations. RESULTS: We discerned pronounced disparities in the mitral annulus and leaflet structures across the groups. The mitral valve apparatus in mutation carriers exhibited a tendency towards a flattened profile. Detailed analysis spotlighted MYBPC3 mutation carriers, whose mitral valves were notably flatter (with notably lower AHCWR values than non-carriers); this contrast was not evident in MYH7 mutation carriers. This mitral valve flattening, manifest in the mutation carriers, suggests it might be an adaptive response to incipient cardiac dysfunction in HCM's nascent stages. CONCLUSIONS: Three-dimensional echocardiography illuminates the initial mitral valve structural changes in HCM patients bearing pathogenic gene mutations. These morphological signatures hold promise as sensitive imaging markers, especially for asymptomatic carriers of the MYBPC3 mutation.

ESCRT-III Component CHMP4C Attenuates Cardiac Hypertrophy by Targeting the Endo-Lysosomal Degradation of EGFR.

BACKGROUND: Cardiac hypertrophy and subsequent heart failure impose a considerable burden on public health worldwide. Impaired protein degradation, especially endo-lysosome-mediated degradation of membrane proteins, is associated with cardiac hypertrophy progression. CHMP4C (charged multivesicular body protein 4C), a critical constituent of multivesicular bodies, is involved in cellular trafficking and signaling. However, the specific role of CHMP4C in the progression of cardiac hypertrophy remains largely unknown. METHODS: Mouse models with CHMP4C knockout or cardiadc-specific overexpression were subjected to transverse aortic constriction surgery for 4 weeks. Cardiac morphology and function were assessed through histological staining and echocardiography. Confocal imaging and coimmunoprecipitation assays were performed to identify the direct target of CHMP4C. An EGFR (epidermal growth factor receptor) inhibitor was administrated to determine whether effects of CHMP4C on cardiac hypertrophy were EGFR dependent. RESULTS: CHMP4C was significantly upregulated in both pressure-overloaded mice and spontaneously hypertensive rats. Compared with wild-type mice, CHMP4C deficiency exacerbated transverse aortic constriction-induced cardiac hypertrophy, whereas CHMP4C overexpression in cardiomyocytes attenuated cardiac dysfunction. Mechanistically, the effect of CHMP4C on cardiac hypertrophy relied on the EGFR signaling pathway. Fluorescent staining and coimmunoprecipitation assays confirmed that CHMP4C interacts directly with EGFR and promotes lysosome-mediated degradation of activated EGFR, thus attenuating cardiac hypertrophy. Notably, an EGFR inhibitor canertinib counteracted the exacerbation of cardiac hypertrophy induced by CHMP4C knockdown in vitro and in vivo. CONCLUSIONS: CHMP4C represses cardiac hypertrophy by modulating lysosomal degradation of EGFR and is a potential therapeutic candidate for cardiac hypertrophy.

Gene-echocardiography: refining genotype-phenotype correlations in hypertrophic cardiomyopathy.

AIMS: This study aims to clarify the association between hypertrophic patterns and genetic variants in hypertrophic cardiomyopathy (HCM) patients, contributing to the advancement of personalized management strategies for HCM. METHODS AND RESULTS: A comprehensive evaluation of genetic mutations was conducted in 392 HCM-affected families using Whole Exome Sequencing. Concurrently, relevant echocardiographic data from these individuals were collected. Our study revealed an increased susceptibility to enhanced septal and interventricular septal thickness in HCM patients harbouring gene mutations compared with those without. Mid-septal hypertrophy was found to be associated predominantly with myosin binding protein C3 (MYBPC3) variants, while a higher septum-to-posterior wall ratio correlated with myosin heavy chain 7 (MYH7) variants. Mutations in MYH7, MYBPC3, and other sarcomeric or myofilament genes (troponin I3 [TNNI3], tropomyosin 1 [TPM1], and troponin T2 [TNNT2]) showed a relationship with increased hypertrophy in the anterior wall, interventricular septum, and lateral wall of the left ventricle. In contrast, alpha kinase 3 (ALPK3)-associated hypertrophy chiefly presented in the apical region, while hypertrophy related to titin (TTN) and obscurin (OBSCN) mutations exhibited a uniform distribution across the myocardium. Hypertrophic patterns varied with the type and category of gene mutations, offering valuable diagnostic insights. CONCLUSION: Our findings underscore a strong link between hypertrophic patterns and genetic variants in HCM, providing a foundation for more accurate genetic testing and personalized management of HCM patients. The novel concept of 'gene-echocardiography' may enhance the precision and efficiency of genetic counselling and testing in HCM.

Echocardiographic characteristics of PRKAG2 syndrome: a research using three-dimensional speckle tracking echocardiography compared with sarcomeric hypertrophic cardiomyopathy.

BACKGROUND: PRKAG2 syndrome is a rare disease characterized as left ventricular hypertrophy (LVH), ventricular preexcitation syndrome, and sudden cardiac death. Its natural course, treatment, and prognosis were significantly different from sarcomeric hypertrophic cardiomyopathy (HCM). However, it is often clinically misdiagnosed as sarcomeric HCM. PRKAG2 patients tend to experience delayed treatment. The delay may lead to adverse outcomes. This study aimed to identify the echocardiographic parameters which can differentiate PRKAG2 syndrome from sarcomeric HCM. METHODS: Nine PRKAG2 patients with LVH, 41 HCM patients with sarcomere gene mutations, and 202 healthy volunteers were enrolled. Clinical characteristics, conventional echocardiography, and three-dimensional images were recorded, and reviewed by an attending cardiologist. We evaluated the parameters of left ventricular strains from three-dimensional speckle tracking echocardiography (3D STE) by TomTec software. Receiver operating characteristic (ROC) curves analysis was used to assess clinical and echocardiographic parameters' differential diagnosis potential. RESULTS: The heart rate (HR) of the PRKAG2 group was significantly lower than both the healthy group (53.11 ± 10.14 vs. 69.22 ± 10.48 bpm, P < 0.001) and the sarcomeric HCM group (53.11 ± 10.14 vs. 67.23 ± 10.32 bpm, P = 0.001). The PRKAG2 group had similar interventricular septal thickness (IVS), posterior wall thickness (PWT), and maximum wall thickness (MWT) to the HCM group (P > 0.05). The absolute value of GLS in the PRKAG2 group was significantly higher than HCM patients (-18.92 ± 4.98 vs. -13.43 ± 4.30%, P = 0.004). SV calculated from EDV and ESV in PRKAG2 syndrome showed a higher value than sarcomeric HCM (61.83 ± 13.52 vs. 44.96 ± 17.53%, P = 0.020). The area under the ROC curve (AUC) for HR + GLS was 0.911 (0.803 -1). For HR + GLS, the sensitivity and specificity of the best cut-off value (0.114) were 69.0% and 100%, respectively. CONCLUSIONS: PRKAG2 patients present deteriorated LV diastolic function and preserved LV systolic function. Bradycardia and preserved GLS are useful to identify PRKAG2 syndrome from sarcomeric HCM, which may be beneficial for clinical decision-making.

Protective effects of cardiac resynchronization therapy in a canine model with experimental heart failure by improving mitochondrial function: a mitochondrial proteomics study.

PURPOSE: Cardiac resynchronization therapy (CRT) is well acknowledged as an effective treatment for dyssynchronous heart failure. However, the molecular mechanism is unclear to date. Mitochondrial dysfunction and impaired energetic metabolism are two important mechanisms that lead to heart failure. Therefore, we aim to screen the changes of mitochondria-associated proteins and signaling pathways involved in heart failure and CRT treatment. METHODS: A total of 24 beagle dogs were randomly assigned into control (CON), heart failure (HF), or CRT group. Myocardial mitochondria from the free wall of left ventricle was extracted for isobaric tags for relative and absolute quantitation (iTRAQ) labeling coupled with two-dimensional liquid chromatography tandem mass spectrometry analysis (2DLC-MS/MS). RESULTS: A total of 2190 proteins were identified, among which 234 proteins were differentially expressed in HF compared with CON group, 151 proteins were differentially expressed in CRT compared with HF group. A total of 192 of the 234 differentially expressed proteins in HF group were changed oppositely by CRT treatment, and 128 of the 151 CRT-induced differentially expressed proteins showed opposite trend of expression to HF/CON. Gene Ontology analysis of the 128 proteins revealed that 16 were localized in mitochondria, 17 were associated with calcium signaling, and 7 could be secreted extracellularly for cell-to-cell signaling. Calpain-1 (CAPN1), which is localized to mitochondria and related to calcium signaling, was upregulated in HF and downregulated after CRT treatment. CRT treatment also improved mitochondrial morphology and function and reduced collagen areas of both interstitial and perivascular fibrosis. CONCLUSIONS: CRT treatment significantly improved cardiac function, reduced myocardial fibrosis, and enhanced mitochondrial function in the failing heart through CAPN1 downregulation.

The mechanical effects of CRT promoting autophagy via mitochondrial calcium uniporter down-regulation and mitochondrial dynamics alteration.

The mechanism of cardiac resynchronization therapy (CRT) remains unclear. In this study, mitochondria calcium uniporter (MCU), dynamin-related protein-1 (DNM1L/Drp1) and their relationship with autophagy in heart failure (HF) and CRT are investigated. Thirteen male beagle's dogs were divided into three groups (sham, HF, CRT). Animals received left bundle branch (LBB) ablation followed by either 8-week rapid atrial pacing or 4-week rapid atrial pacing and 4-week biventricular pacing. Cardiac function was evaluated by echocardiography. Differentially expressed genes (DEGs) were detected by microarray analysis. General morphological changes, mitochondrial ultrastructure, autophagosomes and mitophagosomes were investigated. The cardiomyocyte stretching was adopted to imitate the mechanical effect of CRT. Cells were divided into three groups (control, angiotensin-II and angiotensin-II + stretching). MCU, DNM1L/Drp1 and autophagy markers were detected by western blots or immunofluorescence. In the present study, CRT could correct cardiac dysfunction, decrease cardiomyocyte's size, alleviate cardiac fibrosis, promote the formation of autophagosome and mitigate mitochondrial injury. CRT significantly influenced gene expression profile, especially down-regulating MCU and up-regulating DNM1L/Drp1. Cell stretching reversed the angiotensin-II induced changes of MCU and DNM1L/Drp1 and partly restored autophagy. CRT's mechanical effects down-regulated MCU, up-regulated DNM1L/Drp1 and subsequently enhanced autophagy. Besides, the mechanical stretching prevented the angiotensin-II-induced cellular enlargement.

A family with Danon disease caused by a splice site mutation in LAMP2 that generates a truncated protein.

BACKGROUND: Danon disease is an X-linked dominant hereditary condition caused by mutations in the gene encoding lysosomal-associated membrane protein 2 (LAMP2), leading to failure of lysosome binding to autophagosomes, accumulation of glycogen in the heart, and abnormal cardiac function. METHODS: We describe identification of a mutation in LAMP2, c.741+1G>T, in a family with Danon disease by whole exome sequencing. RESULTS: Pathology examination of patient skeletal muscle biopsy showed myogenic damage and autophagic vacuoles with sarcolemmal features (AVSF). Numerous autophagic vacuoles accumulated in muscle cells were detected by electron microscopy, indicating abnormal autophagy function. CONCLUSION: The mutation did not result in loss of mRNA exons; rather, a 6-nucleotide (two-codon) insertion, where the latter was a stop codon, leading to early termination of LAMP2 protein translation. The resulting truncated protein lacks an important transmembrane domain, which will impair lysosome/autophagosome fusion, damage autophagy function, and result in the clinical manifestations of Danon disease.

Whole-exome sequencing reveals a novel mutation of MT-ND5 gene in a mitochondrial cardiomyopathy pedigree: Patients who show biventricular hypertrophy, hyperlactacidemia, pulmonary hypertension, and decreased exercise tolerance.

OBJECTIVE: The aim of the present study was to determine whether pathogenic mutations were present in families with mitochondrial cardiomyopathy that presented during adolescence. METHODS: The proband was a 21-year-old man who presented clinically with palpitations, chest tightness, pulmonary hypertension, and limited exercise tolerance. Cardiac magnetic resonance imaging studies showed biventricular cardiac hypertrophy. We determine whether pathogenic mutations were present by whole-exome sequencing (WES) in families. RESULTS: Screening of the family using tandem mass spectrometry showed elevated lactic acid levels, glutaric aciduria, a mildly increased glutarylcarnitine-to-octanoylcarnitine ratio, and normal blood α-glucosidase, which was consistent with a respiratory chain complex 1 metabolic disorder. We identified a novel mutation of MT-ND5, c.1315A>G (p.Thr439Ala). Skeletal muscle biopsy histology showed predominantly ragged red fibers and few ragged blue fibers, which was consistent with mitochondrial myopathy. CONCLUSION: In the present study, we identified a novel mutation of MT-ND5, c.1315A>G (p.Thr439Ala), in a family pedigree using WES.

Whole-exome sequencing identifies rare compound heterozygous mutations in the MYBPC3 gene associated with severe familial hypertrophic cardiomyopathy.

Most patients with hypertrophic cardiomyopathy have single-gene autosomal dominant mutations in loci that encode for sarcomeric proteins. The aim of this study was to determine whether pathogenic mutations were present by whole-exome sequencing (WES) in two families with hypertrophic cardiomyopathy (HCM) that presented during adolescence. Blood samples and clinical data were collected from individuals in two families with HCM. DNA was extracted. Mutations were identified using whole-exome sequencing (WES), and the genotypes of family members were identified using Sanger sequencing. Compound heterozygous mutations in the MYBPC3 gene (c.659A > G, p.Tyr220Cys; c.772G > A, p.Glu258Lys,NM_000256, Family 1), (c.873delG, p. Ile292PhefsTer8; c.3G > A, p.Met1?, NM_000256, Family 2) were identified by WES. Patient 1 carried the maternally inherited c.659A > G mutation and the paternally inherited c.772G > A mutation. Patient 2 carried the maternally inherited frameshift mutation c.873delG and the paternally inherited mutation c.3G > A. Two families with HCM presenting during adolescence (age of onset is about 11 years old) demonstrated compound heterozygous mutations in the MYBPC3 gene. These findings suggested an association of MYBPC3 mutations with the early onset of symptoms and worsened prognoses. Our study highlights the importance of genetic screening of all family members in cases of HCM.

Effect of Cardiac Resynchronization Therapy on Myocardial Fibrosis and Relevant Cytokines in a Canine Model With Experimental Heart Failure.

INTRODUCTION: Though cardiac resynchronization therapy (CRT) has now proved to be effective on cardiac reverse remodeling, data on the underlying molecular changes are limited. The present study aims to investigate the expression of cytokines concerning myocardial fibrosis in dyssynchronous heart failure (HF) and the potential benefits of CRT. METHODS AND RESULTS: Left bundle branch ablation and rapid pacing was performed to induce a canine model of asynchronous HF. Animals were randomly divided into sham group, HF control group, and CRT group. Echocardiographic data including septum-to-posterior wall motion delay (SPWMD) and standard deviation of the time to peak systolic velocity (Ts-SD) were collected. Histologic samples from lateral left ventricular (LV) and right ventricular (RV) free wall were analyzed and compared among different groups. Serum concentrations of NT-proBNP, TGF-ß1 , and osteopontin (OPN) were measured using enzyme-linked immunosorbent assay (ELISA). Protein and mRNA expressions of TGF-ß1 /Smad and OPN from myocardial tissues were also detected and compared. CRT improved cardiac function and corrected intraventricular dyssynchrony with increased LV ejection fraction (LVEF) and decreased SPWMD and Ts-SD (P < 0.05). Histological analysis showed that CRT restored cardiomyocyte diameter (from 4.50 to 6.08 µm) and collagen volume fraction (from 19.33% to 11.21%) of LV (P < 0.01), but had little effect on RV. Serum TGF-ß1 and OPN level were also reversed toward normal level after CRT (P < 0.05). Compared with sham group, a significantly higher protein and mRNA expressions of TGF-ß1 /Smad and OPN were observed in HF control group, which were significantly downregulated in CRT group (P < 0.01). CONCLUSION: By means of coordinating LV dyssynchrony, cellular and molecular reverse remodeling relevant to fibrosis inhibition could also be invoked by CRT.

A novel method for sensitive determination of subclinical right ventricular systolic dysfunction in patients with obstructive sleep apnea.

OBJECTIVE: The aim of this study was to evaluate right ventricular (RV) regional systolic function and dyssynchrony in patients with newly diagnosed obstructive sleep apnea using real-time three-dimensional (3D) echocardiography. METHODS: Eighty-two subjects without hypertension, diabetes mellitus or any cardiac or pulmonary disease referred for evaluation of obstructive sleep apnea (OSA) had overnight polysomnography and complete echocardiographic assessment. According to the apnea hypopnea index (AHI), subjects were divided into four groups: group 1: control subjects (AHI < 5, n = 19), group 2: patients with mild OSA (AHI: 5-14, n = 21), group 3: moderate OSA (AHI: 15-30, n = 18), group 4: severe OSA (AHI > 30, n = 24). Real-time three-dimensional echocardiographic images were acquired to obtain RV regional (inflow, body and outflow) ejection fraction (EF) and time to minimum systolic volume in all subjects. RESULTS: Body weight and body mass index were greater in the severe and moderate OSA group than those of mild and controls group (P < 0.05). There was a significant decrease in mean SaO2 and the lowest SaO2 in severe OSA when compared to other groups (P < 0.001). Inflow EF and global EF were significantly lower in moderate and severe OSA patients than in controls (P < 0.05). Inflow EF and global EF were negatively correlated with AHI (r = -0.534 and r = -0.479, respectively, P < 0.001). CONCLUSIONS: In patients with OSA, RV inflow and global systolic function were impaired and were in inverse relationship with AHI. Evaluation of RV regional systolic function using real-time three-dimensional echocardiography may play a potential role in the noninvasive assessment of the severity of OSA.

"Pacing Bigeminal".

A rapid pacing-induced heart failure model is commonly used in developing dilated cardiomyopathy (DCM). Traditionally, the right ventricular lead was connected with a single chamber pacemaker specific for animals that had a high frequency. However, the pacemaker used in this model is commercially unavailable. We developed a "pacing bigeminal" method using a commercially available dual-chamber (DDD) pacemaker to achieve high-frequency pacing. Twenty beagles were assigned to group A (n = 10) (pacing bigeminal method) and group B (n = 10) (traditional method). Echocardiographic measurements and electrocardiograms were obtained at baseline, at two weeks of pacing, and at 4 weeks of end pacing. LV anterior wall cardiac samples were obtained at 2 weeks of pacing and 4 weeks of end pacing for myocardial microscopic evaluation. Clinical manifestation and exposure time were also observed. After pacing for 10.5 ± 2.3 (714) days, the beagles in group B experienced heart failure, whereas in group A, only 7.9 ± 2.5 (5-12) days (P < 0.05) were needed to reach heart failure. Both methods could induce wide QRS duration, heart rate elevation, and myocardial microscopic changes (P > 0.05). In conclusion, this pacing bigeminal-induced heart failure method is feasible and can induce heart failure faster than the traditional method, which makes it a promising alternative method.

A Novel Method for Sensitive Determination of Subclinical Left-Ventricular Systolic Dysfunction in Subjects With Obstructive Sleep Apnea.

BACKGROUND: This study was to evaluate the subclinical left-ventricular (LV) systolic dysfunction with 2-dimensional speckle-tracking echocardiography in subjects with obstructive sleep apnea (OSA) with normal left ventricular ejection fraction and without any confounding disease that can cause myocardial dysfunction. METHODS: Nineteen healthy individuals and 60 subjects with OSA were included in this study. According to the severity of disease, OSA subjects were examined in 3 groups: mild, moderate, and severe OSA. LV apical views (for longitudinal strain) and short-axis views (for circumferential strain) were acquired for evaluation. Three-layer longitudinal strain values and circumferential strain values were determined for each view, and averages of these were used in comparison with other groups. RESULTS: Three-layer longitudinal strain values of the subjects with OSA were lower than those of the healthy individuals, and these values were decreased along with the OSA severity. The difference was significant between severe OSA and all other groups. Three-layer circumferential strain values of the OSA subjects were lower than those of the healthy individuals, and the difference was significant between the control group and all other groups. The apnea hypopnea index was found to be correlated with the 3-layer longitudinal strain (r = -0.74, P < .001; r = -0.72, P < .001; r = -0.69, P = <.001). CONCLUSIONS: Three-layer longitudinal and circumferential LV systolic functions in OSA subjects with normal left ventricular ejection fraction are deteriorated in the subclinical stage. Two-dimensional speckle-tracking echocardiography can be used as an effective method in the determination of subclinical myocardial dysfunction in subjects with OSA.