Role of Early Left Atrial Functional Decline in Predicting Cardiotoxicity in HER2 Positive Breast Cancer Patients Treated With Trastuzumab.

Trastuzumab is widely used in HER2 breast cancer. However, it may cause left ventricular (LV) dysfunction. A decrease in LV global longitudinal strain (GLS) has been previously demonstrated to be a good predictor of subsequent cancer therapy related dysfunction (CTRCD). Left atrial morphological remodeling during Trastuzumab therapy has also been shown. The aim of this study is exploring the relationship between early changes in left atrial function and the development of Trastuzumab-induced cardiotoxicity. Consecutive patients with diagnosis of HER2+non-metastatic breast cancer treated with Trastuzumab were prospectively enrolled. A clinical, conventional, and advanced echocardiographic assessment was performed at baseline and every three months, until a one-year follow-up was reached. One-hundred-sixteen patients completed the 12 months follow-up, 10 (9%) cases of CTRCD were observed, all after the sixth month. GLS and LVEF significantly decreased in the CTRCD group at 6 months of follow-up, with an earlier (3 months) significant worsening in left atrial morpho-functional parameters. Systolic blood pressure, early peak atrial longitudinal strain (PALS), peak atrial contraction (PACS) and left atrial volume (LAVI) changes resulted independent predictors of CTRCD at multivariable logistic regression analysis. Moreover, early changes in PALS and PACS resulted good predictors of CTRCD development (AUC 0.85; p = 0.008, p < 0.001 and 0.77; p = 0.008, respectively). This prospective study emphasizes that the decline in PALS and PACS among trastuzumab-treated patients could possibly increase the accuracy in identifying future CTRCD in non-metastatic HER2 breast cancer cases, adding predictive value to conventional echocardiographic assessment.

Gender Differences in Cardiac Organ Damage in Arterial Hypertension: Assessing the Role of Drug Nonadherence.

INTRODUCTION: Cardiac organ damage like left ventricular (LV) hypertrophy and left atrial (LA) enlargement is more prevalent in women than men with hypertension, but the mechanisms underlying this gender difference remain unclear. METHODS: We tested the association of drug nonadherence with the presence of LV hypertrophy and LA enlargement by echocardiography in 186 women and 337 men with uncontrolled hypertension defined as daytime systolic blood pressure (BP) ≥ 135mmHg despite the prescription of at least two antihypertensive drugs. Drug adherence was assessed by measurements of serum drug concentrations interpreted by an experienced pharmacologist. Aldosterone-renin-ratio (ARR) was measured on actual medication. RESULTS: Women had a higher prevalence of LV hypertrophy (46% vs. 33%) and LA enlargement (79% vs 65%, both p < 0.05) than men, while drug nonadherence (8% vs. 9%, p > 0.514) did not differ. Women were older and had lower serum renin concentration and higher ARR than men, while 24-h systolic BP (141 ± 9 mmHg vs. 142 ± 9 mmHg), and the prevalences of obesity (43% vs. 50%) did not differ (all p > 0.10). In multivariable analyses, female gender was independently associated with a two-fold increased risk of LV hypertrophy (OR 2.01[95% CI 1.30-3.10], p = 0.002) and LA enlargement (OR 1.90 [95% CI 1.17-3.10], p = 0.010), while no association with drug nonadherence was found. Higher ARR was independently associated with LV hypertrophy in men only (OR 2.12 [95% CI 1.12-4.00] p = 0.02). CONCLUSIONS: Among patients with uncontrolled hypertension, the higher prevalence of LV hypertrophy and LA enlargement in women was not explained by differences in drug nonadherence. REGISTRATION: URL:  https://www. CLINICALTRIALS: gov ; Unique identifier: NCT03209154.

Treatment-Related Changes in Left Atrial Structure in Atrial Fibrillation: Findings From the CABANA Imaging Substudy.

[Figure: see text].

Effect of sodium-glucose cotransporter 2 inhibitors on cardiac structure and function in type 2 diabetes mellitus patients with or without chronic heart failure: a meta-analysis.

BACKGROUND: Although the benefits of sodium-glucose cotransporter 2 inhibitors (SGLT2i) on cardiovascular events have been reported in patients with type 2 diabetes mellitus (T2DM) with or without heart failure (HF), the impact of SGLT2i on cardiac remodelling remains to be established. METHODS: We searched the PubMed, Embase, Cochrane Library and Web of Science databases up to November 16th, 2020, for randomized controlled trials reporting the effects of SGLT2i on parameters of cardiac structure, cardiac function, plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) level or the Kansas City Cardiomyopathy Questionnaire (KCCQ) score in T2DM patients with or without chronic HF. The effect size was expressed as the mean difference (MD) or standardized mean difference (SMD) and its 95% confidence interval (CI). Subgroup analyses were performed based on the stage A-B or stage C HF population and HF types. RESULTS: Compared to placebo or other antidiabetic drugs, SGLT2i showed no significant effects on left ventricular mass index, left ventricular end diastolic volume index, left ventricular end systolic volume index, or left atrial volume index. SGLT2i improved left ventricular ejection fraction only in the subgroup of HF patients with reduced ejection fraction (MD 3.16%, 95% CI 0.11 to 6.22, p = 0.04; I2 = 0%), and did not affect the global longitudinal strain in the overall analysis including stage A-B HF patients. SGLT2i showed benefits in the E/e' ratio (MD - 0.45, 95% CI - 0.88 to - 0.03, p = 0.04; I2 = 0%), plasma NT-proBNP level (SMD - 0.09, 95% CI - 0.16 to - 0.03, p = 0.004; I2 = 0%), and the KCCQ score (SMD 3.12, 95% CI 0.76 to 5.47, p  = 0.01; I2 = 0%) in the overall population. CONCLUSION: The use of SGLT2i was associated with significant improvements in cardiac diastolic function, plasma NT-proBNP level, and the KCCQ score in T2DM patients with or without chronic HF, but did not significantly affect cardiac structural parameters indexed by body surface area. The LVEF level was improved only in HF patients with reduced ejection fraction.

Dual SGLT-1 and SGLT-2 inhibition improves left atrial dysfunction in HFpEF.

BACKGROUND: Sodium-glucose linked transporter type 2 (SGLT-2) inhibition has been shown to reduce cardiovascular mortality in heart failure independently of glycemic control and prevents the onset of atrial arrhythmias, a common co-morbidity in heart failure with preserved ejection fraction (HFpEF). The mechanism behind these effects is not fully understood, and it remains unclear if they could be further enhanced by additional SGLT-1 inhibition. We investigated the effects of chronic treatment with the dual SGLT-1&2 inhibitor sotagliflozin on left atrial (LA) remodeling and cellular arrhythmogenesis (i.e. atrial cardiomyopathy) in a metabolic syndrome-related rat model of HFpEF. METHODS: 17 week-old ZSF-1 obese rats, a metabolic syndrome-related model of HFpEF, and wild type rats (Wistar Kyoto), were fed 30 mg/kg/d sotagliflozin for 6 weeks. At 23 weeks, LA were imaged in-vivo by echocardiography. In-vitro, Ca2+ transients (CaT; electrically stimulated, caffeine-induced) and spontaneous Ca2+ release were recorded by ratiometric microscopy using Ca2+-sensitive fluorescent dyes (Fura-2) during various experimental protocols. Mitochondrial structure (dye: Mitotracker), Ca2+ buffer capacity (dye: Rhod-2), mitochondrial depolarization (dye: TMRE) and production of reactive oxygen species (dye: H2DCF) were visualized by confocal microscopy. Statistical analysis was performed with 2-way analysis of variance followed by post-hoc Bonferroni and student's t-test, as applicable. RESULTS: Sotagliflozin ameliorated LA enlargement in HFpEF in-vivo. In-vitro, LA cardiomyocytes in HFpEF showed an increased incidence and amplitude of arrhythmic spontaneous Ca2+ release events (SCaEs). Sotagliflozin significantly reduced the magnitude of SCaEs, while their frequency was unaffected. Sotagliflozin lowered diastolic [Ca2+] of CaT at baseline and in response to glucose influx, possibly related to a ~ 50% increase of sodium sodium-calcium exchanger (NCX) forward-mode activity. Sotagliflozin prevented mitochondrial swelling and enhanced mitochondrial Ca2+ buffer capacity in HFpEF. Sotagliflozin improved mitochondrial fission and reactive oxygen species (ROS) production during glucose starvation and averted Ca2+ accumulation upon glycolytic inhibition. CONCLUSION: The SGLT-1&2 inhibitor sotagliflozin ameliorated LA remodeling in metabolic HFpEF. It also improved distinct features of Ca2+-mediated cellular arrhythmogenesis in-vitro (i.e. magnitude of SCaEs, mitochondrial Ca2+ buffer capacity, diastolic Ca2+ accumulation, NCX activity). The safety and efficacy of combined SGLT-1&2 inhibition for the treatment and/or prevention of atrial cardiomyopathy associated arrhythmias should be further evaluated in clinical trials.

Assessing the left atrium of childhood cancer survivors.

Survivors of childhood cancer are at risk of cancer therapy-related cardiac dysfunction (CTRCD) characterized by systolic impairment, with little known about diastolic function. Left atrial strain (LAS) is a surrogate measure of left ventricular filling. We hypothesized that survivors (1) have lower LAS versus controls, and (2) survivors exposed to higher anthracycline dosage have even lower LAS. Cross-sectional study of 45 survivors exposed to anthracyclines ≥ 1 year after chemotherapy and 45 healthy controls. Echo variables included mitral spectral and tissue Doppler, left ventricular ejection fraction (LV EF), LV dimension, LA volume, LV global longitudinal strain (GLS), and LAS. Peak strain (Ɛ) and strain rate (SR) at three phases were obtained: atrial contraction (ac), reservoir (res), and conduit (con). Two sub-analyses of cancer survivors were performed: (1) those with anthracycline dosage ≥ 250 mg/m2, and (2) those with Ɛres in the lowest quartile. On the whole, survivors had lower Ɛres and Ɛcon values. The majority of survivors had relatively normal LAS, while a subset had very low LAS values and were more likely to be older. Survivors exposed to ≥ 250 mg/m2 anthracycline also had lower Ɛres than those < 250 mg/m2. There were no differences in mitral spectral/tissue Doppler, LV dimension, left atrial volume, or GLS. A subset of childhood cancer survivors have lower LAS than their healthy counterparts, while most are essentially normal. Those exposed to higher anthracycline dosage have even lower Ɛres. Longitudinal study of LAS may prove useful in monitoring for CTRCD.

Ibrutinib-Mediated Atrial Fibrillation Attributable to Inhibition of C-Terminal Src Kinase.

BACKGROUND: Ibrutinib is a Bruton tyrosine kinase inhibitor with remarkable efficacy against B-cell cancers. Ibrutinib also increases the risk of atrial fibrillation (AF), which remains poorly understood. METHODS: We performed electrophysiology studies on mice treated with ibrutinib to assess inducibility of AF. Chemoproteomic analysis of cardiac lysates identified candidate ibrutinib targets, which were further evaluated in genetic mouse models and additional pharmacological experiments. The pharmacovigilance database, VigiBase, was queried to determine whether drug inhibition of an identified candidate kinase was associated with increased reporting of AF. RESULTS: We demonstrate that treatment of mice with ibrutinib for 4 weeks results in inducible AF, left atrial enlargement, myocardial fibrosis, and inflammation. This effect was reproduced in mice lacking Bruton tyrosine kinase, but not in mice treated with 4 weeks of acalabrutinib, a more specific Bruton tyrosine kinase inhibitor, demonstrating that AF is an off-target side effect. Chemoproteomic profiling identified a short list of candidate kinases that was narrowed by additional experimentation leaving CSK (C-terminal Src kinase) as the strongest candidate for ibrutinib-induced AF. Cardiac-specific Csk knockout in mice led to increased AF, left atrial enlargement, fibrosis, and inflammation, phenocopying ibrutinib treatment. Disproportionality analyses in VigiBase confirmed increased reporting of AF associated with kinase inhibitors blocking Csk versus non-Csk inhibitors, with a reporting odds ratio of 8.0 (95% CI, 7.3-8.7; P<0.0001). CONCLUSIONS: These data identify Csk inhibition as the mechanism through which ibrutinib leads to AF. Registration: URL: https://ww.clinicaltrials.gov; Unique identifier: NCT03530215.

Sacubitril/valsartan attenuates atrial electrical and structural remodelling in a rabbit model of atrial fibrillation.

Atrial structural and electrical remodelling play important roles in atrial fibrillation (AF). Sacubitril/valsartan attenuates cardiac remodelling in heart failure. However, the effect of sacubitril/valsartan on AF is unclear. The aim of this study was to evaluate the effect of sacubitril/valsartan on atrial electrical and structural remodelling in AF and investigate the underlying mechanism of action. Thirty-three rabbits were randomized into sham, RAP, and sac/val groups. HL-1 cells were subjected to control treatment or rapid pacing with or without LBQ657 and valsartan. Echocardiography, atrial electrophysiology, and histological examination were performed. The concentration of Ca2+ and expression levels of calcineurin, NFAT, p-NFAT, Cav1.2, collagen Ⅰ and Ⅲ, ANP, BNP, CNP, NT-proBNP, and ST2 in HL-1 cells, and IcaL in left atrial cells, were determined. We observed that compared to that in the sham group, the atrium and right ventricle were enlarged, myocardial fibrosis was markedly higher, AF inducibility was significantly elevated, and atrial effective refractory periods were shortened in the RAP group. These effects were significantly reversed by sacubitril/valsartan. Compared to that in the sham group, collagen Ⅰ and Ⅲ, NT-proBNP, ST2, calcineurin, and NFAT were significantly up-regulated, while p-NFAT and Cav1.2 were down-regulated in the RAP group, and sacubitril/valsartan inhibited these changes. Ca2+ concentration increased and ICaL density decreased in in vivo and in vitro AF models, reversed by sacubitril/valsartan. Sacubitril/valsartan attenuates atrial electrical remodelling and ameliorates structure remodelling in AF. This study paves the way for the possibility of clinical use of sacubitril/valsartan in AF patients.

Effect of pimobendan on left atrial function: an echocardiographic pilot study in 11 healthy cats.

OBJECTIVES: - To evaluate the effect of a single dose of pimobendan on left atrial (LA) function in healthy cats. ANIMALS: - Eleven client owned healthy cats. MATERIAL AND METHODS: - Standardized and repeated echocardiographic examinations were performed on healthy and conscious cats before and after a single dose of orally administered pimobendan (1.25 mg/cat). Left atrial systolic functional parameters were assessed. RESULTS: - Some of the tested parameters of LA function showed significant improvement after pimobendan administration, whereas no significant effect on left ventricular function was observed. In particular, LA minimal diameters obtained from M-mode images in short (p=0.018) and long (p=0.009) axis reduced after pimobendan administration, whereas LA fractional shortening from short (p=0.027) and long (p=0.042) axis and LA appendage emptying velocity (p<0.001) significantly increased. A mild increase in heart rate (p=0.001), and a transient increase on the peak systolic wave pulmonary vein velocity (p=0.008) were also recorded as a possible effect. CONCLUSIONS: - A single dose of pimobendan appears to impact LA function in healthy cats. However, because of the small number of cats included, and the absence of a placebo group, these results cannot be definitively separated from the effect of time. Additional studies are needed to understand if similar effects are observed in cats with cardiomyopathy and LA dilatation.

Effects of atenolol on left atrial and left ventricular function in healthy cats and in cats with hypertrophic cardiomyopathy.

This study aimed to assess the effects of atenolol on left ventricular (LV) and left atrial (LA) function in healthy cats and investigate the relationship between atenolol administration and LA enlargement (LAE) in cats with hypertrophic cardiomyopathy (HCM). In study 1, nine experimental cats were used to assess the effects of atenolol in healthy subjects. Cats were administered one of three medication protocols for 7 days: atenolol 6.25 mg/cat twice daily, 12.5 mg/cat twice daily, or placebo (biofermin) 1 tab/cat twice daily. In study 2, cats with HCM were retrospectively recruited and divided into four groups according to atenolol administration [(control group (Cont) or atenolol administration group (Ate)] and the presence or absence of LAE as follows: Cont LAE (-) group (n=42), Cont LAE (+) group (n=20), Ate LAE (-) group (n=17), and Ate LAE (+) group (n=12). LV and LA functions were compared in both studies. LV and LA functions were decreased by atenolol administration in study 1. In study 2, the peak myocardial velocity during early diastole (E') was significantly decreased in the Cont LAE (+), Ate LAE (-), and Ate LAE (+) groups compared to that in the Cont LAE (-) group, but there were no significant differences between LAE (+) groups. Multivariate logistic analysis revealed that atenolol administration was not associated with LAE. Diastolic dysfunction may be associated with LAE; however, atenolol administration did not affect LAE in cats with HCM.

Metformin improves lipid metabolism and reverses the Warburg effect in a canine model of chronic atrial fibrillation.

BACKGROUND: Previous studies demonstrated impaired lipid metabolism and augmented aerobic glycolysis in AF. The authors aimed to investigate whether the use of metformin, an AMPK activator, could reverse this metabolic remodeling in chronic AF and to explore the underlying mechanisms. METHODS: We conducted chronic AF animal models with 18 beagle dogs and divided them into SR (pacemaker implanted without pacing), AF (pacemaker implanted with sustained pacing at a frequency of 400 beats/min for 6 weeks), and metformin+AF group (daily oral administration of metformin was initiated 1 week before surgery and continued throughout the study period). After electrophysiological measurements, the left atrial appendage tissue samples were taken from the beating heart for further analysis. Protein expression, histological analysis, and biochemical measurements were conducted. RESULTS: The AF groups showed decreased expression of FAT/CD36, CPT-1, VLCAD, increased concentration of free fatty acid and triglyceride, and increased lipid deposition. The activation of AMPK/PGC-1α/PPARα pathway was decreased. The key factors of the Warburg effect, including HIF-1α, GLUT-1, PDK1, HK, and LDH, increased in AF group compared to SR group. The expression of PDH decreased significantly, accompanied by increased atrial lactate production. The extent of fibrosis increased significantly in the left atrial appendage of AF group. dERP, ∑WOV, and AF inducibility increased while ERP decreased in AF group compared to SR group. The use of metformin attenuated all these changes effectively. CONCLUSIONS: Metformin improves lipid metabolism and reverses the Warburg effect in chronic AF via AMPK activation. It attenuates atrial electrical and structural remodeling.

Role of NLRP3-Inflammasome/Caspase-1/Galectin-3 Pathway on Atrial Remodeling in Diabetic Rabbits.

Both diabetes mellitus (DM) and atrial fibrillation (AF) are usually associated with enhanced inflammatory response. The effect of the "NACHT, LRR and PYD domain containing protein 3" (NLRP3)-inflammasome/caspase-1/galectin-3 pathway and the potential benefits of NLRP3-inflammasome inhibitor glibenclamide (GLB) on atrial remodeling in the DM state are still unknown. Here, we demonstrated that higher AF inducibility and conduction inhomogeneity, slower epicardial conduction velocity, and increased amount of fibrosis in diabetic rabbits as against normal ones were markedly reduced by GLB. Atrial caspase-1 activity as well as serum IL-1ß and IL-18 levels were elevated in diabetic animals but suppressed by GLB. Moreover, GLB decreased the DM-induced protein expression enhancement of NLRP3, Gal-3, TGF-ß1, and CaV1.2 according to western blot analysis. Summarily, our findings indicate that the NLRP3-inflammasome/caspase-1/Gal-3 signaling pathway is related to the pathogenesis of AF in the diabetic state. NLRP3-inflammasome inhibitor GLB prevents AF inducibility and moderates atrial structural remodeling in DM.

Effect of pimobendan on left atrial function in dogs with preclinical myxomatous mitral valve disease.

Background: Left atrial (LA) function is an important determinant of the left ventricular (LV) filling, playing a key role in maintaining optimal cardiac performance. Pimobendan is a phosphodiesterase III inhibitor with positive inotropic and vasodilator effects. The present study aims to investigate the effects of pimobendan on LA function in dogs with stage B2 myxomatous mitral valve disease (MMVD). Aim: The aim of this investigation was to study the effects of pimobendan on LA function in dogs with preclinical MMVD. Methods: Twenty-seven dogs with stage B2 MMVD were retrospectively included. LA function was assessed before and 1-6 months following pimobendan initiation. For each dog, two-dimensional (2D) echocardiography was performed to assess LA diameter and volume for each phase of the LA cycle and to assess complete, passive, and active LA function. Pulsed-wave tissue Doppler imaging (TDI) of the left ventricular longitudinal myocardial velocity associated with atrial contraction (A'), both at the level of the interventricular septum and the LV free wall, was also used as an indicator of LA function. Results: There were no significant differences in any of the left atrial variables pre- and posttreatment. Conclusion: Echocardiographic estimates of LA function by 2D diameters and volumes and TDI A' in dogs with MMVD do not change after treatment with pimobendan.

LA Mechanics in Decompensated Heart Failure: Insights From Strain Echocardiography With Invasive Hemodynamics.

OBJECTIVES: The aim of this study was to assess the effect of congestion and decongestive therapy on left atrial (LA) mechanics and to determine the relationship between LA improvement after decongestive therapy and clinical outcome in immediate or chronic heart failure with reduced ejection fraction (HFrEF). BACKGROUND: LA mechanics are affected by volume/pressure overload in decompensated HFrEF. METHODS: A total of 31 patients with HFrEF and immediate heart failure (age 64 ± 15 years, 74% male, left ventricular ejection fraction 20 ± 12%) underwent serial echocardiography during decongestive therapy with simultaneous hemodynamic monitoring. LA function was assessed by strain (rate) imaging. Patients were re-evaluated 6 weeks after discharge and prospectively followed up for the composite endpoint of heart failure readmission and all-cause mortality. RESULTS: LA reservoir function was markedly reduced at baseline and improved with decongestion (peak atrial longitudinal strain from 6.4 ± 2.2% to 8.8 ± 3.0% and strain rate from 0.29 ± 0.11 s-1 to 0.38 ± 0.13 s-1), independent of changes in left ventricular global longitudinal strain, LA end-diastolic volume, and mitral regurgitation severity (p < 0.001). Both measures continued to rise at 6 weeks (up to 13.4 ± 6.1% and 0.50 ± 0.19 s-1, respectively; p < 0.001). LA pump strain rate only increased 6 weeks after discharge (-0.25 ± 0.12 s-1 to -0.55 ± 0.29 s-1; p < 0.010). Changes in LA mechanics correlated with changes in wedge pressure (r = -0.61; p < 0.001). Lower peak atrial longitudinal strain values after decongestion were associated with increased risk for the composite endpoint of heart failure and mortality (p < 0.019). CONCLUSIONS: LA reservoir and booster function, while severely impaired during immediate decompensation, significantly improve during and after decongestive therapy. Poor LA reservoir function after decongestion is associated with worse outcome.

Arnebiae Radix prevents atrial fibrillation in rats by ameliorating atrial remodeling and cardiac function.

ETHNOPHARMACOLOGICAL RELEVANCE: Arnebiae Radix, a common herbal medicine in China, is often utilized to treat blood-heat syndrome and has been reported to exert an effect on the heart. AIM OF THE STUDY: The combination of acetylcholine (Ach) and CaCl2 has been widely used to induce atrial fibrillation (AF) in animals. However, whether Arnebiae Radix displays any preventive action on Ach-CaCl2 induced AF in rats remains uncertain. In our study, we attempted to investigate the protective effects of Arnebiae Radix on Ach-CaCl2 induced AF compared to amiodarone, which was employed as the positive control. MATERIALS AND METHODS: To establish the AF model, SD rats were treated with a mixture of 0.1 mL/100 g Ach-CaCl2 (60 µg/mL Ach and 10 mg/mL CaCl2) by tail vein injection for 7 days. Rats were also given a gavage of Arnebiae Radix (0.18 g/mL) one week before or concurrently with the establishment of the AF model. At the end of the experimental period, the induction, duration and timing of AF were monitored using electrocardiogram recordings. Left atrial tissues were stained to observe the level of fibrosis. Electrophysiological measurements were used to examine atrial size and function. RESULTS: In Ach-CaCl2-induced AF rats, Arnebiae Radix decreased AF induction, duration and susceptibility to AF. In addition, Arnebiae Radix significantly reduced atrial fibrosis and inhibited atrial enlargement induced by Ach-CaCl2. Moreover, there was an apparent improvement in cardiac function in the Arnebiae Radix-treated group. CONCLUSIONS: Our findings indicate that Arnebiae Radix treatment can attenuate Ach-CaCl2-induced atrial injury and serve as an effective therapeutic strategy for the treatment of AF in the future.

Sphingosine-1-Phosphate Receptor Modulator, FTY720, Improves Diastolic Dysfunction and Partially Reverses Atrial Remodeling in a Tm-E180G Mouse Model Linked to Hypertrophic Cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is a genetic cardiovascular disorder, primarily involving mutations in sarcomeric proteins. HCM patients present with hypertrophy, diastolic dysfunction, and fibrosis, but there is no specific treatment. The sphingosine-1-phosphate receptor modulator, FTY720/fingolimod, is approved for treatment of multiple sclerosis. We hypothesize that modulation of the sphingosine-1-phosphate receptor by FTY720 would be of therapeutic benefit in sarcomere-linked HCM. METHODS: We treated mice with an HCM-linked mutation in tropomyosin (Tm-E180G) and nontransgenic littermates with FTY720 or vehicle for 6 weeks. Compared with vehicle-treated, FTY720-treated Tm-E180G mice had a significant reduction in left atrial size (1.99±0.19 [n=7] versus 2.70±0.44 [n=6] mm; P<0.001) and improvement in diastolic function (E/A ratio: 2.69±0.38 [n=7] versus 5.34±1.19 [n=6]; P=0.004) as assessed by echocardiography. RESULTS: Pressure-volume relations revealed significant improvements in the end-diastolic pressure volume relationship, relaxation kinetics, preload recruitable stroke work, and ejection fraction. Detergent-extracted fiber bundles revealed a significant decrease in myofilament Ca2+-responsiveness (pCa50=6.15±0.11 [n=13] versus 6.24±0.06 [n=14]; P=0.041). We attributed these improvements to a downregulation of S-glutathionylation of cardiac myosin binding protein-C in FTY720-treated Tm-E180G mice and reduction in oxidative stress by downregulation of NADPH oxidases with no changes in fibrosis. CONCLUSIONS: This is the first demonstration that modulation of S1PR results in decreased myofilament-Ca2+-responsiveness and improved diastolic function in HCM. We associated these changes with decreased oxidative modification of myofilament proteins via downregulation of NOX2. Our data support the hypothesis that modification of sphingolipid signaling may be a novel therapeutic approach in HCM.

Empagliflozin, a sodium glucose co-transporter-2 inhibitor, alleviates atrial remodeling and improves mitochondrial function in high-fat diet/streptozotocin-induced diabetic rats.

BACKGROUND: Diabetes mellitus is an important risk factor for atrial fibrillation (AF) development. Sodium-glucose co-transporter-2 (SGLT-2) inhibitors are used for the treatment of type 2 diabetes mellitus (T2DM). Their cardioprotective effects have been reported but whether they prevent AF in T2DM patients are less well-explored. We tested the hypothesis that the SGLT-2 inhibitor, empagliflozin, can prevent atrial remodeling in a diabetic rat model. METHODS: High-fat diet and low-dose streptozotocin (STZ) treatment were used to induce T2DM. A total of 96 rats were randomized into the following four groups: (i) control (ii) T2DM, (iii) low-dose empagliflozin (10 mg/kg/day)/T2DM; and (iv) high-dose empagliflozin (30 mg/kg/day)/T2DM by the intragastric route for 8 weeks. RESULTS: Compared with the control group, left atrial diameter, interstitial fibrosis and the incidence of AF inducibility were significantly increased in the DM group. Moreover, atrial mitochondrial respiratory function, mitochondrial membrane potential, and mitochondrial biogenesis were impaired. Empagliflozin treatment significantly prevented the development of these abnormalities in DM rats, likely via the peroxisome proliferator-activated receptor-c coactivator 1α (PGC-1α)/nuclear respiratory factor-1 (NRF-1)/mitochondrial transcription factor A (Tfam) signaling pathway. CONCLUSIONS: Empagliflozin can ameliorate atrial structural and electrical remodeling as well as improve mitochondrial function and mitochondrial biogenesis in T2DM, hence may be potentially used in the prevention of T2DM-related atrial fibrillation.

Longitudinal study of electrical, functional and structural remodelling in an equine model of atrial fibrillation.

BACKGROUND: Large animal models are important in atrial fibrillation (AF) research, as they can be used to study the pathophysiology of AF and new therapeutic approaches. Unlike other animal models, horses spontaneously develop AF and could therefore serve as a bona fide model in AF research. We therefore aimed to study the electrical, functional and structural remodelling caused by chronic AF in a horse model. METHOD: Nine female horses were included in the study, with six horses tachypaced into self-sustained AF and three that served as a time-matched sham-operated control group. Acceleration in atrial fibrillatory rate (AFR), changes in electrocardiographic and echocardiographic variables and response to medical treatment (flecainide 2 mg/kg) were recorded over a period of 2 months. At the end of the study, changes in ion channel expression and fibrosis were measured and compared between the two groups. RESULTS: AFR increased from 299 ± 33 fibrillations per minute (fpm) to 376 ± 12 fpm (p < 0.05) and atrial function (active left atrial fractional area change) decreased significantly during the study (p < 0.05). No changes were observed in heart rate or ventricular function. The AF group had more atrial fibrosis compared to the control group (p < 0.05). No differences in ion channel expression were observed. CONCLUSION: Horses with induced AF show signs of atrial remodelling that are similar to humans and other animal models.