Empagliflozin prevents heart failure through inhibition of the NHE1-NO pathway, independent of SGLT2.

Sodium glucose cotransporter 2 inhibitors (SGLT2i) constitute the only medication class that consistently prevents or attenuates human heart failure (HF) independent of ejection fraction. We have suggested earlier that the protective mechanisms of the SGLT2i Empagliflozin (EMPA) are mediated through reductions in the sodium hydrogen exchanger 1 (NHE1)-nitric oxide (NO) pathway, independent of SGLT2. Here, we examined the role of SGLT2, NHE1 and NO in a murine TAC/DOCA model of HF. SGLT2 knockout mice only showed attenuated systolic dysfunction without having an effect on other signs of HF. EMPA protected against systolic and diastolic dysfunction, hypertrophy, fibrosis, increased Nppa/Nppb mRNA expression and lung/liver edema. In addition, EMPA prevented increases in oxidative stress, sodium calcium exchanger expression and calcium/calmodulin-dependent protein kinase II activation to an equal degree in WT and SGLT2 KO animals. In particular, while NHE1 activity was increased in isolated cardiomyocytes from untreated HF, EMPA treatment prevented this. Since SGLT2 is not required for the protective effects of EMPA, the pathway between NHE1 and NO was further explored in SGLT2 KO animals. In vivo treatment with the specific NHE1-inhibitor Cariporide mimicked the protection by EMPA, without additional protection by EMPA. On the other hand, in vivo inhibition of NOS with L-NAME deteriorated HF and prevented protection by EMPA. In conclusion, the data support that the beneficial effects of EMPA are mediated through the NHE1-NO pathway in TAC/DOCA-induced heart failure and not through SGLT2 inhibition.

Bariatric surgery partially reverses subclinical proarrhythmic structural, electrophysiological, and autonomic changes in obesity.

BACKGROUND: Obesity confers higher risks of cardiac arrhythmias. The extent to which weight loss reverses subclinical proarrhythmic adaptations in arrhythmia-free obese individuals is unknown. OBJECTIVE: The purpose of this study was to study structural, electrophysiological, and autonomic remodeling in arrhythmia-free obese patients and their reversibility with bariatric surgery using electrocardiographic imaging (ECGi). METHODS: Sixteen arrhythmia-free obese patients (mean age 43 ± 12 years; 13 (81%) female participants; BMI 46.7 ± 5.5 kg/m2) had ECGi pre-bariatric surgery, of whom 12 (75%) had ECGi postsurgery (BMI 36.8 ± 6.5 kg/m2). Sixteen age- and sex-matched lean healthy individuals (mean age 42 ± 11 years; BMI 22.8 ± 2.6 kg/m2) acted as controls and had ECGi only once. RESULTS: Obesity was associated with structural (increased epicardial fat volumes and left ventricular mass), autonomic (blunted heart rate variability), and electrophysiological (slower atrial conduction and steeper ventricular repolarization time gradients) remodeling. After bariatric surgery, there was partial structural reverse remodeling, with a reduction in epicardial fat volumes (68.7 cm3 vs 64.5 cm3; P = .0010) and left ventricular mass (33 g/m2.7 vs 25 g/m2.7; P < .0005). There was also partial electrophysiological reverse remodeling with a reduction in mean spatial ventricular repolarization gradients (26 mm/ms vs 19 mm/ms; P = .0009), although atrial activation remained prolonged. Heart rate variability, quantified by standard deviation of successive differences in R-R intervals, was also partially improved after bariatric surgery (18.7 ms vs 25.9 ms; P = .017). Computational modeling showed that presurgical obese hearts had a larger window of vulnerability to unidirectional block and had an earlier spiral-wave breakup with more complex reentry patterns than did postsurgery counterparts. CONCLUSION: Obesity is associated with adverse electrophysiological, structural, and autonomic remodeling that is partially reversed after bariatric surgery. These data have important implications for bariatric surgery weight thresholds and weight loss strategies.

Empagliflozin mitigates cardiac hypertrophy through cardiac RSK/NHE-1 inhibition.

BACKGROUND: SGLT2i reduce cardiac hypertrophy, but underlying mechanisms remain unknown. Here we explore a role for serine/threonine kinases (STK) and sodium hydrogen exchanger 1(NHE1) activities in SGLT2i effects on cardiac hypertrophy. METHODS: Isolated hearts from db/db mice were perfused with 1 µM EMPA, and STK phosphorylation sites were examined using unbiased multiplex analysis to detect the most affected STKs by EMPA. Subsequently, hypertrophy was induced in H9c2 cells with 50 µM phenylephrine (PE), and the role of the most affected STK (p90 ribosomal S6 kinase (RSK)) and NHE1 activity in hypertrophy and the protection by EMPA was evaluated. RESULTS: In db/db mice hearts, EMPA most markedly reduced STK phosphorylation sites regulated by RSKL1, a member of the RSK family, and by Aurora A and B kinases. GO and KEGG analysis suggested that EMPA inhibits hypertrophy, cell cycle, cell senescence and FOXO pathways, illustrating inhibition of growth pathways. EMPA prevented PE-induced hypertrophy as evaluated by BNP and cell surface area in H9c2 cells. EMPA blocked PE-induced activation of NHE1. The specific NHE1 inhibitor Cariporide also prevented PE-induced hypertrophy without added effect of EMPA. EMPA blocked PE-induced RSK phosphorylation. The RSK inhibitor BIX02565 also suppressed PE-induced hypertrophy without added effect of EMPA. Cariporide mimicked EMPA's effects on PE-treated RSK phosphorylation. BIX02565 decreased PE-induced NHE1 activity, with no further decrease by EMPA. CONCLUSIONS: RSK inhibition by EMPA appears as a novel direct cardiac target of SGLT2i. Direct cardiac effects of EMPA exert their anti-hypertrophic effect through NHE-inhibition and subsequent RSK pathway inhibition.

Sleep apnea, the risk of out-of-hospital cardiac arrest, and potential benefits of continuous positive airway pressure therapy: A nationwide study.

OBJECTIVE: Patients with sleep apnea (SA) are at increased cardiovascular risk. However, little is known about the risk of out-of-hospital cardiac arrest (OHCA) in patients with SA. Therefore, we studied the relation between SA patients who did and did not receive continuous positive airway pressure (CPAP) therapy with OHCA in the general population. METHODS: Using nationwide databases, we conducted a nested case-control study with OHCA-cases of presumed cardiac causes and age/sex/OHCA-date matched non-OHCA-controls from the general population. Conditional logistic regression models with adjustments for well-known OHCA risk factors were performed to generate odds ratio (OR) of OHCA comparing patients with SA receiving and not receiving CPAP therapy with individuals without SA. RESULTS: We identified 46,578 OHCA-cases and 232,890 matched non-OHCA-controls [mean: 71 years, 68.8% men]. Compared to subjects without SA, having SA without CPAP therapy was associated with increased odds of OHCA after controlling for relevant confounders (OR:1.20, 95%-Cl:1.06-1.36), while having SA with CPAP therapy was not associated with OHCA (OR:1.04, 95%-Cl:0.93-1.36). Regardless of CPAP therapy, age and sex did not significantly influence our findings. Our findings were confirmed in: (I) patients with neither ischemic heart disease nor heart failure (untreated SA, OR:1.24, 95%-CI:1.04-1.47; SA with CPAP, OR:1.08, 95%-CI:0.93-1.25); and (II) in patients without cardiovascular disease (untreated SA, OR:1.33, 95%-CI:1.07-1.65; SA with CPAP, OR:1.14, 95%-CI:0.94-1.39). CONCLUSION: SA not treated with CPAP was associated with OHCA, while no increased risk of OHCA was found for SA patients treated with CPAP.

Sodium-glucose cotransporter-2 inhibitors and the risk of atrial fibrillation in patients with type 2 diabetes: a population-based cohort study.

AIMS: Sodium-glucose cotransporter-2 inhibitors (SGLT-2is) have a direct cardiac effect that is likely to be independent of its glucose lowering renal effect. Previous research has shown that SGLT2-is mitigate heart failure and prevent arrhythmic cardiac death. Our objective is to determine whether SGLT-2is reduce atrial fibrillation (AF) in comparison to other second-to third-line antidiabetic drugs in type 2 diabetes. METHODS AND RESULTS: We conducted a population-based, new-user active comparator cohort study using data from the UK Clinical Practice Research Datalink. We identified a cohort of patients initiating a new antidiabetic drug class between January 2013 and September 2020. This cohort included patients initiating their first ever non-insulin antidiabetic drug, as well as those who switched to or added-on an antidiabetic drug class not previously used in their treatment history. Individuals with a diagnosis of AF or atrial flutter at any time before cohort entry were excluded. Cox regression analysis with time-dependent covariates was used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) of AF comparing SGLT-2-is with other second-line to third-line antidiabetic drugs. Stratified analyses were performed according to sex, diabetes duration (<5 or ≥ 5 years), body mass index (BMI), HbA1c, and presence of heart failure.The cohort comprised 142 447 patients. SGLT-2is were associated with a statistically significant reduced hazard of AF compared to other second-line to third-line antidiabetic drugs (adjusted HR: 0.77 [95% CI: 0.68-0.88]). This reduced risk was present in both sexes but was more prominently among women (adjusted HRwomen: 0.60 [95% CI: 0.45-0.79]; HRmen: 0.85 [95% CI: 0.73-0.98]; P-value interaction: 0.012). There was no evidence for effect modification when stratifying on duration of diabetes, BMI, HbA1c, or presence of heart failure. CONCLUSION: SGLT-2is were associated with a reduced risk of AF in patients with type 2 diabetes compared to other second-line to third-line antidiabetic drugs. This reduced risk occurs in both sexes but more prominently among women.

Use of proton pump inhibitors is associated with increased risk of out-of-hospital cardiac arrest in the general population: a nested case-control study.

AIMS: Proton pump inhibitors (PPIs) impair cardiac repolarization, prolong the QT interval, and may potentially be pro-arrhythmic. However, the risk of out-of-hospital cardiac arrest (OHCA) is scarcely investigated. We studied whether past or current PPI use is associated with OHCA in the general population. METHODS AND RESULTS: We conducted a nationwide nested case-control study with OHCA-cases of presumed cardiac causes and age/sex/OHCA-date-matched non-OHCA-controls from the general population. Exposure to PPI was categorized into three mutually exclusive groups of current-, past-, and non-use. Conditional logistic regression analyses with adjustments for risk factors of OHCA were used to calculate the odds ratio (OR) of OHCA comparing PPI use with non-users. We identified 46 578 OHCA cases and 232 890 matched non-OHCA controls (mean: 71 years, 68.8% men). PPI was used by 8769 OHCA-cases and 21 898 non-OHCA controls, and current use of PPI was associated with increased odds of OHCA compared with non-users [OR: 1.32 (95% CI: 1.28-1.37)], while past use conferred no increase in the odds of OHCA [OR: 1.01 (95% CI: 0.98-1.04)]. This increased odds of OHCA occurred in both sexes. Finally, the ORs remained elevated when we repeated the analyses in individuals without registered ischaemic heart disease [OR: 1.36 (95% CI: 1.31-1.41)], without heart failure [OR: 1.33 (95% CI: 1.29-1.38)], or without any cardiovascular comorbidities [OR: 1.84 (95% CI: 1.70-2.00)]. Also, the OR remained elevated when H2-antagonists served as the reference group [OR: 1.28 (95% CI: 1.11-1.47)]. CONCLUSION: PPI use is associated with an increased risk of OHCA in the general population. Considering the widespread use of PPIs, this study raises concerns and the need for awareness to balance the benefit and risk of treatment.

Interpretation of field and LEAP potentials recorded from cardiomyocyte monolayers.

Multielectrode arrays (MEAs) are the method of choice for electrophysiological characterization of cardiomyocyte monolayers. The field potentials recorded using an MEA are like extracellular electrograms recorded from the myocardium using conventional electrodes. Nevertheless, different criteria are used to interpret field potentials and extracellular electrograms, which hamper correct interpretation and translation to the patient. To validate the criteria for interpretation of field potentials, we used neonatal rat cardiomyocytes to generate monolayers. We recorded field potentials using an MEA and simultaneously recorded action potentials using sharp microelectrodes. In parallel, we recreated our experimental setting in silico and performed simulations. We show that the amplitude of the local RS complex of a field potential correlated with conduction velocity in silico but not in vitro. The peak time of the T wave in field potentials exhibited a strong correlation with APD90 while the steepest upslope correlated well with APD50. However, this relationship only holds when the T wave displayed a biphasic pattern. Next, we simulated local extracellular action potentials (LEAPs). The shape of the LEAP differed markedly from the shape of the local action potential, but the final duration of the LEAP coincided with APD90. Criteria for interpretation of extracellular electrograms should be applied to field potentials. This will provide a strong basis for the analysis of heterogeneity in conduction velocity and repolarization in cultured monolayers of cardiomyocytes. Finally, a LEAP is not a recording of the local action potential but is generated by intracellular current provided by neighboring cardiomyocytes and is superior to field potential duration in estimating APD90.NEW & NOTEWORTHY We present a physiological basis for the interpretation of multielectrode array-derived, extracellular, electrical signals.

Fluoroquinolones do not provide added risk of out-of-hospital cardiac arrest: a nationwide study.

AIM: Conflicting results have been reported regarding the association between fluoroquinolones (FQs) and the risk of out-of-hospital cardiac arrest (OHCA). In particular, it has not become clear whether OHCA in FQ users is related to the inherent comorbidities or whether there is a direct pro-arrhythmic effect of FQs. Therefore, we studied the relation between FQs and OHCA in the general population. METHODS: Through Danish nationwide registries, we conducted a nested case-control study with OHCA cases of presumed cardiac causes and age/sex/OHCA date-matched non-OHCA controls from the general population. Conditional logistic regression models with adjustments for well-known risk factors of OHCA were employed to estimate the OR with 95% CI of OHCA comparing FQs with amoxicillin. RESULTS: The study population consisted of 46 578 OHCA cases (mean: 71 years (SD: 14.40), 68.8% men) and 232 890 matched controls. FQ was used by 276 cases and 328 controls and conferred no increase in the odds of OHCA compared with amoxicillin use after controlling for the relevant confounders (OR: 0.91 (95% CI: 0.71 to 1.16)). The OR of OHCA associated with FQ use did not vary significantly by age (OR≤65: 0.96 (95% CI: 0.53 to 1.74), OR>65: 0.88 (95% CI: 0.67 to 1.16), p value interaction=0.7818), sex (ORmen: 0.96 (95% CI: 0.70 to 1.31), ORwomen: 0.80 (95% CI: 0.53 to 1.20), p value interaction=0.9698) and pre-existing cardiovascular disease (ORabsent: 1.02 (95% CI: 0.57 to 1.82), ORpresent: 0.98 (95% CI: 0.75 to 1.28), p value interaction=0.3884), including heart failure (ORabsent: 0.93 (95% CI: 0.72 to 1.22), ORpresent: 1.11 (95% CI: 0.61 to 2.02), p value interaction=0.7083) and ischaemic heart disease (ORabsent: 0.85 (95% CI: 0.64 to 1.12), ORpresent: 1.38 (95% CI: 0.86 to 2.21), p value interaction=0.6230). CONCLUSION: Our findings do not support an association between FQ exposure and OHCA in the general population. This lack of association was consistent in men and women, in all age categories, and in the presence or absence of cardiovascular disease.

Basis and applicability of noninvasive inverse electrocardiography: a comparison between cardiac source models.

The body surface electrocardiogram (ECG) is a direct result of electrical activity generated by the myocardium. Using the body surface ECGs to reconstruct cardiac electrical activity is called the inverse problem of electrocardiography. The method to solve the inverse problem depends on the chosen cardiac source model to describe cardiac electrical activity. In this paper, we describe the theoretical basis of two inverse methods based on the most commonly used cardiac source models: the epicardial potential model and the equivalent dipole layer model. We discuss similarities and differences in applicability, strengths and weaknesses and sketch a road towards improved inverse solutions by targeted use, sequential application or a combination of the two methods.

MicroRNAs in extracellular vesicles released from epicardial adipose tissue promote arrhythmogenic conduction slowing.

Background: Patients with excess epicardial adipose tissue (EAT) are at increased risk of developing cardiac arrhythmias. EAT promotes arrhythmias by depolarizing the resting membrane of cardiomyocytes, which slows down conduction and facilitates re-entrant arrhythmias. We hypothesized that EAT slows conduction by secreting extracellular vesicles (EVs) and their microRNA (miRNA) cargo. Objective: We aimed to determine the role of EAT-derived EVs and their miRNA cargo in conduction slowing. Methods: EAT and subcutaneous adipose tissue (SAT) were collected from patients with atrial fibrillation. Adipose tissue explants were incubated in culture medium and secretome was collected. The numbers of EVs in the EAT and SAT secretome were measured by calibrated flow cytometry. EVs in the EAT secretome were isolated by size exclusion chromatography and miRNAs were sequenced. Pathway analysis was performed to predict candidates involved in cardiac electrophysiology. The candidates were validated in the EAT and SAT by quantitative real-time polymerase chain reaction. Finally, miRNA candidates were overexpressed in neonatal rat ventricular myocytes. Results: The EV concentration was higher in the EAT secretome than in the SAT and control secretomes. miRNA sequencing of EAT-derived EVs detected a total of 824 miRNAs. Pathway analysis led to the identification of 7 miRNAs potentially involved in regulation of cardiac resting membrane potential. Validation of those miRNA candidates showed that they were all expressed in EAT, and that miR-1-3p and miR-133a-3p were upregulated in EAT in comparison with SAT. Overexpression of miR-1-3p and miR-133a-3p in neonatal rat ventricular myocytes led to conduction slowing and reduced Kcnj2 and Kcnj12 expression. Conclusion: miR-1-3p and miR-133a-3p are potential mediators of EAT arrhythmogenicity.

High-rate pacing suppresses Torsade de Pointes arrhythmias and reduces spatial dispersion of repolarization in the chronic AV-block dog model.

Background: An electrical storm of Torsade de Pointes arrhythmias (TdP) can be reproducibly induced in the anesthetized chronic AV-block (CAVB) dog by infusion of the IKr-blocker dofetilide. Earlier studies showed that these arrhythmias 1) arise from locations with high spatial dispersion in repolarization (SDR) and 2) can be suppressed by high-rate pacing. We examined whether suppression of TdP by high-rate pacing is established through a decrease in SDR in the CAVB dog. Methods: Dofetilide (25 µg/kg in 5 min) was administered to 5 anesthetized CAVB dogs to induce TdP arrhythmias. During the experiments, animals were continuously paced from the right ventricular apex at 50 beats/minute (RVA50). Upon TdP occurrence and conversion, RVA pacing was consecutively set to 100, 80 and 60 beats/minute for 2 min, referred to as pacing blocks. To determine the additional anti-arrhythmic effects of HRP over defibrillation alone, the number of arrhythmic events and SDR at RVA100 were compared to data from three previously conducted experiments, in which dogs underwent the same experimental protocol but were paced at RVA60 upon TdP occurrence (RVA60retro). In all experiments, recordings included surface electrocardiogram and mapping by 56 intramural needles, each recording four electrograms, evenly inserted into the ventricular walls and septum. For each pacing block, the number of ectopic beats (EB), and TdP severity were scored. SDR was quantified as the average difference in repolarization time within four squared needles (SDRcubic). Results: In 4 out of 5 animals, pacing at RVA100 suppressed TdP occurrence. One dog could not be converted by defibrillation after the initial TdP. Compared to RVA50, pacing at RVA100, but not RVA80 and RVA60, significantly reduced the TdP score (78 ± 33 vs. 0 ± 0, p < 0.05 and vs. 12.5 ± 25 and 25 ± 50, both p > 0.05). The reduction in TdP score was reflected by a significant decrease in SDRcubic (125 ± 46 ms before TdP vs. 49 ± 18 ms during RVA100, p < 0.05), and SDR was smaller than in the RVA60retro animals (101 ± 52 ms, p < 0.05 vs. RVA100). Conclusion: In CAVB dogs, high-rate pacing effectively suppresses TdP, which, at least in part, results from a spatial homogenization of cardiac repolarization, as reflected by a decrease in SDR.