Enhanced CaMKII-Dependent Late INa Induces Atrial Proarrhythmic Activity in Patients With Sleep-Disordered Breathing.

RATIONALE: Sleep-disordered breathing (SDB) is frequently associated with atrial arrhythmias. Increased CaMKII (Ca/calmodulin-dependent protein kinase II) activity has been previously implicated in atrial arrhythmogenesis. OBJECTIVE: We hypothesized that CaMKII-dependent dysregulation of Na current (INa) may contribute to atrial proarrhythmic activity in patients with SDB. METHODS AND RESULTS: We prospectively enrolled 113 patients undergoing elective coronary artery bypass grafting for cross-sectional study and collected right atrial appendage biopsies. The presence of SDB (defined as apnea-hypopnea index ≥15/h) was assessed with a portable SDB monitor the night before surgery. Compared with 56 patients without SDB, patients with SDB (57) showed a significantly increased level of activated CaMKII. Patch clamp was used to measure INa. There was a significantly enhanced late INa, but reduced peak INa due to enhanced steady-state inactivation in atrial myocytes of patients with SDB consistent with significantly increased CaMKII-dependent cardiac Na channel phosphorylation (NaV1.5, at serine 571, Western blotting). These gating changes could be fully reversed by acute CaMKII inhibition (AIP [autocamtide-2 related inhibitory peptide]). As a consequence, we observed significantly more cellular afterdepolarizations and more severe premature atrial contractions in atrial trabeculae of patients with SDB, which could be blocked by either AIP or KN93 (N-[2-[[[(E)-3-(4-chlorophenyl)prop-2-enyl]-methylamino]methyl]phenyl]-N-(2-hydroxyethyl)-4-methoxybenzenesulfonamide). In multivariable linear regression models incorporating age, sex, body mass index, existing atrial fibrillation, existing heart failure, diabetes mellitus, and creatinine levels, apnea-hypopnea index was independently associated with increased CaMKII activity, enhanced late INa and correlated with premature atrial contraction severity. CONCLUSIONS: In atrial myocardium of patients with SDB, increased CaMKII-dependent phosphorylation of NaV1.5 results in dysregulation of INa with proarrhythmic activity that was independent from preexisting comorbidities. Inhibition of CaMKII may be useful for prevention or treatment of arrhythmias in SDB. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02877745. Visual Overview: An online visual overview is available for this article.

Empagliflozin inhibits increased Na influx in atrial cardiomyocytes of patients with HFpEF.

AIMS: Heart failure with preserved ejection fraction (HFpEF) causes substantial morbidity and mortality. Importantly, atrial remodelling and atrial fibrillation are frequently observed in HFpEF. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have recently been shown to improve clinical outcomes in HFpEF, and post-hoc analyses suggest atrial anti-arrhythmic effects. We tested if isolated human atrial cardiomyocytes from patients with HFpEF exhibit an increased Na influx, which is known to cause atrial arrhythmias, and if that is responsive to treatment with the SGTL2i empagliflozin. METHODS AND RESULTS: Cardiomyocytes were isolated from atrial biopsies of 124 patients (82 with HFpEF) undergoing elective cardiac surgery. Na influx was measured with the Na-dye Asante Natrium Green-2 AM (ANG-2). Compared to patients without heart failure (NF), Na influx was doubled in HFpEF patients (NF vs. HFpEF: 0.21 ± 0.02 vs. 0.38 ± 0.04 mmol/L/min (N = 7 vs. 18); P = 0.0078). Moreover, late INa (measured via whole-cell patch clamp) was significantly increased in HFpEF compared to NF. Western blot and HDAC4 pulldown assay indicated a significant increase in CaMKII expression, CaMKII autophosphorylation, CaMKII activity, and CaMKII-dependent NaV1.5 phosphorylation in HFpEF compared to NF, whereas NaV1.5 protein and mRNA abundance remained unchanged. Consistently, increased Na influx was significantly reduced by treatment not only with the CaMKII inhibitor autocamtide-2-related inhibitory peptide (AIP), late INa inhibitor tetrodotoxin (TTX) but also with sodium/hydrogen exchanger 1 (NHE1) inhibitor cariporide. Importantly, empagliflozin abolished both increased Na influx and late INa in HFpEF. Multivariate linear regression analysis, adjusting for important clinical confounders, revealed HFpEF to be an independent predictor for changes in Na handling in atrial cardiomyocytes. CONCLUSION: We show for the first time increased Na influx in human atrial cardiomyocytes from HFpEF patients, partly due to increased late INa and enhanced NHE1-mediated Na influx. Empagliflozin inhibits Na influx and late INa, which could contribute to anti-arrhythmic effects in patients with HFpEF.

Wireless handheld focused ultrasound in student teaching during the COVID-19 pandemic: Initial results of a pilot study1.

OBJECTIVE: The study aim was to investigate the use of a novel device, the Vscan Air™, for rapidly and effectively performing ultrasound in student teaching during the COVID-19 pandemic. MATERIAL AND METHODS: As part of the ultrasound practical course with integrated hands-on activity required by the regular medical curriculum, 100 medical students were instructed in the use of the Vscan Air™, including duplex mode. They then evaluated the quality of the ultrasound images obtained by the Vscan Air™ from previously selected organs. RESULTS: 100 students were interviewed (female n = 68, male n = 32; age >18 years n = 100). The rated image quality never fell below a mean of 3 for the examined organs and portal vein flow (liver 4,58; spleen 3,99; kidneys 4,29; aorta 4,16; Douglas/rectovesical space 4,14; portal vein 4,43; pancreas 3,53; Focused Assessment with Sonography for Trauma 4,38). Scores below 3 were found sporadically in ultrasounds of the spleen (n = 4), kidneys (n = 3), Douglas/rectovesical space (n = 2), and pancreas (n = 15). The liver was rated the lowest for 59 ratings. The portal vein was evaluated in 68 cases. The hepatic artery and hepatic veins could be also visualized in all 68 examinations. The aorta was evaluated in 62 cases. CONCLUSION: The Vscan Air™ technology offered adequate image quality and provided a new, fast and patient-oriented technique to support continuous ultrasound examinations and education of students, especially during a pandemic. Particularly noteworthy is the uncomplicated compliance with the required high level of hygiene.

A novel mouse model of obstructive sleep apnea by bulking agent-induced tongue enlargement results in left ventricular contractile dysfunction.

AIMS: Obstructive sleep apnea (OSA) is a widespread disease with high global socio-economic impact. However, detailed pathomechanisms are still unclear, partly because current animal models of OSA do not simulate spontaneous airway obstruction. We tested whether polytetrafluoroethylene (PTFE) injection into the tongue induces spontaneous obstructive apneas. METHODS AND RESULTS: PTFE (100 µl) was injected into the tongue of 31 male C57BL/6 mice and 28 mice were used as control. Spontaneous apneas and inspiratory flow limitations were recorded by whole-body plethysmography and mRNA expression of the hypoxia marker KDM6A was quantified by qPCR. Left ventricular function was assessed by echocardiography and ventricular CaMKII expression was measured by Western blotting. After PTFE injection, mice showed features of OSA such as significantly increased tongue diameters that were associated with significantly and sustained increased frequencies of inspiratory flow limitations and apneas. Decreased KDM6A mRNA levels indicated chronic hypoxemia. 8 weeks after surgery, PTFE-treated mice showed a significantly reduced left ventricular ejection fraction. Moreover, the severity of diastolic dysfunction (measured as E/e') correlated significantly with the frequency of apneas. Accordingly, CaMKII expression was significantly increased in PTFE mice and correlated significantly with the frequency of apneas. CONCLUSIONS: We describe here the first mouse model of spontaneous inspiratory flow limitations, obstructive apneas, and hypoxia by tongue enlargement due to PTFE injection. These mice develop systolic and diastolic dysfunction and increased CaMKII expression. This mouse model offers great opportunities to investigate the effects of obstructive apneas.