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.

We hypothesized that CaMKII-dependent dysregulation of Na current (I_Na) may contribute to atrial proarrhythmic activity in patients with SDB.

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 I_Na. There was a significantly enhanced late I_Na, but reduced peak I_Na due to enhanced steady-state inactivation in atrial myocytes of patients with SDB consistent with significantly increased CaMKII-dependent cardiac Na channel phosphorylation (Na_V1.5, 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 I_Na and correlated with premature atrial contraction severity.

In atrial myocardium of patients with SDB, increased CaMKII-dependent phosphorylation of Na_V1.5 results in dysregulation of I_Na with proarrhythmic activity that was independent from preexisting comorbidities. Inhibition of CaMKII may be useful for prevention or treatment of arrhythmias in SDB.

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02877745.

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