Downregulation of the muscle-specific microRNA-1 (miR-1) mediates the induction of pathologic cardiac hypertrophy. Dysfunction of the gap junction protein connexin 43 (Cx43), an established miR-1 target, during cardiac hypertrophy leads to ventricular tachyarrhythmias (VT). However, it is still unknown whether miR-1 and Cx43 are interconnected in the pro-arrhythmic context of hypertrophy. Thus, in this study we investigated whether a reduction in the extent of cardiac hypertrophy could limit the pathological electrical remodeling of Cx43 and the onset of VT by modulating miR-1 levels. Wistar male rats underwent mechanical constriction of the ascending aorta to induce pathologic left ventricular hypertrophy (LVH) and afterwards were randomly assigned to receive 10mg/kg valsartan, VAL (LVH+VAL) delivered in the drinking water or placebo (LVH) for 12 weeks. Sham surgery was performed for control groups. Programmed ventricular stimulation reproducibly induced VT in LVH compared to LVH+VAL group. When compared to sham controls, rats from LVH group showed a significant decrease of miR-1 and an increase of Cx43 expression and its ERK1/2-dependent phosphorylation, which displaces Cx43 from the gap junction. Interestingly, VAL administration to rats with aortic banding significantly reduced cardiac hypertrophy and prevented miR-1 down-regulation and Cx43 up-regulation and phosphorylation. Gain- and loss-of-function experiments in neonatal cardiomyocytes (NCMs) in vitro confirmed that Cx43 is a direct target of miR-1. Accordingly, in vitro angiotensin II stimulation reduced miR-1 levels and increased Cx43 expression and phosphorylation compared to un-stimulated NCMs. Finally, in vivo miR-1 cardiac overexpression by an adenoviral vector intra-myocardial injection reduced Cx43 expression and phosphorylation in mice with isoproterenol-induced LVH. In conclusion, miR-1 regulates Cx43 expression and activity in hypertrophic cardiomyocytes in vitro and in vivo. Treatment of pressure overload-induced myocyte hypertrophy reduces the risk of life-threatening VT by normalizing miR-1 expression levels with the consequent stabilization of Cx43 expression and activity within the gap junction.

Failure of mitral restrictive annuloplasty is responsible for follow-up mortality and congestive heart failure and correlates with absence of cardiac reverse remodeling. Prognosis of patients having mitral restrictive annuloplasty for ischemic cardiomyopathy with chronic mitral regurgitation is good, as long as a low postoperative coaptation depth is achieved. Patients with significant left ventricular dilation should be considered for different surgical strategies.

Effective restrictive mitral annuloplasty induces reverse left ventricular remodeling. Absence of recurrent chronic ischemic mitral regurgitation improves tricuspid insufficiency grading, systolic pulmonary arterial pressure, right ventricular ejection fraction, tricuspid annular plane systolic excursion, New York Heart Association, and diuretic need in patients who do not undergo tricuspid surgery, but only tricuspid insufficiency grading, New York Heart Association, and daily diuretic need in patients who undergo tricuspid surgery.

Recurrent CIMR correlates with absent ventricular reverse remodelling. Despite a higher trans-mitral gradient, complete rings achieve better results in the treatment of CIMR.

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