Abstract 164: β-adrenergic Stimulation Exacerbates Preclinical Arrhythmogenic Right Ventricular Cardiomyopathy Due To Desmoplakin Mutation

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Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is associated with ventricular arrhythmias and sudden cardiac death. We previously demonstrated that cardiac-specific overexpression of human mutant desmoplakin (DSPR2834H) leads to ARVC in mice at 6 months of age. However, the potential role and mechanism(s) of DSP in preclinical ARVC under cardiac stress remains unclear.

Objectives: This study is aimed to elucidate the impact of DSP in the development of ARVC under adrenergic stimulation.

Methods: Three-month-old non-transgenic (NTg), wild-type DSP (Tg-DSPWT) and Tg-DSPR2834H mice without obvious signs of ARVC, including right and left ventricular dysfunction, arrhythmias, were infused with either vehicle or isoproterenol (30mg/kg/d) for 2 weeks using mini-osmotic pumps. During isoproterenol infusion, electrocardiography (ECG) was monitored daily on conscious mice. Echocardiography and cardiac MRI were performed before and after 2-week of isoproterenol infusion. Myocardial tissues from both RV and LV were subjected to cellular, biochemical and histopathological analysis.

Results: Isoproterenol resulted in cardiac hypertrophy to a similar degree amongst all genotypes; however, mortality occurred only in Tg-DSPR2834H mice. Vehicle-treated mice from all genotypes showed largely normal ECGs, whereas isoproterenol led to various types of arrhythmia in Tg-DSPR2834H mice including ventricular tachycardia and QT prolongation. Echocardiography analysis revealed LV dysfunction (decreased factional shortening) in isoproterenol-treated Tg-DSPR2834H mice compared to other treatment groups. Interstitial fibrosis and lipid infiltration was prominent in the Tg-DSPR2834H myocardium. MRI analysis is being performed to understand the RV and LV geometry and function.

Conclusion: Our preliminary data confirms the essential role of desmoplakin in response to adrenergic stimulation. Studies investigating the electrophysiological, geometrical and cellular mechanisms of the pro-arrhythmic nature of DSPR2834H dysfunction are ongoing which may ultimately provide critical experimental data on prevention of asymptomatic preclinical ARVC in humans.

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