We used a murine model of arrhythmogenic right ventricular cardiomyopathy (ARVC) to test whether reducing ventricular load prevents or slows development of this cardiomyopathy.
At present, no therapy exists to slow progression of ARVC. Genetically conferred dysfunction of the mechanical cell-cell connections, often associated with reduced expression of plakoglobin, is thought to cause ARVC.
Littermate pairs of heterozygous plakoglobin-deficient mice (plako(+/-)) and wild-type (WT) littermates underwent 7 weeks of endurance training (daily swimming). Mice were randomized to blinded load-reducing therapy (furosemide and nitrates) or placebo.
Therapy prevented training-induced right ventricular (RV) enlargement in plako(+/-) mice (RV volume: untreated plako(+/-) 136 ± 5 μl; treated plako(+/-) 78 ± 5 μl; WT 81 ± 5 μl; p <0.01 for untreated vs. WT and untreated vs. treated; mean ± SEM). In isolated, Langendorff-perfused hearts, ventricular tachycardias (VTs) were more often induced in untreated plako(+/-) hearts (15 of 25), than in treated plako(+/-) hearts (5 of 19) or in WT hearts (6 of 21, both p <0.05). Epicardial mapping of the RV identified macro-re-entry as the mechanism of ventricular tachycardia. The RV longitudinal conduction velocity was reduced in untreated but not in treated plako(+/-) mice (p <0.01 for untreated vs. WT and untreated vs. treated). Myocardial concentration of phosphorylated connexin43 was lower in plako(+/-) hearts with VTs compared with hearts without VTs and was reduced in untreated plako(+/-) compared with WT (both p <0.05). Plako(+/-) hearts showed reduced myocardial plakoglobin concentration, whereas β-catenin and N-cadherin concentration was not changed.
Load-reducing therapy prevents training-induced development of ARVC in plako(+/-) mice.