Elevated Strain and Structural Disarray Occur at the Right Ventricular Apex

The right ventricular apex (RVA) is a potential hot spot for development of cardiac rhythm anomalies. Many conditions, including arrhythmogenic right ventricular cardiomyopathy and Brugada's syndrome affect the RVA, and further, the RVA remains an incompletely characterized pacing region. Whether there are structural reasons underlying these conduction properties remains unsettled. In the current study, we characterize the mechanical strains and structural attributes of the right ventricular wall, and test the hypothesis that the right ventricular apex experiences heterogeneous strain distributions and altered fiber organization, and is thus susceptible to conduction alterations. Electromechanical wave imaging (EWI), or elastography, of hearts was used to quantify mechanical strains occurring through a cardiac cycle. Histological and immunofluorescence imaging techniques were used to examine cardiac wall structure and arrangement of junctional proteins. Right ventricular mechanical strains were elevated and sustained throughout systole, compared to the left ventricle and septum. Heterogeneous strain distributions, myocardial fiber disarray, and altered junctional protein localization occured at the RVA. Disarray and altered strain distributions suggest decreased structural strength at the right ventricular apex in particular and increased mechanical impositions in the right ventricle, respectively. Thus, these data demonstrate why the right ventricular apex may be particularly vulnerable to conduction abnormalities.