RYR2 and familial long QT syndrome: These data therefore parallel findings that CPVT carriers of the RyR2-P2328S mutation (Paavola et al. 2007) showed increases in endocardial MAP durations considerably smaller than the clinical QTc prolongations thought to account for the LQTS phenotype (Keating & Sanguinetti, 2001; Scoote & Williams, 2002; Laurita & Katra, 2005; Priori & Napolitano, 2005).