Figure 4.

Analyses of basal heart rates in wild-type and mutant mice. Heart rates were analyzed at 6 and 8 months as described in Table 1. (A) Heart rates are dependent upon Casq2 gene activity in the CCS and upon developmental history. Depicted are basal sinus heart rates (mean ± S.E.M.); N values are described in Table 1. (B) Lower heart rate is associated with subsequent VT episodes. Scatterplots depict basal sinus heart rates of congenital and conditional deletion mice. Open circles, basal sinus heart rates in mice that showed VT episodes after isoproterenol; filled circles, basal sinus heart rates in mice that did not show VT after isoproterenol. Mean and S.E.M. are indicated by horizontal line and gray box. For both A and B, significance was determined using two-tailed Student’s t-test. * P < 0.05; *** P < 0.005.