Figure 4. Box and whisker plots summarising the magnitude of θ ′ alternans in the RV at resting (8 Hz) (open plots) and exercising (13.5 Hz) (filled plots) heart rates.

Horizontal lines denote the Mdn, the box denotes the IQR, and the whisker the range. Little alternans occurred at resting heart rates with all Mdns being close to zero, and no significant differences between groups. However, the magnitude of θ′ alternans is markedly increased by high rate pacing. Significant (P < 0.05) increases in θ′ alternans was demonstrated in the Scn5a^+/− RV epicardium following flecainide challenge as denoted by the asterisk.