Fig. 4.

Increased [Na⁺] and [Ca²⁺] selectively preserves conduction during acute no-flow ischemia. A: representative isochrone maps of action potential activation time at 8 min of ischemia (before the onset of conduction block) demonstrating conduction differences between the perfusates tested. Isochrones represent ∆3 ms; scale bar = 5 mm. B: summary data (n = 6, 6, 6, and 7 for 145Na⁺/1.25Ca²⁺, 145Na⁺/2Ca²⁺, 153Na⁺/1.25Ca²⁺, and 153Na⁺/2Ca²⁺, respectively) for transverse CV (CV_T, top), longitudinal CV (CV_L, middle), and anisotropy ratio (AR, bottom); summary data are presented as means ± SE (left, #P < 0.05 vs. 145Na⁺/1.25Ca²⁺ at the indicated time point), and as a percent change of baseline (right; simple linear regression testing for a time-dependent CV change, *P < 0.01). C: least squares means (LS Means) model of CV_T (top) and CV_L (bottom) slowing during ischemia (presented as estimated value with 95% confidence interval); *adjusted P < 0.05 for slope vs. 145Na⁺/1.25Ca²⁺.