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Figure 2 There is a positive, statistically significant correlation (p < 0.01) between increased heart rate and T-wave alternans level during induction of the angerlike state before (upper left panel) and during left anterior descending coronary artery occlusion (upper right panel). The slope of each line is significantly elevated above the horizontal (p < 0.0003). Beta-adrenergic blockade with metoprolol did not produce a significant decrease in the slope of the heart rate/alternans relationship (middle panels). Right atrial pacing did not increase T-wave alternans magnitude in lead II over baseline in five anesthetized canines (0.129 ± 0.026 mV x ms at spontaneous baseline rate of 107 ± 6 beats/min vs. 0.158 ± 0.023 mV x ms at 180 beats/min; slope vs. baseline, p < 0.47, lowest panel). The r² values are: upper right panel = 0.739; upper left panel = 0.628; middle left panel = 0.764; middle right panel = 0.959; lowest panel = 0.118. These results suggest an association, but not necessarily a causal relationship, between elevated rate and T-wave alternans, as discussed in the text.