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Figure 3 Discordance of TWA (Positive) and APD Restitution (Maximum Slope <1) for Study Subject B in Figure 1

Despite positive T-wave alternans (TWA) at 109 beats/min (BPM) (cycle length 550 ms) and action potential duration (APD) alternans (shown in beat plot), the APD restitution was flat (maximum slope 0.73 from sequential linear plots). Importantly, note that diastolic intervals during alternans lie on the flat portion of the APD restitution curve at this rate. HR = heart rate; LV = left ventricular; Neg = negative; Resp = respiratory alternans; RR Alt = heart rate alternans; VM = voltage of alternation; other abbreviations as in Figure 1.