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Figure 2 (A) ST segment depression at the rebreathing phases of the apneas. This 5-min Holter recording depicts alternating ECG patterns of bradycardia-tachycardia typical of sleep apnea. Horizontal ST segment depressions of 1 mm were recorded at the tachycardia (rebreathing) phase. (B) An enlarged segment of a tachycardia phase, starting at approximately 01:58:30 clearly demonstrating the ST segment depression.