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Figure 1 Top, Trend curve of ST vector magnitude (ST-VM) from a patient with unstable angina as displayed by the vectorcardiography monitoring system. Transient increases of ST-VM 50 µV from the baseline >1 min indicate episodes of myocardial ischemia. Bottom, 12-lead ECG tracings recorded at baseline (1) and during an episode of transient myocardial ischemia (2) as indicated on the trend curve.