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Figure 4 Ultrasound-Mediated Pacing Threshold

Recording of the storage oscilloscope monitoring the receiver electrode output capturing 12 s of ultrasound delivery in triggered mode. The top trace depicts the ultrasound transmit marker and duration of 0.5 ms. The bottom trace depicts 12 s of electrode output waveforms (20 superimposed waveforms). Beat-to-beat variation in output voltage resulted in the appearance of a wide band. The minimal voltage, recorded as the ultrasound-mediated pacing threshold voltage, was measured at the lower boundary of the trailing edge of the superimposed output waveforms. The maximum voltage was measured at the upper boundary of the trailing edge of the superimposed output waveforms. The transmitter-to-receiver distance was calculated from the transmit delay from the onset of the ultrasound transmission to the onset of the electrode output waveform.