First Human Demonstration of Cardiac Stimulation With Transcutaneous Ultrasound Energy DeliveryImplications for Wireless Pacing With Implantable Devices
Kathy L. Lee, MBBS, FACC*,*,
Chu-Pak Lau, MD, FACC*,
Hung-Fat Tse, MD, FACC*,
Debra S. Echt, MD, FACC ,1,
David Heaven, MBChB ,
Warren Smith, MBChB and
Margaret Hood, MBChB
* Cardiology Division, Department of Medicine, University of Hong Kong, Hong Kong SAR, China
EBR Systems, Inc., Sunnyvale, California
Cardiology Division, Greenlane Cardiovascular Service, Auckland City Hospital, Auckland, New Zealand.
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Figure 1 Investigational Device System
Diagram of the investigational device system consisting of an ultrasound generator with an externally applied ultrasound transmit transducer, an intracardiac catheter containing a receiver electrode incorporated into the distal tip, and data collection instrumentation including an electrophysiology recording system and storage oscilloscopes.
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Figure 3 Waveform Recording
Recording of a receiver electrode output waveform taken from a posteroseptal right ventricular site. The voltage is 0.825 V at the leading edge and 1.29 V at the trailing edge, and the pulse width is 0.5 ms.
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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.
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Figure 5 Ultrasound and Electrical Stimulation
Recordings obtained by the investigational catheter positioned at a midlateral left ventricular site during (A) electrical pacing and (B) ultrasound-mediated pacing. Tracing shown from top to bottom are surface electrocardiogram (ECG) lead I, V1, V6, aortic blood pressure (ABP), electrical stimulation (E), and ultrasound transmission (US) marker channels.
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Figure 6 Ultrasound Window
Drawings of the human torso with a grid representing the window used for transmission of ultrasound energy over the chest wall. The central position of the transmitter targeting a site in the (A) RA, (B) RV, and (C) LV is shown as a dot. LV = left ventricle; RA = right atrium; RV = right ventricle.
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