Cardiac activation mapping using ultrasound current source density imaging (UCSDI).
We describe the first mapping of biological current in a live heart using ultrasound current source density imaging (UCSDI). Ablation procedures that treat severe heart arrhythmias require detailed maps of the cardiac activation wave. The conventional procedure is time-consuming and limited by its poor spatial resolution (5-10 mm). UCSDI can potentially improve on existing mapping procedures. It is based on a pressure-induced change in resistivity known as the acousto-electric (AE) effect, which is spatially confined to the ultrasound focus. Data from 2 experiments are presented. A 540 kHz ultrasonic transducer (f/# = 1, focal length = 90 mm, pulse repetition frequency = 1600 Hz) was scanned over an isolated rabbit heart perfused with an excitation-contraction decoupler to reduce motion significantly while retaining electric function. Tungsten electrodes inserted in the left ventricle recorded simultaneously the AE signal and the low-frequency electrocardiogram (ECG). UCSDI displayed spatial and temporal patterns consistent with the spreading activation wave. The propagation velocity estimated from UCSDI was 0.25 +/- 0.05 mm/ms, comparable to the values obtained with the ECG signals. The maximum AE signal-to-noise ratio after filtering was 18 dB, with an equivalent detection threshold of 0.1 mA/ cm(2). This study demonstrates that UCSDI is a potentially powerful technique for mapping current flow and biopotentials in the heart.
Olafsson
Ragnar
R
Biomedical Engineering Department, University of Michigan, Ann Arbor, MI, USA.
Witte
Russell S
RS
Jia
Congxian
C
Huang
Sheng-Wen
SW
Kim
Kang
K
O'Donnell
Matthew
M
D000162:Acoustics; D000465:Algorithms; D000818:Animals; D004452:Echocardiography / Q000379:methods*; D004562:Electrocardiography; D004567:Electrodes, Implanted; D004867:Equipment Design; D006321:Heart / Q000502:physiology; D006329:Heart Conduction System / Q000000981:diagnostic imaging / Q000502:physiology; D011312:Pressure; D011817:Rabbits; D012107:Research Design; D014159:Transducers