Pulse Waveform and Electrode Characteristics
The pulse waveforms used to generate an electric field can have many
different characteristics including voltage amplitude, pulse width,
cycle period, voltage polarity (monophasic vs. biphasic), electrode
polarity (unipolar vs. bipolar), and number of pulses delivered in a
train (Figure 1 ). There is limited data evaluating the impact
of how each of these variables affect lesion safety and efficacy. The
use of biphasic waveforms delivered with a high frequency pulse train
have been found to have less skeletal muscle stimulation, which is
highly desirable to avoid significant map shifts that may be
uncorrectable. Nonetheless, biphasic waveforms may require a greater
number of pulse trains to achieve a similar lesion size compared to
monophasic pulses [19].
Furthermore, electrode polarity has an impact on lesion formation. The
use of a unipolar configuration has been shown to create deeper lesions
compared to a bipolar configuration in a vegetable model [20].
Similarly, the electrode shape can have an impact on electric field
generation. A torus (surface generated by revolving a circle in
three-dimensional space about an axis that is coplanar with the circle)
may allow for reduced electric field attenuation and delivery of deeper
lesions compared to standard ring electrodes (two-dimensional object)(Figure 1) [21]. Future work is needed to better understand
the implications of each of these parameters on patient safety and
lesion efficacy.