Does amount of contact matter for PEF ablation?
While research indicates a relationship between contact force and PEF
treatment depth with focal catheters17, the LAF
catheter investigated in this study did not demonstrate increased
treatment depth with increased contact. LTC and HTC yielded similar
lesion dimensions (approximately 6mm depth, 16mm width across all CTC
ranges >∆10Ω). Unique catheter and electric field geometry
contribute to this difference. Although LI is a measurement of electrode
surface area in contact with resistive myocardium and not a direct
measurement of contact force, LI has been shown to correlate with
contact force over relevant operational ranges for focal
catheters18. Similarly in this study, increased LI
correlated with increased CTC; however, in contrast to a traditional
solid-tip catheter, the LAF spheroid tip compresses in response to
increased contact rather than indenting into the myocardium
(Supplemental Figure 1 ). Additionally, solid-tip catheters
produce small electric fields that are more susceptible to differences
in contact than bigger LAF catheter electric fields 7.
These mechanical behaviors and field-size discrepancies may explain the
differing impacts of increased contact force on PEF treatment sizes for
compressible LAF catheters versus solid-tip catheters. This study also
indicates that the number of splines in contact and the amount of each
spline in contact with myocardium do not influence lesion size if the
spline(s) have stable CTC (Figure 7) .
With RF ablation, increased contact force leads to larger treatments,
but also increased safety risks19. Increased CTC with
the LAF catheter did not yield any additional safety risk. No damage to
collateral structures, steam pops, perforations, or incidences of char
were noted acutely or chronically for any CTC cohort. The spheroid
catheter tip inherently lends itself to reduced risk of perforation and
the flexibility of the nitinol splines allows force to be absorbed by
the catheter rather than tissue, reducing tissue trauma. However,
because the structure of the LAF catheter creates sizeable lesions even
at LTC, splines that are in proximity to critical structures (e.g., AV
node, HIS) should be closely monitored to prevent inadvertent damage.
Tissue thinning and remodeling were noted after 30 days at ventricular
lesion sites; observations similar to previous work with a different LAF
catheter 20 and require further investigation
(Supplemental Figure 2 ).
This study determines that, in relation to PEF treatment size and
safety, the amount of CTC does not matter once CTC is established with a
LAF catheter. These results may extend to “single-shot” catheters
where apposition to myocardium, rather than embedding a catheter tip
into tissue, is the primary mode of operation21. It is
critical to note that both catheter electrode configuration (e.g.,
electrode spacing, size) and system configuration (e.g., monopolar,
bipolar) play important roles in contact dependence. Monopolar
modalities have the ability to create deeper lesions for comparable
energy outputs relative to bipolar configurations, making them more
robust to intermittent contact7. Contact detection
systems will need to be harmonized with PEF platforms to ensure
appropriate feedback for the catheter design and delivery mechanism.