Biophysics of HPSD ablation
RF ablation lesion formation is a result of thermal injury occurring in
the resistive and conductive phases.21 The superficial
tissue (~ 1 to 2 mm) is heated at the catheter-tissue
interface directly by resistive (ohmic) heating.21 The
superficial heated tissue extends the heat passively to deeper tissue
layers in a time dependent manner during the conductive
phase.24 The standard RF lesion using low to moderate
power and relatively long duration is created predominantly by
conductive heating [Figure 1A]. In contrast to standard ablation,
HPSD ablation creates a larger zone of direct resistive heating of
tissue with a shorter temperature decay time. This increases the ratio
of resistive to conductive tissue heating with irreversible injury of
the resistive endocardial zone and less endocardial sparing [Figure
1B]. The lesion geometry in HPSD ablation is altered due to the change
in balance between resistive and conductive heating. The maximal width
of a standard ablation lesion is in the subendocardium resulting in a
tear-drop shaped lesion (endocardial sparing due to smaller resistive
zone). On the other hand, the HPSD ablation lesion width is maximum in
the endocardium as well as the subendocardium.21Lesions with HPSD ablation have lesser depth and bigger diameter with
similar lesion volumes as standard ablation.25Shallower lesions with HPSD ablation may be favorable for thin tissues
like the atria. HPSD ablation can potentially reduce collateral damage
to neighboring structures like the esophagus due to reduction in the
conductive heating phase.