RFA
PATHOPHYSIOLOGY OF RFA LESION FORMATION
-Microvascular injury
-Thermal poration of sarcolemmal membrane
-Non-specific ion transit across membrane resulting in cell depolarization at temperatures
> 45C
-Progressive Calcium overload occurs at temperatures > 50C resulting in irreversible tissue injury

-Membranes are the most thermally sensitive component
-Lesion growth is slower with large tip electrodes, as opposed to irrigated tip electrodes
-After 1 min application lesion growth slows down significantly

AFA: Navistar SF 3.5 mm F-F or F-J (large LA) set at 25 W posterior wall and 40 W anterior wall
Flutter:           3.5 mm Thermocool Navistar single F or F-J, 40-50 W, 60 s
                     8 mm Blazer 60 C, 60 sec (40-70W), temperature limited (non-Carto, non-irrigated)
                     8 mm Celsius Navistar 40-50W, 60 sec (non-irrigated, Carto)
AT: 3.5 mm Thermocool Navistar (F, F-F, F-J)
AVNRT:           Blazer 4 mm (40W, 50-55-60 C, 60 sec)
                    Celsius 4 mm Navistar single F curve
                    Biosense EZ-steer cath, non-irrigated (D-F)
VT:                  Pentaray NAV
                    Thermocool Navistar 3.5 mm (F-J, F-F)


IRRIGATED PROS AND CONS
PROS
-Surface cooling reduces risk of boiling and coagulum formation
-Higher power can be used
-Higher power results in greater depths of penetration
CONS
-Surface cooling prevents monitoring of lesion formation
-High power can cause superheating in subendocardial layers and pop lesions
-If ablation is power limited, power dissipation into the circulating blood pool can yield decreased lesion depth

-Very large catheters can have contact issues and non-uniformity due to edge effect

IMPEDANCE
-Sudden impedance rise correlates with sudden temperature rises
-Magnitude of impedance drop is associated with degree of heating. Severe impedance drops are associated
with pop and thrombus
-If the dispersive electrode (surface) is too small skin heating can also occur. Double dispersive electrodes
will lead to a drop in impedance, drop in voltage, increase in current and increase in temperature

CONTACT is critically important but modest forces are necessary. If excess force is applied just beyond the
sheath, axial forces will be directed more effectively and this increases the risk of perforation and the risk of
collateral damage (esophagus)

Tissue injury occurs reproducibly at temperatures > 50C
Heat transfer in tissue is a predictible biophysical phenomenon
AFA RFA Mark
AFA RFA Russo
AVNRT No Carto Russo
AVNRT Carto Andriulli
Flutter Carto Andriulli
Flutter Carto Mark
Flutter no Carto Russo
RVOT Andriulli
Retrograde VT Russo
Retrograde VT Mark
R AT Russo
L AT Russo