11
23. The ATRICURE ISOLATOR Surgical
Ablation System measures tissue
impedance and temperature
throughout the ablation cycle and uses
this information to control the
application of energy to the tissue. The
amount of energy delivered to the
tissue is driven solely by tissue
impedance. The System determines
the minimum energy delivery required
to create a transmural (full thickness)
lesion based on tissue impedance and
delivers only that amount of energy to
the tissue. Energy delivery changes
throughout the ablation cycle as tissue
impedance changes. The lesion is
visible as a white coloration of the
tissue. The device is designed such
that the lesions will not spread beyond
the jaw width.
Note: Some ISOLATOR devices
include a temperature probe that
measures the surface
temperature of the tissue being
ablated 1.3 mm laterally from
the electrode within the
insulated jaw. An audible tone
sounds when the tissue
temperature reaches 70ºC and
the system automatically shuts
off energy delivery when the
tissue temperature reaches
75ºC. All of the clamps, with and
without a temperature probe,
have been designed to maintain
less than 50ºC temperature
outside of the clamped region.
Note: The time necessary to create a
transmural lesion depends on
tissue thickness, composition,
and the length of tissue
captured between the
electrodes. The following table
describes the average expected
time (seconds) and energy
delivery (joules) for respective
tissue thicknesses. Values are
expressed per unit volume of
tissue captured between the
electrodes. These data were
obtained during ablations on ex
vivo (excised bovine) tissues
and will generally be lower on in
vivo (live human) tissues.
Table1. Average Time vs. Energy Delivery
Tissue
Thickness
Time to
Transmurality per
unit volume
(sec/mm
3
)
Energy Delivered
per Unit Volume
(J/mm
3
) *
Isolator
AVG
STDDEV
AVG
STDDEV
2 mm
0.041
0.014
0.53
0.16
5 mm
0.034
0.013
0.43
0.15
10 mm
0.040
0.011
0.50
0.14
Synergy
2 mm
0.049
0.007
0.76
0.11
5 mm
0.033
0.006
0.57
0.10
10 mm
0.032
0.009
0.55
0.16
*
Energy Delivery per unit volume of tissue
ablated is comparable between the Isolator
and Synergy Product Lines and below the
threshold of 0.94 J/mm3 for 2 mm tissue
thickness reported for other similar
commercially available ablation devices.