Method of confirming safe delivery pathway to patient prior to energy delivery
Systems and methods to confirm safe delivery of treatment energy to a patient by identifying a presence of a fault in an energy delivery pathway and identifying a location of the fault within the device. The system includes a processing unit configured to calculate blood impedances external to the device based on known impedance characteristics of the device, and then to calculate impedances within the device during energy delivery based on the calculated blood impedances. The processing unit prevents the delivery of energy in an energy delivery pathway that is determined to be compromised. The processing unit is also configured to compare times for two different frequencies to travel a predetermined distance, the difference in the times corresponding to a location of a fault within the energy delivery pathway.
1. A system for assessing integrity of an energy delivery pathway, the system comprising:
an energy generator including a processing unit;
an electrode distribution system in communication with the energy generator;
an impedance measuring device in communication with the electrode distribution system;
a medical device in communication with the electrode distribution system including an elongate body having a proximal portion, a distal portion, and a lumen extending between the proximal portion and the distal portion, a treatment element at the distal portion having at least one electrode, and at least two electrode wires in electrical communication with the at least one electrode, the energy delivery pathway including at least a part of each of the at least two electrode wires,
the energy generator being configured to deliver a first current at a first frequency and a second current at a second frequency to the at least one electrode, the impedance measuring device being configured to:
before a delivery of treatment energy from the energy generator, identify a first wire impedance within the device elongate body, a second wire impedance within the device elongate body, and a first shunt admittance within the device elongate body;
during the delivery of the first current at the first frequency and the second current at the second frequency, calculate a first blood impedance external to the device elongate body, a second blood impedance external to the device elongate body, and a blood admittance external to the device elongate body based on the determined first wire impedance within the elongate body, the determined second wire impedance within the device elongate body, and the first shunt admittance within the elongate body;
during the delivery of the first current at the first frequency and the second current at the second frequency, calculate a third wire impedance within the device elongate body, a fourth wire impedance within the device elongate body, and a second shunt admittance within the device elongate body based on the first blood impedance external to the device elongate body, the second blood impedance external to the device elongate body, and the blood admittance external to the device elongate body; and
at least one of:
compare the calculated third wire impedance within the device elongate body and the calculated fourth wire impedance within the device elongate body to determine if a fault in the energy delivery pathway exists; and
compare the second shunt admittance within the device elongate body to a threshold blood admittance value to determine if a fault in the energy delivery pathway exists.
2. The system of claim 1 , wherein the energy generator is configured to deliver ablation energy to the at least one electrode, the processing unit being further configured to prevent delivery of the ablation energy to at least one of the at least one electrode when the processing unit determines a fault in the energy delivery pathway exists.
3. The system of claim 1 , wherein the impedance measuring device is configured to render a real portion and an imaginary portion of a complex impedance measurement.
4. The system of claim 1 , wherein the generator includes a first voltage source having a known voltage and a second voltage source having a known voltage.
5. The system of claim 4 , wherein the at least two electrode wires includes a first electrode wire having a known resistance and series impedance and a second electrode wire having a known resistance and a series impedance.
6. The system of claim 5 , wherein the impedance measuring device is configured to calculate the first blood impedance external to the device elongate body (Z u,1 ), the second blood impedance external to the device elongate body (Z u,2 ), and the blood admittance external to the device elongate body (Y b,1-2 ) by:
applying a first condition, i 1 ≠0, i 2 ≠0, to the equations:
kvl
i
1
:
V
1
=
i
1
(
R
1
+
Z
l
,
1
+
Z
u
,
1
)
+
i
b
Z
u
,
1
;
kvl
i
2
:
V
2
=
i
2
(
R
2
+
Z
l
,
2
+
Z
u
,
2
)
-
i
b
Z
u
,
2
;
kvl
i
b
:
0
=
i
b
(
Z
u
,
1
+
Z
u
,
2
+
1
Y
sh
)
+
i
1
Z
u
,
1
-
i
2
Z
u
,
2
,
where V 1 is the known voltage of the first voltage source, V 2 is the known voltage of the second voltage source, R 1 is the known resistance of the first electrode wire, R 2 is the known resistance of the second electrode wire, Z l,1 is the known series impedance of the first electrode wire, Z l,2 is the known series impedance of the second electrode wire, and Y sh is the sum of a blood admittance within the elongate body of the device (Y l,1-2 ) and the blood admittance external to the elongate body (Y b,1-2 ); and
applying a second condition, i′ 1 ≠0, i′ 2 =0, to the equations:
kvl
i
′
1
:
V
1
′
=
i
1
′
(
R
1
+
Z
l
,
1
+
Z
u
,
1
)
+
i
b
′
Z
u
,
1
;
and
kvl
i
′
b
:
0
=
i
b
′
(
Z
u
,
1
+
Z
u
,
2
+
1
Y
sh
)
+
i
1
′
Z
u
,
1
,
where V′ 1 is the known voltage of the first voltage source, R 1 is the known resistance of the first electrode wire, and Z l,1 is the known series impedance of the first electrode wire.
7. The system of claim 6 , wherein the impedance measuring device calculates the third wire impedance within the device elongate body (Z l,1 ), the fourth wire impedance within the device elongate body (Z 1,2 ), and the second shunt admittance within the device elongate body (Y l,1-2 ) by:
applying the first condition, i 1 ≠0, i 2 ≠0, to the equations:
kvl
i
1
:
V
1
=
i
1
(
R
1
+
Z
l
,
1
+
Z
u
,
1
)
+
i
b
Z
u
,
1
;
kvl
i
2
:
V
2
=
i
2
(
R
2
+
Z
l
,
2
+
Z
u
,
2
)
-
i
b
Z
u
,
2
;
kvl
i
b
:
0
=
i
b
(
Z
u
,
1
+
Z
u
,
2
+
1
Y
sh
)
+
i
1
Z
u
,
1
-
i
2
Z
u
,
2
,
where V 1 is the known voltage of the first voltage source, V 2 is the known voltage of the second voltage source, R 1 is the known resistance of the first electrode wire, R 2 is the known resistance of the second electrode wire, Z l,1 is the known series impedance of the first electrode wire, Z l,2 is the known series impedance of the second electrode wire, and Y sh is the sum of a blood admittance within the elongate body of the device (Y l,1-2 ) and the blood admittance external to the elongate body (Y b,1-2 ); and
applying the second condition, i′ 1 ≠0, i′ 2 =0, to the equations:
kvl
i
′
1
:
V
1
′
=
i
1
′
(
R
1
+
Z
l
,
1
+
Z
u
,
1
)
+
i
b
′
Z
u
,
1
;
and
kvl
i
′
b
:
0
=
i
b
′
(
Z
u
,
1
+
Z
u
,
2
+
1
Y
sh
)
+
i
1
′
Z
u
,
1
.