Method of identifying strategies for treatment or prevention of ventricular fibrillation and ventricular tachycardia
The present invention relates to evaluating the effect of physiological conditions on the occurrence of ventricular fibrillation, identifying strategies for treatment or prevention of ventricular fibrillation or ventricular tachycardia, and evaluating a subject for induction of ventricular fibrillation from a condition of ventricular tachycardia.
1. A system for use in identifying treatment therapies as therapeutic strategies for preventing ventricular tachycardia from developing into ventricular fibrillation, said system comprising:
a medical device programmed to detect ventricular tachycardia in a subject;
monitor intervals between electrical stimuli in the heart of the subject;
determine if an initial 3 stimuli in groups of 4 stimuli from said monitoring in the heart correspond to rest interval values (I) predicted to lead to ventricular fibrillation as defined by a first equation as follows:
I
n
+
1
(
x
i
)
=
τ
+
∑
j
=
0
i
-
1
Δ
x
c
(
I
n
+
1
(
x
j
)
)
-
∑
j
=
0
i
-
1
Δ
x
c
(
I
n
(
x
j
)
)
-
D
n
+
1
(
x
i
)
,
wherein τ is a time interval between activations applied to a pacing site (x i ), Δx is 0.1, I n+1 (x j ) is a rest interval value of the n+1th action potential at a pacing site (x j ), I n (x j ) is a rest interval value of an nth action potential at a pacing site (x j ), D n+1 (x i ) is an action potential duration of an n+1th action potential at pacing site (x i ), c is a velocity recovery function of I n (x j ) and I n+1 (x j ), respectively;
identify treatment therapies which prevent occurrence of a fourth stimuli corresponding to the rest interval values; and
identify treatment therapies which prevent said ventricular tachycardia from becoming ventricular fibrillation as therapeutic strategies for prevention of ventricular fibrillation.
2. The system according to claim 1 , wherein said medical device is further programmed to identify one or more electrical impulses.
3. The system according to claim 1 , wherein said medical device is further programmed to identify therapies which achieve velocity restitution values as defined by c(I)=V max (1−exp(−(I+β/δ)), wherein V max is maximum velocity which is 0.72, δ is a constant which is 14, and β is a velocity variable which is 7.704 to 30.236 as therapeutic strategies for prevention of ventricular fibrillation.
4. The system according to claim 1 , wherein said medical device is further programmed to identify therapies identifies therapies which achieve potential duration values as defined by a second equation as follows:
D
n
+
1
=
f
(
M
n
+
1
,
I
n
)
=
(
1
-
α
M
n
+
1
)
(
A
+
B
1
+
e
-
(
I
n
-
c
)
/
τ
D
)
wherein A, B, and C are constants and A is 88, B is 122, C is 40, M n+1 is a cardiac memory value of an n+1th action potential, I n is a rest interval of an nth action potential, α is a memory variable, and τ D is a time interval between activations as therapeutic strategies for prevention of ventricular fibrillation.
5. The system according to claim 4 , wherein said medical device is further programmed to identify therapies identifies therapies which achieve potential duration values as defined by the second equation and wherein α is 0.58 to 0.8 as therapeutic strategies for prevention of ventricular fibrillation.
6. The system according to claim 4 , wherein said medical device is further programmed to identify therapies identifies therapies which achieve potential duration values as defined by the second equation and wherein τ D is 32 to 40 ms as therapeutic strategies for prevention of ventricular fibrillation.