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 method of identifying treatment therapies as therapeutic strategies for preventing ventricular tachycardia from developing into ventricular fibrillation, said method comprising:
detecting ventricular tachycardia in a subject;
monitoring intervals between electrical stimuli in the heart of the subject;
determining 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;
identifying treatment therapies which prevent occurrence of a fourth stimuli corresponding to the rest interval values; and
identifying treatment therapies which prevent said ventricular tachycardia from becoming ventricular fibrillation as therapeutic strategies for prevention of ventricular fibrillation, wherein said detecting, monitoring, determining and identifying are performed with an implantable medical device.
2. The method according to claim 1 , wherein the treatment therapy is a pharmaceutical compound.
3. The method according to claim 2 , wherein the pharmaceutical compound is a calcium antagonist.
4. The method according to claim 1 , wherein the treatment therapy is one or more electrical impulses.
5. The method according to claim 1 , wherein said identifying identifies treatment 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.
6. The method according to claim 1 , wherein said identifying identifies treatment 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.
7. The method according to claim 6 , wherein said identifying identifies treatment 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.
8. The method according to claim 6 , wherein said identifying identifies treatment 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.