Material characteristics ideal for providing either partial or total mechanical support to the failing or arrested heart and method for developing ideal characteristics for underlying cardiac disorders
A system and method for determining the proper dynamic strain profile of an elastomeric construct. The strain characteristics of a deficient heart are determined and compared to the normal strain characteristics of a healthy heart. A construct having elastomeric elements is provided that can expand along multiple axes. In an unloaded condition remote from the deficient heart, the elastomeric elements are pressurized to determine the pressure differential being experienced. Furthermore, optimal strain characteristics are calculated along a first axis and a second axis as a function of the pressure differential. The first optimal strain characteristic and the second optimal strain characteristic are used to estimate the dynamic strain characteristics that will be applied to the heart. The dynamic strain characteristics are compared to the optimal strain characteristics required by the heart to determine if the construct is proper using an automated drive.
1. A method of determining strain characteristics for a construct being applied to a heart, said method including:
determining a set of strain characteristics required to be applied to the heart to provide an assist the heart that causes the heart to pump in a more efficient manner;
providing a construct with elastomeric elements, wherein each of said elastomeric elements expands along multiple axes when internally pressurized, and wherein said multiple axes include a first axis and a second axis;
in an unloaded condition remote from the heart, internally pressurizing said elastomeric elements to determine a pressure differential experienced by said elastomeric elements within said construct;
in said unloaded condition, calculating a first strain characteristic along said first axis as a function of said pressure differential by multiplying a log of said pressure differential times a first constant and subtracting a second constant;
in said unloaded condition, calculating a second strain characteristic along said second axis as a function of said pressure differential;
utilizing said first strain characteristic and said second strain characteristic to estimate dynamic strain characteristics to be applied by said construct;
comparing said dynamic strain characteristics estimated for said construct to said set of strain characteristics to determine if said construct will assist the heart in pumping;
placing said construct into contact with the heart in vivo; and
operating said construct to determine if said construct provides said assist to the heart.
2. The method according to claim 1 , wherein calculating said second strain characteristic along said second axis includes multiplying a log of said pressure differential times a first constant and subtracting a second constant.
3. The method according to claim 1 , where said first axis is angled relative to said second axis.
4. The method according to claim 1 , wherein said first strain characteristic is a function of a first peak strain measured along said first axis.
5. The method according to claim 4 , wherein said second strain characteristic is a function of a second peak strain measured along said second axis.
6. The method according to claim 5 , wherein said first peak strain along said first axis (εpeak-LA) is calculated using the formula
ε peak-LA =11.676 ln( P )−5.2073
where (P) is said pressure differential.
7. The method according to claim 6 , wherein said first strain characteristic (εx) is calculated using the formula
ε
(
x
)
=
ε
peak
-
LA
40.8
(
4
×
10
-
6
x
4
-
0.0008
x
3
+
0.0324
x
2
+
0.6868
x
-
0.4757
)
where (εpeak-LA) is said first peak strain along said first axis.
8. The method according to claim 5 , wherein said second peak strain along said second axis (εpeak-SA) is calculated using the formula
ε peak-SA =6.5167 ln( P )−5.1506
where (P) is said pressure differential.
9. The method according to claim 8 , wherein said second strain characteristic (εx SA ) is calculated using the formula
ε
(
x
S
A
)
=
ε
p
e
a
k
-
SA
2
0
.
1
(
-
0.00005
x
3
+
0.0004
x
2
+
0
.
5
171
x
+
0.0052
)
where (εpeak-SA) is said second peak strain along said second axis.
10. A method of determining if a pumping construct assists a heart in pumping, said method including:
determining required dynamic forces that need to be applied to the heart to provide an assist to the heart that helps the heart pump in a more effective manner;
providing said pumping construct, wherein said pumping construct has elastomeric elements that expands when internally pressurized, and wherein each of said elastomeric elements has a first axis and a second axis;
internally pressurizing said elastomeric elements to determine a pressure differential experienced by said elastomeric elements within said pumping construct when said elastomeric elements are not in contact with the heart;
measuring said elastomeric elements to obtain deformation measurements as elastomeric elements are internally pressurized, wherein said deformation measurements include a first peak strain measurement along said first axis and a second peak strain measurement along said second axis, and wherein said first peak strain measurement is a log of said pressure differential times a first constant and subtracting a second constant;
utilizing said deformation measurements and said pressure differential to estimate applied dynamic forces;
comparing said applied dynamic forces estimated for said pumping construct to said required dynamic forces to determine if said pumping construct can assist the heart in pumping;
placing said pumping construct into contact with the heart in vivo; and
operating said pumping construct to determine if said pumping construct provides said assist to the heart.
11. The method according to claim 10 , further including calculating said second peak strain measurement along said second axis by multiplying a log of said pressure differential times a third constant and subtracting a fourth constant.
12. The method according to claim 11 , wherein said first peak strain measurement and said second peak strain measurement are used to estimate said applied dynamic forces.
13. The method according to claim 12 , wherein said first peak strain measurement along said first axis (εpeak-LA) is calculated using the formula
ε peak-LA =11.676 ln( P )−5.2073
where (P) is said pressure differential.
14. The method according to claim 13 , wherein said first peak strain measurement (εx) is calculated using the formula
ε
(
x
)
=
ε
peak
-
LA
40.8
(
4
×
10
-
6
x
4
-
0.0008
x
3
+
0.0324
x
2
+
0.6868
x
-
0.4757
)
where (εpeak-LA) is said first peak strain measurement along said first axis.
15. The method according to claim 12 , wherein said second peak strain measurement along said second axis (εpeak-SA) is calculated using the formula
ε peak-SA =6.5167 ln( P )−5.1506
where (P) is said pressure differential.
16. The method according to claim 15 , further including calculating a short axis strain (εx SA ) using the formula
ε
(
x
S
A
)
=
ε
p
e
a
k
-
SA
2
0
.
1
(
-
0.00005
x
3
+
0.0004
x
2
+
0
.
5
171
x
+
0.0052
)
where (εpeak-SA) is said second peak strain measurement along said second axis.