Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
1998-10-30
2001-02-13
Kamm, William E. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
Reexamination Certificate
active
06187032
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a system for measuring electrophysiological phenomena generated in a human heart, and more particularly to providing novel approaches to not only inferably analyze electrophysiological phenomena generated in the heart by detecting potentials and magnetic fluxes generated therefrom but also visualize the analyzed results in consideration of easier interpretation and/or broader applications to cardiac diseases.
One conventional technique for the solution of the electrocardiogram and magnetocardiogram inverse problems is proposed by the inventors in a Japanese patent Laid-open Publication No. 8-289977. In this publication, a diagnostic system provides processing as shown by a flowchart in FIG.
1
. The system has a computer in which a heart model is set therein with software, excitation conduction of the heart is efficiently simulated on the model using known methods, and an electrocardiogram or magnetocardiogram is obtained from the simulation results.
For using this approach, data including the shapes, positions, and directions of the ventricles, one or more early excitation positions and excitation time instants thereat, excitation conduction velocities in the ventricles, and conductance distributions in the ventricles are should be given as parameters.
In the above publication, the present inventors also propose a solution method of an inverse problem on the above propagated excitation simulation method. Specifically, some of the parameters (for example, early excitation positions and excitation time instants thereat) given to the ventricle model are corrected such that differences between measured electrocardiograms or magnetocardiograms and simulated electrocardiograms or magnetocardiograms with the above methods are lowered to values as small as possible. The possible lowest values are outputted as inferred results. The remaining parameters other than the parameters selected (for example, parameters for a distribution of propagated excitation velocities and a distribution of action potential amplitudes, except early excitation positions and excitation time instants thereat) are given as appropriate values, and those parameters are treated as fixed values in the inferring calculation.
Another conventional art is concerned with a method of inferring a distribution of excitation onset times on a ventricular surface from QRS complexes in multi-channels electrocardiograms detected the body surface, which is reported by the paper “H. Roozen et al., “Computing the activation sequence at the ventricular heart surface from body surface potentials”, Medical & Biological Engineering & Computing, may 1987”. In the paper, assumption is made that the conductance in a cardiac muscle is uniform and isotropic and its action potential amplitude is constant, and a volume integral equation (whose integral region is over the entire cardiac muscle) expressing the relationship between a distribution of excitation onset times in the cardiac muscle and QRS complexes guided channel by channel is converted into a boundary integral equation. By solving the equation, the distribution of the excitation onset times on the ventricular surface is analyzed from the measure results of QRS complexes in the electrocardiograms.
however, the forgoing conventional approaches still have various problems which should be overcome.
In the diagnostic system according to the first conventional approach, a magnetocardiogram and parameters to be inferred are in nonlinear relation. To infer the parameters requires calculation to be repeated tremendously many times and a simulation for propagated excitation to be performed every calculation. The simulation needs lots of calculation time. In consequence, a first problem is that time to perform one derivation of the simulation becomes extremely long.
A method of inferring intracardiac electrophysiological phenomena according to the first conventional approach is exemplified in a paper “T.IEE Japan, Vol. 116-A, No. 8, 1996, 698-704”, where an early excitation region and its early excitation time are inferred as variables and distributions of both excitation onset times and action potential amplitudes are given as fixed values.
Owing to the fact that the paper treats a distribution of excitation onset times or action potential amplitudes as fixed values, a problem that inferred information does not fit to actual situations may be brought about. For example, if the inferring method according to the first conventional approach is actually applied to patients having myocardial infraction, a delay in propagated excitation will be caused by the infraction portion and an action potential amplitude will be decreased. Moreover, because an initial excitation portion and/or excitation time vary largely depending on individuals, it is difficult to treat as any fixed value an excitation conduction velocity distribution, action potential amplitude distribution, conductance distribution, initial excitation portion, and initial excitation time. In other words, these parameters should be treated as variables.
On one hand, if those parameters are all handled as variables, the number of parameters to be inferred outstandingly increases, the sizes of parameter spaces to be searched become huge, and it is extremely difficult to stably infer quantities. A second problem is that it is almost inadequate to diagnose abnormalities by applying in actual clinical fields the first conventional approach to patients having myocardial infraction or others.
On the other hand, in the case that the inferring method according to the first conventional approach is applied to patients who suffer from cardiac dysrhythmia and others, but not principal diseases such a myocardial infraction, it is considered that an excitation conduction velocity distribution, action potential amplitude distribution, and/or conductance distribution be given as fixed amounts, and only an early excitation region and early excitation time be inferred, as stated in the foregoing paper.
In this case, a steady analysis requires that propagated excitation velocities and action potential amplitudes in the cardiac muscle as well as a conductance distribution in the heart be given in detail. However, because information about those amounts is not known in detail at present, approximated information is compelled to be given. It is therefore difficult to simulate the propagated excitation in higher accuracy. A third problem is that inferred results are largely influenced by ambiguous amounts of propagated excitation velocities, action potential amplitudes, and conductance values, which have been pre-given, resulting in unstable inferred results.
It is actually frequent that patients who suffer from cardiac dysrhythmia have principal diseases, such as myocardial infraction or myocardial ischemia. A fourth problem is that, as long as an inferring system for intracardiac electrophysiological phenomena is used for patients who have only cardiac dysrhythmia, but do not have such principal diseases, applicable patients are extremely limited, thereby lowering versatility in application.
On one hand, the second conventional approach does not need the simulation for propagated excitation to be performed. Hence a problem that a huge amount of time needs for analysis is lightened. But the approach is based on the assumption that an action potential amplitude distribution and a conductance value distribution are uniform. This assumption is requisite when a volume integral equation adopted as a basic equation is converted into a boundary integral equation in this approach. It is therefore not allowed to apply the second conventional approach to patients who suffer from diseases, such as myocardial infraction. A fifth problem is that patients to which diagnosis according to the second conventional approach is applied are limited, lowering versatility, like the first conventional approach.
Moreover, there are some problems concerning a ventricular model and a chest conductance distribution model, w
Ohyu Shigeharu
Sakuma Yoshihiro
Takada Yoichi
Watanabe Izumi
Kabushiki Kaisha Toshiba
Kamm William E.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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