Device and procedure for visual three-dimensional presentation of ECG data
View Patent ↗The invention relates to the analysis of ECG data by exploiting computerized three-dimensional spatial presentation of the measured data using the vector concept. A three-dimensional presentation of the human heart may be correlated with waveforms specific for standard ECG or derived ECG signals based on the dipole approximation of the heart electrical activity. The three-dimensional heart model may be rotated, and the ECG signals are interactively linked to the model. In the visualization process, different types of signal presentation may be used, including graphical presentation of the heart vector hodograph, graphical presentation of the signal waveform in an arbitrary chosen point on the heart, and graphical presentation of the map of equipotential lines on the heart in a chosen moment. Additional tools for analyzing ECG data are also provided which may be interactively used with the display tools.
1. A method for analyzing cardiac electrical activity comprising:
obtaining ECG data measured from a plurality of actual lead sites on the surface of a patient's body;
computing from the ECG data measured at the plurality of actual lead sites, a time variable heart vector that represents size and orientation of a time varying electrical dipole that approximates electrical heart activity and that has an origin near the center of the patient's heart; and
normalizing the time variable heart vector by a normalization factor without changing the direction of the time variable heart vector, wherein the normalization factor is computed from the patient's ECG data.
2. The method of claim 1 , further comprising:
selecting a position corresponding to a virtual lead; and
producing information concerning electrical potential corresponding to the selected position by scalar multiplication of the produced normalized time variable heart vector and a lead vector that corresponds to the selected position.
3. The method of claim 1 , wherein normalizing the time variable heart vector comprises normalizing the heart vector to a normalization surface having a selected attenuation value.
4. The method of claim 1 , further comprising computing a normalization factor,
wherein computing a normalization factor comprises computing a lead normalization factor, ρ i , for an actual lead site according to the ratio:
ρ
i
=
∫
0
T
V
i
(
t
)
·
[
H
->
(
t
)
·
L
->
i
]
ⅆ
t
∫
0
T
[
H
->
(
t
)
·
L
->
i
]
2
ⅆ
t
wherein V i (t) is the measured voltage over time from an actual lead site, {right arrow over (H)}(t) is the time variable heart vector, {right arrow over (L)} i is a lead vector corresponding to the actual lead site, and T is a time period.
5. The method of claim 4 ,
wherein computing a normalization factor comprises:
computing lead normalization factors from a plurality of actual lead sites; and
selecting a normalization factor from within the range defined by the maximum and the minimum lead normalization factors computed for the plurality of actual lead sites.
6. The method of claim 5 , wherein selecting a normalization factor from within the range defined by the maximum and the minimum lead normalization factors computed for the plurality of actual lead sites includes selecting the average value of the plurality of lead normalization factors.
7. A method for visualizing cardiac electrical activity comprising:
obtaining ECG data measured from a plurality of actual lead sites on the surface of a patient's body;
computing from the ECG data measured at the plurality of actual lead sites, a time variable heart vector that represent size and orientation of a time varying electrical dipole that approximates electrical heart activity and that has an origin near the center of the patient's heart;
normalizing the time variable heart vector by a normalization factor, wherein the normalization factor is computed from the patient's ECG data;
deriving a cardiac electrical signal from the normalized time variable heart vector; and
displaying the cardiac electrical signal using a representation of a three dimensional image of a model heart.
8. A method of analyzing cardiac electrical activity comprising:
obtaining ECG data measured at a plurality of actual lead sites on the surface of a patient's body;
computing from the ECG data measured at the plurality of actual lead sites, a time variable heart vector that represents size and orientation of a time varying electrical dipole that approximates electrical heart activity and that has an origin near the center of the patient's heart;
computing a normalization factor from the ECG data measured at the plurality of actual lead sites; and
producing information concerning a normalized time variable heart vector by scaling the time variable heart vector by the normalization factor.
9. A method of displaying cardiac electrical activity comprising:
obtaining ECG data measured at a plurality of actual lead sites on the surface of a patient's body;
computing from the ECG data measured at the plurality of actual lead sites, a time variable heart vector that represents size and orientation of a time varying electrical dipole that approximates electrical heart activity and that has an origin near the center of the patient's heart;
computing a normalization factor from the ECG data measured at the plurality of actual lead sites;
computing a normalized time variable heart vector by scaling the time variable heart vector by the normalization factor;
producing a three dimensional heart representation on a display screen having the same origin as the time variable heart vector;
indicating on the display screen a designated position on the heart representation; and
producing information concerning electrical potential corresponding to the designated position by scalar multiplication of the normalized time variable heart vector and a lead vector that corresponds to the selected position.