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Cardiac magnetic field map topology quantified by Kullback-Leibler entropy identifies patients with hypertrophic cardiomyopathy
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10.1063/1.2432059
/content/aip/journal/chaos/17/1/10.1063/1.2432059
http://aip.metastore.ingenta.com/content/aip/journal/chaos/17/1/10.1063/1.2432059

Figures

Image of FIG. 1.
FIG. 1.

The layout of cardiac magnetic field map (CMFM) measurement: (a) CMFM measurement grid based on a seven channel system. The dashed lines denote six sequential measurement positions. (b) Cardiac magnetic field waveforms transformed into a regular grid corresponding to the light grey square in panel (a).

Image of FIG. 2.
FIG. 2.

Kullback-Leibler entropy principle for estimation of differences in topology between reference group map (middle) and magnetic field maps of specific subjects (left: healthy control; right: patient with HCM). The difference in map topology between the healthy subject and the reference map is very small and therefore the Kullback-Leibler entropy is near zero. In contrast, the HCM map shows clear differences in topology to the reference map (two local minima as well as a different maximum position), thus the Kullback-Leibler value is higher.

Image of FIG. 3.
FIG. 3.

Mean group Kullback-Leibler (KL) entropy values over time during QRS (a) and STT (b). NoHCM group values are denoted with solid (blue) lines and HCM group values with dashed (red) lines (reference maps: NoHCM group). Lower panels give discriminant index (DI) values during QRS (a) and STT (b) intervals, respectively: KL values for time intervals where DI was higher than 0.8 (dashed lines) are considered for and calculation.

Image of FIG. 4.
FIG. 4.

Group mean distributions of regional magnetic field strength parameters (in normalized units) during QRS time interval for the 36 regular grid points [Fig. 1(b) ]. The NoHCM group shows a higher amplitude at a different position in comparison to the HCM group.

Image of FIG. 5.
FIG. 5.

Mean group Kullback-Leibler (KL) entropy values over time during QRS (a) and STT (b). HOCM group values are denoted with solid (blue) lines and HNCM group values with dashed (red) lines (reference maps: HOCM group). Lower panels give discriminant index (DI) values during QRS (a) and STT (b) intervals, respectively: KL values for time intervals where DI was higher than 0.8 (dashed lines) are considered for the calculation.

Image of FIG. 6.
FIG. 6.

Group mean distributions of regional magnetic field strength parameters for the 36 regular grid points [Fig. 1(b) ] during the QRS time interval [corresponding to the time interval used for calculation]. Clear significant differences in extrema positions between the HOCM and the HNCM groups are visible.

Tables

Generic image for table
Table I.

Descriptive statistics of patient groups without HCM (NoHCM) and with HCM as well as their separability. Data are given as mean values SE and percentage of correctly classified (CC) cases. If “leave one out” cross validated results of discriminant function analysis differ from the original results, they are shown in parentheses. -values were obtained with the Mann-Whitney-U-test (univariate cases) and the Wilks-Lambda test (linear discriminant function). Three classification approaches were used: (a) KL: based on Kullback-Leibler entropy mean values for QRS and STT time intervals where discriminant index (DI) was higher than 0.8; (b) regional: based on selected regional parameters; (c) KL regional: based on selected KL and regional parameters.

Generic image for table
Table II.

Descriptive statistics of patients with HNCM and HOCM as well as their separability. Data are given as mean values SE and percentage of correctly classified (CC) cases. If “leave one out” cross-validated results of discriminant function analysis differ from the original results, they are shown in parentheses. -values were obtained with the Mann-Whitney U-test (univariate cases) and the Wilks-Lambda test (linear discriminant function). Three classification approaches were used: (a) KL: based on Kullback-Leibler entropy mean values for QRS where the discriminant index (DI) was higher than 0.8; (b) regional: based on selected regional parameters; (c) : based on selected KL and regional parameters.

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/content/aip/journal/chaos/17/1/10.1063/1.2432059
2007-03-30
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Cardiac magnetic field map topology quantified by Kullback-Leibler entropy identifies patients with hypertrophic cardiomyopathy
http://aip.metastore.ingenta.com/content/aip/journal/chaos/17/1/10.1063/1.2432059
10.1063/1.2432059
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