Automatic detection of cardiac waves on fetal magnetocardiographic signals

Abstract

Fetal magnetocardiography (fMCG) provides fetal cardiac traces useful for the prenatal monitoring of fetal heart function. In this paper, we describe an analytical model (ACWD) for the automatic detection of cardiac waves boundaries that works on fetal signals reconstructed from fMCG by means of independent component analysis. ACWD was validated for 45 healthy and 4 arrhythmic fetuses ranging from 22 to 37 weeks; ACWD outcomes were compared with the estimates of three independent investigators. Descriptive statistics were used to assess correspondence between the outcomes of the automatic and manual approaches. The parametric two-tailed Pearson correlation test (alpha=0.01) was employed to quantify, by means of the coefficients of determination, the amount of common variation between the sequences of intervals quantified automatically and manually. ACWD performances on short and long rhythm strips were investigated. ACWD demonstrated to be a robust tool providing dependable estimates of cardiac intervals and their variability during the third gestational trimester also in case of fetal arrhythmias. SNR and stability of fetal traces were the factors limiting ACWD performances. ACWD computation time, which was approximately 1:600 with respect to the manual procedure, was comparable with the time required for fCTI estimation on averaged beats.

Fetal cardiac time intervals estimated on fetal magnetocardiograms: single cycle analysis versus average beat inspection

“…Afterward, the fetal cardiac components were separated from the maternal ones on the basis of the heart rate, which is calculated by means of an adaptive detection of the R peaks. For further details on this procedure, the interested reader is addressed to Comani et al (2005b).…”

“…At least three traces were used, and simultaneous rhythm strips of no less than 70 consecutive cardiac cycles were analyzed. The P-QRS-T waves were detected on single cycles (figure 2(b)) with an automatic procedure already assessed by the authors (Comani et al 2005b). For each heartbeat, the instants corresponding to the onset and offset of the P-QRS-T waves were used to calculate the duration of the P wave, PR interval, QRS complex, ST segment, T wave and QT interval.…”

“…Aim of the present study was to compare the outcomes of a system that measures fCTI on single cardiac cycles with those obtained by visual inspection of averaged beats. With respect to preliminary results already published (Comani et al 2005a), the fetal magnetocardiograms used in this study were retrieved with an updated ICA-based procedure; moreover, the fCTI were calculated with a system that detects the onset and offset of the fetal cardiac waves automatically (Comani et al 2005b). This procedure permits to analyze long rhythm strips without increasing the total processing time, and, therefore, to calculate the intervals' variability avoiding any observer-dependent bias.…”

Optimal filter design for shielded and unshielded ambient noise reduction in fetal magnetocardiography

“…In previous studies, we have demonstrated that independent component analysis (ICA) could be efficiently applied to fMCG to reconstruct reliable fetal traces affected by negligible noise contamination (Comani et al 2004a, 2004b, 2004c, 2004d, 2005c, 2005b, Brisinda et al 2005, Mantini et al 2004. However, the effectiveness of ICA is highly dependent on the signal-to-noise ratio of input recordings, as it is particularly evident when fMCG recorded in an unshielded hospital setting is processed: the high level of ambient noise, in fact, may impede the extraction of dependable fetal magnetocardiograms for fetuses of less than 30 weeks (Brisinda et al 2005).…”

The Effect of Pathologic Cardiac Events on the Spectral content of ECG

“…However this method may show multiple errors in case of fluctuation around the R-peak especially if this peak was not precisely situated at the maximum [9][10][11][12]. To resolve these problems, we preformed firstly a local correction of the given position of R-peak by comparing the sign of derivative before and after R-peak in order to ensure that is situated at the maximum.…”