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Noninvasive detection of coronary stenoses before and after angioplasty using eigenvector methods
M Akay1, J L Semmlow, W Welkowitz
1Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08855.
Insights
Eigenvector methods revealed reduced high-frequency heart sounds after coronary angioplasty, supporting turbulent blood flow theories in partially occluded arteries. This noise-robust analysis overcomes limitations of traditional FFT methods.
Area of Science:
- Biomedical Engineering
- Cardiovascular Physiology
- Signal Processing
Background:
- Partially occluded coronary arteries may generate audible sounds from turbulent blood flow.
- Traditional Fast Fourier Transform (FFT) analysis struggles with noise in low-level heart sound signals.
- Previous studies using FFT on this data showed no significant changes post-angioplasty.
Purpose of the Study:
- To compare frequency spectra of diastolic heart sounds before and after angioplasty.
- To investigate the efficacy of advanced eigenvector methods for analyzing noisy heart sounds.
- To support the hypothesis that turbulent blood flow in occluded arteries produces distinct sound signatures.
Main Methods:
- Applied three high-resolution eigenvector methods: Pisarenko, MUSIC, and Minimum-Norm, to analyze heart sound frequency spectra.
- Compared spectral components before and after coronary angioplasty surgery.
- Excluded the Pisarenko method due to spurious zero generation.
Main Results:
- MUSIC and Minimum-Norm eigenvector methods successfully generated frequency spectra from noisy heart sound data.
- These methods revealed a significant decrease in high-frequency spectral components post-angioplasty in most cases.
- This contrasts with previous findings using traditional FFT analysis.
Conclusions:
- Eigenvector methods offer superior resolution for analyzing heart sounds in the presence of noise.
- The observed reduction in high-frequency components supports the link between turbulent flow in coronary arteries and heart sounds.
- Advanced signal processing techniques can enhance the diagnostic potential of phonocardiography.
Abstract:
Previous studies done by our group suggest that partially occluded coronary arteries may generate sounds due to turbulent blood flow. To support these previous findings the frequency spectra of diastolic heart sounds are compared before and after angioplastic surgery. Since the low-level sounds associated with partially occluded coronary arteries are contaminated with considerable background noise, traditional FFT analysis may not produce accurate frequency spectra. Indeed, in a previous study using the same data, no significant differences were found in the diastolic heart sounds before and after angioplastic surgery. In this study, three eigenvector methods (Pisarenko, MUSIC, and Minimum-Norm) have been selected to generate the frequency spectra because of their higher resolution, particularly in the presence of noise. Although the Pisarenko method produced spurious zeros and could not be used, the other two methods produced spectra showing, in most cases, a marked decrease in high-frequency spectral components following angioplasty.