Acoustic cardiac signals analysis: a Kalman filter–based approach

Figures & data

Figure 1 Auscultation area: listening positions for S₁, S₂, S₃, and S₄ heart sounds. (A) QRS complex corresponds to S₁, and T-wave corresponds to S₂. (B) Position of S₃ and S₄.

Figure 2 (A and B) Relationship of ECG and the four heart sounds.

Abbreviation: ECG, electrocardiogram.

Figure 3 (A and B) Average signal of normal patient. (A) Noisy heart signal; (B) clean heart signal.

Figure 4 Processing of the HSS and ECG signals.

Abbreviations: HSS, hybrid spatial spectra; ECG, electrocardiogram.

Table 1 Types of murmurs and number of cycles of heart sound per patient

	Patient 3	Patient 1	Patient 5	Patient 4	Patient 2
Name	Mitral valve prolapsed and lateral wall well. Asymptomatic, no heart failure symptoms. Late systolic murmur apex	Moderate mitral regurgitation. Extensive anteroseptal wall and anterolatera. Severe hypokinetic and akinectic indicating ischemic myocardium. Impaired systolic LV function, EF 28%. LA dilatation	Infracted area noted but no scar tissue. LV systolic function slightly depressed but no elevation of PCWP. No thrombus detected. Diastolic dyfunction grade 2	Tricuspid regurgitation. Systolic murmurs	Mitral regurgitation
Number of cycle	74	110	58	88	84
	Patient 10	Patient 6	Patient 9	Patient 8	Patient 7
	Normal, but mild murmurs	Normal	Normal	Normal, but mild murmur	Normal, but mild murmur
	88	70	75	80	80

Abbreviations: LV, left ventricular; EF, ejection fraction; LA, left atrium; PCWP, pulmonary capillary wedge pressure.

Table 2 Normal and abnormal patients’ signal-to-noise ratio (SNR)

Figure 5 Overall average signal-to-noise ratio (SNR) of the ten patients.

Figure 6 (A) Abnormal heart sound from a patient after the filtering process; (B) normal heart sound from a patient after the filtering process.