Coronary artery disease and low frequency heart sound signatures

The aim of the current study was to study the low-frequency power distribution of diastolic heart sounds in patients with coronary artery disease (CAD). Heart sound recordings were made from the 4th intercostal space in 132 patients referred for elective coronary angiography. CAD patients were defined as subjects with at least one stenosis with a diameter reduction of at least 50% as identified with quantitative coronary angiography. The diastolic heart sounds were analyzed using short-time Fourier transform (STFT) and autoregressive (AR) models. The STFT analyses showed that the energy below 100 Hz was increased approximately 150 ms after the second heart sound in CAD patients. The AR-spectra of the band-pass filtered (20-100 Hz) diastolic heart sound showed that the frequency distribution shifted towards lower frequencies in the case of CAD. The cause of these changes might be due to variations in ventricular filling patterns.