Assessment of severity of aortic stenosis through time-frequency analysis of murmur

The accurate and inexpensive noninvasive assessment of the presence and severity of aortic stenosis remains a challenge. In this study, we performed spectral analysis on the murmurs of a group of patients with this disease in order to assess its severity.

An electronic stethoscope was used to generate a spectral analysis of murmurs in patients with aortic stenosis. The durations of the spectra at different frequencies (ie, 200, 250, and 300 Hz) were correlated to the Doppler echocardiogram-derived mean and peak pressure gradients. Heart murmurs from the patients were recorded, and the spectra of the recordings were produced via fast-Fourier transformation. The duration of the spectra above the three given frequencies was then measured.

Forty-one patients (age range, 45 to 94 years; mean age, 68 years) met the inclusion criteria, which included a minimum ejection fraction of 40% and no other significant systolic murmur or coexistent valve disease.

The peak pressure gradient measured via Doppler echocardiogram ranged from 15.3 to 185 mm Hg with the mean of 63 mm Hg. The duration of the spectra of > 300 Hz correlated best with the peak pressure gradient measured using the Doppler echocardiogram. An exponential regression model was created showing a significant correlation coefficient of r = 0.86 (p < 0.0001).

This study demonstrated a good correlation between the duration of spectra at 300 Hz and the Doppler derived peak pressure gradient. This simple and inexpensive technique may prove to be valuable in the evaluation and monitoring of patients with suspected and proven aortic stenosis.