Table 1.
Characteristics of selected features extracted from acoustic spectra obtained from patients with or without aortic regurgitation
| All sound signals | |||||
|---|---|---|---|---|---|
| Aortic regurgitation (−) | Aortic regurgitation (+) | p value | |||
| (N = 219) | (N = 26) | ||||
| LVAD operation at normal rotational speed | |||||
| Frequency (Hz) | |||||
| First harmonics | 163 ± 15 | 165 ± 16 | 0.74 | ||
| Second harmonics | 326 ± 41 | 328 ± 32 | 0.78 | ||
| Third harmonics | 487 ± 34 | 493 ± 43 | 0.43 | ||
| Amplitude of frequency variation (Hz) | |||||
| First harmonics | 4.2 ± 5.0 | 3.9 ± 3.8 | 0.78 | ||
| Second harmonics | 24 ± 22 | 16 ± 13 | 0.09 | ||
| Third harmonics | 3.1 ± 9.0 | 1.5 ± 2.9 | 0.38 | ||
| Amplitude of harmonic sounds (a.u.) | |||||
| First harmonics | 63 ± 15 | 60 ± 17 | 0.24 | ||
| Second harmonics | 8.4 ± 9.8 | 7.9 ± 7.3 | 0.79 | ||
| Third harmonics | 10 ± 11 | 8 ± 8 | 0.86 | ||
| Amplitude of amplitude variation (a.u.) | |||||
| first harmonics | 7.1 ± 5.3 | 7.6 ± 3.4 | 0.65 | ||
| Amplitude of non-harmonic sounds (a.u.) | |||||
| At low frequency range | 6.6 ± 7.8 | 6.2 ± 2.7 | 0.77 | ||
| At middle frequency range | 4.4 ± 3.1 | 3.7 ± 2.2 | 0.26 | ||
| At high frequency range | 1.2 ± 1.4 | 0.9 ± 0.9 | 0.24 | ||
| LVAD rotational speed (rpm) | 10,033 ± 809 | 10,170 ± 514 | 0.40 | ||
| LVAD operation at intermittent low speed | |||||
| Amplitude of frequency variation (Hz) | |||||
| first harmonics | 5.5 ± 4.9 | 5.6 ± 5.3 | 0.93 | ||
| Amplitude of amplitude variation (a.u.) | |||||
| first harmonics | 3.9 ± 3.5 | 2.5 ± 2.1 | 0.05 | ||
| LVAD rotational speed (rotation per minutes) | 7440 ± 904 | 7072 ± 1001 | 0.05 | ||
| Heart rate (bpm) | 84 ± 14 | 79 ± 13 | 0.09 | ||
| Respiratory rate (per minute) | 20 ± 10 | 20 ± 6 | 0.88 | ||
Variables are expressed as mean ± standard deviation. Frequency ranges are defined as follows: frequency range lower than the frequency of first harmonics is “low”, range between the first and second harmonics is “middle”, and range higher than the second harmonics is “high”. a.u., arbitrary unit; LVAD, left ventricular assist device