Turbulence intensity in aortic stenosis: frequency characteristics and effects of alterations in left ventricular function.

Turbulent blood flow can occur downstream from a stenosis. The purpose of this study was to quantitate turbulence intensity and its frequency characteristics in the ascending aorta in adult patients with and without valvular stenosis, and to use extrasystoles to analyze the effects of changes in left ventricular function on turbulence. Turbulence intensity was determined from the digitized, high frequency oscillations seen in high fidelity pressure recordings of 25 patients with valvular aortic stenosis. The intensity of turbulence was quantitated as the root-mean-square (mmHg) of pressure fluctuations and as the total spectral power (mmHg2/beat) of the frequency spectrum between 25 Hz and 400 Hz. Frequency characteristics were summarized by the mean and median frequency of spectral power and partitioning the spectrum into 25 Hz segments. Ten adult patients without aortic valve or outflow tract abnormalities served as controls. Adult patients with aortic stenosis had significantly more turbulence in the ascending aorta than controls (total spectral power 1577 +/- 450 mmHg2 vs. 198 +/- 22 mmHg2, p < 0.01). Furthermore, the frequency distribution in aortic stenosis was biased towards higher frequencies (mean frequency 35 +/- 14 Hz vs 54 +/- 2 Hz, p < 0.001). Turbulence intensity in aortic stenosis demonstrated beat to beat modulation by left ventricular function. The total spectral power of a sinus beat was 1888 +/- 762 mmHg2, and fell to 137 +/- 63 mmHg2 in a weak premature beat, and rose to 3618 +/- 1178 mmHg2 in a potentiated post- extrasystolic beat (p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)