Time-warping averaging for quantitative evaluation of changes in LV function

Signal averaged acoustic quantification (SAAQ) with time-warping (TW) preserves the morphology of SAAQ waveforms allowing reliable noninvasive quantification of amplitude- and timing-indexes of left ventricular (LV) function, which cannot be assessed with simple signal averaging. We tested the ability of this technique to track pharmacologically induced changes in LV function during residual viability study. LV volume signals obtained (Sonos 5500) in 10 patients with dilated cardiomyopathy under control conditions and during low-dose dobutamine infusion (10 mcg/kg/min) were digitized at 300 Hz. In each subject and for each experimental condition LV volume signals were averaged (16 consecutive beats) with the TW technique. Averaged waveforms and time-derivatives were used to identify the phases of LV filling and calculate end-systolic and end-diastolic volumes, stroke, peak rapid and peak atrial filling rates, peak ejection rate, duration of heart cycle, systole, rapid filling and atrial filling phases. The calculated indices reflected the low-dose dobutamine-induced changes in LV function, evidencing variations both in rapid filling and systolic phases. Signal averaging with TW allows reliable calculation of indices of LV systolic and diastolic function, and can be used to monitor their changes related to residual viability examinations.