An echocardiographic approach to the analysis of the variability in cardiac cycle phases

The dynamic time warping approach was applied to the left ventricular (LV) volume signal obtained by echocardiographic Acoustic Quantification technique. It allowed to track on a cycle-by-cycle basis the diastasis onset and end points, necessary to extract reliable measures in time duration of cardiac sub-intervals (rapid filling, RF; diastasis, DS; atrial contraction, AC; diastole, DI; systole, SY). Autoregressive spectral analysis was applied to study low (LF) and high frequency (HF) contributions to total power in these new variability series. A group of 10 normal young (NY, mean±SE, 24±2years) and a group of 10 normal adult (N, 63±2years) subjects were studied. Results showed an increase in SY duration in N (387±11ms) compared to NY (345±8ms). Moreover, a greater variability in the diastolic phase was found in NY (3890±1062ms2 compared to 1662±251ms2 in N), related with a greater variability in the DS phase (3575±991ms2 compared to 1075±260ms2 in N). A prevalent LF rhythm in DS was observed in NY (33±7n.u.), compared to N (21±5n.u.). Spectral analysis applied to these series appears able to give a new insight of HRV, evidencing changes in LF and HF contributions relevant to the different cardiac phases and related with the ageing process.