Simultaneous accelerometer measurements of arterial activity during benign ventricular ectopy

Over a 180s observation period, a 3-lead (V5) electrocardiogram (ECG) was collected in a 66 y.o. male subject with benign ventricular ectopy. Simultaneous measures were also made from two tri-axial accelerometers, one placed over the sternum and the other on the forehead. The experiment was repeated with the sensors placed over the femoral and carotid arteries. Signals were sampled at 1kHz and filtered. Ensemble averages (with ±S.D.) and raster plots were generated for each filtered time series from 200 ms before to 800 ms after the peak of each R-wave. Lag times between the R-wave peak (taken as t=0) and the prominent peaks (or valleys) of the various accelerometer signals were calculated, Pulse Transit Times (PTT) determined, and Pulse Wave Velocities (PWV) calculated, given the measured distance between each sensor placement. R-R intervals were calculated between each beat pair and sorted by shortest to longest duration. Ensemble averages and PWV calculations were then repeated by separating sinus rhythm interval pairs, and short and long R-R intervals pairs. The peak acceleration values seen in these three sets of ensemble averages were then compared to determine how normal, short and long R-R intervals influenced external pulse pressure measures.