Event detection in ECG, carotid pulse, phonocardiogram, and detection of consecutive systolic time intervals

We developed a program which allows measurement of consecutive time intervals between chosen events in ECG, carotid pulse, and phonocardiogram. Currently it is possible to determine following systolic time intervals (STI): PEP - pre-ejection period, Q-S2 – time between trough of Q wave and aortic valve closure, Q-D - time between trough of Q wave and dicrotic notch, S2-D - time between aortic valve closure and dicrotic notch, as well as QQ interval. Measurements were performed on 30 young, healthy subjects. Subjects were supine, they performed two-minute isometric handgrip (HG) twice. First HG was followed by four-minute rest, second HG by two-minute occlusion of the working arm. Preliminary analyses revealed: 1/ the QQ interval changes were reflected weakly or not at all in changes of STI, 2/ shortening of QQ during handgrip was paralleled by slight decrease of Q-D and Q-S2, 3/ during occlusion, when QQ intervals returned to baseline also Q-D and Q-S2 returned to baseline, despite sustained elevation of arterial pressure, 4/ there were distinct oscillation in the time course of Q-S2 intervals, time course of Q-D intervals was relatively smooth, thus S2 and D may reflect different events contrary to common notation.