Relationship between seismocardiogram and echocardiogram for events in the cardiac cycle

Seismocardiography (SCG) is a noninvasive method to record ultralow-frequency cardiac vibrations from the chest wall using an accelerometer. This research evaluated the relationship between SCG and echocardiography (Echo); 39 subjects had simultaneous SCG and Echo, 28 were normals and 11 had dilated cardiomyopathy. Ten SCG points were compared with their corresponding systolic and diastolic Echo points. The mean absolute difference between SCG and Echo for 5 systolic points was 7.6 ms and 6.8 ms for the 5 diastolic points. Two SCG systolic points showed increased divergence from the Echo points in subjects with cardiomyopathy. Both methods showed approximately equal ability to distinguish longer cardiac time intervals among abnormals compared with normals. Intrasubject variability was lower in the SCG than Echo. The consistency between SCG and Echo points indicates that they are equally accurate in measuring cardiac time intervals.