A voltage-triggered system for adaptive sampling in body surface mapping
Cardiac electrophysiological waveforms are particularly well suited for adaptive sampling since they are periodic and contain some segments of both rapid and slow change. Rather than sampling at a constant rate, adaptive sampling allows the sampling rate to change according to the rate at which new information is received. This study considered the effectiveness of a voltage-triggered system as a means for adaptive sampling during QRST of the cardiac cycle. Five leads in the precordial region were chosen to act as `cueing leads'. When a change in the voltage observed at any of the five (relative to the voltage previously saved for that lead) occurred that was greater than a given triggering voltage, sampling from all 150 body surface leads took place, and a new set of reference voltages for each cueing lead was saved. Potential distributions (maps) were made from simultaneous voltages at the 150 leads, arranged spatially to represent the chest and back, and isopotential lines were added. Increases in the triggering voltage from 25 to 200 μV decreased the number of selected maps from about 90 to about 30. As fewer maps were selected, a larger proportion was chosen during QRS. On the whole, voltage triggering effectively distributed maps throughout QRST, except that too few low-level potential maps and no baseline maps were chosen. The results show that voltage-triggered adaptive sampling is an effective method of concentrating sampling time in intervals of greatest physiological interest; in many (but not all) respects, it provides a basis for more efficient body surface map acquisition
