The Effects of 40 Hz Low-pass Filtering on the Magnitude of the Spatial Ventricular Gradient

Changes in the magnitude of the spatial ventricular
gradient (MSVG) have been associated with an increased
risk of ventricular arrhythmias. This association makes
the MSVG a potentially attractive parameter for ECG
monitoring applications.
The MSVG is typically obtained using 150 Hz low-pass
filtered resting ECGs. However, monitoring applications
typically utilise upon 40 Hz low-pass filtered ECG data.
The extend to which the utilization of 40 Hz low-pass
monitoring ECG filters over the commonly used 150 Hz
low-pass resting ECG filters does affect the MSVG value
has not previously been reported.
The aim of this research was to quantify the
differences between MSVG values computed using 40 Hz
low-pass filtered ECG data (MSVG40) and 150 Hz lowpass filtered ECG data (MSVG150). The differences
between the MSVG40 and the MSVG150 were quantified
as systematic error (mean difference) and random error
(span of Bland-Altman 95% limits of agreement) using a
study population of 726 subjects. The systematic error
was found to be 0.013 mV ms [95% confidence interval:
0.008 mV ms to 0.018 mV ms]. The random error was
quantified as 0.282 mV ms [95% confidence interval:
0.266 mV ms to 0.298 mV ms].
Our findings suggest that it is possible to record
accurate MSVG values in monitoring applications that
require the utilization of 40 Hz low-pass filtered ECG
data.