Table 3.
Components of measurement error for PR interval and P wave indices, based on 247 ECGs
| PR Interval (ms) |
Maximum P wave area (μV*ms) |
P-axis (°)a |
Maximum P wave duration (ms) |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Source of variation | SD | % total variance | CV (%) | SD | % total variance | CV (%) | SD | % total variance | CV (%) | SD | % total variance | CV (%) |
| Between-participant | 26.84 | 93.07 | 15.91 | 1,880.82 | 73.28 | 27.21 | 14.76 | 78.40 | 28.41 | 8.77 | 57.76 | 8.00 |
| Between-visit | 5.45 | 3.83 | 3.23 | 952.05 | 18.78 | 13.77 | 3.03 | 3.30 | 5.83 | 0.00 | 0.00 | 0.00 |
| Within-visit | 4.90 | 3.10 | 2.90 | 619.09 | 7.94 | 8.96 | 7.13 | 18.31 | 13.73 | 7.5 | 42.24 | 6.84 |
| Total | 27.82 | 100.00 | 16.49 | 2,197.08 | 100.00 | 31.79 | 16.67 | 100.00 | 9.00 | 11.54 | 100.00 | 10.52 |
a
244 ECGs
SD: standard deviation; CV: coefficient of variation = 100 × square root of the variance/grand mean.
Grand means are as follows: 168.69 ms for PR interval, 51.94° for P axis, 6,911.74 μV*ms for maximum P wave area, and 109.64 ms for maximum P wave duration.