Table 4.
Absolute differences between the standard 12-lead and handheld 6-lead ECGs under different acquisition conditions
| Supine position | ||||
|---|---|---|---|---|
| Metric | N | < 5 | 5 ≤ < 10 | ≥ 10 |
| Heart rate (bpm) | 107 | 107 (100.0%) | 0 (0.0%) | 0 (0.0%) |
| < 20 | 20 ≤ < 40 | ≥ 40 | ||
| PR interval (ms) | 63 | 45 (71.4%) | 16 (25.4%) | 2 (3.2%) |
| QRS duration (ms) | 107 | 81 (75.7%) | 26 (24.3%) | 0 (0.0%) |
| QT interval (ms) | 107 | 61 (57.0%) | 35 (32.7%) | 11 (10.3%) |
| QTc interval (ms) | 107 | 57 (53.3%) | 33 (30.8%) | 17 (15.9%) |
| < 0.05 | 0.05 ≤ < 0.1 | ≥ 0.1 | ||
| P amplitude (mV) | 63 | 45 (71.4%) | 14 (22.2%) | 4 (6.4%) |
| QRS amplitude (mV) | 107 | 55 (51.4%) | 28 (26.2%) | 24 (22.4%) |
| T amplitude (mV) | 107 | 79 (73.8%) | 26 (24.3%) | 2 (1.9%) |
| Sitting position | ||||
| Metric | N | < 5 | 5 ≤ < 10 | ≥ 10 |
| Heart rate (bpm) | 109 | 107 (98.2%) | 2 (1.8%) | 0 (0.0%) |
| < 20 | 20 ≤ < 40 | ≥ 40 | ||
| PR interval (ms) | 61 | 43 (70.5%) | 17 (27.9%) | 1 (1.6%) |
| QRS duration (ms) | 109 | 80 (73.4%) | 29 (26.6%) | 0 (0.0%) |
| QT interval (ms) | 109 | 67 (61.5%) | 30 (27.5%) | 12 (11.0%) |
| QTc interval (ms) | 109 | 60 (55.1%) | 33 (30.3%) | 16 (14.7%) |
| < 0.05 | 0.05 ≤ < 0.1 | ≥ 0.1 | ||
| P amplitude (mV) | 61 | 50 (82.0%) | 10 (16.4%) | 1 (1.6%) |
| QRS amplitude (mV) | 109 | 56 (51.4%) | 32 (29.4%) | 21 (19.3%) |
| T amplitude (mV) | 109 | 74 (67.9%) | 29 (26.6%) | 6 (5.5%) |
| Asynchronous pairs | ||||
| Metric | N | < 5 | 5 ≤ < 10 | ≥ 10 |
| Heart rate (bpm) | 96 | 44 (45.8%) | 26 (27.1%) | 26 (27.1%) |
| < 20 | 20 ≤ < 40 | ≥ 40 | ||
| PR interval (ms) | 54 | 29 (53.7%) | 18 (33.3%) | 7 (13.0%) |
| QRS duration (ms) | 96 | 66 (68.8%) | 23 (24.0%) | 7 (7.3%) |
| QT interval (ms) | 96 | 46 (47.9%) | 31 (32.3%) | 19 (19.8%) |
| QTc interval (ms) | 96 | 33 (34.4%) | 28 (29.2%) | 35 (36.5%) |
| < 0.05 | 0.05 ≤ < 0.1 | ≥ 0.1 | ||
| P amplitude (mV) | 54 | 37 (68.5%) | 10 (18.5%) | 7 (13.0%) |
| QRS amplitude (mV) | 96 | 22 (22.9%) | 24 (25.0%) | 50 (52.1%) |
| T amplitude (mV) | 96 | 54 (56.3%) | 22 (22.9%) | 20 (20.8%) |
For asynchronous analysis, non-simultaneous ECGs were matched post hoc by pairing a supine 12-lead ECG with a sitting 6-lead ECG from the same patient. The comparisons were restricted to pairs with consistent rhythm classifications for both devices. Rhythms that may be affected by premature complexes (APC and VPC) were grouped into the sinus rhythm categories. Cases without identifiable P waves were excluded from PR interval and P amplitude analyses
ECG electrocardiogram, bpm beats per minute, ms milliseconds, mV millivolts