Table 3.
Distribution of Changes in Device Variables*
| Variable | Patients, n† | Decrease, n (%)
|
≤20% Change, n (%) | Increase, n (%)
|
||||
|---|---|---|---|---|---|---|---|---|
| 41%–50% | 31%–40% | 21%–30% | 21%–30% | 31%–40% | 41%–50% | |||
| Immediately after MRI | ||||||||
|
| ||||||||
| P-wave amplitude | 303 | 0 (0) | 4 (1.3) | 24 (7.9) | 245 (80.9) | 10 (3.3) | 20 (6.6) | 0 (0) |
|
| ||||||||
| Right ventricular R-wave amplitude | 461 | 0 (0) | 5 (1.1) | 19 (4.1) | 419 (90.9) | 7 (1.5) | 11 (2.4) | 0 (0) |
|
| ||||||||
| Left ventricular R-wave amplitude | 20 | 0 (0) | 1 (5) | 3 (15) | 15 (75) | 1 (5) | 0 (0) | 0 (0) |
|
| ||||||||
| Atrial lead impedance | 364 | 0 (0) | 0 (0) | 0 (0) | 363 (99.7) | 1 (0.3) | 0 (0) | 0 (0) |
|
| ||||||||
| Right ventricular lead impedance | 518 | 0 (0) | 0 (0) | 1 (0.2) | 515 (99.4) | 2 (0.4) | 0 (0) | 0 (0) |
|
| ||||||||
| Left ventricular lead impedance | 51 | 0 (0) | 0 (0) | 1 (2) | 50 (98) | 0 (0) | 0 (0) | 0 (0) |
|
| ||||||||
| Atrial capture threshold | 332 | 15 (4.5) | 9 (2.7) | 13 (3.9) | 265 (79.8) | 7 (2.1) | 13 (3.9) | 10 (3.0) |
|
| ||||||||
| Right ventricular capture threshold | 531 | 11(2.1) | 15 (2.8) | 13 (2.5) | 455 (85.7) | 9 (1.7) | 15 (2.8) | 13 (2.5) |
|
| ||||||||
| Left ventricular capture threshold | 55 | 0 (0) | 2 (4) | 3 (5) | 44 (80) | 4 (7) | 2 (4) | 0 (0) |
|
| ||||||||
| Battery voltage | 472 | 0 (0) | 0 (0) | 0 (0) | 472 (100.0) | 0 (0) | 0 (0) | 0 (0) |
| Long-term follow-up after MRI‡ | ||||||||
|
| ||||||||
| P-wave amplitude | 124 | 0 (0) | 6 (5) | 10 (8) | 94 (76) | 6 (5) | 8 (6) | 0 (0) |
|
| ||||||||
| Right ventricular R-wave amplitude | 198 | 0 (0) | 15 (8) | 11 (6) | 155 (78) | 8 (4) | 9 (5) | 0 (0) |
|
| ||||||||
| Left ventricular R-wave amplitude | 9 | 0 (0) | 1 (11) | 1 (11) | 7 (78) | 0 (0) | 0 (0) | 0 (0) |
|
| ||||||||
| Atrial lead impedance | 167 | 0 (0) | 0 (0) | 2 (1) | 162 (97) | 3 (2) | 0 (0) | 0 (0) |
|
| ||||||||
| Right ventricular lead impedance | 234 | 0 (0) | 0 (0) | 3 (1) | 223 (95) | 8 (3) | 0 (0) | 0 (0) |
|
| ||||||||
| Left ventricular lead impedance | 23 | 0 (0) | 0 (0) | 0 (0) | 23 (100) | 0 (0) | 0 (0) | 0 (0) |
|
| ||||||||
| Atrial capture threshold | 105 | 1 (1) | 2 (2) | 6 (6) | 86 (82) | 3 (3) | 3 (3) | 4 (4) |
|
| ||||||||
| Right ventricular capture threshold | 190 | 7 (4) | 10 (5) | 8 (4) | 122 (64) | 7 (4) | 16 (8) | 20 (11) |
|
| ||||||||
| Left ventricular capture threshold | 23 | 2 (9) | 2 (9) | 1 (4) | 10 (43) | 1 (4) | 4 (17) | 3 (13) |
| Battery voltage | 224 | 0 (0) | 0 (0) | 3 (1) | 221 (99) | 0 (0) | 0 (0) | 0 (0) |
MRI = magnetic resonance imaging.
*
Lead impedance variations exceeding 30% (20, 21), capture threshold variations exceeding 50% (22), and sensing variations exceeding 40% (23, 24) indicate clinically significant changes in lead performance.
†
The number of comparisons for each device variable is unique, primarily owing to variability in the number of leads, the absence of intrinsic P/R waves, the presence of atrial arrhythmia, and pulse widths during measurement of capture threshold at follow-up interrogation. The proportion of missing data for each variable is discussed in the Discussion section.
‡
Based on long-term follow-up results available for 266 (61%) patients undergoing 278 MRI examinations.