Table 1.
Characteristics of the Participants at Baseline and Imaging and Lead Information.*
| Characteristic | Value |
|---|---|
| Participants | |
| No. of participants | 1509 |
| Median age (IQR) — yr | 69.3 (57.7–78.1) |
| Female sex — no. (%) | 548 (36) |
| Median ejection fraction (IQR) — % | 50 (30–60) |
| Coronary artery disease — no. (%) | 501 (33) |
| Previous coronary-artery bypass surgery — no. (%) | 233 (15) |
| Previous aortic-valve replacement — no. (%) | 54 (4) |
| Previous mitral-valve replacement — no. (%) | 35 (2) |
| Pacemaker — no. (%) | 880 (58) |
| Implantable cardioverter-defibrillator — no. (%) | 629 (42) |
| Cardiac resynchronization therapy — no. (%) | 163 (11) |
| Reason for device implantation — no. (%)† | |
| Symptomatic bradycardia | 469 (31) |
| Tachycardia-bradycardia syndrome | 99 (7) |
| Complete heart block‡ | 163 (11) |
| Primary prevention of sudden death | 398 (26) |
| Secondary prevention of sudden death | 139 (9) |
| Median time since generator implantation (IQR) — mo | 29 (12–52) |
| Median time since lead implantation (IQR) — mo | |
| Right atrial lead | 40 (15–75) |
| Right ventricular lead | 39 (15–75) |
| Left ventricular lead | 26 (10–56) |
| Dependence on pacing during MRI — no. (%) | 137 (9) |
| MRIs | |
| No. of examinations | 2103 |
| Scan category — no. (%) | |
| First scan | 1509 (72) |
| Second scan | 320 (15) |
| Third or subsequent scan | 274 (13) |
| Region of imaging — no. (%) | |
| Arm or leg§ | 196 (9) |
| Head or neck | 1091 (52) |
| Thorax | 257 (12) |
| Abdomen or pelvis | 559 (27) |
| Lead length — no./total no. (%)¶ | |
| Right atrial lead | |
| ≤45 cm | 257/891 (29) |
| 46–50 cm | 164/891 (18) |
| >50 cm | 470/891 (53) |
| Right ventricular lead | |
| ≤55 cm | 358/1123 (32) |
| 56–60 cm | 502/1123 (45) |
| >60 cm | 263/1123 (23) |
| Left ventricular lead | |
| ≤85 cm | 33/102 (32) |
| 86–90 cm | 43/102 (42) |
| ≥90 cm | 26/102 (25) |
*
IQR denotes interquartile range, and MRI magnetic resonance imaging.
†
The reason for the device was unknown to study personnel in 357 participants (24%) at the time of presentation for MRI. In addition, not all reasons for device implantation were mutually exclusive.
‡
Complete heart block refers to conduction block.
§
Transmit–receive coils were used in 57 MRIs of the knee (3%).
¶
Lead length is presented as the number of leads of a given length divided by the number of leads with implantation data and the percentage.