Clinical characteristics and variant locations between de novo and familial probands
| De novo group | Familial group | P value | |
| Number of probands, n | 58 | 24 | |
| Male sex, n (%) | 34 (58.6) | 11 (45.8) | 0.34 |
| Age at first symptom, years | 6.5(5.0, 9.0) | 10.0(8.3, 12.8) | <0.001 |
| Age at clinical diagnosis, years | 9.0(5.3, 12.0) | 13.0(11.0, 14.8) | <0.001 |
| Syncope*, n (%) | 41 (70.7) | 20 (83.3) | 0.28 |
| Syncope age, years | 7.0(5.0, 9.0) | 10.0(8.0, 13.0) | 0.001 |
| CA*, n (%) | 31 (53.4) | 10 (41.7) | 0.47 |
| CA age, years | 8.0(5.0, 12.0) | 12.0(11.0, 13.8) | 0.010 |
| Initial symptom: syncope/CA, n (%) | 41/17 (70.7/29.3) | 18/4 (81.8/18.2) | 0.40 |
| Worst symptom: syncope/CA, n (%) | 27/31 (46.6/53.4) | 12/10 (54.5/45.5) | 0.62 |
| Reason for the genetic test: syncope/CA/polymorphic VT on exercise stress ECG, n (%) | 27/31/0 (46.6/53.4/0) | 14/8/2 (58.3/33.3/8.3) | 0.036 |
| ECG parameters | |||
| Heart rate, beats per minute | 63(55, 77) | 59(54, 73) | 0.34 |
| QT, ms | 402(380, 441) | 411(400, 432) | 0.42 |
| QTc, ms | 421(397, 440) | 410(396, 447) | 0.95 |
| Bidirectional VT†, n (%) | 26 (44.8) | 4 (16.7) | 0.023 |
| Bradycardia for age, n (%) | 16 (27.6) | 4 (16.7) | 0.40 |
| Atrial fibrillation†, n (%) | 6 (10.3) | 0 (0) | 0.17 |
| Epilepsy, n (%) | 13 (22.4) | 2 (8.3) | 0.21 |
| Intellectual disability, n (%) | 8 (13.8) | 0 (0) | 0.097 |
| Variant location‡, n (%) | |||
| N-terminus domain | 10 (17.5) | 14 (58.3) | <0.001 |
| Central domain | 10 (17.5) | 1 (4.2) | |
| C-terminus domain | 33 (57.9) | 3 (12.5) | |
| Other area | 4 (7.0) | 6 (25.0) | |
Data are represented as n (%) and median (IQR).
*All syncope and CA events before clinical diagnosis were counted on the list and some probands have both events.
†Documentation on any ECG recordings
‡Splicing error is not included.
CA, cardiac arrest; VT, ventricular tachycardia.