Table 1

Clinical characteristics and variant locations between de novo and familial probands

De novo groupFamilial groupP value
Number of probands, n5824
Male sex, n (%)34 (58.6)11 (45.8)0.34
Age at first symptom, years6.5(5.0, 9.0)10.0(8.3, 12.8)<0.001
Age at clinical diagnosis, years9.0(5.3, 12.0)13.0(11.0, 14.8)<0.001
Syncope*, n (%)41 (70.7)20 (83.3)0.28
Syncope age, years7.0(5.0, 9.0)10.0(8.0, 13.0)0.001
CA*, n (%)31 (53.4)10 (41.7)0.47
CA age, years8.0(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 minute63(55, 77)59(54, 73)0.34
 QT, ms402(380, 441)411(400, 432)0.42
 QTc, ms421(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 domain10 (17.5)14 (58.3)<0.001
 Central domain10 (17.5)1 (4.2)
 C-terminus domain33 (57.9)3 (12.5)
 Other area4 (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.