Table 6.
Phenotypes in Carriers of Pathogenic/Likely Pathogenic Variants Associated with Long QT Syndrome
| Carriers (N=23) | Noncarriers (N=115) | P value | |
|---|---|---|---|
| Demographics | |||
| Age, years | 69.2 ± 11.1 | 69.2 ± 10.9 | NA |
| Female | 8 (35%) | 40 (35%) | |
| Genetic ancestry | |||
| European | 18 (78%) | 90 (78%) | |
| African | 5 (22%) | 25 (22%) | |
| Long QT syndrome risk score electrocardiogram categories | |||
| Individuals with electrocardiogram | 18 (78%) | 86 (75%) | 1 |
| QTc ≥480 ms | 7 (39%) | 9 (10%) | 0.01 * |
| QTc = 460–479 ms | 2 (11%) | 12 (14%) | |
| QTc = 450–459 ms in males | 1 (6%) | 5 (6%) | |
| QTc <450 ms in males or <460 ms in females | 8 (44%) | 60 (70%) | |
| Long QT syndrome risk score electrocardiogram and clinical criteria | |||
| Syncope | 2 (9%) | 18 (16%) | 0.5 |
| Syncope with stress | 0 | 0 | NA |
| Congenital deafness | 0 | 0 | NA |
| Torsades de pointes | 0 | 0 | NA |
| Long QT syndrome risk score family history criteria | |||
| Family history of long QT syndrome | 1 (4%) | 0 | 0.2 |
| Family history of unexplained sudden cardiac death | 0 | 0 | NA |
| Long QT syndrome risk score diagnostic probability | |||
| Low probability | 14 (61%) | 93 (81%) | 0.04 * |
| Intermediate probability | 9 (39%) | 21 (18%) | |
| High probability | 0 | 1 (1%) | |
| Other findings | |||
| QTc, ms | 465 ± 39 | 439 ± 34 | 0.005 |
| QTc ≥500 ms in repeated electrocardiograms | 1 (4%) | 0 | 0.2 |
| Atrial fibrillation/flutter | 7 (30%) | 44 (38%) | 0.6 |
| Nonsustained/sustained ventricular tachycardia | 2 (9%) | 28 (24%) | 0.2 |
| Implantable cardioverter-defibrillator | 2 (9%) | 14 (12%) | 1 |
| Obstructive coronary artery disease | 10 (43%) | 76 (66%) | 0.06 |
Continuous measures are described as mean ± standard deviation and are compared using two-sided Student’s t-test. Categorical variables are described as N (%); p values are calculated using Fisher’s exact test for dichotomous variables and Wilcoxon rank-sum test for ordinal variables (indicated by *). P values in bold indicate p <0.05. NA, not applicable; QTc, QT interval corrected for heart rate using Bazett’s formula.