Table 2.
ECG Characteristics
| n = 105 | Baseline ECG | Post-medication ECG | P value1 |
|---|---|---|---|
| HR > 120 | 9 (8.6) | 11 (10.5) | 0.77 |
| Atrial flutter | 1 (1.0) | 2 (1.9) | > 0.99 |
| Atrial fibrillation | 8 (7.6) | 10 (9.5) | 0.69 |
| Supraventricular tachycardia | 1 (1.0) | 3 (2.8) | 0.5 |
| Right bundle branch block | 9 (8.6) | 12 (11.4) | 0.38 |
| Left bundle branch block | 0 (0.0) | 2 (1.9) | 0.5 |
| Non-specific intraventricular conduction block | 4 (3.8) | 0 (0.0) | 0.13 |
| Torsade de pointes | 0 (0.0) | 0 (0.0) | – |
| Ventricular tachycardia | 0 (0.0) | 1 (1.0) | > 0.99 |
| Ventricular fibrillation | 0 (0.0) | 0 (0.0) | – |
| #Days after drug initiation (post-drug ECG only), n [min, max] | – |
2 (1–3) [0, 18] |
|
| QTc, ms, median (IQR) | |||
| Male | 440 (423–457) | 455 (438–483) | < 0.001 |
| Female | 438 (423–460) | 463 (434–484) | < 0.001 |
| Difference between baseline and post-drug QTc, ms | – | 16 (−2–40) | |
| QTc prolongation2 | 15 (14.3) | 36 (34.3) | < 0.001 |
| QTc ≥ 500 ms | 5 (4.8) | 17 (16.2) | < 0.01 |
| Change in QTc ≥ 60 ms | – | 13 (12.4) | |
| Met criteria for medication discontinuation3 | – | 21 (20.0) | |
| Potassium (n = 87)4 | 4.4 ± 0.7 | 4.4 ± 0.7 | 0.61 |
| Calcium (n = 95)4 | 8.7 ± 0.6 | 8.4 ± 0.6 | < 0.001 |
| Magnesium (n = 54)4 | 2.1 (1.9–2.3) | 2.1 (1.9–2.4) | 0.17 |
Reported as mean ± SD, median (IQR), or n (%)
1McNemar’s test was used to analyze differences in HR > 120, atrial flutter/fibrillation, SVT, RBBB, LBBB, TdP, ventricular tachycardia/fibrillation, proportion of people with QTc prolongation, and QTc ≥ 500 ms; Wilcoxon signed-rank test was used to analyze QTc and magnesium levels; paired t test was used to analyze potassium and calcium levels
2QT prolongation defined as QTc ≥ 470 ms in men and ≥ 480 ms in women
3Criteria for medication discontinuation was defined as having a post-drug ECG QTc ≥ 500 ms or an increase from baseline of ≥ 60 ms
4N refers to total number of complete pairs that were analyzed