Characteristics of patients in the original cohort and in that matched by propensity score
| Characteristic | Original cohort, no. (%) of patients* n = 8183 | Matched cohort, no. (%) of patients* n = 1316 | ||||
|---|---|---|---|---|---|---|
| Admitted to hospital n = 743 | Discharged n = 7440 | Standardized difference, % | Admitted to hospital n = 658 | Discharged n = 658 | Standardized difference, % | |
| Age, mean ± SD, yr | 70.6 ± 17.5 | 51.8 ± 22.7 | 92.8 | 69.4 ± 17.9 | 70.6 ± 17.2 | 5.9 |
| Female sex | 299 (40.2) | 4209 (56.6) | 33.1 | 278 (42.2) | 291 (44.2) | 4.0 |
| Arrival by ambulance | 553 (74.4) | 4661 (62.6) | 25.6 | 480 (72.9) | 490 (74.5) | 3.3 |
| Blood pressure | ||||||
| Mean systolic blood pressure during ED stay < 90 mm Hg or > 180 mm Hg† | 215 (28.9) | 745 (10.0) | 49.2 | 179 (27.2) | 186 (28.3) | 2.8 |
| Mean diastolic blood pressure during ED stay < 50 mm Hg or > 110 mm Hg | 188 (25.3) | 678 (9.1) | 44.0 | 160 (24.3) | 155 (23.6) | 2.1 |
| Prodrome (e.g., dizziness, light-headedness, vision changes, nausea or vomiting) | 366 (49.3) | 5701 (76.6) | 59.6 | 342 (52.0) | 347 (52.7) | 1.6 |
| Vasovagal predisposition (e.g., warm crowded place, prolonged standing, fear, emotion or pain)† | 120 (16.2) | 3544 (47.6) | 71.8 | 118 (17.9) | 103 (15.6) | 5.2 |
| Final ED syncope diagnosis | ||||||
| Vasovagal syncope | 108 (14.5) | 4274 (57.4) | 100.0 | 107 (16.3) | 107 (16.3) | 0.0 |
| Cardiac syncope | 216 (29.1) | 236 (3.2) | 75.2 | 146 (22.2) | 131 (19.9) | 6.6 |
| Age-related comorbidities | 464 (62.4) | 2265 (30.4) | 67.7 | |||
| History of hypertension | 424 (57.1) | 2053 (27.6) | 62.5 | 361 (54.9) | 360 (54.7) | 0.3 |
| History of diabetes | 176 (23.7) | 674 (9.1) | 40.3 | 146 (22.2) | 155 (23.6) | 3.8 |
| History of heart disease†‡§ | 356 (47.9) | 1249 (16.8) | 70.5 | 296 (45.0) | 298 (45.3) | 0.7 |
| Elevated troponin level (> 99th percentile of population)† | 155 (20.9) | 248 (3.3) | 55.8 | 100 (15.2) | 98 (14.9) | 1.0 |
| Electrocardiogram characteristics | ||||||
| QRS duration ≥ 130 ms† | 130 (17.5) | 334 (4.5) | 42.5 | 100 (15.2) | 100 (15.2) | 0 |
| QRS axis < 30° or > 110°† | 147 (19.8) | 580 (7.8) | 35.3 | 115 (17.5) | 107 (16.3) | 3.6 |
| Corrected QT interval > 480 ms† | 156 (21.0) | 399 (5.4) | 47.5 | 125 (19.0) | 126 (19.1) | 0.5 |
| Syncope risk category¶ | ||||||
| Very low | 51 (6.9) | 3518 (47.3) | 102.2 | 51 (7.8) | 54 (8.2) | 1.1 |
| Low | 134 (18.0) | 2483 (33.4) | 35.7 | 132 (20.1) | 154 (23.4) | 7.8 |
| Medium | 324 (43.6) | 1155 (15.5) | 64.6 | 317 (48.2) | 298 (45.3) | 6.7 |
| High | 149 (20.0) | 213 (2.9) | 56.0 | 119 (18.1) | 104 (15.8) | 7.5 |
| Very high | 85 (11.4) | 63 (0.8) | 45.2 | 39 (5.9) | 48 (7.3) | 5.9 |
| Serious adverse event | 169 (22.8) | 97 (1.3) | – | 133 (20.2) | 32 (4.9) | – |
Note: ED = emergency department, SD = standard deviation.
↵* Except where noted otherwise.
↵† Canadian Syncope Risk Score predictors were used for deriving the propensity score. Hospital site was also included as a predictor when estimating propensity scores for emergency department disposition.
↵‡ Definition of heart disease included documented history of any 1 of the following: coronary or valvular heart disease, cardiomyopathy, congestive heart failure or on-sinus rhythm (electrocardiogram evidence during index visit or documented history of ventricular or atrial arrhythmia, or device implantation).
↵§ Not included when generating propensity scores for hospital admission.
↵¶ Based on the Canadian Syncope Risk Score (3) predictors, which include mean systolic blood pressure during the emergency department stay < 90 mm Hg or > 180 mm Hg, vasovagal predisposition, history of heart disease, final emergency department diagnosis of vasovagal or cardiac syncope, elevated troponin level, QRS duration ≥ 130 ms, QRS axis < 30° or > 110°, and corrected QT interval > 480 ms. Eight discharged patients had missing values. The syncope risk category was not included when generating propensity scores, as the component predictors were included.