Table 1.
Baseline characteristics of unmatched and matched populations. Propensity score 2 : 1 matching performed using a nearest neighbour matching algorithm.
| Baseline characteristics | Unmatched | Matched | ||||
|---|---|---|---|---|---|---|
| <12 h (n = 1464) | 12–24 h (n = 368) | p-value | <12 h (n = 736) | 12–24 h (n = 368) | p-value | |
| Age, median (IQR) | 63.05 (54.10, 72.40) | 64.65 (55.88, 75.10) | 0.015 | 65.00 (56.00, 75.00) | 64.65 (55.88, 75.10) | 0.853 |
| Female (%) | 308 (21.0) | 91 (24.7) | 0.144 | 178 (24.2) | 91 (24.7) | 0.901 |
| Hypertension (%) | 883 (60.4) | 225 (61.1) | 0.840 | 465 (63.2) | 225 (61.1) | 0.553 |
| Diabetes (%) | 286 (19.5) | 63 (17.1) | 0.324 | 120 (16.3) | 63 (17.1) | 0.797 |
| Hypercholesterolemia (%) | 980 (67.1) | 234 (63.6) | 0.228 | 476 (64.7) | 234 (63.6) | 0.773 |
| Previous MI (%) | 209 (14.3) | 65 (17.7) | 0.119 | 149 (20.2) | 66 (17.9) | 0.405 |
| Previous PCI (%) | 231 (15.8) | 71 (19.4) | 0.113 | 159 (21.6) | 73 (19.8) | 0.548 |
| Previous CABG (%) | 79 (5.4) | 28 (7.6) | 0.136 | 60 (8.2) | 28 (7.6) | 0.844 |
| Previous stroke (%) | 34 (2.3) | 12 (3.3) | 0.401 | 28 (3.8) | 12 (3.3) | 0.776 |
| Previous CVD (%) | 370 (25.3) | 118 (32.1) | 0.010 | 245 (33.3) | 118 (32.1) | 0.734 |
| Valvular disease (%) | 27 (1.8) | 5 (1.4) | 0.678 | 11 (1.5) | 5 (1.4) | 1.000 |
| Chronic lung disease (%) | 67 (4.6) | 18 (4.9) | 0.912 | 34 (4.6) | 18 (4.9) | 0.960 |
| Family history of CAD (%) | 397 (27.4) | 97 (26.4) | 0.759 | 173 (23.5) | 97 (26.4) | 0.334 |
| Smoking (%) | 562 (38.4) | 125 (34.0) | 0.132 | 243 (33.0) | 125 (34.0) | 0.804 |
| BMI (kg/m2) | 27.43 (4.44) | 27.08 (4.73) | 0.191 | 27.14 (4.33) | 27.07 (4.72) | 0.814 |
| Haemoglobin (g/l), mean (SD) | 137.11 (18.17) | 136.28 (18.27) | 0.445 | 136.56 (17.61) | 136.24 (18.10) | 0.777 |
| Anemia (%) | 305 (21.9) | 82 (23.4) | 0.577 | 159 (21.6) | 88 (23.9) | 0.429 |
| Haematocrit, mean (SD) | 40.36 (5.06) | 40.28 (5.18) | 0.787 | 40.26 (4.88) | 40.26 (5.13) | 0.990 |
| eGFR, mean (SD) | 92.75 (27.33) | 89.18 (27.17) | 0.026 | 89.65 (27.16) | 89.22 (27.21) | 0.804 |
| LVEF, mean (SD) | 55.41 (10.12) | 55.92 (10.30) | 0.407 | 55.66 (10.40) | 55.88 (10.37) | 0.733 |
| ECG ischemia (%) | 864 (62.0) | 208 (58.3) | 0.215 | 445 (60.5) | 211 (57.3) | 0.351 |
| Heart rate (beats per minute), mean (SD) | 75.33 (14.65) | 76.40 (15.23) | 0.215 | 75.94 (14.83) | 76.40 (15.23) | 0.634 |
| Systolic blood pressure (mmHg), mean (SD) | 132.78 (22.26) | 133.02 (21.64) | 0.851 | 133.08 (21.96) | 132.88 (21.63) | 0.885 |
| GRACE score, mean (SD) | 126.68 (27.85) | 129.41 (29.15) | 0.099 | 130.12 (27.84) | 129.21 (29.07) | 0.611 |
| GRACE score >140 (%) | 437 (30.8) | 131 (36.0) | 0.068 | 258 (36.4) | 131 (36.0) | 0.951 |
| Killip class 2 (%) | 90 (6.3) | 26 (7.2) | 0.626 | 45 (6.2) | 26 (7.2) | 0.658 |
| Door-to-catheter time in minutes, median (IQR) | 3.50 (1.80, 6.10) | 16.80 (14.40, 19.50) | <0.001 | 3.50 (1.80, 6.00) | 16.80 (14.40, 19.50) | <0.001 |
BMI = body mass index; CABG = coronary artery bypass graft; CAD = coronary artery disease; CVD = cardiovascular disease; eGFR = estimated glomerular filtration rate; GRACE = Global Registry of Acute Coronary Events; IQR = interquartile range; LVEF = left ventricular ejection fraction; MI = myocardial infarction; PCI = percutaneous intervention; SD = standard deviation.