Table 1.
Baseline characteristics of the study population
| Characteristics | Total | Myocardial blood flow reserve |
P-value | ||
|---|---|---|---|---|---|
| N = 12 549 | Low (<1.8) (n = 4836) | Intermediate (1.8–2) (n = 1888) | Normal (≥2) (n = 5825) | ||
| Age (years) | 68.0 ± 12.1 | 71.7 ± 11.4 | 68.8 ± 11.4 | 64.7 ± 11.9 | <0.001 |
| Male gender | 5927 (47.2) | 2155 (44.6) | 846 (44.8) | 2926 (50.2) | <0.001 |
| Body mass index (kg/m2) | 29.68 ± 6.47 | 29.26 ± 5.91 | 29.28 ± 5.91 | 30.16 ± 7.03 | <0.001 |
| Coronary artery disease | <0.001 | ||||
| No known CAD | 9711 (77.4) | 3636 (75.2) | 1450 (76.8) | 4625 (79.4) | |
| Prior MI | 216 (1.7) | 104 (2.2) | 25 (1.3) | 87 (1.5) | |
| Prior PCI | 2622 (20.9) | 1096 (22.7) | 413 (21.9) | 1113 (19.1) | |
| Hypertension | 9813 (78.2) | 4012 (83.0) | 1535 (81.3) | 4266 (73.2) | <0.001 |
| Diabetes | 3472 (27.7) | 1631 (33.7) | 494 (26.2) | 1347 (23.1) | <0.001 |
| Hyperlipidaemia | 9411 (75.0) | 3731 (77.2) | 1441 (76.3) | 4239 (72.8) | <0.001 |
| Current smoker | 1720 (13.7) | 627 (13.0) | 248 (13.1) | 845 (14.5) | 0.05 |
| Family history of CVD | 4743 (37.8) | 1715 (35.5) | 735 (38.9) | 2293 (39.4) | <0.001 |
| Peripheral vascular disease | 1452 (11.6) | 758 (15.7) | 205 (10.9) | 489 (8.4) | <0.001 |
| Cerebrovascular accident | 1071 (8.5) | 543 (11.2) | 148 (7.8) | 380 (6.5) | <0.001 |
| Patient status | <0.001 | ||||
| Inpatient | 4859 (38.7) | 1833 (37.9) | 650 (34.4) | 2376 (40.8) | |
| Outpatient | 7536 (60.1) | 2982 (61.7) | 1221 (64.7) | 3333 (57.2) | |
| Baseline abnormal ECG | 10 436 (83.2) | 4115 (85.1) | 1594 (84.4) | 4727 (81.2) | <0.001 |
| Symptoms | |||||
| Chest pain | <0.001 | ||||
| Atypical | 7398 (59.0) | 2578 (53.3) | 1086 (57.5) | 3734 (64.1) | |
| Non-anginal | 54 (0.4) | 19 (0.4) | 9 (0.5) | 26 (0.4) | |
| Typical | 62 (0.5) | 25 (0.5) | 14 (0.7) | 23 (0.4) | |
| Dyspnoea | 6151 (49.0) | 2529 (52.3) | 929 (49.2) | 2693 (46.2) | <0.001 |
| Syncope | 814 (6.5) | 329 (6.8) | 112 (5.9) | 373 (6.4) | 0.40 |
| Medications at baseline | |||||
| Aspirin | 8134 (64.8) | 3082 (63.7) | 1214 (64.3) | 3838 (65.9) | 0.06 |
| Beta-blocker | 5173 (41.2) | 2237 (46.3) | 783 (41.5) | 2153 (37.0) | <0.001 |
| Statin | 4304 (34.3) | 1732 (35.8) | 685 (36.3) | 1887 (32.4) | <0.001 |
| Calcium channel blocker | 2923 (23.3) | 1357 (28.1) | 452 (23.9) | 1114 (19.1) | <0.001 |
| Stress data | |||||
| Baseline heart rate (b.p.m.) | 70.26 ± 13.53 | 73.82 ± 14.19 | 70.33 ± 13.23 | 67.27 ± 12.30 | <0.001 |
| Peak heart rate (b.p.m.) | 89.93 ± 16.45 | 88.99 ± 16.63 | 89.69 ± 15.69 | 90.78 ± 16.50 | <0.001 |
| Rest systolic BP (mmHg) | 131.85 ± 20.99 | 136.21 ± 22.01 | 132.41 ± 20.68 | 128.06 ± 19.46 | <0.001 |
| Peak systolic BP (mmHg) | 122.19 ± 21.11 | 124.53 ± 22.51 | 122.88 ± 20.73 | 120.02 ± 19.76 | <0.001 |
| ECG response | <0.001 | ||||
| Ischaemic | 488 (3.9) | 263 (5.4) | 62 (3.3) | 163 (2.8) | |
| Non-diagnostic | 2239 (17.8) | 1094 (22.6) | 351 (18.6) | 794 (13.6) | |
| Non-ischaemic | 9644 (76.9) | 3415 (70.6) | 1451 (76.9) | 4778 (82.0) | |
| Equivocal | 178 (1.4) | 64 (1.3) | 24 (1.3) | 90 (1.5) | |
| Imaging data | |||||
| Rest LVEF (%) | 61.84 ± 13.61 | 60.84 ± 13.84 | 62.37 ± 12.76 | 62.51 ± 13.63 | <0.001 |
| % Scarred myocardium >0% | 2453 (19.5) | 1225 (25.3) | 363 (19.2) | 865 (14.8) | <0.001 |
| % Ischaemic myocardium | <0.001 | ||||
| None (0%) | 8498 (67.7) | 2708 (56.0) | 1305 (69.1) | 4485 (77.0) | |
| Mild–moderate (1–10%) | 2638 (21.0) | 1192 (24.6) | 424 (22.5) | 1022 (17.5) | |
| Severe (≥10+%) | 1413 (11.3) | 936 (19.4) | 159 (8.4) | 318 (5.5) | |
| Transient ischaemic dilatation | 1479 (12.1) | 792 (16.9) | 192 (10.5) | 495 (8.8) | <0.001 |
| LVEF reserve | 4.0 (1.0–8.0) | 3.0 (−1.0 to 6.0) | 4.0 (1.0–8.0) | 6.0 (2.0–9.0) | 0.73 |
| Coronary calcium score | <0.001 | ||||
| 0 | 1409 (19.5) | 331 (11.8) | 203 (19.4) | 875 (26.0) | |
| 1–99 | 2128 (29.5) | 640 (22.8) | 290 (27.8) | 1198 (35.6) | |
| 100–399 | 1470 (20.4) | 617 (22.0) | 233 (22.3) | 620 (18.4) | |
| ≥400 | 2211 (30.6) | 1219 (43.4) | 319 (30.5) | 673 (20.0) | |
| Rest MBF (ml/min/g) | 0.77 (0.61–0.97) | 0.88 (0.70–1.12) | 0.79 (0.64–0.99) | 0.69 (0.56–0.85) | <0.001 |
| Stress MBF (ml/min/g) | 1.51 (1.19–1.91) | 1.28 (1.00–1.62) | 1.50 (1.21–1.86) | 1.72 (1.39–2.11) | 0.01 |
Continuous variables presented as mean (SD) except median (IQR); categorical variables presented as frequency (%). Continuous variables compared using ANOVA or Wilcoxon rank sum test (non-normally distributed variables). Categorical variables compared using the χ2 or Fisher’s exact test.
CVD, cardiovascular disease; IQR: interquartile range; MI, myocardial infarction; LVEF, left ventricular ejection fraction; PCI, percutaneous coronary intervention.