Table 1.
Baseline characteristics of ICCU admission
| The 2-day average concentration of PM2.5 before ICCU admission | ||||
|---|---|---|---|---|
| Characteristic | ≤36 μg/m3 | 37-63 μg/m3 | ≥64 μg/m3 | P value |
| (N = 804) | (N = 773) | (N = 760) | ||
| Age, yrs | 65.9 ± 14.0 | 64.9 ± 14.6 | 65.8 ± 13.9 | 0.316 |
| Age ≥ 65 yrs | 473(58.8) | 434(56.1) | 446(58.7) | 0.938 |
| Male, n (%) | 558(69.4) | 531(68.7) | 500(65.8) | 0.128 |
| Source of admission, n (%) | ||||
| Department of Emergency | 503(62.6) | 536(69.3) | 565(74.3) | < 0.001 |
| General Ward of Cardiology | 254(31.6) | 201(26.0) | 165(21.7) | < 0.001 |
| Other Departments | 47(5.8) | 36(4.7) | 30(3.9) | 0.080 |
| Type of admission, n (%) | ||||
| Medical | 176(21.9) | 164(21.2) | 178(23.4) | 0.474 |
| Scheduled procedure | 424(52.7) | 367(47.5) | 292(38.4) | < 0.001 |
| Unscheduled procedure | 204(25.4) | 242(31.3) | 290(38.2) | < 0.001 |
| Vital signs | ||||
| Temperature, °C | 36.4 ± 0.8 | 36.4 ± 0.7 | 36.2 ± 2.7 | 0.208 |
| Respiratory rate, per min | 20.4 ± 3.5 | 20.3 ± 3.1 | 20.2 ± 4.5 | 0.745 |
| Heart rates, beats/min | 79.3 ± 21.5 | 79.8 ± 20.5 | 80.6 ± 22.4 | 0.467 |
| Systolic blood pressure, mmHg | 125.7 ± 45.0 | 124.0 ± 42.5 | 125.5 ± 45.8 | 0.717 |
| Diastolic blood pressure, mmHg | 72.6 ± 15.8 | 72.7 ± 15.8 | 72.6 ± 17.4 | 0.988 |
| Charlson Comorbidity Index | 2.3 ± 1.8 | 2.3 ± 1.9 | 2.4 ± 1.9 | 0.198 |
| Oxford Acute Severity of Illness Score | 21.5 ± 9.8 | 22.4 ± 10.7 | 23.7 ± 10.7 | < 0.001 |
| Cardiovascular comorbidities, n (%) | ||||
| Ischemic heart disease | 578(71.9) | 587(75.9) | 548(72.1) | 0.898 |
| ACS | 434(54.0) | 468(60.5) | 469(61.7) | 0.002 |
| STEMI | 214(26.6) | 264(34.2) | 270(35.5) | < 0.001 |
| NSTEMI | 114(14.2) | 123(15.9) | 120(15.8) | 0.371 |
| UA | 106(13.2) | 81(10.5) | 79(10.4) | 0.080 |
| SIHD | 137(17.0) | 112(14.5) | 75(9.9) | < 0.001 |
| MI mechanical complications | 14(1.7) | 10(1.3) | 13(1.7) | 0.951 |
| Hypertension | 432(53.7) | 391(50.6) | 388(51.1) | 0.283 |
| Myocardial disease | 70(8.7) | 65(8.4) | 64(8.4) | 0.838 |
| Valvar heart disease | 298(37.1) | 285(36.9) | 268(35.3) | 0.463 |
| Heart failure | 472(58.7) | 458(59.2) | 460(60.5) | 0.465 |
| NYHA functional classification | ||||
| I | 260(32.3) | 250(32.3) | 266(35.0) | 0.268 |
| II-III | 291(36.2) | 266(34.4) | 264(34.7) | 0.541 |
| IV | 167(20.8) | 179(23.2) | 180(23.7) | 0.166 |
| Cardiac shock | 53(6.6) | 64(8.3) | 59(7.8) | 0.372 |
| Cardiac arrest | 45(5.6) | 52(6.7) | 67(8.8) | 0.013 |
| Atrial arrhythmia | 140(17.4) | 130(16.8) | 142(18.7) | 0.517 |
| Ventricular arrhythmia | 63(7.8) | 45(5.8) | 51(6.7) | 0.366 |
| Bradycardia | 92(11.4) | 90(11.6) | 68(8.9) | 0.114 |
| Congenital heart disease | 13(1.6) | 13(1.7) | 14(1.8) | 0.733 |
| Pericardial disease | 10(1.2) | 9(1.2) | 8(1.1) | 0.724 |
| Aortic disease | 6(0.7) | 13(1.7) | 14(1.8) | 0.065 |
| Acute aortic syndrome | 2(0.2) | 3(0.4) | 6(0.8) | 0.120 |
| Cerebrovascular disease | 75(9.3) | 55(7.1) | 78(10.3) | 0.539 |
| Acute stroke/TIA | 9(1.1) | 5(0.6) | 12(1.6) | 0.400 |
| Peripheral arterial disease | 18(2.2) | 14(1.8) | 18(2.4) | 0.869 |
| Venous thromboembolism | 11(1.4) | 7(0.9) | 11(1.4) | 0.901 |
| Noncardiovascular comorbidities, n (%) | ||||
| Tobacco abuse | 279(34.7) | 275(35.6) | 245(32.2) | 0.312 |
| Alcohol abuse | 56(7.0) | 70(9.1) | 57(7.5) | 0.676 |
| Diabetes mellitus | 237(29.5) | 210(27.2) | 212(27.9) | 0.479 |
| Chronic kidney disease | 155(19.3) | 127(16.4) | 153(20.1) | 0.688 |
| Hypercholesterolemia | 118(14.7) | 122(15.8) | 139(18.3) | 0.054 |
| Chronic lung disease | 120(14.9) | 102(13.2) | 101(13.3) | 0.344 |
| Malignancy | 30(3.7) | 25(3.2) | 23(3.0) | 0.436 |
| Thyroid Disease | 17(2.1) | 8(1.0) | 20(2.6) | 0.479 |
| Connective tissue disease | 7(0.9) | 9(1.2) | 10(1.3) | 0.400 |
| Gout | 23(2.9) | 29(3.8) | 19(2.5) | 0.695 |
| Moderate/severe anemia | 76(9.5) | 67(8.7) | 75(10.0) | 0.802 |
| Hepatic dysfunction | 56(7.0) | 75(9.7) | 70(9.2) | 0.109 |
| Dyskalemia | 216(26.9) | 232(30.0) | 228(30.0) | 0.168 |
| Pneumonia/LRTI | 214(26.6) | 217(28.1) | 231(30.4) | 0.908 |
| Major acute nonCV critical illnesses | 147(18.3) | 168(21.7) | 193(25.4) | 0.001 |
| Acute respiratory failure | 95(11.8) | 114(14.7) | 133(17.5) | 0.001 |
| Acute kidney injury | 96(11.9) | 107(13.8) | 118(15.5) | 0.039 |
| Sepsis | 29(3.6) | 31(4.0) | 38(5.0) | 0.171 |
| Gastrointestinal hemorrhage | 22(2.7) | 24(3.1) | 32(4.2) | 0.106 |
Data are expressed as means ± standard variation or counts and percentage, as appropriate
Abbreviation: PM2.5 particulate matter with an aerodynamic diameter less than 2.5 μm, ACS acute coronary syndrome, STEMI ST-segment elevation myocardial infarction, NSTEMI non-ST-segment elevation myocardial elevation, UA unstable angina, SIHD stable ischemic heart disease, MI myocardial infarction, TIA transient ischemic attack, CV cardiovascular, LRTI low respiratory tract infection