Baseline characteristics of the study population
| Characteristics | BB | No BB | Partial BB | p-value |
| Subjects n | 133 | 375 | 60 | |
| Age years | 59±14 | 57±16 | 55±16 | 0.22 |
| BMI kg·m-2 | 29±8 | 28±8 | 26±6 | 0.12 |
| Race | 0.84 | |||
| Caucasian | 97 (73) | 280 (75) | 40 (67) | |
| African-American | 27 (20) | 70 (18) | 12 (20) | |
| Hispanic | 4 (3) | 15 (4) | 7 (1) | |
| Asian | 5 (4) | 10 (3) | 3 (0.5) | |
| Sex | 0.24 | |||
| Male | 46 (35) | 109 (29) | 23 (38) | |
| Female | 87 (65) | 265 (71) | 37 (62) | |
| Smoking history | 0.27 | |||
| Never smoked | 74 (56) | 229 (61) | 37 (62) | |
| Ex-/current smoker | 59 (44) | 149 (39) | 23 (38) | |
| Aetiology of PAH | 0.005 | |||
| Idiopathic | 47 (35) | 186 (50) | 27 (45) | |
| Connective tissue disease | 86 (65) | 189 (50) | 33 (55) | |
| Co-existing cardiac illness | ||||
| Coronary artery disease | 13 (9) | 47 (12) | 7 (12) | 0.38 |
| Valvular heart disease | 13 (10) | 36 (10) | 9 (15) | 0.95 |
| Cardiac arrhythmias | 27 (20) | 80 (21) | 13 (22) | 0.79 |
| Dyslipidaemia | 54 (41) | 158 (42) | 20 (33) | 0.76 |
| Pericardial effusion | 21 (27) | 54 (21) | 10 (17) | 0.24 |
| Comorbidities | ||||
| Diabetes mellitus | 27 (22) | 73 (20) | 14 (23) | 0.63 |
| Renal failure | 31 (23) | 88 (23) | 16 (26) | 0.64 |
| Hypertension | 27 (20) | 72 (19) | 13 (22) | 0.78 |
| Sleep apnoea | 12 (9) | 45 (12) | 7 (13) | 0.94 |
| LVEF % | 56±7 | 56±8 | 58±8 | 0.56 |
| Heart rate beats·min-1 | 71±17 | 84±15 | 74±19 | 0.01 |
| Pro-BNP pg·mL−1 | 780±218 | 349±852 | 511±403 | <0.016 |
| Baseline NYHA functional class# | 0.52 | |||
| I | 2 (0.5) | 0 | ||
| II | 48 (38) | 125 (34) | 10 (19) | |
| III | 58 (46) | 180 (48) | 26 (43) | |
| IV | 20 (16) | 62 (17) | 16 (25) | |
| Baseline 6MWD m | 286±111 | 303±102 | 221±59 | 0.15 |
| Follow-up months median (range) | 81 (1.5–247) | 75 (1–388) | 31 (1.5–145) | 0.41 |
| Transplant | 9 (7) | 25 (7) | 4 (7) | 0.97 |
| Mortality | 69 (52) | 184 (49) | 32 (53) | 0.57 |
Data are presented as mean±sd or n (%), unless otherwise stated. BB: patients who had continued to use β-blockers until they reached the end-points of the study; no BB: patients who had never used β-blockers; partial BB: patients who were started on β-blocker therapy but discontinued after a period; BMI: body mass index; PAH: pulmonary arterial hypertension; LVEF: left ventricular ejection fraction; BNP: brain natriuretic peptide; NYHA: New York Heart Association; 6MWD: 6-min walking distance. #: n=126 (BB), n=369 (no BB) and n=52 (partial BB).