Table 1.
Clinical Characteristics and Exercise Data of Studied Population, According to Resting Heart Rate (HR; beats/min) Quartiles
| Overall | Resting HR Q1 | Resting HR Q2 | Resting HR Q3 | Resting HR Q4 | ||
|---|---|---|---|---|---|---|
| Characteristic | (n = 718) | (34–62; n= 186) | (63–70; n= 175) | (71–82; n= 191) | (82–136; n= 166) | P Value |
| Age, y | 53 ± 14 | 55 ± 14 | 53 ± 14 | 53 ± 14 | 50 ± 14 | .006 |
| Male sex | 477 (66%) | 131 (70%) | 113 (65%) | 119(62%) | 114 (69%) | .58 |
| Race | .10 | |||||
| White | 596 (83%) | 159 (86%) | 148 (85%) | 156 (82%) | 133 (80%) | |
| Black | 62 (9%) | 10 (5%) | 15 (9%) | 20(11%) | 17 (10%) | |
| Hispanic | 26 (4%) | 7 (4%) | 7 (4%) | 5 (3%) | 7 (4%) | |
| BMI, kg/m2 | 28.4 ± 5.9 | 27.9 ± 5.5 | 28.1 ± 5.4 | 28.4 ± 6.3 | 29.1 ± 6.2 | .05 |
| Cardiomyopathy | ||||||
| Ischemic | 148 (21%) | 50 (27%) | 42 (24%) | 32 (17%) | 24 (15%) | .001 |
| Symptomatic HF | 586 (82%) | 146 (79%) | 132 (75%) | 158 (83%) | 150 (90%) | .001 |
| NYHA functional class | .001 | |||||
| 1 | 253 (35%) | 68 (37%) | 75 (43%) | 65 (34%) | 45 (27%) | |
| 2 | 256 (36%) | 76 (41%) | 53 (30%) | 71 (37%) | 56 (34%) | |
| 3 | 173 (24%) | 37 (20%) | 41 (23%) | 43 (23%) | 52 (31%) | |
| 4 | 35 (5%) | 5 (3%) | 6 (3%) | 11 (6%) | 13 (8%) | |
| Comorbidities | ||||||
| Hypertension | 401 (56%) | 95 (51%) | 92 (53%) | 114 (60%) | 100 (60%) | .04 |
| Diabetes | 171 (24%) | 33 (18%) | 32(18%) | 54 (28%) | 52 (31%) | <0.001 |
| Coronary artery disease | 225 (31%) | 69 (37%) | 59 (34%) | 54 (28%) | 43 (26%) | .01 |
| Stroke | 53 (7%) | 21 (11%) | 13 (7%) | 9 (5%) | 10 (6%) | .03 |
| Atrial fibrillation | 192 (27%) | 62 (33%) | 41 (23%) | 51 (27%) | 38 (23%) | .06 |
| COPD | 57 (8%) | 11 (6%) | 13 (7%) | 16 (8%) | 17 (10%) | .13 |
| CKD | 148 (21%) | 40 (22%) | 37(21%) | 40(21%) | 31 (19%) | .54 |
| Treatment | ||||||
| β-Blockers | 596 (83%) | 162 (87%) | 147 (84%) | 158 (83%) | 129 (78%) | .02 |
| % of recommended β-blockade | 35 ± 28 | 38 ± 28 | 37 ± 29 | 34 ± 27 | 30 ± 27 | .006 |
| ACEi/ARBs | 562 (78%) | 145 (78%) | 138 (79%) | 146 (76%) | 133 (80%) | .79 |
| Diuretics | 439(61%) | 97 (52%) | 100 (57%) | 119(62%) | 123 (74%) | <.001 |
| MRA | 169 (24%) | 38 (20%) | 48 (27%) | 41 (22%) | 42 (25%) | .54 |
| Antiarrhythmic | 183 (26%) | 60 (32%) | 45 (26%) | 33 (17%) | 45 (27%) | .07 |
| CRT/ICD | 220 (31%) | 69 (37%) | 50 (29%) | 51 (27%) | 50 (30%) | .12 |
| Laboratory tests and echocardiography | ||||||
| Hemoglobin, g/dL | 13.5 ± 1.8 | 13.7 ± 1.6 | 13.4 ± 1.9 | 13.4 ± 1.7 | 13.6 ± 1.8 | .61 |
| Anemia | 168 (23%) | 40 (22%) | 36 (21%) | 49 (26%) | 43 (26%) | .20 |
| Creatinine, g/dL | 1.2 ± 1.0 | 1.2 ± 0.7 | 1.2 ± 1.0 | 1.2 ± 1.0 | 1.2 ± 1.1 | .82 |
| eGFR, mL. min−1·1.73 m−2 | 78 ± 25 | 76 ± 24 | 77 ± 24 | 78 ± 27 | 80 ± 25 | .15 |
| LVEF, % | 34 ± 15 | 40 ± 13 | 34 ± 13 | 35 ± 16 | 28 ± 14 | <.001 |
| CPET data | ||||||
| Resting SBP, mm Hg | 117 ± 20 | 121 ± 20 | 118 ± 21 | 117 ± 18 | 114 ± 19 | .02 |
| Resting DBP, mm Hg | 75 ± 11 | 74 ± 11 | 75 ± 12 | 75 ± 11 | 75 ± 11 | .80 |
| Peak SBP, mm Hg | 145 ± 29 | 151 ± 29 | 146 ± 30 | 143 ± 29 | 139 ± 29 | .004 |
| Peak DBP, mm Hg | 77 ± 12 | 76 ± 11 | 77 ± 13 | 76 ± 12 | 78 ± 13 | .63 |
| Resting HR, beats/min | 73 ± 15 | 57 ± 5 | 66 ± 2 | 75 ± 3 | 94 ± 10 | <0.001 |
| Peak HR, beats/min | 129 ± 27 | 119 ± 27 | 127 ± 28 | 130 ± 27 | 142 ± 21 | <.001 |
| Change in HR, beats/min | 57 ± 27 | 63 ± 28 | 61 ± 28 | 54 ± 26 | 48 ± 21 | <.001 |
| Peak HR, % of predicted | 77 ± 15 | 72 ± 14 | 76 ± 15 | 78 ± 15 | 84 ± 13 | <.001 |
| Chronotropic index | 0.60 ± 0.26 | 0.57 ± 0.22 | 0.60 ± 0.26 | 0.60 ± 0.28 | 0.64 ± 0.30 | .08 |
| Chronotropic index <0.60 | 379 (53%) | 107 (58%) | 89 (51%) | 97 (51%) | 86 (52%) | .51 |
| Peak RER | 1.21 ± 0.11 | 1.22 ± 0.12 | 1.21 ± 0.11 | 1.20 ± 0.11 | 1.21 ± 0.11 | .64 |
| PeakVO2, mL·min−1·kg−1 | 16.5 ± 6.4 | 18.3 ± 7.1 | 16.9 ± 6.6 | 16.0 ± 6.2 | 14.5 ± 4.6 | <.001 |
| Peak VO2, % pred | 64 ± 20 | 71 ± 19 | 66 ± 20 | 63 ± 20 | 57 ± 18 | <.001 |
| Peak O2 pulse, mL/beat | 11 ± 4 | 13 ± 4 | 11 ± 4 | 10.1 ± 3.4 | 8.9 ± 2.9 | <.001 |
| VE/VCO2 slope | 31.9 ± 7.9 | 29.7 ± 6.4 | 32.1 ± 9.0 | 32.1 ± 7.2 | 33.8 ± 8.7 | <.001 |
Values presented as mean ± SD or n (%). ACEi, angiotensin-converting-enzyme inhibitor; ARB, angiotensin receptor blocker; BMI, body mass index; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; CRT, cardiac resynchronization therapy; DBP, diastolic blood pressure; FC, functional class; eGFR, estimatedglomerular filtration rate; HF, heart failure; HR, heart rate; ICD, implantable cardioverter-defibrillator; LVEF, left ventricular ejection fraction; MRA, mineralocorticoid receptor antagonist; NYHA, New York Heart Association; RER, respiratory exchange ratio; SBP, systolic blood pressure; VCO2, carbon dioxide output; VE, minute volume; VO2, oxygen uptake.