Outpatient cardiac rehabilitation (CR) is most beneficial when delivered 1 to 3 weeks after the index cardiac event. The effects of delayed enrollment on subsequent outcomes are unclear. A total of 1,241 patients were enrolled in CR after recent (<1 year) treatment of cardiac events or postcardiac surgery. Risk factors and metabolic equivalent levels (METs) during aerobic exercise were calculated before and after CR. The mean CR delay time was 34 days (maximum of 327). Delay time >30 days was associated with older age, female gender, nonwhite race, being unemployed, and increased length of hospital stay before CR after index cardiac event (p <0.05 vs 0 to 15 and 16 to 30 days for all comparisons). Patients with delay time >30 days had significant improvements in all CR metrics, but peak METs and weight improvements were lesser in magnitude compared with patients with CR delay times 0 to 15 and 16 to 30 days. After multivariate adjustment, delay time >30 days remained an independent predictor of decreased MET improvement compared with delay time 0 to 15 days (β = −0.59, p <0.001). In conclusion, time to enrollment in CR varies substantially and is independently linked to demographics and length of index hospital stay. Delayed enrollment in CR is directly related to patient outcomes. Although all patients showed improvements in key metrics regardless of delay time, CR was of greatest benefit, particularly for weight and exercise capacity, when initiated within 15 days of the index event.
Cardiac rehabilitation (CR) improves risk factors, exercise capacity, and survival after myocardial infarction and cardiac surgery. Many factors may influence how early patients enter CR after an index cardiac event, including strength of the physician’s recommendation, co-morbidities, financial issues, or occupational considerations. Although early and routine referral may enhance participation in CR, the relation between delay time from index event to initiation of CR and subsequent outcomes is unclear. The aim of this study was to explore the relation between delay time to initiation of CR and risk factor and exercise outcomes after completion of CR. CR delay time was defined as the number of days between index hospitalization discharge and CR commencement.
Methods
From January 2004 to August 2012, 1,241 consecutive patients were enrolled in the outpatient CR program at Wake Forest Baptist Medical Center within 1 year after interventions for coronary artery disease and/or valvular heart disease, including cardiothoracic surgery. Clinical data for this study were taken from patient records, and the study was approved by our institutional review board.
The details of our CR program have been previously outlined. Briefly, it consists of 3 sessions per week for 12 weeks (total of 36 sessions of exercise) and health and nutrition education. Recruitment begins in the hospital with an interview with a specialized nurse. If the patient is able and willing to participate, relevant patient data are sent to a nurse or exercise physiologist in the CR program for review. CR staff then schedule an appointment for a formal rehabilitation consultation. Occasionally, patients attending our program have undergone interventions and/or treatment elsewhere (about 1% of total). At the appointment, an exercise physiologist creates individualized exercise plans based on patient history, co-morbidities, physical fitness, and clinical status and using recommendations of the American College of Sports Medicine Guidelines for Exercise Testing and Prescription. Each session lasts 30 to 40 minutes, with warm-up and cool-down activity, upper and lower body training (walking on a track, cycle ergometry, treadmills, and stairclimbers), and resistance exercises. Activity level is increased by 0.5 to 1.0 metabolic equivalents (METs) as tolerated, to perceived exertion of 11 to 14 on a 6 to 20 Borg scale. Heart rates are obtained at the highest level of exercise during each technique by telemetry. MET levels are documented by the exercise physiologist or nurse and represent the highest level of exertion for the patient for that specific session. MET levels are recorded at baseline during the first session and then at each subsequent visit, with peak METs representing the maximal MET level attained by the patient during the course of CR. At each visit, vital signs are recorded for all patients, including weight, systolic and diastolic pressures, heart rate at rest, and MET level. An exercise device or a standardized MET formula is used to obtain and record steady-state MET levels. Blood pressure is measured at each visit in the sitting position after resting for 5 minutes by a registered nurse using a standardized cuff. Normal blood pressure is defined as systolic blood pressure <120 mm Hg and diastolic blood pressure <80 mm Hg and hypertension as systolic blood pressure >140 mm Hg or diastolic blood pressure >90 mm Hg. Baseline is the first and, post, the last blood pressure measurement for a specific patient.
Adult Treatment Panel III guidelines were used to define optimal goals for low-density lipoprotein <100 mg/dl, high-density lipoprotein >40 mg/dl, and triglycerides <150 mg/dl, which were measured within a month of initiation and completion of CR.
Quality of life score is calculated at the beginning and end of the program using Ferrans and Powers Quality of Life Index Cardiac Version IV questionnaire. Additional baseline blood measurements include hemoglobin A1C. Left ventricular function was measured by standard techniques. Chronic obstructive pulmonary disease was documented by chart review and diagnosed by standard criteria.
Descriptive statistics (frequency and percent for categorical factors, mean and SD for continuous factors) were calculated and compared for statistical significance by length of delay time using the chi-square or Fisher’s exact tests for categorical variables and the Student t test for continuous variables. Changes in CR metrics were calculated as mean (95% confidence interval) of postrehabilitation minus baseline levels and compared using analysis of variance with Tukey’s multiple comparisons test for differences between delay time groups. Multivariate linear regression models were constructed with change in METs at peak as the dependent variable, and independent predictors were selected for inclusion using F testing. Variables with F-test statistics significant at the level of p <0.10 were added 1 by 1 to the model; as new variables were added, all existing variables were reevaluated for significance at the level of p <0.05 and any not meeting this threshold were removed from the model. This continued until all remaining variables in the model were significant independent predictors of change in METs at peak. SAS version 9.1 statistical software package (SAS Institute, Cary, North Carolina) was used for all statistical analysis.
Results
The distribution of time to enrollment in days was as follows: mean = 34.1 ± 34.8, median = 24, interquartile range = 16 to 37, ninety-ninth percentile = 197. Patients who enrolled >30 days after treatment of the index cardiac event were more often women, nonwhite, and older compared with those enrolling within 30 days (p <0.05 vs 0 to 15 days and 16 to 30 days for all comparisons; Table 1 ). Compared with those enrolling within 15 days, those who enrolled later than 30 days also had a higher prevalence of diabetes (32% vs 23%, p = 0.008), as well as hypertension (83% vs 73%, p <0.001), and decreased baseline exercise capacity (2.5 ± 0.9 vs 2.8 ± 0.9, p <0.001). Referral rates for coronary artery disease and valvular disease were similar across delay time groups, as was quality of life, tobacco use, weight measurements, and other cardiac risk factors. On average, patients attended 75% of CR sessions regardless of delay time.
| Characteristic | 0-15 days (N = 305) | 16-30 days (N = 488) | >30 days (N = 448) |
|---|---|---|---|
| Demographics | |||
| Age (years) | 60 ± 12 † | 62 ± 11 ∗ | 64 ± 12 † |
| Male gender | 240 (79%) | 361 (74%) | 288 (64%) † |
| White race | 269 (88%) | 423 (87%) | 345 (77%) † |
| Insured | 298 (98%) | 473 (97%) | 429 (96%) |
| Private | 171 (56%) | 219 (45%) ∗ | 163 (36%) † |
| Government | 97 (32%) | 202 (41%) ∗ | 217 (48%) † |
| Other/unknown | 30 (10%) | 52 (11%) | 49 (11%) |
| Median household income ($1k) | 45 ± 9 | 44 ± 9 | 42 ± 9 † |
| Unemployed | 26 (9%) | 81 (17%) [CR] | 100 (22%) † |
| Highest education level completed | |||
| Some high school | 3 (1%) | 2 (1%) | 3 (1%) |
| High school graduate | 72 (24%) | 122 (25%) | 126 (28%) |
| College graduate | 74 (24%) | 123 (25%) | 92 (21%) |
| Post-graduate degree | 52 (17%) | 60 (12%) | 38 (8%) ∗ |
| Not reported | 104 (34%) | 181 (37%) | 189 (42%) ∗ |
| Driving distance from CR (miles) | 26 ± 91 | 16 ± 22 | 17 ± 26 |
| Reason for referral | |||
| Coronary artery disease | 257 (85%) | 404 (84%) | 353 (81%) |
| Valvular disease | 40 (13%) | 82 (17%) | 74 (17%) |
| Length of hospital stay pre-CR (days) | 4.3 ± 3.8 | 5.3 ± 4.3 ∗ | 6.5 ± 6.1 † |
| Medical history | |||
| Quality of life | 23 ± 4 | 23 ± 5 | 23 ± 4 |
| Current smoker | 25 (8%) | 44 (9%) | 43 (10%) |
| Lung disease | 98 (32%) | 146 (30%) | 170 (38%) |
| Hypertension | 222 (73%) | 380 (78%) | 372 (83%) ∗ |
| Systolic pressure (mm Hg) | 120 ± 17 | 121 ± 18 | 124 ± 20 † |
| Diastolic pressure (mm Hg) | 70 ± 10 | 70 ± 10 | 71 ± 11 |
| Resting heart rate (bpm) | 76 ± 14 | 77 ± 14 | 76 ± 15 |
| Hyperlipidemia | 236 (77%) | 376 (77%) | 346 (77%) |
| Diabetes mellitus | 70 (23%) | 140 (29%) | 142 (32%) ∗ |
| Glucose (mg/dL) | 107 ± 30 | 106 ± 30 | 104 ± 29 |
| Hemoglobin A1C (mg/dL) | 6.2 ± 1.3 | 6.3 ± 1.3 | 6.6 ± 1.5 † |
| Ejection fraction (%) | 50 ± 12 | 49 ± 11 | 49 ± 13 |
| Multi-vessel disease | 201 (66%) | 328 (67%) | 273 (61%) |
| Body mass index (kg/m ˆ 2) | 29 ± 6 | 29 ± 6 | 29 ± 6 |
| Weight (lbs) | 194 ± 39 | 193 ± 42 | 191 ± 44 |
| Weight (kg) | 88 ± 18 | 87 ± 19 | 87 ± 20 |
| Waist circumference (in) | 40 ± 5 | 41 ± 5 | 40 ± 6 |
| Waist circumference (cm) | 102 ± 13 | 104 ± 13 | 102 ± 15 |
| Medication use at start of CR | |||
| ACE inhibitors | 192 (63%) | 292 (60%) | 295 (66%) |
| Beta blockers | 265 (87%) | 431 (88%) | 390 (87%) |
| Statins | 267 (88%) | 423 (87%) | 385 (86%) |
| Baseline metabolic equivalents | 2.8 ± 0.9 | 2.7 ± 0.8 ∗ | 2.5 ± 0.9 † |
| No. sessions attended | 27 ± 12 | 27 ± 12 | 26 ± 12 |
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