Exercise stress testing is routinely performed to evaluate suspected coronary artery disease in older adults. However, the available data to predict and compare relative exercise capacity in the general population were developed using predominantly younger, healthy cohorts with few or no women. This study aimed to describe the exercise capacity of patients older than 75 years who underwent a clinically indicated Bruce protocol exercise stress test. This was a retrospective, cross-sectional study of 2,041 consecutive patients older than 75 years who performed a Bruce protocol exercise stress echocardiogram that was terminated because of maximal effort without ischemia at Columbia University Medical Center between April 10, 2009, and July 30, 2020. The analytic sample included 2,041 exercise stress tests in 786 women (median [interquartile range] age 79 [77 to 81] years) and 1,255 men (median [interquartile range] age 79 [77 to 82] years). Cardiovascular risk factors and clinical coronary disease were common and more prevalent in men than women. The median exercise time for men aged 76 to 80 years was 7:22 (minutes:seconds) and for women was 6:00 and significantly decreased in both genders as age increased (p <0.001). The mean (SD) METs achieved for women and men were 6.5 (1.6) and 7.7 (1.7), respectively. Most women (85%) and men (95%) completed the first stage, whereas only 32% of women and 64% of men completed the second stage. It was uncommon for women (3%) or men (15%) to complete the third stage. Fewer than 1% of patients completed the fourth stage, and none completed the fifth stage. At all ages, women had a lower exercise capacity than men. These data allow physicians to compare the exercise capacity of older patients who underwent a Bruce protocol exercise stress test more accurately to a representative sample of similarly aged adults.
Exercise stress testing (EST) is routinely performed to noninvasively evaluate suspected coronary artery disease (CAD). Recent census data indicate that by 2060 the number of individuals aged ≥85 years will triple, suggesting that the number of ESTs performed in older adults will increase in tandem with the growth of that demographic. , The available data to predict and compare relative exercise capacity were developed using predominantly young and healthy cohorts with few or no women. , , Thus, the paucity of data describing expected exercise capacity in adults aged >75 years limits the interpretation of EST results in this growing population and forces clinicians to extrapolate and make assumptions about their patient’s expected performance. To address these limitations, herein we describe the exercise capacity of a large cohort of men and women >75 years of age who performed a clinically indicated, symptom-limited Bruce protocol EST.
Methods
This project was approved by the Columbia University Institutional Review Board, which granted a waiver of informed consent and authorization under the Health Insurance Portability and Accountability Act. We followed the Strengthening the Reporting of Observational Studies in Epidemiology reporting guideline for cohort studies. Patients were not directly involved in the study design or interpretation of data, although their inquiries about relative exercise capacity compared with age- and gender-matched peers served as the impetus for the study.
Columbia University Irving Medical Center is a quaternary care medical center in Northern Manhattan. Patients were included in this cross-sectional analysis if they were >75 years at the time of a clinically indicated Bruce protocol exercise stress echocardiogram performed between April 10, 2009, and July 30, 2020 (n = 2,907). Patients were excluded for: submaximal tests, defined as <85% of maximum predicted heart rate by the equation (0.85 × [220−age]) (n = 636) ; echocardiographic evidence of ischemia (n = 219), defined as new or worsened wall motion abnormalities with exercise; or nondiagnostic echocardiographic images (n = 11), yielding a final analytic sample of 2,041 ESTs ( Figure 1 ).
Patient characteristics including demographics and co-morbidities are part of the clinical history obtained at the time of the EST and were extracted from the EST report. Hypertension, dyslipidemia, and diabetes mellitus were defined as the combination of self-reported history and/or use of a medication to treat the condition.
All included patients underwent a standard Bruce protocol, which consists of 7 3-minute stages with increased speed and incline of the treadmill at each stage with the first stage starting at 1.7 miles/hour and 10% incline. Patients were considered to have reached the next stage if they tolerated the complete incline and speed increase of the next stage for >5 seconds of the stage. Handrail use with several fingers was allowed as needed to maintain balance and prevent falls. Blood pressure was measured using a manual aneroid sphygmomanometer immediately before exercise, approximately 1:30 minutes into each stage, and during the 5 minutes of recovery. As described in the original Bruce protocol, blood pressure was often indeterminate at the highest workloads because of body movement and machine noise, and as such, the maximum stress-associated blood pressure was documented in early recovery in some patients. Patients had continuous electrocardiographic monitoring starting immediately before the EST through recovery. Heart rate at rest was obtained immediately before the start of the stress protocol, and peak heart rate was extracted from the software report after the test. ESTs were stopped at maximal effort or the clinical discretion of the attending cardiologist supervising the test. No ESTs were stopped solely because of the achievement of the target heart rate. Referring clinicians decided on an individualized basis whether any medications were held before the EST.
METs, defined as the quantity of oxygen consumed by the body from inspired air at rest and equal to 3.5 ml of oxygen/kg/min, were estimated based on the final treadmill grade and speed and determined using the FRIEND (Fitness Registry and the Importance of Exercise National Database) formula. This registry included older adults in the derivation cohort, is validated in patients with CAD, and more accurately predicts the maximal rate of oxygen consumption, and thus METs, than the historically used American College of Sports Medicine method.
Data are presented as mean ± SD, median (interquartile range), or n (%). All analyses were performed stratified by gender. The exercise stage completed was compared between men and women overall using the Kruskal-Wallis test, and at each stage using Fisher’s exact test. A total of 4 age group categories were created including those who were aged 76 to 80, 81 to 85, 86 to 90, and ≥91 years at the time of EST. Average METs achieved between ordered age groups of women and men were assessed using nonparametric tests of trend. Linear regression was used to examine the association between exercise time and age in women and men, and in sensitivity analyses, the effect of diabetes mellitus and β-blocker use on these associations was examined. All statistical analyses used a 2-tailed p value with a threshold of <0.05 for significance and were performed using Stata Statistical Software: Release 15 (StataCorp LLC, College Station, Texas).
Results
The study population included 2041 ESTs performed in 786 women and 1,255 men. Cardiovascular risk factors including hypertension, dyslipidemia, diabetes mellitus, and smoking were common and more prevalent in men than women ( Table 1 ). Clinical CAD, which included a history of percutaneous coronary intervention, myocardial infarction, and/or coronary artery bypass grafting, was present in 9% of women and 29% of men. EST hemodynamics, including blood pressure at rest and peak blood pressure, and heart rate, were similar between women and men.
| Variable | Women(n = 786) | Men(n = 1,255) |
|---|---|---|
| Age, years, median [IQR] | 79 [77-81] | 79 [77-82] |
| Hypertension | 559 (71.1%) | 950 (75.7%) |
| Dyslipidemia | 527 (67.0%) | 983 (78.3%) |
| Diabetes mellitus | 84 (10.7%) | 199 (15.9%) |
| Current or former smoker | 112 (14.2%) | 221 (17.6%) |
| CAD (prior PCI/MI/CABG) | 73 (9.3%) | 368 (29.3%) |
| Beta-blocker | 232 (29.5%) | 423 (33.7%) |
| Statin | 404 (51.4%) | 883 (70.4%) |
| Systolic blood pressure at rest, mean ± SD (mm Hg) | 139 ± 18 | 140 ± 20 |
| Diastolic blood pressure at rest, mean ± SD (mm Hg) | 76 ± 9 | 73 ± 9 |
| Heart rate at rest, mean ± SD (bpm) | 77 ± 13 | 72 ± 13 |
| Peak systolic blood pressure, mean ± SD (mm Hg) | 166 ± 19 | 170 ± 21 |
| Peak diastolic blood pressure, mean ± SD (mm Hg) | 78 ± 10 | 79 ± 10 |
| Peak heart rate, mean ± SD (bpm) | 138 ± 14 | 139 ± 14 |
| Peak heart rate % of age predicted maximum, mean ± SD | 98 ± 10 | 99 ± 10 |
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