Fatigue Assessment and Management During Stress Testing
Fatigue should be used as a subjective indicator of relative exertion during stress testing, with a Borg scale rating >18 indicating maximal exercise and values >15-16 suggesting the ventilatory threshold has been exceeded. 1
Understanding Fatigue in Stress Testing
Fatigue during cardiac stress testing serves as a valuable clinical endpoint that helps clinicians determine:
- The degree of exertion achieved during testing
- When to terminate a test appropriately
- Correlation between test fatigue and daily activity limitations
Rating Perceived Exertion
The 6-to-20 Borg scale is the recommended tool for assessing subjective fatigue during stress testing:
| Borg Scale | Rating | Clinical Significance |
|---|---|---|
| 6-9 | Very, very light to very light | Minimal exertion |
| 10-12 | Light to fairly light | Low-moderate exertion |
| 13-14 | Somewhat hard | Moderate exertion |
| 15-16 | Hard | Approaching ventilatory threshold |
| 17-19 | Very hard | Near maximal exertion |
| 20 | Maximal exertion | Test termination point |
While there is individual variation in fatigue ratings, patients tend to rate consistently from test to test, making the Borg scale valuable for comparing exertion levels across multiple tests 1.
Clinical Application of Fatigue Assessment
Test Termination Criteria
Fatigue should be considered alongside other clinical parameters when determining when to terminate a stress test:
- Borg scale rating >18 indicates maximal exercise has been achieved
- Ratings >15-16 suggest ventilatory threshold has been exceeded
- Severe fatigue combined with other symptoms (dyspnea, chest pain) warrants test termination
Test Supervision Requirements
The level of fatigue and patient characteristics influence supervision requirements:
- Tests should be supervised by properly trained personnel (nurse, physician assistant, exercise physiologist)
- A physician should be immediately available during all exercise tests except for young, apparently healthy individuals
- Direct physician supervision is required for patients with recent acute coronary syndrome, severe left ventricular dysfunction, severe valvular stenosis, or complex arrhythmias 1
Special Considerations
Cancer-Related Fatigue
For patients with cancer history undergoing stress testing:
- Use the 0-10 numeric rating scale for initial fatigue screening
- Scores ≥4 warrant more comprehensive assessment
- Consider energy conservation strategies and appropriate pacing of activities 1, 2
Post-Test Monitoring
- A cool-down period of walking slowly in early recovery is recommended
- Monitoring should continue for 6-8 minutes after exercise, or longer if symptoms persist
- Be alert for abnormal responses that may occur only during recovery 1
Common Pitfalls and Caveats
Overlooking fatigue as a clinical endpoint: Fatigue is not just a subjective complaint but a valuable clinical indicator of exertion level and test adequacy.
Failing to correlate test fatigue with daily activities: The Borg scale helps correlate fatigue during testing with that experienced during daily activities, providing practical clinical context.
Inadequate supervision: While non-physicians can supervise many stress tests, physician presence is required for high-risk patients or those with specific cardiac conditions.
Premature test termination: Distinguish between expected exertional fatigue and abnormal fatigue that warrants test termination.
Missing recovery phase abnormalities: Some abnormal responses occur only during recovery, so monitoring should continue after exercise completion 1.
By systematically assessing fatigue during stress testing using validated tools like the Borg scale, clinicians can optimize test interpretation, ensure patient safety, and gather valuable clinical information that impacts patient management decisions.